openssh unix dev - Jul 2002 - [Bug 354] New: sshd with privsep doesn't do pam session setup properly

http://bugzilla.mindrot.org/show_bug.cgi?id=354

           Summary: sshd with privsep doesn't do pam session setup properly
           Product: Portable OpenSSH
           Version: -current
          Platform: ix86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: sshd
        AssignedTo: openssh-unix-dev at mindrot.org
        ReportedBy: rudolph at getsystems.com


when logging in to an openssh >=3.4p1 sshd (I haven't tested earlier than
that,
but I have tested up to the snapshot from the 14/7/2002) setrlimit, through the
pam session setup, isn't called in the appropriate place to allow specified
users to have higher ulimits than the server is started with. This ought to
work, as pam limits are allowed to specify arbitrarily high limits for users
listed. The problem appears to be that do_pam_session is being called after we
drop to the user's uid. Without privsep turned on, this all work, as we drop
to
the user's uid after do_pam_session. Specifically: with privsep on,
do_setusercontext in privsep_postauth (sshd.c) is called before do_pam_session
in do_exec_pty (session.c). Without privsep, we only drop root privs in do_child
(session.c), which is after we do_exec_pty, since (obviously) the former
code/call to do_setusercontext is unreached.
A possible (does appear to work, though not properly tested) solution is to
simply call do_pam_session in privsep_postauth before the do_setusercontext
call, though I am unsure of the ramifications of this.



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