pam.conf(5) — Linux manual page


PAM.CONF(5)                 Linux-PAM Manual                 PAM.CONF(5)

NAME         top

       pam.conf, pam.d - PAM configuration files

DESCRIPTION         top

       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.

       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:

           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

           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.

           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.

           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:

           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.

           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.

           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.

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

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

           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:

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

           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. This is the default action for all
           return codes.

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

           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.

           equivalent to ok with the side effect of terminating the
           module stack and PAM immediately returning to the application
           unless there was a non-ignored module failure before.

       N (an unsigned integer)
           jump over the next N modules in the stack. Note that N equal
           to 0 is not allowed, it would be treated as ignore in such
           case. The side effect depends on the PAM function call: for
           pam_authenticate, pam_acct_mgmt, pam_chauthtok, and
           pam_open_session it is ignore; for pam_setcred and
           pam_close_session it is one of ignore, ok, or bad depending
           on the module's return value.

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

       If a return code's action is not specifically defined via a
       valueN token, and the default value is not specified, that return
       code's action defaults to bad.

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

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

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

           [success=done new_authtok_reqd=done default=ignore]

           [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 user=passwd_query passwd=mada \
                     db=eminence [query=select user_name from internet_service \
                     where user_name='%u' and password=PASSWORD('%p') and \

       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

       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.

SEE ALSO         top

       pam(3), PAM(8), pam_start(3)

COLOPHON         top

       This page is part of the linux-pam (Pluggable Authentication
       Modules for Linux) project.  Information about the project can be
       found at ⟨⟩.  If you have a bug report
       for this manual page, see ⟨//⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-12-18.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Linux-PAM Manual               12/22/2023                    PAM.CONF(5)

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