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
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
This module does not recognise any options.
MODULE TYPES PROVIDED
Only the auth module type is provided.
group membership was granted.
Not all relevant data could be gotten.
Memory buffer error.
Group membership was not granted.
pam_sm_authenticate was called which does nothing.
The user is not known to the system.
Linux-PAM Manual 09/19/2013 PAM_GROUP(8)
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