Bugtraq mailing list archives
Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service)
From: avalon () COOMBS ANU EDU AU (Darren Reed)
Date: Sat, 9 Jan 1999 01:39:09 +1100
On Tue, 5 Jan 1999, D. J. Bernstein wrote:
Venema further claims that ``a set-uid posting program cannot guarantee user identification.'' That claim is false. The user id is provided by the standard UNIX getuid() system call.
Just to be pedantic, Venema is correct. "User identification" is a lot more than just a getuid() system call as I'm sure you would be well aware. If I find some other avenue to obtain a different uid to the one I normally use, i.e. exploit some other setuid-root program, getuid() will (if I've done my homework) thereafter fail to identity correctly which user is sending the email. A userid is provided by getuid() but it does not identify the user, just the system's internal owner of the process. Even then, there are better choices than getuid() (depending on your POV) to determine "who" the user "is". For example, in any situation where a password is shared (i.e. the root password), it is not sufficient to identify a user by uid. Maybe getuid() is the "best" you can do, maybe not. A lot of the OS's these days have some sort of audit id which is sometimes less flexible than uid's when it comes to change. When all email is cryptographically signed (and signitures enforced) with keys that are not trivial to guess and aren't easily forged, then we will have a better chance of being assured of a "user's identity".
Current thread:
- Re: Anonymous Qmail Denial of Service D. J. Bernstein (Jan 05)
- setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Ian R. Justman (Jan 06)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Darren Reed (Jan 08)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Nick Maclaren (Jan 08)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Mark Crosbie (Jan 09)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Pete Kruckenberg (Jan 09)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Thamer Al-Herbish (Jan 09)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Len Budney (Jan 08)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Thamer Al-Herbish (Jan 08)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Kragen Sitaker (Jan 09)
- Re: setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Darren Reed (Jan 08)
- setuid vs. setgid (was Re: Anonymous Qmail Denial of Service) Ian R. Justman (Jan 06)
- ff.core exploit on Solaris (2.)7 Daniel J. Frasnelli (Jan 08)
- Re: ff.core exploit on Solaris (2.)7 Casper Dik (Jan 15)