WU-FTPD core dump vulnerability (the old patch doesn't work)

Description:A common problem with many OS's is that you can cause ftpd (or other network services) to crash and find remnants of the shadowed password file in the resultant corefile. wu-ftpd was patched, but is apparently still broken.
Author:Vadim Kolontsov <vadim@tversu.ac.ru>
Compromise:read crypt(8)ed passwords, which could lead to root (local)
Vulnerable Systems:Systems running wu-ftpd v2.1, 2.2, 3.0, possibly others.
Date:13 April 1997

Date: Sun, 13 Apr 1997 11:34:46 +0400
From: Vadim Kolontsov 
Reply-To: best-of-security@suburbia.net
To: best-of-security@suburbia.net
Subject: BoS:  ftpd bug (yes, again..)
Resent-Date: Sun, 13 Apr 1997 19:27:50 +1000 (EST)
Resent-From: best-of-security@suburbia.net


  do you remeber a bug with "argc > 100" in ftpd_popen(), when users was
able to kill your ftpd to produce core dump with shadow password? Ok, this 
(which was reported when 2.1 was the latest release) still presents
in 2.2 & 3.0
  Yes, ftpd was patched, but incompletely. It seems that this patches was 
never tested (although I didn't check a patch against "kill -11" yet)

  Here is an additional patch for 3.0's ftpd

============================== cut here ================================
*** popen.c.old Sun Apr 13 11:22:59 1997
--- popen.c     Sun Apr 13 11:23:16 1997
*** 95,101 ****
        /* glob each piece */
        gargv[0] = argv[0];
!       for (gargc = argc = 1; argv[argc] && gargc < (MAXGLOBARGS-1); argc++) 
                glob_t gl;
--- 95,101 ----
        /* glob each piece */
        gargv[0] = argv[0];
!       for (gargc = argc = 1; argv[argc] && gargc < (MAXGLOBARGS-1) && argc 
< MAXUSRARGS; argc++) {
                glob_t gl;
============================== cut here ================================
  See the source code to understand why previous patch was incomplete -
it's easy...
  BTW, wu-ftpd latest beta (13) still can be killed in this way... although
wu-ftpd's maintainer was informed by me about 3 monthes ago.

With best regards, Vadim.

P.S. to test ftpd, do the following:

telnet your.host 21
user ftp (or your userid, if you have no anonymous ftp)
pass ftp@ (or your password)
list x x x x x x x x x x x ... (around 3 lines will be enough ;)

Bugged ftpdwill die here - "Connection closed by foreigh host".
Now look for core dump, extract password, start your Crack :)
Vadim Kolontsov                                          SysAdm/Programmer 
Tver Regional Center of New Information Technologies          Networks Lab

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