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.
The following flags are supported:
Turns on debugging messages sent to syslog.
Evaluate conditions using the account of the user whose UID the application is running under instead of the user being authenticated.
Don't log failure or success to the system log.
Don't log failure to the system log.
Don't log success to the system log.
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[:group:....]
User is in given group(s).
user notingroup group[:group:....]
User is not in given group(s).
user innetgr netgroup
(user,host) is in given netgroup.
user notinnetgr group
(user,host) is not in given netgroup.
The condition was true.
The condition was false.
A service error occurred or the arguments can't be parsed correctly.
To emulate the behaviour of pam_wheel, except there is no fallback to group 0 being only approximated by checking also the root group membership:
auth required pam_succeed_if.so quiet user ingroup wheel:root
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...