Re: ipop3d (x2) / pine (x2) / Linux kernel (x2) / Midnight

[viktor () DTEK CHALMERS SE (Viktor Fougstedt)]

On Tue, 6 Apr 1999, Stefan Rompf wrote:

> > Exploited overflow in ipop3d could be used to gain superuser access (the
> > only thing done by ipop3d is setuid+setgid, no seteuid/setreuid).
>
> Fortunately, you are wrong here. Quoting from the Solaris' setuid() manpage:
>
>     If the effective user ID of the process calling setuid()  is
>     the  super-user, the real, effective, and saved user IDs are
>     set to the uid parameter.

You make an important point.

In fact I have several times seen the opposite problem to what which
the original poster suggested. Some programs running setuid root only
does a seteuid(), which does not touch the saved-user-id. The
programmers have done this in the belief that it drops all root
priviledges (the programs did not need to re-aquire priviledges at a
later time, and the comments in the code suggested that the call's
intention was to get rid of all priviledges).

These programs should probably do a setuid() instead, which affects
saved-user-id as well.

This problem isn't huge, you might say, because whenever you do a
fork() or similar, the saved-user-id should be reset. But if you can
take control of the application via a buffer overflow or the like, and
saved-user-id is root then you have no problem of getting the root
priviledges back before doing a fork().

Just my $.02 worth.


/Viktor...

--|     Viktor Fougstedt, system administrator at dtek.chalmers.se     |--
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