PAM.CONF manpage

Search topic Section

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

       pam.conf, pam.d - PAM configuration files

       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

       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

       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

	   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

		 [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

	       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 \

       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

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

Linux-PAM Manual		  09/19/2013			   PAM.CONF(5)