Re: pam_timestamp internals

[Sebastian Krahmer <krahmer () suse de>]

Hi

On Mon, Mar 31, 2014 at 03:37:02PM +0400, Dmitry V. Levin wrote:
> On Mon, Mar 31, 2014 at 12:57:11PM +0200, Sebastian Krahmer wrote:
> > On Mon, Mar 31, 2014 at 02:32:09PM +0400, Dmitry V. Levin wrote:
> > > On Mon, Mar 24, 2014 at 01:46:43PM +0100, Sebastian Krahmer wrote:
> > > > When playing with some PAM modules for my own projects, I came
> > > > across some implications of pam_timestamp (which is part of
> > > > upstream linux-pam) that should probably be addressed.
> > > >
> > > > Most importantly, there seems to be a path traversal issue:
> > >
> > > Thanks, Sebastian!  The issue has been fixed in upstream linux-pam by commit
> > > https://git.fedorahosted.org/cgit/linux-pam.git/commit/?id=Linux-PAM-1_1_8-32-g9dcead8
> >
> > Thanks for taking care. I was about to write a patch on my own, but seems
> > not necessary anymore.
> >
> > However, I think that
> >
> > +   if (!strlen(tty) || !strcmp(tty, ".") || !strcmp(tty, "..")) {
> >
> > could be insufficient.
>
> There is a code in check_tty() that handles '/':
>       if (strchr(tty, '/') != NULL) {
>               ...
>               tty = strrchr(tty, '/') + 1;
>       }

Ok, I was missing this; so it makes sense to just use strcmp().

> > Any occurence of "." inside tty name should be evil.
>
> Strange - yes, but why evil?

Any strange input in authentication code considered evil. :)

thx,
Sebastian


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~ krahmer () suse de - SuSE Security Team