Red Hat Bugzilla – Bug 507727
setuid/setgid programs execed by straced process don't change user/group
Last modified: 2010-06-28 09:15:57 EDT
Description of problem:
I'm trying to trace a problem in a program than spawns sendmail. Unfortunately, sendmail needs to run setgid smmsp, but I get the following:
WARNING: RunAsUser for MSP ignored, check group ids (egid=6, want=51)
because when run under strace, it doens't change the egid.
I'm running the following command:
/usr/sbin/setuidstrace -f -o amreport.strace su amandabackup -c '/usr/sbin/amreport Offsite -l /var/lib/amanda/Offsite/log.20090620110551.0'
# ls -ld /usr/sbin/setuidstrace
-rwsr-sr-x. 1 root root 294440 2009-06-23 15:34 /usr/sbin/setuidstrace
Unfortunately, amreport has to be run with the proper uid/gid combo as well.
Version-Release number of selected component (if applicable):
Not a bug.
If user would be able to ptrace setuid program and still have it change its uid, then user can alter this program's behavior. As in: "overwrite /etc/passwd".
This would be a security breach.
I'm not talking about any user running strace, just root, which I guess I didn't state above. The first setuid/gid works, but if it spawns a second setuid/gid program, that doesn't work.
I think it's possible to relax the restriction that kernel ignores setuig/gid bits in execve if process is ptraced: if we can see that tracer process is privileged enough, then we can allow it.
If this is acceptable at all, it is to be done in kernel code, not in strace.
This needs to be fixed in the kernel.
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