[CentOS] pam_succeed_if
John Hodrien
J.H.Hodrien at leeds.ac.uk
Fri Jun 10 09:43:37 UTC 2011
On Fri, 10 Jun 2011, John Doe wrote:
> From: Daniel De Marco <ddm at bartol.udel.edu>
>
>> auth required pam_env.so
>> auth sufficient pam_unix.so nullok try_first_pass
>> auth requisite pam_succeed_if.so uid >= 500 quiet
>> auth required pam_deny.so
>> What's the use of the pam_succeed_if line? It will only be reached if
>> the pam_unix doesn't succeed and from my understanding it will prevent
>> system accounts from logging in. Is it useless or am I missing
>> something?
>
> Pure speculation:
> 1. pam_unix just allows/disallows to go further in the checks.
> 2. succeed_if only let users accounts login
> 3. everything else, deny.
Isn't it redundant as is, but makes a whole lot more sense once you have a
network login in there.
If you succeed on pam_unix, you're done. So a local account doesn't need
further checks. The next check ensures that a non-local source (say NIS/LDAP)
doesn't allow logins to system accounts (UID<500). Since you've got none, it
makes no difference, since you either fail on that line, or you fail on the
pam_deny.
Just imagine an ldap lookup after the pam_succeed_if line. It's presumably
left in because it makes authconfig's life easier, and doesn't really matter
anyway.
jh
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