Bug 4389 - /usr/libexec/pt_chown doesn't have to be setuid root
/usr/libexec/pt_chown doesn't have to be setuid root
Status: CLOSED CURRENTRELEASE
Product: Red Hat Linux
Classification: Retired
Component: glibc (Show other bugs)
6.0
All Linux
medium Severity medium
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Assigned To: Cristian Gafton
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Depends On:
Blocks:
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Reported: 1999-08-06 00:33 EDT by wingc
Modified: 2008-05-01 11:37 EDT (History)
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Doc Type: Bug Fix
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Last Closed: 1999-08-16 14:29:21 EDT
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Description wingc 1999-08-06 00:33:54 EDT
The program /usr/libexec/pt_chown is setuid to root on Red
Hat 6.0. This is unnecessary if you are using Unix98-style
ptys with devfs, which is how Red Hat 6.0 is set up by
default.

In fact, pt_chown doesn't seem to be used at all-- for
instance, 'strace xterm' reveals that only /dev/ptmx is used
and no attempt to look for or execute /usr/libexec/pt_chown
is made.

I've taken the setuid bit off it on my systems with no ill
effects.

In the interest of removing all unncecessary setuid
programs, I would recommend leaving the setuid bit off
pt_chown in future releases of Red Hat.

Thanks,

Chris Wing
wingc@engin.umich.edu
Comment 1 Cristian Gafton 1999-08-10 21:50:59 EDT
The binary has to be setuid root for the apps that are using UNix98
ptys and have no root priviledges - unlike xterm.
Comment 2 wingc 1999-08-10 22:24:59 EDT
a1% rpm -q redhat-release
redhat-release-6.0-1
a1% ls -l `which xterm`
-rwxr-xr-x   2 root     root       249024 Jun 14 13:53
/usr/X11R6/bin/xterm

One of the main benefits of Unix98 ptys is that you don't need to be
setuid root to use them; the devpts filesystem automatically fills in
the uid and gid of the pty to match that of the process which
requested it via /dev/ptmx:

from /usr/src/linux/fs/devpts/inode.c: devpts_pty_new():
|
|  inode->i_uid = sbi->setuid ? sbi->uid : current->fsuid;
|  inode->i_gid = sbi->setgid ? sbi->gid : current->fsgid;

The only reason why you'd need to keep pt_chown set-uid to root is if
you are using glibc2.1 applications without Unix98 ptys; this isn't
the case on RedHat 6.0, and hopefully won't be in the future.

So, I'd recommend stomping out another unnecessary set-uid root
program :)

Thank you very much,

Chris Wing
wingc@engin.umich.edu
Comment 3 Cristian Gafton 1999-08-16 14:29:59 EDT
Fixed in glibc-2.1.2-5  and later

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