Re: Linux UID/GID 'Feature'

[morgan () PARC POWER NET (Andrew G. Morgan)]

Jon Lewis wrote:
> This looks like Red Hat PAM breakage.  I verified it works (gives root) on
> my Red Hat 4.1 box, but it does not on any of my Slackware based boxes
> that are shadow upgraded.

As has been pointed out, it is actually a libc problem.  The pam_unix_....so
modules use libc, so these modules will exhibit this unfortunate behavior.
Admins should beware that if libc has a hand in the process of changing a
user's password the corresponding UID entry in /etc/passwd will be
explicitly reset to 0.

Fortunately, pam_pwdb (a plug-in replacement for pam_unix_..), which does
not use libc for any authentication related actions, does not suffer from
this problem.  So Linux-PAM based systems can be made resistant to this
"administrative problem" by putting pam_pwdb in all the places that their
pam configuration refers to pam_unix_...

PS.  I'd really like to hear from anyone that _can_ break Linux-PAM in any
way...  [Use the "source" (Luke ;^)]

Cheers

Andrew
--
               Linux-PAM, libpwdb, Orange-Linux and Linux-GSS
                  http://parc.power.net/morgan/index.html