Bug 507727 - setuid/setgid programs execed by straced process don't change user/group
setuid/setgid programs execed by straced process don't change user/group
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
All Linux
low Severity medium
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Assigned To: Kernel Maintainer List
Fedora Extras Quality Assurance
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Reported: 2009-06-23 17:58 EDT by Orion Poplawski
Modified: 2010-06-28 09:15 EDT (History)
4 users (show)

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Last Closed: 2010-06-28 09:15:57 EDT
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Description Orion Poplawski 2009-06-23 17:58:13 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):
Comment 1 Denys Vlasenko 2009-07-07 10:18:14 EDT
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.
Comment 2 Orion Poplawski 2009-07-07 10:33:27 EDT
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.
Comment 3 Denys Vlasenko 2009-07-09 09:56:43 EDT
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.
Comment 4 Andreas Schwab 2009-08-05 06:18:24 EDT
This needs to be fixed in the kernel.
Comment 5 Bug Zapper 2010-04-27 11:12:57 EDT
This message is a reminder that Fedora 11 is nearing its end of life.
Approximately 30 (thirty) days from now Fedora will stop maintaining
and issuing updates for Fedora 11.  It is Fedora's policy to close all
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Comment 6 Bug Zapper 2010-06-28 09:15:57 EDT
Fedora 11 changed to end-of-life (EOL) status on 2010-06-25. Fedora 11 is 
no longer maintained, which means that it will not receive any further 
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of 
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