XZY_403

The Linux-PAM System Administrators' Guide

Andrew G. Morgan

<morgan@kernel.org>

Thorsten Kukuk

<kukuk@thkukuk.de>

Version 1.1.2, 31. August 2010

Abstract

This manual documents what a system-administrator needs to know about the
   Linux-PAM library. It covers the correct syntax of the PAM configuration
   file and discusses strategies for maintaining a secure system.

--------------------------------------------------------------------------

1. Introduction

2. Some comments on the text

3. Overview

4. The Linux-PAM configuration file

4.1. Configuration file syntax

4.2. Directory based configuration

4.3. Example configuration file entries

5. Security issues

5.1. If something goes wrong

5.2. Avoid having a weak `other' configuration

6. A reference guide for available modules

6.1. pam_access - logdaemon style login access control

6.2. pam_cracklib - checks the password against dictionary
                words

6.3. pam_debug - debug the PAM stack

6.4. pam_deny - locking-out PAM module

6.5. pam_echo - print text messages

6.6. pam_env - set/unset environment variables

6.7. pam_exec - call an external command

6.8. pam_faildelay - change the delay on failure
                per-application

6.9. pam_filter - filter module

6.10. pam_ftp - module for anonymous access

6.11. pam_group - module to modify group access

6.12. pam_issue - add issue file to user prompt

6.13. pam_keyinit - display the keyinit file

6.14. pam_lastlog - display date of last login

6.15. pam_limits - limit resources

6.16. pam_listfile - deny or allow services based on an
                arbitrary file

6.17. pam_localuser - require users to be listed in
                /etc/passwd

6.18. pam_loginuid - record user's login uid to the process
                attribute

6.19. pam_mail - inform about available mail

6.20. pam_mkhomedir - create users home directory

6.21. pam_motd - display the motd file

6.22. pam_namespace - setup a private namespace

6.23. pam_nologin - prevent non-root users from login

6.24. pam_permit - the promiscuous module

6.25. pam_pwhistory - grant access using .pwhistory file

6.26. pam_rhosts - grant access using .rhosts file

6.27. pam_rootok - gain only root access

6.28. pam_securetty - limit root login to special devices

6.29. pam_selinux - set the default security context

6.30. pam_shells - check for valid login shell

6.31. pam_succeed_if - test account characteristics

6.32. pam_tally - login counter (tallying) module

6.33. pam_tally2 - login counter (tallying) module

6.34. pam_time - time controled access

6.35. pam_timestamp - authenticate using cached successful
                authentication attempts

6.36. pam_umask - set the file mode creation mask

6.37. pam_unix - traditional password authentication

6.38. pam_userdb - authenticate against a db database

6.39. pam_warn - logs all PAM items

6.40. pam_wheel - only permit root access to members of group
                wheel

6.41. pam_xauth - forward xauth keys between users

7. See also

8. Author/acknowledgments

9. Copyright information for this document

Chapter 1. Introduction

Linux-PAM (Pluggable Authentication Modules for Linux) is a suite of
   shared libraries that enable the local system administrator to choose how
   applications authenticate users.

In other words, without (rewriting and) recompiling a PAM-aware
   application, it is possible to switch between the authentication
   mechanism(s) it uses. Indeed, one may entirely upgrade the local
   authentication system without touching the applications themselves.

Historically an application that has required a given user to be
   authenticated, has had to be compiled to use a specific authentication
   mechanism. For example, in the case of traditional UN*X systems, the
   identity of the user is verified by the user entering a correct password.
   This password, after being prefixed by a two character ``salt'', is
   encrypted (with crypt(3)). The user is then authenticated if this
   encrypted password is identical to the second field of the user's entry in
   the system password database (the /etc/passwd file). On such systems, most
   if not all forms of privileges are granted based on this single
   authentication scheme. Privilege comes in the form of a personal
   user-identifier (UID) and membership of various groups. Services and
   applications are available based on the personal and group identity of the
   user. Traditionally, group membership has been assigned based on entries
   in the /etc/group file.

It is the purpose of the Linux-PAM project to separate the development of
   privilege granting software from the development of secure and appropriate
   authentication schemes. This is accomplished by providing a library of
   functions that an application may use to request that a user be
   authenticated. This PAM library is configured locally with a system file,
   /etc/pam.conf (or a series of configuration files located in /etc/pam.d/)
   to authenticate a user request via the locally available authentication
   modules. The modules themselves will usually be located in the directory
   /lib/security or /lib64/security and take the form of dynamically loadable
   object files (see dlopen(3)).

Chapter 2. Some comments on the text

Before proceeding to read the rest of this document, it should be noted
   that the text assumes that certain files are placed in certain
   directories. Where they have been specified, the conventions we adopt here
   for locating these files are those of the relevant RFC (RFC-86.0, see
   bibliography"). If you are using a distribution of Linux (or some other
   operating system) that supports PAM but chooses to distribute these files
   in a different way you should be careful when copying examples directly
   from the text.

As an example of the above, where it is explicit, the text assumes that
   PAM loadable object files (the modules) are to be located in the following
   directory: /lib/security/ or /lib64/security depending on the
   architecture. This is generally the location that seems to be compatible
   with the Filesystem Hierarchy Standard (FHS). On Solaris, which has its
   own licensed version of PAM, and some other implementations of UN*X, these
   files can be found in /usr/lib/security. Please be careful to perform the
   necessary transcription when using the examples from the text.

Chapter 3. Overview

For the uninitiated, we begin by considering an example. We take an
   application that grants some service to users; login is one such program.
   Login does two things, it first establishes that the requesting user is
   whom they claim to be and second provides them with the requested service:
   in the case of login the service is a command shell (bash, tcsh, zsh,
   etc.) running with the identity of the user.

Traditionally, the former step is achieved by the login application
   prompting the user for a password and then verifying that it agrees with
   that located on the system; hence verifying that as far as the system is
   concerned the user is who they claim to be. This is the task that is
   delegated to Linux-PAM.

From the perspective of the application programmer (in this case the
   person that wrote the login application), Linux-PAM takes care of this
   authentication task -- verifying the identity of the user.

The flexibility of Linux-PAM is that you, the system administrator, have
   the freedom to stipulate which authentication scheme is to be used. You
   have the freedom to set the scheme for any/all PAM-aware applications on
   your Linux system. That is, you can authenticate from anything as naive as
   simple trust (pam_permit) to something as paranoid as a combination of a
   retinal scan, a voice print and a one-time password!

To illustrate the flexibility you face, consider the following situation:
   a system administrator (parent) wishes to improve the mathematical ability
   of her users (children). She can configure their favorite ``Shoot 'em up
   game'' (PAM-aware of course) to authenticate them with a request for the
   product of a couple of random numbers less than 12. It is clear that if
   the game is any good they will soon learn their multiplication tables. As
   they mature, the authentication can be upgraded to include (long)
   division!

Linux-PAM deals with four separate types of (management) task. These are:
   authentication management; account management; session management; and
   password management. The association of the preferred management scheme
   with the behavior of an application is made with entries in the relevant
   Linux-PAM configuration file. The management functions are performed by
   modules specified in the configuration file. The syntax for this file is
   discussed in the section below.

Here is a figure that describes the overall organization of Linux-PAM:

+----------------+
   | application: X |
   +----------------+       /  +----------+     +================+
   | authentication-[---->--\--] Linux-   |--<--| PAM config file|
   |       +        [----<--/--]   PAM    |     |================|
   |[conversation()][--+    \  |          |     | X auth .. a.so |
   +----------------+  |    /  +-n--n-----+     | X auth .. b.so |
   |                |  |       __|  |           |           _____/
   |  service user  |  A      |     |           |____,-----'
   |                |  |      V     A
   +----------------+  +------|-----|---------+ -----+------+
                          +---u-----u----+    |      |      |
                          |   auth....   |--[ a ]--[ b ]--[ c ]
                          +--------------+
                          |   acct....   |--[ b ]--[ d ]
                          +--------------+
                          |   password   |--[ b ]--[ c ]
                          +--------------+
                          |   session    |--[ e ]--[ c ]
                          +--------------+

By way of explanation, the left of the figure represents the application;
   application X. Such an application interfaces with the Linux-PAM library
   and knows none of the specifics of its configured authentication method.
   The Linux-PAM library (in the center) consults the contents of the PAM
   configuration file and loads the modules that are appropriate for
   application-X. These modules fall into one of four management groups
   (lower-center) and are stacked in the order they appear in the
   configuration file. These modules, when called by Linux-PAM, perform the
   various authentication tasks for the application. Textual information,
   required from/or offered to the user, can be exchanged through the use of
   the application-supplied conversation function.

If a program is going to use PAM, then it has to have PAM functions
   explicitly coded into the program. If you have access to the source code
   you can add the appropriate PAM functions. If you do not have access to
   the source code, and the binary does not have the PAM functions included,
   then it is not possible to use PAM.

Chapter 4. The Linux-PAM configuration file

When a PAM aware privilege granting application is started, it activates
   its attachment to the PAM-API. This activation performs a number of tasks,
   the most important being the reading of the configuration file(s):
   /etc/pam.conf. Alternatively, this may be the contents of the /etc/pam.d/
   directory. The presence of this directory will cause Linux-PAM to ignore
   /etc/pam.conf.

These files list the PAMs that will do the authentication tasks required
   by this service, and the appropriate behavior of the PAM-API in the event
   that individual PAMs fail.

4.1. Configuration file syntax

The syntax of the /etc/pam.conf configuration file is as follows. The file
   is made up of a list of rules, each rule is typically placed on a single
   line, but may be extended with an escaped end of line: `\<LF>'. Comments
   are preceded with `#' marks and extend to the next end of line.

The format of each rule is a space separated collection of tokens, the
   first three being case-insensitive:

service type control module-path module-arguments

The syntax of files contained in the /etc/pam.d/ directory, are identical
   except for the absence of any service field. In this case, the service is
   the name of the file in the /etc/pam.d/ directory. This filename must be
   in lower case.

An important feature of PAM, is that a number of rules may be stacked to
   combine the services of a number of PAMs for a given authentication task.

The service is typically the familiar name of the corresponding
   application: login and su are good examples. The service-name, other, is
   reserved for giving default rules. Only lines that mention the current
   service (or in the absence of such, the other entries) will be associated
   with the given service-application.

The type is the management group that the rule corresponds to. It is used
   to specify which of the management groups the subsequent module is to be
   associated with. Valid entries are:

account

this module type performs non-authentication based account
           management. It is typically used to restrict/permit access to a
           service based on the time of day, currently available system
           resources (maximum number of users) or perhaps the location of the
           applicant user -- 'root' login only on the console.

auth

this module type provides two aspects of authenticating the user.
           Firstly, it establishes that the user is who they claim to be, by
           instructing the application to prompt the user for a password or
           other means of identification. Secondly, the module can grant
           group membership or other privileges through its credential
           granting properties.

password

this module type is required for updating the authentication token
           associated with the user. Typically, there is one module for each
           'challenge/response' based authentication (auth) type.

session

this module type is associated with doing things that need to be
           done for the user before/after they can be given service. Such
           things include the logging of information concerning the
           opening/closing of some data exchange with a user, mounting
           directories, etc.

If the type value from the list above is prepended with a - character the
   PAM library will not log to the system log if it is not possible to load
   the module because it is missing in the system. This can be useful
   especially for modules which are not always installed on the system and
   are not required for correct authentication and authorization of the login
   session.

The third field, control, indicates the behavior of the PAM-API should the
   module fail to succeed in its authentication task. There are two types of
   syntax for this control field: the simple one has a single simple keyword;
   the more complicated one involves a square-bracketed selection of
   value=action pairs.

For the simple (historical) syntax valid control values are:

required

failure of such a PAM will ultimately lead to the PAM-API
           returning failure but only after the remaining stacked modules
           (for this service and type) have been invoked.

requisite

like required, however, in the case that such a module returns a
           failure, control is directly returned to the application or to the
           superior PAM stack. The return value is that associated with the
           first required or requisite module to fail. Note, this flag can be
           used to protect against the possibility of a user getting the
           opportunity to enter a password over an unsafe medium. It is
           conceivable that such behavior might inform an attacker of valid
           accounts on a system. This possibility should be weighed against
           the not insignificant concerns of exposing a sensitive password in
           a hostile environment.

sufficient

if such a module succeeds and no prior required module has failed
           the PAM framework returns success to the application or to the
           superior PAM stack immediately without calling any further modules
           in the stack. A failure of a sufficient module is ignored and
           processing of the PAM module stack continues unaffected.

optional

the success or failure of this module is only important if it is
           the only module in the stack associated with this service+type.

include

include all lines of given type from the configuration file
           specified as an argument to this control.

substack

include all lines of given type from the configuration file
           specified as an argument to this control. This differs from
           include in that evaluation of the done and die actions in a
           substack does not cause skipping the rest of the complete module
           stack, but only of the substack. Jumps in a substack also can not
           make evaluation jump out of it, and the whole substack is counted
           as one module when the jump is done in a parent stack. The reset
           action will reset the state of a module stack to the state it was
           in as of beginning of the substack evaluation.

For the more complicated syntax valid control values have the following
   form:

[value1=action1 value2=action2 ...]

Where valueN corresponds to the return code from the function invoked in
   the module for which the line is defined. It is selected from one of
   these: success, open_err, symbol_err, service_err, system_err, buf_err,
   perm_denied, auth_err, cred_insufficient, authinfo_unavail, user_unknown,
   maxtries, new_authtok_reqd, acct_expired, session_err, cred_unavail,
   cred_expired, cred_err, no_module_data, conv_err, authtok_err,
   authtok_recover_err, authtok_lock_busy, authtok_disable_aging, try_again,
   ignore, abort, authtok_expired, module_unknown, bad_item, conv_again,
   incomplete, and default.

The last of these, default, implies 'all valueN's not mentioned
   explicitly. Note, the full list of PAM errors is available in
   /usr/include/security/_pam_types.h. The actionN can take one of the
   following forms:

ignore

when used with a stack of modules, the module's return status will
           not contribute to the return code the application obtains.

bad

this action indicates that the return code should be thought of as
           indicative of the module failing. If this module is the first in
           the stack to fail, its status value will be used for that of the
           whole stack.

die

equivalent to bad with the side effect of terminating the module
           stack and PAM immediately returning to the application.

this tells PAM that the administrator thinks this return code
           should contribute directly to the return code of the full stack of
           modules. In other words, if the former state of the stack would
           lead to a return of PAM_SUCCESS, the module's return code will
           override this value. Note, if the former state of the stack holds
           some value that is indicative of a modules failure, this 'ok'
           value will not be used to override that value.

done

equivalent to ok with the side effect of terminating the module
           stack and PAM immediately returning to the application.

N (an unsigned integer)

equivalent to ok with the side effect of jumping over the next N
           modules in the stack. Note that N equal to 0 is not allowed (and
           it would be identical to ok in such case).

reset

clear all memory of the state of the module stack and start again
           with the next stacked module.

Each of the four keywords: required; requisite; sufficient; and optional,
   have an equivalent expression in terms of the [...] syntax. They are as
   follows:

required

[success=ok new_authtok_reqd=ok ignore=ignore default=bad]

requisite

[success=ok new_authtok_reqd=ok ignore=ignore default=die]

sufficient

[success=done new_authtok_reqd=done default=ignore]

optional

[success=ok new_authtok_reqd=ok default=ignore]

module-path is either the full filename of the PAM to be used by the
   application (it begins with a '/'), or a relative pathname from the
   default module location: /lib/security/ or /lib64/security/, depending on
   the architecture.

module-arguments are a space separated list of tokens that can be used to
   modify the specific behavior of the given PAM. Such arguments will be
   documented for each individual module. Note, if you wish to include spaces
   in an argument, you should surround that argument with square brackets.

squid auth required pam_mysql.so user=passwd_query passwd=mada \
           db=eminence [query=select user_name from internet_service \
           where user_name='%u' and password=PASSWORD('%p') and \
         service='web_proxy']

When using this convention, you can include `[' characters inside the
   string, and if you wish to include a `]' character inside the string that
   will survive the argument parsing, you should use `\]'. In other words:

[..[..\]..]    -->   ..[..]..

Any line in (one of) the configuration file(s), that is not formatted
   correctly, will generally tend (erring on the side of caution) to make the
   authentication process fail. A corresponding error is written to the
   system log files with a call to syslog(3).

4.2. Directory based configuration

More flexible than the single configuration file is it to configure libpam
   via the contents of the /etc/pam.d/ directory. In this case the directory
   is filled with files each of which has a filename equal to a service-name
   (in lower-case): it is the personal configuration file for the named
   service.

The syntax of each file in /etc/pam.d/ is similar to that of the
   /etc/pam.conf file and is made up of lines of the following form:

type  control  module-path  module-arguments

The only difference being that the service-name is not present. The
   service-name is of course the name of the given configuration file. For
   example, /etc/pam.d/login contains the configuration for the login
   service.

4.3. Example configuration file entries

In this section, we give some examples of entries that can be present in
   the Linux-PAM configuration file. As a first attempt at configuring your
   system you could do worse than to implement these.

If a system is to be considered secure, it had better have a reasonably
   secure 'other entry. The following is a paranoid setting (which is not a
   bad place to start!):

#
 # default; deny access
 #
 other   auth     required       pam_deny.so
 other   account  required       pam_deny.so
 other   password required       pam_deny.so
 other   session  required       pam_deny.so

Whilst fundamentally a secure default, this is not very sympathetic to a
   misconfigured system. For example, such a system is vulnerable to locking
   everyone out should the rest of the file become badly written.

The module pam_deny (documented in a later section) is not very
   sophisticated. For example, it logs no information when it is invoked so
   unless the users of a system contact the administrator when failing to
   execute a service application, the administrator may go for a long while
   in ignorance of the fact that his system is misconfigured.

The addition of the following line before those in the above example would
   provide a suitable warning to the administrator.

#
 # default; wake up! This application is not configured
 #
 other   auth     required       pam_warn.so
 other   password required       pam_warn.so

Having two 'other auth' lines is an example of stacking.

On a system that uses the /etc/pam.d/ configuration, the corresponding
   default setup would be achieved with the following file:

#
 # default configuration: /etc/pam.d/other
 #
 auth     required       pam_warn.so
 auth     required       pam_deny.so
 account  required       pam_deny.so
 password required       pam_warn.so
 password required       pam_deny.so
 session  required       pam_deny.so

This is the only explicit example we give for an /etc/pam.d/ file. In
   general, it should be clear how to transpose the remaining examples to
   this configuration scheme.

On a less sensitive computer, one on which the system administrator wishes
   to remain ignorant of much of the power of Linux-PAM, the following
   selection of lines (in /etc/pam.d/other) is likely to mimic the
   historically familiar Linux setup.

#
 # default; standard UN*X access
 #
 auth     required       pam_unix.so
 account  required       pam_unix.so
 password required       pam_unix.so
 session  required       pam_unix.so

In general this will provide a starting place for most applications.

Chapter 5. Security issues

5.1. If something goes wrong

Linux-PAM has the potential to seriously change the security of your
   system. You can choose to have no security or absolute security (no access
   permitted). In general, Linux-PAM errs towards the latter. Any number of
   configuration errors can disable access to your system partially, or
   completely.

The most dramatic problem that is likely to be encountered when
   configuring Linux-PAM is that of deleting the configuration file(s):
   /etc/pam.d/* and/or /etc/pam.conf. This will lock you out of your own
   system!

To recover, your best bet is to restore the system from a backup or boot
   the system into a rescue system and correct things from there.

5.2. Avoid having a weak `other' configuration

It is not a good thing to have a weak default (other) entry. This service
   is the default configuration for all PAM aware applications and if it is
   weak, your system is likely to be vulnerable to attack.

Here is a sample "other" configuration file. The pam_deny module will deny
   access and the pam_warn module will send a syslog message to auth.notice:

#
 # The PAM configuration file for the `other' service
 #
 auth      required   pam_deny.so
 auth      required   pam_warn.so
 account   required   pam_deny.so
 account   required   pam_warn.so
 password  required   pam_deny.so
 password  required   pam_warn.so
 session   required   pam_deny.so
 session   required   pam_warn.so

Chapter 6. A reference guide for available modules

Here, we collect together the descriptions of the various modules coming
   with Linux-PAM.

6.1. pam_access - logdaemon style login access control

pam_access.so [ debug ] [ noaudit ] [ nodefgroup ] [ nodns ] [
   accessfile=file ] [ fieldsep=sep ] [ listsep=sep ]

6.1.1. DESCRIPTION

The pam_access PAM module is mainly for access management. It provides
   logdaemon style login access control based on login names, host or domain
   names, internet addresses or network numbers, or on terminal line names, X
   $DISPLAY values, or PAM service names in case of non-networked logins.

By default rules for access management are taken from config file
   /etc/security/access.conf if you don't specify another file. Then
   individual *.conf files from the /etc/security/access.d/ directory are
   read. The files are parsed one after another in the order of the system
   locale. The effect of the individual files is the same as if all the files
   were concatenated together in the order of parsing. This means that once a
   pattern is matched in some file no further files are parsed. If a config
   file is explicitly specified with the accessfile option the files in the
   above directory are not parsed.

If Linux PAM is compiled with audit support the module will report when it
   denies access based on origin (host, tty, etc.).

6.1.2. DESCRIPTION

The /etc/security/access.conf file specifies (user/group, host),
   (user/group, network/netmask), (user/group, tty), (user/group,
   X-$DISPLAY-value), or (user/group, pam-service-name) combinations for
   which a login will be either accepted or refused.

When someone logs in, the file access.conf is scanned for the first entry
   that matches the (user/group, host) or (user/group, network/netmask)
   combination, or, in case of non-networked logins, the first entry that
   matches the (user/group, tty) combination, or in the case of non-networked
   logins without a tty, the first entry that matches the (user/group,
   X-$DISPLAY-value) or (user/group, pam-service-name/) combination. The
   permissions field of that table entry determines whether the login will be
   accepted or refused.

Each line of the login access control table has three fields separated by
   a ":" character (colon):

permission:users/groups:origins

The first field, the permission field, can be either a "+" character
   (plus) for access granted or a "-" character (minus) for access denied.

The second field, the users/group field, should be a list of one or more
   login names, group names, or ALL (which always matches). To differentiate
   user entries from group entries, group entries should be written with
   brackets, e.g. (group).

The third field, the origins field, should be a list of one or more tty
   names (for non-networked logins), X $DISPLAY values or PAM service names
   (for non-networked logins without a tty), host names, domain names (begin
   with "."), host addresses, internet network numbers (end with "."),
   internet network addresses with network mask (where network mask can be a
   decimal number or an internet address also), ALL (which always matches) or
   LOCAL. The LOCAL keyword matches when the user connects without a network
   connection (e.g., su, login). A connection through the loopback device
   (e.g., ssh user@localhost) is considered a network connection, and thus,
   the LOCAL keyword does not match.

If supported by the system you can use @netgroupname in host or user
   patterns. The @@netgroupname syntax is supported in the user pattern only
   and it makes the local system hostname to be passed to the netgroup match
   call in addition to the user name. This might not work correctly on some
   libc implementations causing the match to always fail.

The EXCEPT operator makes it possible to write very compact rules.

If the nodefgroup is not set, the group file is searched when a name does
   not match that of the logged-in user. Only groups are matched in which
   users are explicitly listed. However the PAM module does not look at the
   primary group id of a user.

The "#" character at start of line (no space at front) can be used to mark
   this line as a comment line.

6.1.3. OPTIONS

accessfile=/path/to/access.conf

Indicate an alternative access.conf style configuration file to
           override the default. This can be useful when different services
           need different access lists.

debug

A lot of debug information is printed with syslog(3).

noaudit

Do not report logins from disallowed hosts and ttys to the audit
           subsystem.

nodefgroup

User tokens which are not enclosed in parentheses will not be
           matched against the group database. The backwards compatible
           default is to try the group database match even for tokens not
           enclosed in parentheses.

nodns

Do not try to resolve tokens as hostnames, only IPv4 and IPv6
           addresses will be resolved. Which means to allow login from a
           remote host, the IP addresses need to be specified in access.conf.

quiet_log

Do not log denials with syslog(3).

fieldsep=separators

This option modifies the field separator character that pam_access
           will recognize when parsing the access configuration file. For
           example: fieldsep=| will cause the default `:' character to be
           treated as part of a field value and `|' becomes the field
           separator. Doing this may be useful in conjunction with a system
           that wants to use pam_access with X based applications, since the
           PAM_TTY item is likely to be of the form "hostname:0" which
           includes a `:' character in its value. But you should not need
           this.

listsep=separators

This option modifies the list separator character that pam_access
           will recognize when parsing the access configuration file. For
           example: listsep=, will cause the default ` ' (space) and `\t'
           (tab) characters to be treated as part of a list element value and
           `,' becomes the only list element separator. Doing this may be
           useful on a system with group information obtained from a Windows
           domain, where the default built-in groups "Domain Users", "Domain
           Admins" contain a space.

6.1.4. MODULE TYPES PROVIDED

All module types (auth, account, password and session) are provided.

6.1.5. RETURN VALUES

PAM_SUCCESS

Access was granted.

PAM_PERM_DENIED

Access was not granted.

PAM_IGNORE

pam_setcred was called which does nothing.

PAM_ABORT

Not all relevant data or options could be gotten.

PAM_USER_UNKNOWN

The user is not known to the system.

6.1.6. FILES

/etc/security/access.conf

Default configuration file

6.1.7. EXAMPLES

These are some example lines which might be specified in
   /etc/security/access.conf.

User root should be allowed to get access via cron, X11 terminal :0, tty1,
   ..., tty5, tty6.

+:root:crond :0 tty1 tty2 tty3 tty4 tty5 tty6

User root should be allowed to get access from hosts which own the IPv4
   addresses. This does not mean that the connection have to be a IPv4 one, a
   IPv6 connection from a host with one of this IPv4 addresses does work,
   too.

+:root:192.168.200.1 192.168.200.4 192.168.200.9

+:root:127.0.0.1

User root should get access from network 192.168.201. where the term will
   be evaluated by string matching. But it might be better to use
   network/netmask instead. The same meaning of 192.168.201. is
   192.168.201.0/24 or 192.168.201.0/255.255.255.0.

+:root:192.168.201.

User root should be able to have access from hosts foo1.bar.org and
   foo2.bar.org (uses string matching also).

+:root:foo1.bar.org foo2.bar.org

User root should be able to have access from domain foo.bar.org (uses
   string matching also).

+:root:.foo.bar.org

User root should be denied to get access from all other sources.

-:root:ALL

User foo and members of netgroup admins should be allowed to get access
   from all sources. This will only work if netgroup service is available.

+:@admins foo:ALL

User john and foo should get access from IPv6 host address.

+:john foo:2001:db8:0:101::1

User john should get access from IPv6 net/mask.

+:john:2001:db8:0:101::/64

Disallow console logins to all but the shutdown, sync and all other
   accounts, which are a member of the wheel group.

-:ALL EXCEPT (wheel) shutdown sync:LOCAL

All other users should be denied to get access from all sources.

-:ALL:ALL

6.1.8. AUTHORS

The logdaemon style login access control scheme was designed and
   implemented by Wietse Venema. The pam_access PAM module was developed by
   Alexei Nogin <alexei@nogin.dnttm.ru>. The IPv6 support and the
   network(address) / netmask feature was developed and provided by Mike
   Becher <mike.becher@lrz-muenchen.de>.

6.2. pam_cracklib - checks the password against dictionary words

pam_cracklib.so [ ... ]

6.2.1. DESCRIPTION

This module can be plugged into the password stack of a given application
   to provide some plug-in strength-checking for passwords.

The action of this module is to prompt the user for a password and check
   its strength against a system dictionary and a set of rules for
   identifying poor choices.

The first action is to prompt for a single password, check its strength
   and then, if it is considered strong, prompt for the password a second
   time (to verify that it was typed correctly on the first occasion). All
   being well, the password is passed on to subsequent modules to be
   installed as the new authentication token.

The strength checks works in the following manner: at first the Cracklib
   routine is called to check if the password is part of a dictionary; if
   this is not the case an additional set of strength checks is done. These
   checks are:

Palindrome

Is the new password a palindrome?

Case Change Only

Is the new password the the old one with only a change of case?

Similar

Is the new password too much like the old one? This is primarily
           controlled by one argument, difok which is a number of character
           changes (inserts, removals, or replacements) between the old and
           new password that are enough to accept the new password. This
           defaults to 5 changes.

Simple

Is the new password too small? This is controlled by 6 arguments
           minlen, maxclassrepeat, dcredit, ucredit, lcredit, and ocredit.
           See the section on the arguments for the details of how these work
           and there defaults.

Rotated

Is the new password a rotated version of the old password?

Same consecutive characters

Optional check for same consecutive characters.

Too long monotonic character sequence

Optional check for too long monotonic character sequence.

Contains user name

Optional check whether the password contains the user's name in
           some form.

This module with no arguments will work well for standard unix password
   encryption. With md5 encryption, passwords can be longer than 8 characters
   and the default settings for this module can make it hard for the user to
   choose a satisfactory new password. Notably, the requirement that the new
   password contain no more than 1/2 of the characters in the old password
   becomes a non-trivial constraint. For example, an old password of the form
   "the quick brown fox jumped over the lazy dogs" would be difficult to
   change... In addition, the default action is to allow passwords as small
   as 5 characters in length. For a md5 systems it can be a good idea to
   increase the required minimum size of a password. One can then allow more
   credit for different kinds of characters but accept that the new password
   may share most of these characters with the old password.

6.2.2. OPTIONS

debug

This option makes the module write information to syslog(3)
           indicating the behavior of the module (this option does not write
           password information to the log file).

authtok_type=XXX

The default action is for the module to use the following prompts
           when requesting passwords: "New UNIX password: " and "Retype UNIX
           password: ". The example word UNIX can be replaced with this
           option, by default it is empty.

retry=N

Prompt user at most N times before returning with error. The
           default is 1.

difok=N

This argument will change the default of 5 for the number of
           character changes in the new password that differentiate it from
           the old password.

minlen=N

The minimum acceptable size for the new password (plus one if
           credits are not disabled which is the default). In addition to the
           number of characters in the new password, credit (of +1 in length)
           is given for each different kind of character (other, upper, lower
           and digit). The default for this parameter is 9 which is good for
           a old style UNIX password all of the same type of character but
           may be too low to exploit the added security of a md5 system. Note
           that there is a pair of length limits in Cracklib itself, a "way
           too short" limit of 4 which is hard coded in and a defined limit
           (6) that will be checked without reference to minlen. If you want
           to allow passwords as short as 5 characters you should not use
           this module.

dcredit=N

(N >= 0) This is the maximum credit for having digits in the new
           password. If you have less than or N digits, each digit will count
           +1 towards meeting the current minlen value. The default for
           dcredit is 1 which is the recommended value for minlen less than
           10.

(N < 0) This is the minimum number of digits that must be met for
           a new password.

ucredit=N

(N >= 0) This is the maximum credit for having upper case letters
           in the new password. If you have less than or N upper case letters
           each letter will count +1 towards meeting the current minlen
           value. The default for ucredit is 1 which is the recommended value
           for minlen less than 10.

(N < 0) This is the minimum number of upper case letters that must
           be met for a new password.

lcredit=N

(N >= 0) This is the maximum credit for having lower case letters
           in the new password. If you have less than or N lower case
           letters, each letter will count +1 towards meeting the current
           minlen value. The default for lcredit is 1 which is the
           recommended value for minlen less than 10.

(N < 0) This is the minimum number of lower case letters that must
           be met for a new password.

ocredit=N

(N >= 0) This is the maximum credit for having other characters in
           the new password. If you have less than or N other characters,
           each character will count +1 towards meeting the current minlen
           value. The default for ocredit is 1 which is the recommended value
           for minlen less than 10.

(N < 0) This is the minimum number of other characters that must
           be met for a new password.

minclass=N

The minimum number of required classes of characters for the new
           password. The default number is zero. The four classes are digits,
           upper and lower letters and other characters. The difference to
           the credit check is that a specific class if of characters is not
           required. Instead N out of four of the classes are required.

maxrepeat=N

Reject passwords which contain more than N same consecutive
           characters. The default is 0 which means that this check is
           disabled.

maxsequence=N

Reject passwords which contain monotonic character sequences
           longer than N. The default is 0 which means that this check is
           disabled. Examples of such sequence are '12345' or 'fedcb'. Note
           that most such passwords will not pass the simplicity check unless
           the sequence is only a minor part of the password.

maxclassrepeat=N

Reject passwords which contain more than N consecutive characters
           of the same class. The default is 0 which means that this check is
           disabled.

reject_username

Check whether the name of the user in straight or reversed form is
           contained in the new password. If it is found the new password is
           rejected.

gecoscheck

Check whether the words from the GECOS field (usualy full name of
           the user) longer than 3 characters in straight or reversed form
           are contained in the new password. If any such word is found the
           new password is rejected.

enforce_for_root

The module will return error on failed check also if the user
           changing the password is root. This option is off by default which
           means that just the message about the failed check is printed but
           root can change the password anyway. Note that root is not asked
           for an old password so the checks that compare the old and new
           password are not performed.

use_authtok

This argument is used to force the module to not prompt the user
           for a new password but use the one provided by the previously
           stacked password module.

dictpath=/path/to/dict

Path to the cracklib dictionaries.

6.2.3. MODULE TYPES PROVIDED

Only the password module type is provided.

6.2.4. RETURN VALUES

PAM_SUCCESS

The new password passes all checks.

PAM_AUTHTOK_ERR

No new password was entered, the username could not be determined
           or the new password fails the strength checks.

PAM_AUTHTOK_RECOVERY_ERR

The old password was not supplied by a previous stacked module or
           got not requested from the user. The first error can happen if
           use_authtok is specified.

PAM_SERVICE_ERR

A internal error occurred.

6.2.5. EXAMPLES

For an example of the use of this module, we show how it may be stacked
   with the password component of pam_unix(8)

#
 # These lines stack two password type modules. In this example the
 # user is given 3 opportunities to enter a strong password. The
 # "use_authtok" argument ensures that the pam_unix module does not
 # prompt for a password, but instead uses the one provided by
 # pam_cracklib.
 #
 passwd  password required       pam_cracklib.so retry=3
 passwd  password required       pam_unix.so use_authtok

Another example (in the /etc/pam.d/passwd format) is for the case that you
   want to use md5 password encryption:

#%PAM-1.0
 #
 # These lines allow a md5 systems to support passwords of at least 14
 # bytes with extra credit of 2 for digits and 2 for others the new
 # password must have at least three bytes that are not present in the
 # old password
 #
 password  required pam_cracklib.so \
                difok=3 minlen=15 dcredit= 2 ocredit=2
 password  required pam_unix.so use_authtok nullok md5

And here is another example in case you don't want to use credits:

#%PAM-1.0
 #
 # These lines require the user to select a password with a minimum
 # length of 8 and with at least 1 digit number, 1 upper case letter,
 # and 1 other character
 #
 password  required pam_cracklib.so \
                dcredit=-1 ucredit=-1 ocredit=-1 lcredit=0 minlen=8
 password  required pam_unix.so use_authtok nullok md5

6.2.6. AUTHOR

pam_cracklib was written by Cristian Gafton <gafton@redhat.com>

6.3. pam_debug - debug the PAM stack

pam_debug.so [ auth=value ] [ cred=value ] [ acct=value ] [
   prechauthtok=value ] [ chauthtok=value ] [ auth=value ] [
   open_session=value ] [ close_session=value ]

6.3.1. DESCRIPTION

The pam_debug PAM module is intended as a debugging aide for determining
   how the PAM stack is operating. This module returns what its module
   arguments tell it to return.

6.3.2. OPTIONS

auth=value

The pam_sm_authenticate(3) function will return value.

cred=value

The pam_sm_setcred(3) function will return value.

acct=value

The pam_sm_acct_mgmt(3) function will return value.

prechauthtok=value

The pam_sm_chauthtok(3) function will return value if the
           PAM_PRELIM_CHECK flag is set.

chauthtok=value

The pam_sm_chauthtok(3) function will return value if the
           PAM_PRELIM_CHECK flag is not set.

open_session=value

The pam_sm_open_session(3) function will return value.

close_session=value

The pam_sm_close_session(3) function will return value.

Where value can be one of: success, open_err, symbol_err, service_err,
   system_err, buf_err, perm_denied, auth_err, cred_insufficient,
   authinfo_unavail, user_unknown, maxtries, new_authtok_reqd, acct_expired,
   session_err, cred_unavail, cred_expired, cred_err, no_module_data,
   conv_err, authtok_err, authtok_recover_err, authtok_lock_busy,
   authtok_disable_aging, try_again, ignore, abort, authtok_expired,
   module_unknown, bad_item, conv_again, incomplete.

6.3.3. MODULE TYPES PROVIDED

All module types (auth, account, password and session) are provided.

6.3.4. RETURN VALUES

PAM_SUCCESS

Default return code if no other value was specified, else
           specified return value.

6.3.5. EXAMPLES

auth    requisite       pam_permit.so
 auth    [success=2 default=ok]  pam_debug.so auth=perm_denied cred=success
 auth    [default=reset]         pam_debug.so auth=success cred=perm_denied
 auth    [success=done default=die] pam_debug.so
 auth    optional        pam_debug.so auth=perm_denied cred=perm_denied
 auth    sufficient      pam_debug.so auth=success cred=success

6.3.6. AUTHOR

pam_debug was written by Andrew G. Morgan <morgan@kernel.org>.

6.4. pam_deny - locking-out PAM module

pam_deny.so

6.4.1. DESCRIPTION

This module can be used to deny access. It always indicates a failure to
   the application through the PAM framework. It might be suitable for using
   for default (the OTHER) entries.

6.4.2. OPTIONS

This module does not recognise any options.

6.4.3. MODULE TYPES PROVIDED

All module types (account, auth, password and session) are provided.

6.4.4. RETURN VALUES

PAM_AUTH_ERR

This is returned by the account and auth services.

PAM_CRED_ERR

This is returned by the setcred function.

PAM_AUTHTOK_ERR

This is returned by the password service.

PAM_SESSION_ERR

This is returned by the session service.

6.4.5. EXAMPLES

#%PAM-1.0
 #
 # If we don't have config entries for a service, the
 # OTHER entries are used. To be secure, warn and deny
 # access to everything.
 other auth     required       pam_warn.so
 other auth     required       pam_deny.so
 other account  required       pam_warn.so
 other account  required       pam_deny.so
 other password required       pam_warn.so
 other password required       pam_deny.so
 other session  required       pam_warn.so
 other session  required       pam_deny.so

6.4.6. AUTHOR

pam_deny was written by Andrew G. Morgan <morgan@kernel.org>

6.5. pam_echo - print text messages

pam_echo.so [ file=/path/message ]

6.5.1. DESCRIPTION

The pam_echo PAM module is for printing text messages to inform user about
   special things. Sequences starting with the % character are interpreted in
   the following way:

The name of the remote host (PAM_RHOST).

The name of the local host.

The service name (PAM_SERVICE).

The name of the controlling terminal (PAM_TTY).

The remote user name (PAM_RUSER).

The local user name (PAM_USER).

All other sequences beginning with % expands to the characters following
   the % character.

6.5.2. OPTIONS

file=/path/message

The content of the file /path/message will be printed with the PAM
           conversion function as PAM_TEXT_INFO.

6.5.3. MODULE TYPES PROVIDED

All module types (auth, account, password and session) are provided.

6.5.4. RETURN VALUES

PAM_BUF_ERR

Memory buffer error.

PAM_SUCCESS

Message was successful printed.

PAM_IGNORE

PAM_SILENT flag was given or message file does not exist, no
           message printed.

6.5.5. EXAMPLES

For an example of the use of this module, we show how it may be used to
   print information about good passwords:

password optional pam_echo.so file=/usr/share/doc/good-password.txt
 password required pam_unix.so

6.5.6. AUTHOR

Thorsten Kukuk <kukuk@thkukuk.de>

6.6. pam_env - set/unset environment variables

pam_env.so [ debug ] [ conffile=conf-file ] [ envfile=env-file ] [
   readenv=0|1 ] [ user_envfile=env-file ] [ user_readenv=0|1 ]

6.6.1. DESCRIPTION

The pam_env PAM module allows the (un)setting of environment variables.
   Supported is the use of previously set environment variables as well as
   PAM_ITEMs such as PAM_RHOST.

By default rules for (un)setting of variables are taken from the config
   file /etc/security/pam_env.conf. An alternate file can be specified with
   the conffile option.

Second a file (/etc/environment by default) with simple KEY=VAL pairs on
   separate lines will be read. With the envfile option an alternate file can
   be specified. And with the readenv option this can be completly disabled.

Third it will read a user configuration file ($HOME/.pam_environment by
   default). The default file file can be changed with the user_envfile
   option and it can be turned on and off with the user_readenv option.

Since setting of PAM environment variables can have side effects to other
   modules, this module should be the last one on the stack.

6.6.2. DESCRIPTION

The /etc/security/pam_env.conf file specifies the environment variables to
   be set, unset or modified by pam_env(8). When someone logs in, this file
   is read and the environment variables are set according.

Each line starts with the variable name, there are then two possible
   options for each variable DEFAULT and OVERRIDE. DEFAULT allows and
   administrator to set the value of the variable to some default value, if
   none is supplied then the empty string is assumed. The OVERRIDE option
   tells pam_env that it should enter in its value (overriding the default
   value) if there is one to use. OVERRIDE is not used, "" is assumed and no
   override will be done.

VARIABLE [DEFAULT=[value]] [OVERRIDE=[value]]

(Possibly non-existent) environment variables may be used in values using
   the ${string} syntax and (possibly non-existent) PAM_ITEMs as well as HOME
   and SHELL may be used in values using the @{string} syntax. Both the $ and
   @ characters can be backslash escaped to be used as literal values values
   can be delimited with "", escaped " not supported. Note that many
   environment variables that you would like to use may not be set by the
   time the module is called. For example, ${HOME} is used below several
   times, but many PAM applications don't make it available by the time you
   need it. The special variables @{HOME} and @{SHELL} are expanded to the
   values for the user from his passwd entry.

The "#" character at start of line (no space at front) can be used to mark
   this line as a comment line.

The /etc/environment file specifies the environment variables to be set.
   The file must consist of simple NAME=VALUE pairs on separate lines. The
   pam_env(8) module will read the file after the pam_env.conf file.

6.6.3. OPTIONS

conffile=/path/to/pam_env.conf

Indicate an alternative pam_env.conf style configuration file to
           override the default. This can be useful when different services
           need different environments.

debug

A lot of debug information is printed with syslog(3).

envfile=/path/to/environment

Indicate an alternative environment file to override the default.
           The syntax are simple KEY=VAL pairs on separate lines. The export
           instruction can be specified for bash compatibility, but will be
           ignored. This can be useful when different services need different
           environments.

readenv=0|1

Turns on or off the reading of the file specified by envfile (0 is
           off, 1 is on). By default this option is on.

user_envfile=filename

Indicate an alternative .pam_environment file to override the
           default.The syntax is the same as for /etc/environment. The
           filename is relative to the user home directory. This can be
           useful when different services need different environments.

user_readenv=0|1

Turns on or off the reading of the user specific environment file.
           0 is off, 1 is on. By default this option is off as user supplied
           environment variables in the PAM environment could affect behavior
           of subsequent modules in the stack without the consent of the
           system administrator.

6.6.4. MODULE TYPES PROVIDED

The auth and session module types are provided.

6.6.5. RETURN VALUES

PAM_ABORT

Not all relevant data or options could be gotten.

PAM_BUF_ERR

Memory buffer error.

PAM_IGNORE

No pam_env.conf and environment file was found.

PAM_SUCCESS

Environment variables were set.

6.6.6. FILES

/etc/security/pam_env.conf

Default configuration file

/etc/environment

Default environment file

$HOME/.pam_environment

User specific environment file

6.6.7. EXAMPLES

These are some example lines which might be specified in
   /etc/security/pam_env.conf.

Set the REMOTEHOST variable for any hosts that are remote, default to
   "localhost" rather than not being set at all

REMOTEHOST     DEFAULT=localhost OVERRIDE=@{PAM_RHOST}

Set the DISPLAY variable if it seems reasonable

DISPLAY        DEFAULT=${REMOTEHOST}:0.0 OVERRIDE=${DISPLAY}

Now some simple variables

PAGER          DEFAULT=less
       MANPAGER       DEFAULT=less
       LESS           DEFAULT="M q e h15 z23 b80"
       NNTPSERVER     DEFAULT=localhost
       PATH           DEFAULT=${HOME}/bin:/usr/local/bin:/bin\
       :/usr/bin:/usr/local/bin/X11:/usr/bin/X11
       XDG_DATA_HOME  @{HOME}/share/

Silly examples of escaped variables, just to show how they work.

DOLLAR         DEFAULT=\$
       DOLLARDOLLAR   DEFAULT=        OVERRIDE=\$${DOLLAR}
       DOLLARPLUS     DEFAULT=\${REMOTEHOST}${REMOTEHOST}
       ATSIGN         DEFAULT=""      OVERRIDE=\@

6.6.8. AUTHOR

pam_env was written by Dave Kinchlea <kinch@kinch.ark.com>.

6.7. pam_exec - call an external command

pam_exec.so [ debug ] [ expose_authtok ] [ seteuid ] [ quiet ] [ stdout ]
   [ log=file ] [ type=type ] command [ ... ]

6.7.1. DESCRIPTION

pam_exec is a PAM module that can be used to run an external command.

The child's environment is set to the current PAM environment list, as
   returned by pam_getenvlist(3) In addition, the following PAM items are
   exported as environment variables: PAM_RHOST, PAM_RUSER, PAM_SERVICE,
   PAM_TTY, PAM_USER and PAM_TYPE, which contains one of the module types:
   account, auth, password, open_session and close_session.

Commands called by pam_exec need to be aware of that the user can have
   controll over the environment.

6.7.2. OPTIONS

debug

Print debug information.

expose_authtok

During authentication the calling command can read the password
           from stdin(3). Only first PAM_MAX_RESP_SIZE bytes of a password
           are provided to the command.

log=file

The output of the command is appended to file

type=type

Only run the command if the module type matches the given type.

stdout

Per default the output of the executed command is written to
           /dev/null. With this option, the stdout output of the executed
           command is redirected to the calling application. It's in the
           responsibility of this application what happens with the output.
           The log option is ignored.

quiet

Per default pam_exec.so will echo the exit status of the external
           command if it fails. Specifying this option will suppress the
           message.

seteuid

Per default pam_exec.so will execute the external command with the
           real user ID of the calling process. Specifying this option means
           the command is run with the effective user ID.

6.7.3. MODULE TYPES PROVIDED

All module types (auth, account, password and session) are provided.

6.7.4. RETURN VALUES

PAM_SUCCESS

The external command was run successfully.

PAM_SERVICE_ERR

No argument or a wrong number of arguments were given.

PAM_SYSTEM_ERR

A system error occurred or the command to execute failed.

PAM_IGNORE

pam_setcred was called, which does not execute the command. Or,
           the value given for the type= parameter did not match the module
           type.

6.7.5. EXAMPLES

Add the following line to /etc/pam.d/passwd to rebuild the NIS database
   after each local password change:

password optional pam_exec.so seteuid /usr/bin/make -C /var/yp

This will execute the command

make -C /var/yp

with effective user ID.

6.7.6. AUTHOR

pam_exec was written by Thorsten Kukuk <kukuk@thkukuk.de> and Josh
   Triplett <josh@joshtriplett.org>.

6.8. pam_faildelay - change the delay on failure per-application

pam_faildelay.so [ debug ] [ delay=microseconds ]

6.8.1. DESCRIPTION

pam_faildelay is a PAM module that can be used to set the delay on failure
   per-application.

If no delay is given, pam_faildelay will use the value of FAIL_DELAY from
   /etc/login.defs.

6.8.2. OPTIONS

debug

Turns on debugging messages sent to syslog.

delay=N

Set the delay on failure to N microseconds.

6.8.3. MODULE TYPES PROVIDED

Only the auth module type is provided.

6.8.4. RETURN VALUES

PAM_IGNORE

Delay was successful adjusted.

PAM_SYSTEM_ERR

The specified delay was not valid.

6.8.5. EXAMPLES

The following example will set the delay on failure to 10 seconds:

auth  optional  pam_faildelay.so  delay=10000000

6.8.6. AUTHOR

pam_faildelay was written by Darren Tucker <dtucker@zip.com.au>.

6.9. pam_filter - filter module

pam_filter.so [ debug ] [ new_term ] [ non_term ] run1|run2 filter [ ... ]

6.9.1. DESCRIPTION

This module is intended to be a platform for providing access to all of
   the input/output that passes between the user and the application. It is
   only suitable for tty-based and (stdin/stdout) applications.

To function this module requires filters to be installed on the system.
   The single filter provided with the module simply transposes upper and
   lower case letters in the input and output streams. (This can be very
   annoying and is not kind to termcap based editors).

Each component of the module has the potential to invoke the desired
   filter. The filter is always execv(2) with the privilege of the calling
   application and not that of the user. For this reason it cannot usually be
   killed by the user without closing their session.

6.9.2. OPTIONS

debug

Print debug information.

new_term

The default action of the filter is to set the PAM_TTY item to
           indicate the terminal that the user is using to connect to the
           application. This argument indicates that the filter should set
           PAM_TTY to the filtered pseudo-terminal.

non_term

don't try to set the PAM_TTY item.

runX

In order that the module can invoke a filter it should know when
           to invoke it. This argument is required to tell the filter when to
           do this.

Permitted values for X are 1 and 2. These indicate the precise
           time that the filter is to be run. To understand this concept it
           will be useful to have read the pam(3) manual page. Basically, for
           each management group there are up to two ways of calling the
           module's functions. In the case of the authentication and session
           components there are actually two separate functions. For the case
           of authentication, these functions are pam_authenticate(3) and
           pam_setcred(3), here run1 means run the filter from the
           pam_authenticate function and run2 means run the filter from
           pam_setcred. In the case of the session modules, run1 implies that
           the filter is invoked at the pam_open_session(3) stage, and run2
           for pam_close_session(3).

For the case of the account component. Either run1 or run2 may be
           used.

For the case of the password component, run1 is used to indicate
           that the filter is run on the first occasion of pam_chauthtok(3)
           (the PAM_PRELIM_CHECK phase) and run2 is used to indicate that the
           filter is run on the second occasion (the PAM_UPDATE_AUTHTOK
           phase).

filter

The full pathname of the filter to be run and any command line
           arguments that the filter might expect.

6.9.3. MODULE TYPES PROVIDED

All module types (auth, account, password and session) are provided.

6.9.4. RETURN VALUES

PAM_SUCCESS

The new filter was set successfully.

PAM_ABORT

Critical error, immediate abort.

6.9.5. EXAMPLES

Add the following line to /etc/pam.d/login to see how to configure login
   to transpose upper and lower case letters once the user has logged in:

session required pam_filter.so run1 /lib/security/pam_filter/upperLOWER

6.9.6. AUTHOR

pam_filter was written by Andrew G. Morgan <morgan@kernel.org>.

6.10. pam_ftp - module for anonymous access

pam_ftp.so [ debug ] [ ignore ] [ users=XXX,YYY, ...]

6.10.1. DESCRIPTION

pam_ftp is a PAM module which provides a pluggable anonymous ftp mode of
   access.

This module intercepts the user's name and password. If the name is ftp or
   anonymous, the user's password is broken up at the @ delimiter into a
   PAM_RUSER and a PAM_RHOST part; these pam-items being set accordingly. The
   username (PAM_USER) is set to ftp. In this case the module succeeds.
   Alternatively, the module sets the PAM_AUTHTOK item with the entered
   password and fails.

This module is not safe and easily spoofable.

6.10.2. OPTIONS

debug

Print debug information.

ignore

Pay no attention to the email address of the user (if supplied).

ftp=XXX,YYY,...

Instead of ftp or anonymous, provide anonymous login to the comma
           separated list of users: XXX,YYY,.... Should the applicant enter
           one of these usernames the returned username is set to the first
           in the list: XXX.

6.10.3. MODULE TYPES PROVIDED

Only the auth module type is provided.

6.10.4. RETURN VALUES

PAM_SUCCESS

The authentication was successful.

PAM_USER_UNKNOWN

User not known.

6.10.5. EXAMPLES

Add the following line to /etc/pam.d/ftpd to handle ftp style anonymous
   login:

#
 # ftpd; add ftp-specifics. These lines enable anonymous ftp over
 #       standard UN*X access (the listfile entry blocks access to
 #       users listed in /etc/ftpusers)
 #
 auth    sufficient  pam_ftp.so
 auth    required    pam_unix.so use_first_pass
 auth    required    pam_listfile.so \
            onerr=succeed item=user sense=deny file=/etc/ftpusers

6.10.6. AUTHOR

pam_ftp was written by Andrew G. Morgan <morgan@kernel.org>.

6.11. pam_group - module to modify group access

pam_group.so

6.11.1. DESCRIPTION

The pam_group PAM module does not authenticate the user, but instead it
   grants group memberships (in the credential setting phase of the
   authentication module) to the user. Such memberships are based on the
   service they are applying for.

By default rules for group memberships are taken from config file
   /etc/security/group.conf.

This module's usefulness relies on the file-systems accessible to the
   user. The point being that once granted the membership of a group, the
   user may attempt to create a setgid binary with a restricted group
   ownership. Later, when the user is not given membership to this group,
   they can recover group membership with the precompiled binary. The reason
   that the file-systems that the user has access to are so significant, is
   the fact that when a system is mounted nosuid the user is unable to create
   or execute such a binary file. For this module to provide any level of
   security, all file-systems that the user has write access to should be
   mounted nosuid.

The pam_group module functions in parallel with the /etc/group file. If
   the user is granted any groups based on the behavior of this module, they
   are granted in addition to those entries /etc/group (or equivalent).

6.11.2. DESCRIPTION

For this module to function correctly there must be a correctly formatted
   /etc/security/group.conf file present. White spaces are ignored and lines
   maybe extended with '\' (escaped newlines). Text following a '#' is
   ignored to the end of the line.

The syntax of the lines is as follows:

services;ttys;users;times;groups

The first field, the services field, is a logic list of PAM service names
   that the rule applies to.

The second field, the tty field, is a logic list of terminal names that
   this rule applies to.

The third field, the users field, is a logic list of users, or a UNIX
   group, or a netgroup of users to whom this rule applies. Group names are
   preceded by a '%' symbol, while netgroup names are preceded by a '@'
   symbol.

For these items the simple wildcard '*' may be used only once. With UNIX
   groups or netgroups no wildcards or logic operators are allowed.

The times field is used to indicate "when" these groups are to be given to
   the user. The format here is a logic list of day/time-range entries. The
   days are specified by a sequence of two character entries, MoTuSa for
   example is Monday Tuesday and Saturday. Note that repeated days are unset
   MoMo = no day, and MoWk = all weekdays bar Monday. The two character
   combinations accepted are Mo Tu We Th Fr Sa Su Wk Wd Al, the last two
   being week-end days and all 7 days of the week respectively. As a final
   example, AlFr means all days except Friday.

Each day/time-range can be prefixed with a '!' to indicate "anything but".
   The time-range part is two 24-hour times HHMM, separated by a hyphen,
   indicating the start and finish time (if the finish time is smaller than
   the start time it is deemed to apply on the following day).

The groups field is a comma or space separated list of groups that the
   user inherits membership of. These groups are added if the previous fields
   are satisfied by the user's request.

For a rule to be active, ALL of service+ttys+users must be satisfied by
   the applying process.

6.11.3. OPTIONS

This module does not recognise any options.

6.11.4. MODULE TYPES PROVIDED

Only the auth module type is provided.

6.11.5. RETURN VALUES

PAM_SUCCESS

group membership was granted.

PAM_ABORT

Not all relevant data could be gotten.

PAM_BUF_ERR

Memory buffer error.

PAM_CRED_ERR

Group membership was not granted.

PAM_IGNORE

pam_sm_authenticate was called which does nothing.

PAM_USER_UNKNOWN

The user is not known to the system.

6.11.6. FILES

/etc/security/group.conf

Default configuration file

6.11.7. EXAMPLES

These are some example lines which might be specified in
   /etc/security/group.conf.

Running 'xsh' on tty* (any ttyXXX device), the user 'us' is given access
   to the floppy (through membership of the floppy group)

xsh;tty*&!ttyp*;us;Al0000-2400;floppy

Running 'xsh' on tty* (any ttyXXX device), the users 'sword', 'pike' and
   'shield' are given access to games (through membership of the floppy
   group) after work hours.

xsh; tty* ;sword|pike|shield;!Wk0900-1800;games, sound
 xsh; tty* ;*;Al0900-1800;floppy

Any member of the group 'admin' running 'xsh' on tty*, is granted access
   (at any time) to the group 'plugdev'

xsh; tty* ;%admin;Al0000-2400;plugdev

6.11.8. AUTHORS

pam_group was written by Andrew G. Morgan <morgan@kernel.org>.

6.12. pam_issue - add issue file to user prompt

pam_issue.so [ noesc ] [ issue=issue-file-name ]

6.12.1. DESCRIPTION

pam_issue is a PAM module to prepend an issue file to the username prompt.
   It also by default parses escape codes in the issue file similar to some
   common getty's (using \x format).

Recognized escapes:

current day

name of this tty

machine architecture (uname -m)

machine's network node hostname (uname -n)

domain name of this system

release number of operating system (uname -r)

current time

operating system name (uname -s)

number of users currently logged in

same as \u except it is suffixed with "user" or "users" (eg. "1
           user" or "10 users")

operating system version and build date (uname -v)

6.12.2. OPTIONS

noesc

Turns off escape code parsing.

issue=issue-file-name

The file to output if not using the default.

6.12.3. MODULE TYPES PROVIDED

Only the auth module type is provided.

6.12.4. RETURN VALUES

PAM_BUF_ERR

Memory buffer error.

PAM_IGNORE

The prompt was already changed.

PAM_SERVICE_ERR

A service module error occurred.

PAM_SUCCESS

The new prompt was set successfully.

6.12.5. EXAMPLES

Add the following line to /etc/pam.d/login to set the user specific issue
   at login:

auth optional pam_issue.so issue=/etc/issue

6.12.6. AUTHOR

pam_issue was written by Ben Collins <bcollins@debian.org>.

6.13. pam_keyinit - display the keyinit file

pam_keyinit.so [ debug ] [ force ] [ revoke ]

6.13.1. DESCRIPTION

The pam_keyinit PAM module ensures that the invoking process has a session
   keyring other than the user default session keyring.

The session component of the module checks to see if the process's session
   keyring is the user default, and, if it is, creates a new anonymous
   session keyring with which to replace it.

If a new session keyring is created, it will install a link to the user
   common keyring in the session keyring so that keys common to the user will
   be automatically accessible through it.

The session keyring of the invoking process will thenceforth be inherited
   by all its children unless they override it.

This module is intended primarily for use by login processes. Be aware
   that after the session keyring has been replaced, the old session keyring
   and the keys it contains will no longer be accessible.

This module should not, generally, be invoked by programs like su, since
   it is usually desirable for the key set to percolate through to the
   alternate context. The keys have their own permissions system to manage
   this.

This module should be included as early as possible in a PAM
   configuration, so that other PAM modules can attach tokens to the keyring.

The keyutils package is used to manipulate keys more directly. This can be
   obtained from:

Keyutils

6.13.2. OPTIONS

debug

Log debug information with syslog(3).

force

Causes the session keyring of the invoking process to be replaced
           unconditionally.

revoke

Causes the session keyring of the invoking process to be revoked
           when the invoking process exits if the session keyring was created
           for this process in the first place.

6.13.3. MODULE TYPES PROVIDED

Only the session module type is provided.

6.13.4. RETURN VALUES

PAM_SUCCESS

This module will usually return this value

PAM_AUTH_ERR

Authentication failure.

PAM_BUF_ERR

Memory buffer error.

PAM_IGNORE

The return value should be ignored by PAM dispatch.

PAM_SERVICE_ERR

Cannot determine the user name.

PAM_SESSION_ERR

This module will return this value if its arguments are invalid or
           if a system error such as ENOMEM occurs.

PAM_USER_UNKNOWN

User not known.

6.13.5. EXAMPLES

Add this line to your login entries to start each login session with its
   own session keyring:

session  required  pam_keyinit.so

This will prevent keys from one session leaking into another session for
   the same user.

6.13.6. AUTHOR

pam_keyinit was written by David Howells, <dhowells@redhat.com>.

6.14. pam_lastlog - display date of last login

pam_lastlog.so [ debug ] [ silent ] [ never ] [ nodate ] [ nohost ] [
   noterm ] [ nowtmp ] [ noupdate ] [ showfailed ] [ inactive=<days> ] [
   unlimited ]

6.14.1. DESCRIPTION

pam_lastlog is a PAM module to display a line of information about the
   last login of the user. In addition, the module maintains the
   /var/log/lastlog file.

Some applications may perform this function themselves. In such cases,
   this module is not necessary.

If the module is called in the auth or account phase, the accounts that
   were not used recently enough will be disallowed to log in. The check is
   not performed for the root account so the root is never locked out.

6.14.2. OPTIONS

debug

Print debug information.

silent

Don't inform the user about any previous login, just update the
           /var/log/lastlog file. This option does not affect display of bad
           login attempts.

never

If the /var/log/lastlog file does not contain any old entries for
           the user, indicate that the user has never previously logged in
           with a welcome message.

nodate

Don't display the date of the last login.

noterm

Don't display the terminal name on which the last login was
           attempted.

nohost

Don't indicate from which host the last login was attempted.

nowtmp

Don't update the wtmp entry.

noupdate

Don't update any file.

showfailed

Display number of failed login attempts and the date of the last
           failed attempt from btmp. The date is not displayed when nodate is
           specified.

inactive=<days>

This option is specific for the auth or account phase. It
           specifies the number of days after the last login of the user when
           the user will be locked out by the module. The default value is
           90.

unlimited

If the fsize limit is set, this option can be used to override it,
           preventing failures on systems with large UID values that lead
           lastlog to become a huge sparse file.

6.14.3. MODULE TYPES PROVIDED

The auth and account module type allows to lock out users which did not
   login recently enough. The session module type is provided for displaying
   the information about the last login and/or updating the lastlog and wtmp
   files.

6.14.4. RETURN VALUES

PAM_SUCCESS

Everything was successful.

PAM_SERVICE_ERR

Internal service module error.

PAM_USER_UNKNOWN

User not known.

PAM_AUTH_ERR

User locked out in the auth or account phase due to inactivity.

PAM_IGNORE

There was an error during reading the lastlog file in the auth or
           account phase and thus inactivity of the user cannot be
           determined.

6.14.5. EXAMPLES

Add the following line to /etc/pam.d/login to display the last login time
   of an user:

session  required  pam_lastlog.so nowtmp

To reject the user if he did not login during the previous 50 days the
   following line can be used:

auth  required  pam_lastlog.so inactive=50

6.14.6. AUTHOR

pam_lastlog was written by Andrew G. Morgan <morgan@kernel.org>.

Inactive account lock out added by Tomas Mraz <tm@t8m.info>.

6.15. pam_limits - limit resources

pam_limits.so [ conf=/path/to/limits.conf ] [ debug ] [ set_all ] [
   utmp_early ] [ noaudit ]

6.15.1. DESCRIPTION

The pam_limits PAM module sets limits on the system resources that can be
   obtained in a user-session. Users of uid=0 are affected by this limits,
   too.

By default limits are taken from the /etc/security/limits.conf config
   file. Then individual *.conf files from the /etc/security/limits.d/
   directory are read. The files are parsed one after another in the order of
   "C" locale. The effect of the individual files is the same as if all the
   files were concatenated together in the order of parsing. If a config file
   is explicitly specified with a module option then the files in the above
   directory are not parsed.

The module must not be called by a multithreaded application.

If Linux PAM is compiled with audit support the module will report when it
   denies access based on limit of maximum number of concurrent login
   sessions.

6.15.2. DESCRIPTION

The pam_limits.so module applies ulimit limits, nice priority and number
   of simultaneous login sessions limit to user login sessions. This
   description of the configuration file syntax applies to the
   /etc/security/limits.conf file and *.conf files in the
   /etc/security/limits.d directory.

The syntax of the lines is as follows:

The fields listed above should be filled as follows:

* a username

* a groupname, with @group syntax. This should not be confused
                with netgroups.

* the wildcard *, for default entry.

* the wildcard %, for maxlogins limit only, can also be used
                with %group syntax. If the % wildcard is used alone it is
                identical to using * with maxsyslogins limit. With a group
                specified after % it limits the total number of logins of all
                users that are member of the group.

* an uid range specified as <min_uid>:<max_uid>. If min_uid is
                omitted, the match is exact for the max_uid. If max_uid is
                omitted, all uids greater than or equal min_uid match.

* a gid range specified as @<min_gid>:<max_gid>. If min_gid is
                omitted, the match is exact for the max_gid. If max_gid is
                omitted, all gids greater than or equal min_gid match. For
                the exact match all groups including the user's supplementary
                groups are examined. For the range matches only the user's
                primary group is examined.

* a gid specified as %:<gid> applicable to maxlogins limit
                only. It limits the total number of logins of all users that
                are member of the group with the specified gid.

<type>

hard

for enforcing hard resource limits. These limits are
                        set by the superuser and enforced by the Kernel. The
                        user cannot raise his requirement of system resources
                        above such values.

soft

for enforcing soft resource limits. These limits are
                        ones that the user can move up or down within the
                        permitted range by any pre-existing hard limits. The
                        values specified with this token can be thought of as
                        default values, for normal system usage.

for enforcing both soft and hard resource limits
                        together.

Note, if you specify a type of '-' but neglect to
                        supply the item and value fields then the module will
                        never enforce any limits on the specified user/group
                        etc. .

<item>

core

limits the core file size (KB)

data

maximum data size (KB)

fsize

maximum filesize (KB)

memlock

maximum locked-in-memory address space (KB)

nofile

maximum number of open file descriptors

rss

maximum resident set size (KB) (Ignored in Linux
                        2.4.30 and higher)

stack

maximum stack size (KB)

cpu

maximum CPU time (minutes)

nproc

maximum number of processes

address space limit (KB)

maxlogins

maximum number of logins for this user (this limit
                        does not apply to user with uid=0)

maxsyslogins

maximum number of all logins on system; user is not
                        allowed to log-in if total number of all user logins
                        is greater than specified number (this limit does not
                        apply to user with uid=0)

priority

the priority to run user process with (negative
                        values boost process priority)

locks

maximum locked files (Linux 2.4 and higher)

sigpending

maximum number of pending signals (Linux 2.6 and
                        higher)

msgqueue

maximum memory used by POSIX message queues (bytes)
                        (Linux 2.6 and higher)

nice

maximum nice priority allowed to raise to (Linux
                        2.6.12 and higher) values: [-20,19]

rtprio

maximum realtime priority allowed for non-privileged
                        processes (Linux 2.6.12 and higher)

All items support the values -1, unlimited or infinity indicating no
   limit, except for priority and nice. If nofile is to be set to one of
   these values, it will be set to the contents of /proc/sys/fs/nr_open
   instead (see setrlimit(3)).

If a hard limit or soft limit of a resource is set to a valid value, but
   outside of the supported range of the local system, the system may reject
   the new limit or unexpected behavior may occur. If the control value
   required is used, the module will reject the login if a limit could not be
   set.

In general, individual limits have priority over group limits, so if you
   impose no limits for admin group, but one of the members in this group
   have a limits line, the user will have its limits set according to this
   line.

Also, please note that all limit settings are set per login. They are not
   global, nor are they permanent; existing only for the duration of the
   session. One exception is the maxlogin option, this one is system wide.
   But there is a race, concurrent logins at the same time will not always be
   detect as such but only counted as one.

In the limits configuration file, the '#' character introduces a comment -
   after which the rest of the line is ignored.

The pam_limits module does report configuration problems found in its
   configuration file and errors via syslog(3).

6.15.3. OPTIONS

conf=/path/to/limits.conf

Indicate an alternative limits.conf style configuration file to
           override the default.

debug

Print debug information.

set_all

Set the limits for which no value is specified in the
           configuration file to the one from the process with the PID 1.

utmp_early

Some broken applications actually allocate a utmp entry for the
           user before the user is admitted to the system. If some of the
           services you are configuring PAM for do this, you can selectively
           use this module argument to compensate for this behavior and at
           the same time maintain system-wide consistency with a single
           limits.conf file.

noaudit

Do not report exceeded maximum logins count to the audit
           subsystem.

6.15.4. MODULE TYPES PROVIDED

Only the session module type is provided.

6.15.5. RETURN VALUES

PAM_ABORT

Cannot get current limits.

PAM_IGNORE

No limits found for this user.

PAM_PERM_DENIED

New limits could not be set.

PAM_SERVICE_ERR

Cannot read config file.

PAM_SESSION_ERR

Error recovering account name.

PAM_SUCCESS

Limits were changed.

PAM_USER_UNKNOWN

The user is not known to the system.

6.15.6. FILES

/etc/security/limits.conf

Default configuration file

6.15.7. EXAMPLES

These are some example lines which might be specified in
   /etc/security/limits.conf.

*               soft    core            0
 *               hard    nofile          512
 @student        hard    nproc           20
 @faculty        soft    nproc           20
 @faculty        hard    nproc           50
 ftp             hard    nproc           0
 @student        -       maxlogins       4
 :123            hard    cpu             5000
 @500:           soft    cpu             10000
 600:700         hard    locks           10

6.15.8. AUTHORS

pam_limits was initially written by Cristian Gafton <gafton@redhat.com>

6.16. pam_listfile - deny or allow services based on an arbitrary file

6.16.1. DESCRIPTION

pam_listfile is a PAM module which provides a way to deny or allow
   services based on an arbitrary file.

The module gets the item of the type specified -- user specifies the
   username, PAM_USER; tty specifies the name of the terminal over which the
   request has been made, PAM_TTY; rhost specifies the name of the remote
   host (if any) from which the request was made, PAM_RHOST; and ruser
   specifies the name of the remote user (if available) who made the request,
   PAM_RUSER -- and looks for an instance of that item in the file=filename.
   filename contains one line per item listed. If the item is found, then if
   sense=allow, PAM_SUCCESS is returned, causing the authorization request to
   succeed; else if sense=deny, PAM_AUTH_ERR is returned, causing the
   authorization request to fail.

If an error is encountered (for instance, if filename does not exist, or a
   poorly-constructed argument is encountered), then if onerr=succeed,
   PAM_SUCCESS is returned, otherwise if onerr=fail, PAM_AUTH_ERR or
   PAM_SERVICE_ERR (as appropriate) will be returned.

An additional argument, apply=, can be used to restrict the application of
   the above to a specific user (apply=username) or a given group
   (apply=@groupname). This added restriction is only meaningful when used
   with the tty, rhost and shell items.

Besides this last one, all arguments should be specified; do not count on
   any default behavior.

No credentials are awarded by this module.

6.16.2. OPTIONS

What is listed in the file and should be checked for.

sense=[allow|deny]

Action to take if found in file, if the item is NOT found in the
           file, then the opposite action is requested.

file=/path/filename

File containing one item per line. The file needs to be a plain
           file and not world writable.

onerr=[succeed|fail]

What to do if something weird happens like being unable to open
           the file.

apply=[user|@group]

Restrict the user class for which the restriction apply. Note that
           with item=[user|ruser|group] this does not make sense, but for
           item=[tty|rhost|shell] it have a meaning.

quiet

Do not treat service refusals or missing list files as errors that
           need to be logged.

6.16.3. MODULE TYPES PROVIDED

All module types (auth, account, password and session) are provided.

6.16.4. RETURN VALUES

PAM_AUTH_ERR

Authentication failure.

PAM_BUF_ERR

Memory buffer error.

PAM_IGNORE

The rule does not apply to the apply option.

PAM_SERVICE_ERR

Error in service module.

PAM_SUCCESS

Success.

6.16.5. EXAMPLES

Classic 'ftpusers' authentication can be implemented with this entry in
   /etc/pam.d/ftpd:

#
 # deny ftp-access to users listed in the /etc/ftpusers file
 #
 auth    required       pam_listfile.so \
         onerr=succeed item=user sense=deny file=/etc/ftpusers

Note, users listed in /etc/ftpusers file are (counterintuitively) not
   allowed access to the ftp service.

To allow login access only for certain users, you can use a
   /etc/pam.d/login entry like this:

#
 # permit login to users listed in /etc/loginusers
 #
 auth    required       pam_listfile.so \
         onerr=fail item=user sense=allow file=/etc/loginusers

For this example to work, all users who are allowed to use the login
   service should be listed in the file /etc/loginusers. Unless you are
   explicitly trying to lock out root, make sure that when you do this, you
   leave a way for root to log in, either by listing root in /etc/loginusers,
   or by listing a user who is able to su to the root account.

6.16.6. AUTHOR

pam_listfile was written by Michael K. Johnson <johnsonm@redhat.com> and
   Elliot Lee <sopwith@cuc.edu>.

6.17. pam_localuser - require users to be listed in /etc/passwd

pam_localuser.so [ debug ] [ file=/path/passwd ]

6.17.1. DESCRIPTION

pam_localuser is a PAM module to help implementing site-wide login
   policies, where they typically include a subset of the network's users and
   a few accounts that are local to a particular workstation. Using
   pam_localuser and pam_wheel or pam_listfile is an effective way to
   restrict access to either local users and/or a subset of the network's
   users.

This could also be implemented using pam_listfile.so and a very short awk
   script invoked by cron, but it's common enough to have been separated out.

6.17.2. OPTIONS

debug

Print debug information.

file=/path/passwd

Use a file other than /etc/passwd.

6.17.3. MODULE TYPES PROVIDED

All module types (account, auth, password and session) are provided.

6.17.4. RETURN VALUES

PAM_SUCCESS

The new localuser was set successfully.

PAM_SERVICE_ERR

No username was given.

PAM_PERM_DENIED

The user is not listed in the passwd file.

6.17.5. EXAMPLES

Add the following lines to /etc/pam.d/su to allow only local users or
   group wheel to use su.

account sufficient pam_localuser.so
 account required pam_wheel.so

6.17.6. AUTHOR

pam_localuser was written by Nalin Dahyabhai <nalin@redhat.com>.

6.18. pam_loginuid - record user's login uid to the process attribute

pam_loginuid.so [ require_auditd ]

6.18.1. DESCRIPTION

The pam_loginuid module sets the loginuid process attribute for the
   process that was authenticated. This is necessary for applications to be
   correctly audited. This PAM module should only be used for entry point
   applications like: login, sshd, gdm, vsftpd, crond and atd. There are
   probably other entry point applications besides these. You should not use
   it for applications like sudo or su as that defeats the purpose by
   changing the loginuid to the account they just switched to.

6.18.2. OPTIONS

require_auditd

This option, when given, will cause this module to query the audit
           daemon status and deny logins if it is not running.

6.18.3. MODULE TYPES PROVIDED

Only the session module type is provided.

6.18.4. RETURN VALUES

PAM_SUCCESS

The loginuid value is set and auditd is running if check
           requested.

PAM_IGNORE

The /proc/self/loginuid file is not present on the system or the
           login process runs inside uid namespace and kernel does not
           support overwriting loginuid.

PAM_SESSION_ERR

Any other error prevented setting loginuid or auditd is not
           running.

6.18.5. EXAMPLES

#%PAM-1.0
 auth       required     pam_unix.so
 auth       required     pam_nologin.so
 account    required     pam_unix.so
 password   required     pam_unix.so
 session    required     pam_unix.so
 session    required     pam_loginuid.so

6.18.6. AUTHOR

pam_loginuid was written by Steve Grubb <sgrubb@redhat.com>

6.19. pam_mail - inform about available mail

pam_mail.so [ close ] [ debug ] [ dir=maildir ] [ empty ] [ hash=count ] [
   noenv ] [ nopen ] [ quiet ] [ standard ]

6.19.1. DESCRIPTION

The pam_mail PAM module provides the "you have new mail" service to the
   user. It can be plugged into any application that has credential or
   session hooks. It gives a single message indicating the newness of any
   mail it finds in the user's mail folder. This module also sets the PAM
   environment variable, MAIL, to the user's mail directory.

If the mail spool file (be it /var/mail/$USER or a pathname given with the
   dir= parameter) is a directory then pam_mail assumes it is in the Maildir
   format.

6.19.2. OPTIONS

Indicate if the user has any mail also on logout.

debug

Print debug information.

dir=maildir

Look for the user's mail in an alternative location defined by
           maildir/<login>. The default location for mail is
           /var/mail/<login>. Note, if the supplied maildir is prefixed by a
           '~', the directory is interpreted as indicating a file in the
           user's home directory.

empty

Also print message if user has no mail.

hash=count

Mail directory hash depth. For example, a hashcount of 2 would
           make the mail file be /var/spool/mail/u/s/user.

noenv

Do not set the MAIL environment variable.

nopen

Don't print any mail information on login. This flag is useful to
           get the MAIL environment variable set, but to not display any
           information about it.

quiet

Only report when there is new mail.

standard

Old style "You have..." format which doesn't show the mail spool
           being used. This also implies "empty".

6.19.3. MODULE TYPES PROVIDED

The session and auth (on establishment and deletion of credentials) module
   types are provided.

6.19.4. RETURN VALUES

PAM_BUF_ERR

Memory buffer error.

PAM_SERVICE_ERR

Badly formed arguments.

PAM_SUCCESS

Success.

PAM_USER_UNKNOWN

User not known.

6.19.5. EXAMPLES

Add the following line to /etc/pam.d/login to indicate that the user has
   new mail when they login to the system.

session  optional  pam_mail.so standard

6.19.6. AUTHOR

pam_mail was written by Andrew G. Morgan <morgan@kernel.org>.

6.20. pam_mkhomedir - create users home directory

pam_mkhomedir.so [ silent ] [ umask=mode ] [ skel=skeldir ]

6.20.1. DESCRIPTION

The pam_mkhomedir PAM module will create a users home directory if it does
   not exist when the session begins. This allows users to be present in
   central database (such as NIS, kerberos or LDAP) without using a
   distributed file system or pre-creating a large number of directories. The
   skeleton directory (usually /etc/skel/) is used to copy default files and
   also sets a umask for the creation.

The new users home directory will not be removed after logout of the user.

6.20.2. OPTIONS

silent

Don't print informative messages.

umask=mask

The user file-creation mask is set to mask. The default value of
           mask is 0022.

skel=/path/to/skel/directory

Indicate an alternative skel directory to override the default
           /etc/skel.

6.20.3. MODULE TYPES PROVIDED

Only the session module type is provided.

6.20.4. RETURN VALUES

PAM_BUF_ERR

Memory buffer error.

PAM_CRED_INSUFFICIENT

Insufficient credentials to access authentication data.

PAM_PERM_DENIED

Not enough permissions to create the new directory or read the
           skel directory.

PAM_USER_UNKNOWN

User not known to the underlying authentication module.

PAM_SUCCESS

Environment variables were set.

6.20.5. EXAMPLES

A sample /etc/pam.d/login file:

auth       requisite   pam_securetty.so
   auth       sufficient  pam_ldap.so
   auth       required    pam_unix.so
   auth       required    pam_nologin.so
   account    sufficient  pam_ldap.so
   account    required    pam_unix.so
   password   required    pam_unix.so
   session    required    pam_mkhomedir.so skel=/etc/skel/ umask=0022
   session    required    pam_unix.so
   session    optional    pam_lastlog.so
   session    optional    pam_mail.so standard

6.20.6. AUTHOR

pam_mkhomedir was written by Jason Gunthorpe <jgg@debian.org>.

6.21. pam_motd - display the motd file

pam_motd.so [ motd=/path/filename ] [ motd_dir=/path/dirname.d ]

6.21.1. DESCRIPTION

pam_motd is a PAM module that can be used to display arbitrary motd
   (message of the day) files after a successful login. By default, pam_motd
   shows files in the following locations:

/etc/motd
   /run/motd
   /usr/lib/motd
   /etc/motd.d/
   /run/motd.d/
   /usr/lib/motd.d/

Each message size is limited to 64KB.

If /etc/motd does not exist, then /run/motd is shown. If /run/motd does
   not exist, then /usr/lib/motd is shown.

Similar overriding behavior applies to the directories. Files in
   /etc/motd.d/ override files with the same name in /run/motd.d/ and
   /usr/lib/motd.d/. Files in /run/motd.d/ override files with the same name
   in /usr/lib/motd.d/.

Files in the directories listed above are displayed in lexicographic order
   by name. Moreover, the files are filtered by reading them with the
   credentials of the target user authenticating on the system.

To silence a message, a symbolic link with target /dev/null may be placed
   in /etc/motd.d with the same filename as the message to be silenced.
   Example: Creating a symbolic link as follows silences
   /usr/lib/motd.d/my_motd.

ln -s /dev/null /etc/motd.d/my_motd

6.21.2. OPTIONS

motd=/path/filename

The /path/filename file is displayed as message of the day.
           Multiple paths to try can be specified as a colon-separated list.
           By default this option is set to
           /etc/motd:/run/motd:/usr/lib/motd.

motd_dir=/path/dirname.d

The /path/dirname.d directory is scanned and each file contained
           inside of it is displayed. Multiple directories to scan can be
           specified as a colon-separated list. By default this option is set
           to /etc/motd.d:/run/motd.d:/usr/lib/motd.d.

When no options are given, the default behavior applies for both options.
   Specifying either option (or both) will disable the default behavior for
   both options.

6.21.3. MODULE TYPES PROVIDED

Only the session module type is provided.

6.21.4. RETURN VALUES

PAM_IGNORE

This is the only return value of this module.

6.21.5. EXAMPLES

The suggested usage for /etc/pam.d/login is:

session  optional  pam_motd.so

To use a motd file from a different location:

session  optional  pam_motd.so motd=/elsewhere/motd

To use a motd file from elsewhere, along with a corresponding .d
   directory:

session  optional  pam_motd.so motd=/elsewhere/motd motd_dir=/elsewhere/motd.d

6.21.6. AUTHOR

pam_motd was written by Ben Collins <bcollins@debian.org>.

The motd_dir= option was added by Allison Karlitskaya
   <allison.karlitskaya@redhat.com>.

6.22. pam_namespace - setup a private namespace

pam_namespace.so [ debug ] [ unmnt_remnt ] [ unmnt_only ] [
   require_selinux ] [ gen_hash ] [ ignore_config_error ] [
   ignore_instance_parent_mode ] [ unmount_on_close ] [ use_current_context ]
   [ use_default_context ] [ mount_private ]

6.22.1. DESCRIPTION

The pam_namespace PAM module sets up a private namespace for a session
   with polyinstantiated directories. A polyinstantiated directory provides a
   different instance of itself based on user name, or when using SELinux,
   user name, security context or both. If an executable script
   /etc/security/namespace.init exists, it is used to initialize the instance
   directory after it is set up and mounted on the polyinstantiated
   directory. The script receives the polyinstantiated directory path, the
   instance directory path, flag whether the instance directory was newly
   created (0 for no, 1 for yes), and the user name as its arguments.

The pam_namespace module disassociates the session namespace from the
   parent namespace. Any mounts/unmounts performed in the parent namespace,
   such as mounting of devices, are not reflected in the session namespace.
   To propagate selected mount/unmount events from the parent namespace into
   the disassociated session namespace, an administrator may use the special
   shared-subtree feature. For additional information on shared-subtree
   feature, please refer to the mount(8) man page and the shared-subtree
   description at http://lwn.net/Articles/159077 and
   http://lwn.net/Articles/159092.

6.22.2. DESCRIPTION

The pam_namespace.so module allows setup of private namespaces with
   polyinstantiated directories. Directories can be polyinstantiated based on
   user name or, in the case of SELinux, user name, sensitivity level or
   complete security context. If an executable script
   /etc/security/namespace.init exists, it is used to initialize the
   namespace every time an instance directory is set up and mounted. The
   script receives the polyinstantiated directory path and the instance
   directory path as its arguments.

The /etc/security/namespace.conf file specifies which directories are
   polyinstantiated, how they are polyinstantiated, how instance directories
   would be named, and any users for whom polyinstantiation would not be
   performed.

When someone logs in, the file namespace.conf is scanned. Comments are
   marked by # characters. Each non comment line represents one
   polyinstantiated directory. The fields are separated by spaces but can be
   quoted by " characters also escape sequences \b, \n, and \t are
   recognized. The fields are as follows:

polydir instance_prefix method list_of_uids

The first field, polydir, is the absolute pathname of the directory to
   polyinstantiate. The special string $HOME is replaced with the user's home
   directory, and $USER with the username. This field cannot be blank.

The second field, instance_prefix is the string prefix used to build the
   pathname for the instantiation of <polydir>. Depending on the
   polyinstantiation method it is then appended with "instance
   differentiation string" to generate the final instance directory path.
   This directory is created if it did not exist already, and is then bind
   mounted on the <polydir> to provide an instance of <polydir> based on the
   <method> column. The special string $HOME is replaced with the user's home
   directory, and $USER with the username. This field cannot be blank.

The third field, method, is the method used for polyinstantiation. It can
   take these values; "user" for polyinstantiation based on user name,
   "level" for polyinstantiation based on process MLS level and user name,
   "context" for polyinstantiation based on process security context and user
   name, "tmpfs" for mounting tmpfs filesystem as an instance dir, and
   "tmpdir" for creating temporary directory as an instance dir which is
   removed when the user's session is closed. Methods "context" and "level"
   are only available with SELinux. This field cannot be blank.

The fourth field, list_of_uids, is a comma separated list of user names
   for whom the polyinstantiation is not performed. If left blank,
   polyinstantiation will be performed for all users. If the list is preceded
   with a single "~" character, polyinstantiation is performed only for users
   in the list.

The method field can contain also following optional flags separated by :
   characters.

create=mode,owner,group - create the polyinstantiated directory. The mode,
   owner and group parameters are optional. The default for mode is
   determined by umask, the default owner is the user whose session is
   opened, the default group is the primary group of the user.

iscript=path - path to the instance directory init script. The base
   directory for relative paths is /etc/security/namespace.d.

noinit - instance directory init script will not be executed.

shared - the instance directories for "context" and "level" methods will
   not contain the user name and will be shared among all users.

mntopts=value - value of this flag is passed to the mount call when the
   tmpfs mount is done. It allows for example the specification of the
   maximum size of the tmpfs instance that is created by the mount call. In
   addition to options specified in the tmpfs(5) manual the nosuid, noexec,
   and nodev flags can be used to respectively disable setuid bit effect,
   disable running executables, and disable devices to be interpreted on the
   mounted tmpfs filesystem.

The directory where polyinstantiated instances are to be created, must
   exist and must have, by default, the mode of 0000. The requirement that
   the instance parent be of mode 0000 can be overridden with the command
   line option ignore_instance_parent_mode

In case of context or level polyinstantiation the SELinux context which is
   used for polyinstantiation is the context used for executing a new process
   as obtained by getexeccon. This context must be set by the calling
   application or pam_selinux.so module. If this context is not set the
   polyinstatiation will be based just on user name.

The "instance differentiation string" is <user name> for "user" method and
   <user name>_<raw directory context> for "context" and "level" methods. If
   the whole string is too long the end of it is replaced with md5sum of
   itself. Also when command line option gen_hash is used the whole string is
   replaced with md5sum of itself.

6.22.3. OPTIONS

debug

A lot of debug information is logged using syslog

unmnt_remnt

For programs such as su and newrole, the login session has already
           setup a polyinstantiated namespace. For these programs,
           polyinstantiation is performed based on new user id or security
           context, however the command first needs to undo the
           polyinstantiation performed by login. This argument instructs the
           command to first undo previous polyinstantiation before proceeding
           with new polyinstantiation based on new id/context

unmnt_only

For trusted programs that want to undo any existing bind mounts
           and process instance directories on their own, this argument
           allows them to unmount currently mounted instance directories

require_selinux

If selinux is not enabled, return failure

gen_hash

Instead of using the security context string for the instance
           name, generate and use its md5 hash.

ignore_config_error

If a line in the configuration file corresponding to a
           polyinstantiated directory contains format error, skip that line
           process the next line. Without this option, pam will return an
           error to the calling program resulting in termination of the
           session.

ignore_instance_parent_mode

Instance parent directories by default are expected to have the
           restrictive mode of 000. Using this option, an administrator can
           choose to ignore the mode of the instance parent. This option
           should be used with caution as it will reduce security and
           isolation goals of the polyinstantiation mechanism.

unmount_on_close

Explicitly unmount the polyinstantiated directories instead of
           relying on automatic namespace destruction after the last process
           in a namespace exits. This option should be used only in case it
           is ensured by other means that there cannot be any processes
           running in the private namespace left after the session close. It
           is also useful only in case there are multiple pam session calls
           in sequence from the same process.

use_current_context

Useful for services which do not change the SELinux context with
           setexeccon call. The module will use the current SELinux context
           of the calling process for the level and context
           polyinstantiation.

use_default_context

Useful for services which do not use pam_selinux for changing the
           SELinux context with setexeccon call. The module will use the
           default SELinux context of the user for the level and context
           polyinstantiation.

mount_private

This option can be used on systems where the / mount point or its
           submounts are made shared (for example with a mount --make-rshared
           / command). The module will mark the whole directory tree so any
           mount and unmount operations in the polyinstantiation namespace
           are private. Normally the pam_namespace will try to detect the
           shared / mount point and make the polyinstantiated directories
           private automatically. This option has to be used just when only a
           subtree is shared and / is not.

Note that mounts and unmounts done in the private namespace will
           not affect the parent namespace if this option is used or when the
           shared / mount point is autodetected.

6.22.4. MODULE TYPES PROVIDED

Only the session module type is provided. The module must not be called
   from multithreaded processes.

6.22.5. RETURN VALUES

PAM_SUCCESS

Namespace setup was successful.

PAM_SERVICE_ERR

Unexpected system error occurred while setting up namespace.

PAM_SESSION_ERR

Unexpected namespace configuration error occurred.

6.22.6. FILES

/etc/security/namespace.conf

Main configuration file

/etc/security/namespace.d

Directory for additional configuration files

/etc/security/namespace.init

Init script for instance directories

6.22.7. EXAMPLES

These are some example lines which might be specified in
   /etc/security/namespace.conf.

# The following three lines will polyinstantiate /tmp,
         # /var/tmp and user's home directories. /tmp and /var/tmp
         # will be polyinstantiated based on the security level
         # as well as user name, whereas home directory will be
         # polyinstantiated based on the full security context and user name.
         # Polyinstantiation will not be performed for user root
         # and adm for directories /tmp and /var/tmp, whereas home
         # directories will be polyinstantiated for all users.
         #
         # Note that instance directories do not have to reside inside
         # the polyinstantiated directory. In the examples below,
         # instances of /tmp will be created in /tmp-inst directory,
         # where as instances of /var/tmp and users home directories
         # will reside within the directories that are being
         # polyinstantiated.
         #
         /tmp     /tmp-inst/               level      root,adm
         /var/tmp /var/tmp/tmp-inst/    level      root,adm
         $HOME    $HOME/$USER.inst/inst- context

For the <service>s you need polyinstantiation (login for example) put the
   following line in /etc/pam.d/<service> as the last line for session group:

session required pam_namespace.so [arguments]

This module also depends on pam_selinux.so setting the context.

6.22.8. AUTHORS

The namespace setup scheme was designed by Stephen Smalley, Janak Desai
   and Chad Sellers. The pam_namespace PAM module was developed by Janak
   Desai <janak@us.ibm.com>, Chad Sellers <csellers@tresys.com> and Steve
   Grubb <sgrubb@redhat.com>. Additional improvements by Xavier Toth
   <txtoth@gmail.com> and Tomas Mraz <tmraz@redhat.com>.

6.23. pam_nologin - prevent non-root users from login

pam_nologin.so [ file=/path/nologin ] [ successok ]

6.23.1. DESCRIPTION

pam_nologin is a PAM module that prevents users from logging into the
   system when /var/run/nologin or /etc/nologin exists. The contents of the
   file are displayed to the user. The pam_nologin module has no effect on
   the root user's ability to log in.

6.23.2. OPTIONS

file=/path/nologin

Use this file instead the default /var/run/nologin or
           /etc/nologin.

successok

Return PAM_SUCCESS if no file exists, the default is PAM_IGNORE.

6.23.3. MODULE TYPES PROVIDED

The auth and acct module types are provided.

6.23.4. RETURN VALUES

PAM_AUTH_ERR

The user is not root and /etc/nologin exists, so the user is not
           permitted to log in.

PAM_BUF_ERR

Memory buffer error.

PAM_IGNORE

This is the default return value.

PAM_SUCCESS

Success: either the user is root or the nologin file does not
           exist.

PAM_USER_UNKNOWN

User not known to the underlying authentication module.

6.23.5. EXAMPLES

The suggested usage for /etc/pam.d/login is:

auth  required  pam_nologin.so

6.23.6. AUTHOR

pam_nologin was written by Michael K. Johnson <johnsonm@redhat.com>.

6.24. pam_permit - the promiscuous module

pam_permit.so

6.24.1. DESCRIPTION

pam_permit is a PAM module that always permit access. It does nothing
   else.

In the case of authentication, the user's name will be set to nobody if
   the application didn't set one. Many applications and PAM modules become
   confused if this name is unknown.

This module is very dangerous. It should be used with extreme caution.

6.24.2. OPTIONS

This module does not recognise any options.

6.24.3. MODULE TYPES PROVIDED

The auth, account, password and session module types are provided.

6.24.4. RETURN VALUES

PAM_SUCCESS

This module always returns this value.

6.24.5. EXAMPLES

Add this line to your other login entries to disable account management,
   but continue to permit users to log in.

account  required  pam_permit.so

6.24.6. AUTHOR

pam_permit was written by Andrew G. Morgan, <morgan@kernel.org>.

6.25. pam_pwhistory - grant access using .pwhistory file

pam_pwhistory.so [ debug ] [ use_authtok ] [ enforce_for_root ] [
   remember=N ] [ retry=N ] [ authtok_type=STRING ] [
   conf=/path/to/config-file ]

6.25.1. DESCRIPTION

This module saves the last passwords for each user in order to force
   password change history and keep the user from alternating between the
   same password too frequently.

This module does not work together with kerberos. In general, it does not
   make much sense to use this module in conjunction with NIS or LDAP, since
   the old passwords are stored on the local machine and are not available on
   another machine for password history checking.

6.25.2. OPTIONS

debug

Turns on debugging via syslog(3).

use_authtok

When password changing enforce the module to use the new password
           provided by a previously stacked password module (this is used in
           the example of the stacking of the pam_cracklib module documented
           below).

enforce_for_root

If this option is set, the check is enforced for root, too.

remember=N

The last N passwords for each user are saved. The default is 10.
           Value of 0 makes the module to keep the existing contents of the
           opasswd file unchanged.

retry=N

Prompt user at most N times before returning with error. The
           default is 1.

authtok_type=STRING

See pam_get_authtok(3) for more details.

conf=/path/to/config-file

Use another configuration file instead of the default
           /etc/security/pwhistory.conf.

The options for configuring the module behavior are described in the
   pwhistory.conf(5) manual page. The options specified on the module command
   line override the values from the configuration file.

6.25.3. MODULE TYPES PROVIDED

Only the password module type is provided.

6.25.4. RETURN VALUES

PAM_AUTHTOK_ERR

No new password was entered, the user aborted password change or
           new password couldn't be set.

PAM_IGNORE

Password history was disabled.

PAM_MAXTRIES

Password was rejected too often.

PAM_USER_UNKNOWN

User is not known to system.

6.25.5. FILES

/etc/security/opasswd

File with password history

6.25.6. EXAMPLES

An example password section would be:

#%PAM-1.0
 password     required       pam_pwhistory.so
 password     required       pam_unix.so        use_authtok

In combination with pam_cracklib:

#%PAM-1.0
 password     required       pam_cracklib.so    retry=3
 password     required       pam_pwhistory.so   use_authtok
 password     required       pam_unix.so        use_authtok

6.25.7. AUTHOR

pam_pwhistory was written by Thorsten Kukuk <kukuk@thkukuk.de>

6.26. pam_rhosts - grant access using .rhosts file

pam_rhosts.so

6.26.1. DESCRIPTION

This module performs the standard network authentication for services, as
   used by traditional implementations of rlogin and rsh etc.

The authentication mechanism of this module is based on the contents of
   two files; /etc/hosts.equiv (or and ~/.rhosts. Firstly, hosts listed in
   the former file are treated as equivalent to the localhost. Secondly,
   entries in the user's own copy of the latter file is used to map
   "remote-host remote-user" pairs to that user's account on the current
   host. Access is granted to the user if their host is present in
   /etc/hosts.equiv and their remote account is identical to their local one,
   or if their remote account has an entry in their personal configuration
   file.

The module authenticates a remote user (internally specified by the item
   PAM_RUSER connecting from the remote host (internally specified by the
   item PAM_RHOST). Accordingly, for applications to be compatible this
   authentication module they must set these items prior to calling
   pam_authenticate(). The module is not capable of independently probing the
   network connection for such information.

6.26.2. OPTIONS

debug

Print debug information.

silent

Don't print informative messages.

superuser=account

Handle account as root.

6.26.3. MODULE TYPES PROVIDED

Only the auth module type is provided.

6.26.4. RETURN VALUES

PAM_AUTH_ERR

The remote host, remote user name or the local user name couldn't
           be determined or access was denied by .rhosts file.

PAM_USER_UNKNOWN

User is not known to system.

6.26.5. EXAMPLES

To grant a remote user access by /etc/hosts.equiv or .rhosts for rsh add
   the following lines to /etc/pam.d/rsh:

#%PAM-1.0
 #
 auth     required       pam_rhosts.so
 auth     required       pam_nologin.so
 auth     required       pam_env.so
 auth     required       pam_unix.so

6.26.6. AUTHOR

pam_rhosts was written by Thorsten Kukuk <kukuk@thkukuk.de>

6.27. pam_rootok - gain only root access

pam_rootok.so [ debug ]

6.27.1. DESCRIPTION

pam_rootok is a PAM module that authenticates the user if their UID is 0.
   Applications that are created setuid-root generally retain the UID of the
   user but run with the authority of an enhanced effective-UID. It is the
   real UID that is checked.

6.27.2. OPTIONS

debug

Print debug information.

6.27.3. MODULE TYPES PROVIDED

The auth, acct and password module types are provided.

6.27.4. RETURN VALUES

PAM_SUCCESS

The UID is 0.

PAM_AUTH_ERR

The UID is not 0.

6.27.5. EXAMPLES

In the case of the su(1) application the historical usage is to permit the
   superuser to adopt the identity of a lesser user without the use of a
   password. To obtain this behavior with PAM the following pair of lines are
   needed for the corresponding entry in the /etc/pam.d/su configuration
   file:

# su authentication. Root is granted access by default.
 auth  sufficient   pam_rootok.so
 auth  required     pam_unix.so

6.27.6. AUTHOR

pam_rootok was written by Andrew G. Morgan, <morgan@kernel.org>.

6.28. pam_securetty - limit root login to special devices

pam_securetty.so [ debug ]

6.28.1. DESCRIPTION

pam_securetty is a PAM module that allows root logins only if the user is
   logging in on a "secure" tty, as defined by the listing in /etc/securetty.
   pam_securetty also checks to make sure that /etc/securetty is a plain file
   and not world writable. It will also allow root logins on the tty
   specified with console= switch on the kernel command line and on ttys from
   the /sys/class/tty/console/active.

This module has no effect on non-root users and requires that the
   application fills in the PAM_TTY item correctly.

For canonical usage, should be listed as a required authentication method
   before any sufficient authentication methods.

6.28.2. OPTIONS

debug

Print debug information.

noconsole

Do not automatically allow root logins on the kernel console
           device, as specified on the kernel command line or by the sys
           file, if it is not also specified in the /etc/securetty file.

6.28.3. MODULE TYPES PROVIDED

Only the auth module type is provided.

6.28.4. RETURN VALUES

PAM_SUCCESS

The user is allowed to continue authentication. Either the user is
           not root, or the root user is trying to log in on an acceptable
           device.

PAM_AUTH_ERR

Authentication is rejected. Either root is attempting to log in
           via an unacceptable device, or the /etc/securetty file is world
           writable or not a normal file.

PAM_INCOMPLETE

An application error occurred. pam_securetty was not able to get
           information it required from the application that called it.

PAM_SERVICE_ERR

An error occurred while the module was determining the user's name
           or tty, or the module could not open /etc/securetty.

PAM_USER_UNKNOWN

The module could not find the user name in the /etc/passwd file to
           verify whether the user had a UID of 0. Therefore, the results of
           running this module are ignored.

6.28.5. EXAMPLES

auth  required  pam_securetty.so
 auth  required  pam_unix.so

6.28.6. AUTHOR

pam_securetty was written by Elliot Lee <sopwith@cuc.edu>.

6.29. pam_selinux - set the default security context

pam_selinux.so [ open ] [ close ] [ restore ] [ nottys ] [ debug ] [
   verbose ] [ select_context ] [ env_params ] [ use_current_range ]

6.29.1. DESCRIPTION

pam_selinux is a PAM module that sets up the default SELinux security
   context for the next executed process.

When a new session is started, the open_session part of the module
   computes and sets up the execution security context used for the next
   execve(2) call, the file security context for the controlling terminal,
   and the security context used for creating a new kernel keyring.

When the session is ended, the close_session part of the module restores
   old security contexts that were in effect before the change made by the
   open_session part of the module.

Adding pam_selinux into the PAM stack might disrupt behavior of other PAM
   modules which execute applications. To avoid that, pam_selinux.so open
   should be placed after such modules in the PAM stack, and pam_selinux.so
   close should be placed before them. When such a placement is not feasible,
   pam_selinux.so restore could be used to temporary restore original
   security contexts.

6.29.2. OPTIONS

open

Only execute the open_session part of the module.

Only execute the close_session part of the module.

restore

In open_session part of the module, temporarily restore the
           security contexts as they were before the previous call of the
           module. Another call of this module without the restore option
           will set up the new security contexts again.

nottys

Do not setup security context of the controlling terminal.

debug

Turn on debug messages via syslog(3).

verbose

Attempt to inform the user when security context is set.

select_context

Attempt to ask the user for a custom security context role. If MLS
           is on, ask also for sensitivity level.

env_params

Attempt to obtain a custom security context role from PAM
           environment. If MLS is on, obtain also sensitivity level. This
           option and the select_context option are mutually exclusive. The
           respective PAM environment variables are SELINUX_ROLE_REQUESTED,
           SELINUX_LEVEL_REQUESTED, and SELINUX_USE_CURRENT_RANGE. The first
           two variables are self describing and the last one if set to 1
           makes the PAM module behave as if the use_current_range was
           specified on the command line of the module.

use_current_range

Use the sensitivity level of the current process for the user
           context instead of the default level. Also suppresses asking of
           the sensitivity level from the user or obtaining it from PAM
           environment.

6.29.3. MODULE TYPES PROVIDED

Only the session module type is provided.

6.29.4. RETURN VALUES

PAM_SUCCESS

The security context was set successfully.

PAM_SESSION_ERR

Unable to get or set a valid context.

PAM_USER_UNKNOWN

The user is not known to the system.

PAM_BUF_ERR

Memory allocation error.

6.29.5. EXAMPLES

auth     required  pam_unix.so
 session  required  pam_permit.so
 session  optional  pam_selinux.so

6.29.6. AUTHOR

pam_selinux was written by Dan Walsh <dwalsh@redhat.com>.

6.30. pam_shells - check for valid login shell

pam_shells.so

6.30.1. DESCRIPTION

pam_shells is a PAM module that only allows access to the system if the
   user's shell is listed in /etc/shells.

It also checks if /etc/shells is a plain file and not world writable.

6.30.2. OPTIONS

This module does not recognise any options.

6.30.3. MODULE TYPES PROVIDED

The auth and account module types are provided.

6.30.4. RETURN VALUES

PAM_AUTH_ERR

Access to the system was denied.

PAM_SUCCESS

The user's login shell was listed as valid shell in /etc/shells.

PAM_SERVICE_ERR

The module was not able to get the name of the user.

6.30.5. EXAMPLES

auth  required  pam_shells.so

6.30.6. AUTHOR

pam_shells was written by Erik Troan <ewt@redhat.com>.

6.31. pam_succeed_if - test account characteristics

pam_succeed_if.so [flag...] [condition...]

6.31.1. DESCRIPTION

pam_succeed_if.so is designed to succeed or fail authentication based on
   characteristics of the account belonging to the user being authenticated
   or values of other PAM items. One use is to select whether to load other
   modules based on this test.

The module should be given one or more conditions as module arguments, and
   authentication will succeed only if all of the conditions are met.

6.31.2. OPTIONS

The following flags are supported:

debug

Turns on debugging messages sent to syslog.

use_uid

Evaluate conditions using the account of the user whose UID the
           application is running under instead of the user being
           authenticated.

quiet

Don't log failure or success to the system log.

quiet_fail

Don't log failure to the system log.

quiet_success

Don't log success to the system log.

audit

Log unknown users to the system log.

Conditions are three words: a field, a test, and a value to test for.

Available fields are user, uid, gid, shell, home, ruser, rhost, tty and
   service:

field < number

Field has a value numerically less than number.

field <= number

Field has a value numerically less than or equal to number.

field eq number

Field has a value numerically equal to number.

field >= number

Field has a value numerically greater than or equal to number.

field > number

Field has a value numerically greater than number.

field ne number

Field has a value numerically different from number.

field = string

Field exactly matches the given string.

field != string

Field does not match the given string.

field =~ glob

Field matches the given glob.

field !~ glob

Field does not match the given glob.

field in item:item:...

Field is contained in the list of items separated by colons.

field notin item:item:...

Field is not contained in the list of items separated by colons.

user ingroup group

User is in given group.

user notingroup group

User is not in given group.

user innetgr netgroup

(user,host) is in given netgroup.

user notinnetgr group

(user,host) is not in given netgroup.

6.31.3. MODULE TYPES PROVIDED

All module types (account, auth, password and session) are provided.

6.31.4. RETURN VALUES

PAM_SUCCESS

The condition was true.

PAM_AUTH_ERR

The condition was false.

PAM_SERVICE_ERR

A service error occurred or the arguments can't be parsed
           correctly.

6.31.5. EXAMPLES

To emulate the behaviour of pam_wheel, except there is no fallback to
   group 0:

auth required pam_succeed_if.so quiet user ingroup wheel

Given that the type matches, only loads the othermodule rule if the UID is
   over 500. Adjust the number after default to skip several rules.

type [default=1 success=ignore] pam_succeed_if.so quiet uid > 500
 type required othermodule.so arguments...

6.31.6. AUTHOR

Nalin Dahyabhai <nalin@redhat.com>

6.32. pam_tally - login counter (tallying) module

pam_tally.so [ file=/path/to/counter ] [ onerr=[fail|succeed] ] [
   magic_root ] [ even_deny_root_account ] [ deny=n ] [ lock_time=n ] [
   unlock_time=n ] [ per_user ] [ no_lock_time ] [ no_reset ] [ audit ] [
   silent ] [ no_log_info ]

pam_tally [ --file /path/to/counter ] [ --user username ] [ --reset[=n] ]
   [ --quiet ]

6.32.1. DESCRIPTION

This module maintains a count of attempted accesses, can reset count on
   success, can deny access if too many attempts fail.

pam_tally has several limitations, which are solved with pam_tally2. For
   this reason pam_tally is deprecated and will be removed in a future
   release.

pam_tally comes in two parts: pam_tally.so and pam_tally. The former is
   the PAM module and the latter, a stand-alone program. pam_tally is an
   (optional) application which can be used to interrogate and manipulate the
   counter file. It can display user counts, set individual counts, or clear
   all counts. Setting artificially high counts may be useful for blocking
   users without changing their passwords. For example, one might find it
   useful to clear all counts every midnight from a cron job. The faillog(8)
   command can be used instead of pam_tally to to maintain the counter file.

Normally, failed attempts to access root will not cause the root account
   to become blocked, to prevent denial-of-service: if your users aren't
   given shell accounts and root may only login via su or at the machine
   console (not telnet/rsh, etc), this is safe.

6.32.2. OPTIONS

GLOBAL OPTIONS

This can be used for auth and account module types.

onerr=[fail|succeed]

If something weird happens (like unable to open the
                        file), return with PAM_SUCCESS if onerr=succeed is
                        given, else with the corresponding PAM error code.

file=/path/to/counter

File where to keep counts. Default is
                        /var/log/faillog.

audit

Will log the user name into the system log if the
                        user is not found.

silent

Don't print informative messages.

no_log_info

Don't log informative messages via syslog(3).

AUTH OPTIONS

Authentication phase first checks if user should be denied access
           and if not it increments attempted login counter. Then on call to
           pam_setcred(3) it resets the attempts counter.

deny=n

Deny access if tally for this user exceeds n.

lock_time=n

Always deny for n seconds after failed attempt.

unlock_time=n

Allow access after n seconds after failed attempt. If
                        this option is used the user will be locked out for
                        the specified amount of time after he exceeded his
                        maximum allowed attempts. Otherwise the account is
                        locked until the lock is removed by a manual
                        intervention of the system administrator.

magic_root

If the module is invoked by a user with uid=0 the
                        counter is not incremented. The sysadmin should use
                        this for user launched services, like su, otherwise
                        this argument should be omitted.

no_lock_time

Do not use the .fail_locktime field in
                        /var/log/faillog for this user.

no_reset

Don't reset count on successful entry, only
                        decrement.

even_deny_root_account

Root account can become unavailable.

per_user

If /var/log/faillog contains a non-zero
                        .fail_max/.fail_locktime field for this user then use
                        it instead of deny=n/ lock_time=n parameter.

no_lock_time

Don't use .fail_locktime filed in /var/log/faillog
                        for this user.

ACCOUNT OPTIONS

Account phase resets attempts counter if the user is not magic
           root. This phase can be used optionally for services which don't
           call pam_setcred(3) correctly or if the reset should be done
           regardless of the failure of the account phase of other modules.

magic_root

no_reset

Don't reset count on successful entry, only
                        decrement.

6.32.3. MODULE TYPES PROVIDED

The auth and account module types are provided.

6.32.4. RETURN VALUES

PAM_AUTH_ERR

A invalid option was given, the module was not able to retrieve
           the user name, no valid counter file was found, or too many failed
           logins.

PAM_SUCCESS

Everything was successful.

PAM_USER_UNKNOWN

User not known.

6.32.5. EXAMPLES

Add the following line to /etc/pam.d/login to lock the account after too
   many failed logins. The number of allowed fails is specified by
   /var/log/faillog and needs to be set with pam_tally or faillog(8) before.

auth     required       pam_securetty.so
 auth     required       pam_tally.so per_user
 auth     required       pam_env.so
 auth     required       pam_unix.so
 auth     required       pam_nologin.so
 account  required       pam_unix.so
 password required       pam_unix.so
 session  required       pam_limits.so
 session  required       pam_unix.so
 session  required       pam_lastlog.so nowtmp
 session  optional       pam_mail.so standard

6.32.6. AUTHOR

pam_tally was written by Tim Baverstock and Tomas Mraz.

6.33. pam_tally2 - login counter (tallying) module

pam_tally2.so [ file=/path/to/counter ] [ onerr=[fail|succeed] ] [
   magic_root ] [ even_deny_root ] [ deny=n ] [ lock_time=n ] [ unlock_time=n
   ] [ root_unlock_time=n ] [ serialize ] [ audit ] [ silent ] [ no_log_info
   ] [ debug ]

pam_tally2 [ --file /path/to/counter ] [ --user username ] [ --reset[=n] ]
   [ --quiet ]

6.33.1. DESCRIPTION

This module maintains a count of attempted accesses, can reset count on
   success, can deny access if too many attempts fail.

pam_tally2 comes in two parts: pam_tally2.so and pam_tally2. The former is
   the PAM module and the latter, a stand-alone program. pam_tally2 is an
   (optional) application which can be used to interrogate and manipulate the
   counter file. It can display user counts, set individual counts, or clear
   all counts. Setting artificially high counts may be useful for blocking
   users without changing their passwords. For example, one might find it
   useful to clear all counts every midnight from a cron job.

6.33.2. OPTIONS

GLOBAL OPTIONS

This can be used for auth and account module types.

onerr=[fail|succeed]

file=/path/to/counter

File where to keep counts. Default is
                        /var/log/tallylog.

audit

Will log the user name into the system log if the
                        user is not found.

silent

Don't print informative messages.

no_log_info

Don't log informative messages via syslog(3).

debug

Always log tally count when it is incremented as a
                        debug level message to the system log.

AUTH OPTIONS

Authentication phase first increments attempted login counter and
           checks if user should be denied access. If the user is
           authenticated and the login process continues on call to
           pam_setcred(3) it resets the attempts counter.

deny=n

Deny access if tally for this user exceeds n.

lock_time=n

Always deny for n seconds after failed attempt.

unlock_time=n

magic_root

even_deny_root

Root account can become unavailable.

root_unlock_time=n

This option implies even_deny_root option. Allow
                        access after n seconds to root account after failed
                        attempt. If this option is used the root user will be
                        locked out for the specified amount of time after he
                        exceeded his maximum allowed attempts.

serialize

Serialize access to the tally file using locks. This
                        option might be used only for non-multithreaded
                        services because it depends on the fcntl locking of
                        the tally file. Also it is a good idea to use this
                        option only in such configurations where the time
                        between auth phase and account or setcred phase is
                        not dependent on the authenticating client. Otherwise
                        the authenticating client will be able to prevent
                        simultaneous authentications by the same user by
                        simply artificially prolonging the time the file
                        record lock is held.

ACCOUNT OPTIONS

magic_root

If the module is invoked by a user with uid=0 the
                        counter is not changed. The sysadmin should use this
                        for user launched services, like su, otherwise this
                        argument should be omitted.

6.33.3. MODULE TYPES PROVIDED

The auth and account module types are provided.

6.33.4. RETURN VALUES

PAM_AUTH_ERR

A invalid option was given, the module was not able to retrieve
           the user name, no valid counter file was found, or too many failed
           logins.

PAM_SUCCESS

Everything was successful.

PAM_USER_UNKNOWN

User not known.

6.33.5. NOTES

pam_tally2 is not compatible with the old pam_tally faillog file format.
   This is caused by requirement of compatibility of the tallylog file format
   between 32bit and 64bit architectures on multiarch systems.

There is no setuid wrapper for access to the data file such as when the
   pam_tally2.so module is called from xscreensaver. As this would make it
   impossible to share PAM configuration with such services the following
   workaround is used: If the data file cannot be opened because of
   insufficient permissions (EACCES) the module returns PAM_IGNORE.

6.33.6. EXAMPLES

Add the following line to /etc/pam.d/login to lock the account after 4
   failed logins. Root account will be locked as well. The accounts will be
   automatically unlocked after 20 minutes. The module does not have to be
   called in the account phase because the login calls pam_setcred(3)
   correctly.

auth     required       pam_securetty.so
 auth     required       pam_tally2.so deny=4 even_deny_root unlock_time=1200
 auth     required       pam_env.so
 auth     required       pam_unix.so
 auth     required       pam_nologin.so
 account  required       pam_unix.so
 password required       pam_unix.so
 session  required       pam_limits.so
 session  required       pam_unix.so
 session  required       pam_lastlog.so nowtmp
 session  optional       pam_mail.so standard

6.33.7. FILES

/var/log/tallylog

failure count logging file

6.33.8. AUTHOR

pam_tally2 was written by Tim Baverstock and Tomas Mraz.

6.34. pam_time - time controled access

pam_time.so [ debug ] [ noaudit ]

6.34.1. DESCRIPTION

The pam_time PAM module does not authenticate the user, but instead it
   restricts access to a system and or specific applications at various times
   of the day and on specific days or over various terminal lines. This
   module can be configured to deny access to (individual) users based on
   their name, the time of day, the day of week, the service they are
   applying for and their terminal from which they are making their request.

By default rules for time/port access are taken from config file
   /etc/security/time.conf.

If Linux PAM is compiled with audit support the module will report when it
   denies access.

6.34.2. DESCRIPTION

For this module to function correctly there must be a correctly formatted
   /etc/security/time.conf file present. White spaces are ignored and lines
   maybe extended with '\' (escaped newlines). Text following a '#' is
   ignored to the end of the line.

The syntax of the lines is as follows:

services;ttys;users;times

In words, each rule occupies a line, terminated with a newline or the
   beginning of a comment; a '#'. It contains four fields separated with
   semicolons, ';'.

The first field, the services field, is a logic list of PAM service names
   that the rule applies to.

The second field, the tty field, is a logic list of terminal names that
   this rule applies to.

The third field, the users field, is a logic list of users or a netgroup
   of users to whom this rule applies.

For these items the simple wildcard '*' may be used only once. With
   netgroups no wildcards or logic operators are allowed.

The times field is used to indicate the times at which this rule applies.
   The format here is a logic list of day/time-range entries. The days are
   specified by a sequence of two character entries, MoTuSa for example is
   Monday Tuesday and Saturday. Note that repeated days are unset MoMo = no
   day, and MoWk = all weekdays bar Monday. The two character combinations
   accepted are Mo Tu We Th Fr Sa Su Wk Wd Al, the last two being week-end
   days and all 7 days of the week respectively. As a final example, AlFr
   means all days except Friday.

For a rule to be active, ALL of service+ttys+users must be satisfied by
   the applying process.

Note, currently there is no daemon enforcing the end of a session. This
   needs to be remedied.

Poorly formatted rules are logged as errors using syslog(3).

6.34.3. OPTIONS

debug

Some debug information is printed with syslog(3).

noaudit

Do not report logins at disallowed time to the audit subsystem.

6.34.4. MODULE TYPES PROVIDED

Only the account type is provided.

6.34.5. RETURN VALUES

PAM_SUCCESS

Access was granted.

PAM_ABORT

Not all relevant data could be gotten.

PAM_BUF_ERR

Memory buffer error.

PAM_PERM_DENIED

Access was not granted.

PAM_USER_UNKNOWN

The user is not known to the system.

6.34.6. FILES

/etc/security/time.conf

Default configuration file

6.34.7. EXAMPLES

These are some example lines which might be specified in
   /etc/security/time.conf.

All users except for root are denied access to console-login at all times:

Games (configured to use PAM) are only to be accessed out of working
   hours. This rule does not apply to the user waster:

games ; * ; !waster ; Wd0000-2400 | Wk1800-0800

6.34.8. AUTHOR

pam_time was written by Andrew G. Morgan <morgan@kernel.org>.

6.35. pam_timestamp - authenticate using cached successful authentication
attempts

pam_timestamp.so [ timestampdir=directory ] [ timestamp_timeout=number ] [
   verbose ] [ debug ]

6.35.1. DESCRIPTION

In a nutshell, pam_timestamp caches successful authentication attempts,
   and allows you to use a recent successful attempt as the basis for
   authentication. This is similar mechanism which is used in sudo.

When an application opens a session using pam_timestamp, a timestamp file
   is created in the timestampdir directory for the user. When an application
   attempts to authenticate the user, a pam_timestamp will treat a
   sufficiently recent timestamp file as grounds for succeeding.

6.35.2. OPTIONS

timestampdir=directory

Specify an alternate directory where pam_timestamp creates
           timestamp files.

timestamp_timeout=number

How long should pam_timestamp treat timestamp as valid after their
           last modification date (in seconds). Default is 300 seconds.

verbose

Attempt to inform the user when access is granted.

debug

Turns on debugging messages sent to syslog(3).

6.35.3. MODULE TYPES PROVIDED

The auth and session module types are provided.

6.35.4. RETURN VALUES

PAM_AUTH_ERR

The module was not able to retrieve the user name or no valid
           timestamp file was found.

PAM_SUCCESS

Everything was successful.

PAM_SESSION_ERR

Timestamp file could not be created or updated.

6.35.5. NOTES

Users can get confused when they are not always asked for passwords when
   running a given program. Some users reflexively begin typing information
   before noticing that it is not being asked for.

6.35.6. EXAMPLES

auth sufficient pam_timestamp.so verbose
 auth required   pam_unix.so

session required pam_unix.so
 session optional pam_timestamp.so

6.35.7. FILES

/var/run/pam_timestamp/...

timestamp files and directories

6.35.8. AUTHOR

pam_timestamp was written by Nalin Dahyabhai.

6.36. pam_umask - set the file mode creation mask

pam_umask.so [ debug ] [ silent ] [ usergroups ] [ umask=mask ]

6.36.1. DESCRIPTION

pam_umask is a PAM module to set the file mode creation mask of the
   current environment. The umask affects the default permissions assigned to
   newly created files.

The PAM module tries to get the umask value from the following places in
   the following order:

* umask= entry in the user's GECOS field

* umask= argument

* UMASK entry from /etc/login.defs

* UMASK= entry from /etc/default/login

The GECOS field is split on comma ',' characters. The module also in
   addition to the umask= entry recognizes pri= entry, which sets the nice
   priority value for the session, and ulimit= entry, which sets the maximum
   size of files the processes in the session can create.

6.36.2. OPTIONS

debug

Print debug information.

silent

Don't print informative messages.

usergroups

If the user is not root and the username is the same as primary
           group name, the umask group bits are set to be the same as owner
           bits (examples: 022 -> 002, 077 -> 007).

umask=mask

Sets the calling process's file mode creation mask (umask) to mask
           & 0777. The value is interpreted as Octal.

6.36.3. MODULE TYPES PROVIDED

Only the session type is provided.

6.36.4. RETURN VALUES

PAM_SUCCESS

The new umask was set successfully.

PAM_SERVICE_ERR

No username was given.

PAM_USER_UNKNOWN

User not known.

6.36.5. EXAMPLES

Add the following line to /etc/pam.d/login to set the user specific umask
   at login:

session optional pam_umask.so umask=0022

6.36.6. AUTHOR

pam_umask was written by Thorsten Kukuk <kukuk@thkukuk.de>.

6.37. pam_unix - traditional password authentication

pam_unix.so [ ... ]

6.37.1. DESCRIPTION

This is the standard Unix authentication module. It uses standard calls
   from the system's libraries to retrieve and set account information as
   well as authentication. Usually this is obtained from the /etc/passwd and
   the /etc/shadow file as well if shadow is enabled.

The account component performs the task of establishing the status of the
   user's account and password based on the following shadow elements:
   expire, last_change, max_change, min_change, warn_change. In the case of
   the latter, it may offer advice to the user on changing their password or,
   through the PAM_AUTHTOKEN_REQD return, delay giving service to the user
   until they have established a new password. The entries listed above are
   documented in the shadow(5) manual page. Should the user's record not
   contain one or more of these entries, the corresponding shadow check is
   not performed.

The authentication component performs the task of checking the users
   credentials (password). The default action of this module is to not permit
   the user access to a service if their official password is blank.

A helper binary, unix_chkpwd(8), is provided to check the user's password
   when it is stored in a read protected database. This binary is very simple
   and will only check the password of the user invoking it. It is called
   transparently on behalf of the user by the authenticating component of
   this module. In this way it is possible for applications like xlock(1) to
   work without being setuid-root. The module, by default, will temporarily
   turn off SIGCHLD handling for the duration of execution of the helper
   binary. This is generally the right thing to do, as many applications are
   not prepared to handle this signal from a child they didn't know was
   fork()d. The noreap module argument can be used to suppress this temporary
   shielding and may be needed for use with certain applications.

The maximum length of a password supported by the pam_unix module via the
   helper binary is PAM_MAX_RESP_SIZE - currently 512 bytes. The rest of the
   password provided by the conversation function to the module will be
   ignored.

The password component of this module performs the task of updating the
   user's password. The default encryption hash is taken from the
   ENCRYPT_METHOD variable from /etc/login.defs

The session component of this module logs when a user logins or leave the
   system.

Remaining arguments, supported by others functions of this module, are
   silently ignored. Other arguments are logged as errors through syslog(3).

6.37.2. OPTIONS

debug

Turns on debugging via syslog(3).

audit

A little more extreme than debug.

quiet

Turns off informational messages namely messages about session
           open and close via syslog(3).

nullok

The default action of this module is to not permit the user access
           to a service if their official password is blank. The nullok
           argument overrides this default.

try_first_pass

Before prompting the user for their password, the module first
           tries the previous stacked module's password in case that
           satisfies this module as well.

use_first_pass

The argument use_first_pass forces the module to use a previous
           stacked modules password and will never prompt the user - if no
           password is available or the password is not appropriate, the user
           will be denied access.

nodelay

This argument can be used to discourage the authentication
           component from requesting a delay should the authentication as a
           whole fail. The default action is for the module to request a
           delay-on-failure of the order of two second.

use_authtok

When password changing enforce the module to set the new password
           to the one provided by a previously stacked password module (this
           is used in the example of the stacking of the pam_cracklib module
           documented below).

authtok_type=type

This argument can be used to modify the password prompt when
           changing passwords to include the type of the password. Empty by
           default.

nis

NIS RPC is used for setting new passwords.

remember=n

The last n passwords for each user are saved in
           /etc/security/opasswd in order to force password change history
           and keep the user from alternating between the same password too
           frequently. The MD5 password hash algorithm is used for storing
           the old passwords. Instead of this option the pam_pwhistory module
           should be used.

shadow

Try to maintain a shadow based system.

md5

When a user changes their password next, encrypt it with the MD5
           algorithm.

bigcrypt

When a user changes their password next, encrypt it with the DEC
           C2 algorithm.

sha256

When a user changes their password next, encrypt it with the
           SHA256 algorithm. The SHA256 algorithm must be supported by the
           crypt(3) function.

sha512

When a user changes their password next, encrypt it with the
           SHA512 algorithm. The SHA512 algorithm must be supported by the
           crypt(3) function.

blowfish

When a user changes their password next, encrypt it with the
           blowfish algorithm. The blowfish algorithm must be supported by
           the crypt(3) function.

rounds=n

Set the optional number of rounds of the SHA256, SHA512 and
           blowfish password hashing algorithms to n.

broken_shadow

Ignore errors reading shadow information for users in the account
           management module.

minlen=n

Set a minimum password length of n characters. The max. for DES
           crypt based passwords are 8 characters.

no_pass_expiry

When set ignore password expiration as defined by the shadow entry
           of the user. The option has an effect only in case pam_unix was
           not used for the authentication or it returned authentication
           failure meaning that other authentication source or method
           succeeded. The example can be public key authentication in sshd.
           The module will return PAM_SUCCESS instead of eventual
           PAM_NEW_AUTHTOK_REQD or PAM_AUTHTOK_EXPIRED.

Invalid arguments are logged with syslog(3).

6.37.3. MODULE TYPES PROVIDED

All module types (account, auth, password and session) are provided.

6.37.4. RETURN VALUES

PAM_IGNORE

Ignore this module.

6.37.5. EXAMPLES

An example usage for /etc/pam.d/login would be:

# Authenticate the user
 auth       required   pam_unix.so
 # Ensure users account and password are still active
 account    required   pam_unix.so
 # Change the user's password, but at first check the strength
 # with pam_cracklib(8)
 password   required   pam_cracklib.so retry=3 minlen=6 difok=3
 password   required   pam_unix.so use_authtok nullok md5
 session    required   pam_unix.so

6.37.6. AUTHOR

pam_unix was written by various people.

6.38. pam_userdb - authenticate against a db database

pam_userdb.so db=/path/database [ debug ] [ crypt=[crypt|none] ] [ icase ]
   [ dump ] [ try_first_pass ] [ use_first_pass ] [ unknown_ok ] [ key_only ]

6.38.1. DESCRIPTION

The pam_userdb module is used to verify a username/password pair against
   values stored in a Berkeley DB database. The database is indexed by the
   username, and the data fields corresponding to the username keys are the
   passwords.

6.38.2. OPTIONS

crypt=[crypt|none]

Indicates whether encrypted or plaintext passwords are stored in
           the database. If it is crypt, passwords should be stored in the
           database in crypt(3) form. If none is selected, passwords should
           be stored in the database as plaintext.

db=/path/database

Use the /path/database database for performing lookup. There is no
           default; the module will return PAM_IGNORE if no database is
           provided. Note that the path to the database file should be
           specified without the .db suffix.

debug

Print debug information. Note that password hashes, both from db
           and computed, will be printed to syslog.

dump

Dump all the entries in the database to the log. Don't do this by
           default!

icase

Make the password verification to be case insensitive (ie when
           working with registration numbers and such). Only works with
           plaintext password storage.

try_first_pass

Use the authentication token previously obtained by another module
           that did the conversation with the application. If this token can
           not be obtained then the module will try to converse. This option
           can be used for stacking different modules that need to deal with
           the authentication tokens.

use_first_pass

Use the authentication token previously obtained by another module
           that did the conversation with the application. If this token can
           not be obtained then the module will fail. This option can be used
           for stacking different modules that need to deal with the
           authentication tokens.

unknown_ok

Do not return error when checking for a user that is not in the
           database. This can be used to stack more than one pam_userdb
           module that will check a username/password pair in more than a
           database.

key_only

The username and password are concatenated together in the
           database hash as 'username-password' with a random value. if the
           concatenation of the username and password with a dash in the
           middle returns any result, the user is valid. this is useful in
           cases where the username may not be unique but the username and
           password pair are.

6.38.3. MODULE TYPES PROVIDED

The auth and account module types are provided.

6.38.4. RETURN VALUES

PAM_AUTH_ERR

Authentication failure.

PAM_AUTHTOK_RECOVERY_ERR

Authentication information cannot be recovered.

PAM_BUF_ERR

Memory buffer error.

PAM_CONV_ERR

Conversation failure.

PAM_SERVICE_ERR

Error in service module.

PAM_SUCCESS

Success.

PAM_USER_UNKNOWN

User not known to the underlying authentication module.

6.38.5. EXAMPLES

auth  sufficient pam_userdb.so icase db=/etc/dbtest

6.38.6. AUTHOR

pam_userdb was written by Cristian Gafton >gafton@redhat.com<.

6.39. pam_warn - logs all PAM items

pam_warn.so

6.39.1. DESCRIPTION

pam_warn is a PAM module that logs the service, terminal, user, remote
   user and remote host to syslog(3). The items are not probed for, but
   instead obtained from the standard PAM items. The module always returns
   PAM_IGNORE, indicating that it does not want to affect the authentication
   process.

6.39.2. OPTIONS

This module does not recognise any options.

6.39.3. MODULE TYPES PROVIDED

The auth, account, password and session module types are provided.

6.39.4. RETURN VALUES

PAM_IGNORE

This module always returns PAM_IGNORE.

6.39.5. EXAMPLES

6.39.6. AUTHOR

pam_warn was written by Andrew G. Morgan <morgan@kernel.org>.

6.40. pam_wheel - only permit root access to members of group wheel

pam_wheel.so [ debug ] [ deny ] [ group=name ] [ root_only ] [ trust ] [
   use_uid ]

6.40.1. DESCRIPTION

The pam_wheel PAM module is used to enforce the so-called wheel group. By
   default it permits root access to the system if the applicant user is a
   member of the wheel group. If no group with this name exist, the module is
   using the group with the group-ID 0.

6.40.2. OPTIONS

debug

Print debug information.

deny

Reverse the sense of the auth operation: if the user is trying to
           get UID 0 access and is a member of the wheel group (or the group
           of the group option), deny access. Conversely, if the user is not
           in the group, return PAM_IGNORE (unless trust was also specified,
           in which case we return PAM_SUCCESS).

group=name

Instead of checking the wheel or GID 0 groups, use the name group
           to perform the authentication.

root_only

The check for wheel membership is done only when the target user
           UID is 0.

trust

The pam_wheel module will return PAM_SUCCESS instead of PAM_IGNORE
           if the user is a member of the wheel group (thus with a little
           play stacking the modules the wheel members may be able to su to
           root without being prompted for a passwd).

use_uid

The check will be done against the real uid of the calling
           process, instead of trying to obtain the user from the login
           session associated with the terminal in use.

6.40.3. MODULE TYPES PROVIDED

The auth and account module types are provided.

6.40.4. RETURN VALUES

PAM_AUTH_ERR

Authentication failure.

PAM_BUF_ERR

Memory buffer error.

PAM_IGNORE

The return value should be ignored by PAM dispatch.

PAM_PERM_DENY

Permission denied.

PAM_SERVICE_ERR

Cannot determine the user name.

PAM_SUCCESS

Success.

PAM_USER_UNKNOWN

User not known.

6.40.5. EXAMPLES

The root account gains access by default (rootok), only wheel members can
   become root (wheel) but Unix authenticate non-root applicants.

su      auth     sufficient     pam_rootok.so
 su      auth     required       pam_wheel.so
 su      auth     required       pam_unix.so

6.40.6. AUTHOR

pam_wheel was written by Cristian Gafton <gafton@redhat.com>.

6.41. pam_xauth - forward xauth keys between users

pam_xauth.so [ debug ] [ xauthpath=/path/to/xauth ] [ systemuser=UID ] [
   targetuser=UID ]

6.41.1. DESCRIPTION

The pam_xauth PAM module is designed to forward xauth keys (sometimes
   referred to as "cookies") between users.

Without pam_xauth, when xauth is enabled and a user uses the su(1) command
   to assume another user's privileges, that user is no longer able to access
   the original user's X display because the new user does not have the key
   needed to access the display. pam_xauth solves the problem by forwarding
   the key from the user running su (the source user) to the user whose
   identity the source user is assuming (the target user) when the session is
   created, and destroying the key when the session is torn down.

This means, for example, that when you run su(1) from an xterm session,
   you will be able to run X programs without explicitly dealing with the
   xauth(1) xauth command or ~/.Xauthority files.

pam_xauth will only forward keys if xauth can list a key connected to the
   $DISPLAY environment variable.

Primitive access control is provided by ~/.xauth/export in the invoking
   user's home directory and ~/.xauth/import in the target user's home
   directory.

If a user has a ~/.xauth/import file, the user will only receive cookies
   from users listed in the file. If there is no ~/.xauth/import file, the
   user will accept cookies from any other user.

If a user has a .xauth/export file, the user will only forward cookies to
   users listed in the file. If there is no ~/.xauth/export file, and the
   invoking user is not root, the user will forward cookies to any other
   user. If there is no ~/.xauth/export file, and the invoking user is root,
   the user will not forward cookies to other users.

Both the import and export files support wildcards (such as *). Both the
   import and export files can be empty, signifying that no users are
   allowed.

6.41.2. OPTIONS

debug

Print debug information.

xauthpath=/path/to/xauth

Specify the path the xauth program (it is expected in
           /usr/X11R6/bin/xauth, /usr/bin/xauth, or /usr/bin/X11/xauth by
           default).

systemuser=UID

Specify the highest UID which will be assumed to belong to a
           "system" user. pam_xauth will refuse to forward credentials to
           users with UID less than or equal to this number, except for root
           and the "targetuser", if specified.

targetuser=UID

Specify a single target UID which is exempt from the systemuser
           check.

6.41.3. MODULE TYPES PROVIDED

Only the session type is provided.

6.41.4. RETURN VALUES

PAM_BUF_ERR

Memory buffer error.

PAM_PERM_DENIED

Permission denied by import/export file.

PAM_SESSION_ERR

Cannot determine user name, UID or access users home directory.

PAM_SUCCESS

Success.

PAM_USER_UNKNOWN

User not known.

6.41.5. EXAMPLES

Add the following line to /etc/pam.d/su to forward xauth keys between
   users when calling su:

session  optional  pam_xauth.so

6.41.6. AUTHOR

pam_xauth was written by Nalin Dahyabhai <nalin@redhat.com>, based on
   original version by Michael K. Johnson <johnsonm@redhat.com>.

Chapter 7. See also

* The Linux-PAM Application Writers' Guide.

* The Linux-PAM Module Writers' Guide.

* The V. Samar and R. Schemers (SunSoft), ``UNIFIED LOGIN WITH PLUGGABLE
       AUTHENTICATION MODULES'', Open Software Foundation Request For
       Comments 86.0, October 1995.

Chapter 8. Author/acknowledgments

This document was written by Andrew G. Morgan (morgan@kernel.org) with
   many contributions from Chris Adams, Peter Allgeyer, Tim Baverstock, Tim
   Berger, Craig S. Bell, Derrick J. Brashear, Ben Buxton, Seth Chaiklin,
   Oliver Crow, Chris Dent, Marc Ewing, Cristian Gafton, Emmanuel Galanos,
   Brad M. Garcia, Eric Hester, Michel D'Hooge, Roger Hu, Eric Jacksch,
   Michael K. Johnson, David Kinchlea, Olaf Kirch, Marcin Korzonek, Thorsten
   Kukuk, Stephen Langasek, Nicolai Langfeldt, Elliot Lee, Luke Kenneth
   Casson Leighton, Al Longyear, Ingo Luetkebohle, Marek Michalkiewicz,
   Robert Milkowski, Aleph One, Martin Pool, Sean Reifschneider, Jan
   Rekorajski, Erik Troan, Theodore Ts'o, Jeff Uphoff, Myles Uyema, Savochkin
   Andrey Vladimirovich, Ronald Wahl, David Wood, John Wilmes, Joseph S. D.
   Yao and Alex O. Yuriev.

Thanks are also due to Sun Microsystems, especially to Vipin Samar and
   Charlie Lai for their advice. At an early stage in the development of
   Linux-PAM, Sun graciously made the documentation for their implementation
   of PAM available. This act greatly accelerated the development of
   Linux-PAM.

Chapter 9. Copyright information for this document

Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are
   met:

1. Redistributions of source code must retain the above copyright
    notice, and the entire permission notice in its entirety,
    including the disclaimer of warranties.

2. Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

3. The name of the author may not be used to endorse or promote
    products derived from this software without specific prior
    written permission.

Alternatively, this product may be distributed under the terms of the GNU
   General Public License (GPL), in which case the provisions of the GNU GPL
   are required instead of the above restrictions. (This clause is necessary
   due to a potential bad interaction between the GNU GPL and the
   restrictions contained in a BSD-style copyright.)

THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
 TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH

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