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 console.

           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 service+type.

           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 obtains.

           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.

           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.

           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).

           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:

           [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

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

       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).

       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
       tarball Linux-PAM-1.3.0.tar.bz2 fetched from
       ⟨⟩ on 2020-11-01.  If you discover
       any rendering problems in this HTML version of the page, or you be‐
       lieve 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

Linux-PAM Manual                 04/01/2016                      PAM.CONF(5)

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