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Re: man bugs might lead to root compromise (RH 6.1 and other boxes)
From: aleph1 () SECURITYFOCUS COM (Elias Levy)
Date: Wed, 1 Mar 2000 11:59:37 -0800


Summary of comments on ths thread:

"Dehner, Ben" <Btd () valmont com>:

HPUX 10.20 also does not have suid/sgid /usr/bin/man, so I would guess is
not exploitable.

Thomas Molina <tmolina () home com>:

babcia padlina exploit did not work under RedHat 6.1

Przemyslaw Frasunek <venglin () own3d freebsd lublin pl>:

so try other offsets. -1000 should work on most redhat 6.1/6.0/5.2 boxes.

Stefan Schneider <stefan.schneider () comsat com ve>:

No problems here...

Tested on SuSE 6.3, no SIGSEV either.... The box is a regular SuSE 6.3
install (No patches, fresh install from the CD's) and the package status
is man-db ver 2.3.10-69d69i.

krasel () wpxx02 toxi uni-wuerzburg de (Cornelius Krasel):

SuSE man (at least on SuSE 6.3 which is the same version) uses PAGER
instead of MANPAGER and blissfully crashes when subjected to 4000 'A'
letters in this variable.

I didn't manage to get the redhat exploit to work properly, but I
got several times "sh: =FC=FF=BF: command not found" which indicates to
me that a more skillful programmer than me would be able to get it
to work.

Phil Stracchino <alaric () babcom com>:

Slackware 7.0 does not appear to be vulnerable.  /usr/bin/man is not
setgid in slackware, so although it does indeed SEGV at the expected
location, no privileges are gained.

"Licquia, Jeff" <JLicquia () SpringfieldClinic com>:

On my aforementioned Debian system, this fails with:

sh: AAAA...AAAA: command not found
man: command exited with status 32512: /bin/gzip -dc
'/var/cache/man/cat1/ls.1.gz' | { export MAN_PN LESS; MAN_PN='ls(1)';
LESS="$LESS\$-Pm\:\$ix8mPm Manual page $MAN_PN ?ltline %lt?L/%L.:byte
%bB?s/%s..?e (END):?pB %pB\\%.."; AAAA....AAAA; }

(AAA's truncated for readability)

Greg Olszewski <noop () nwonknu org>:

This does not create a sigsegv on Debian GNU/Linux slink, potato, or woody.
With man -V of:
slink:
man, version 2.3.10, db 2.3.1, July 12th, 1995 (G.Wilford () ee surrey ac uk)
debian version 2.3.10-69FIX.1, (Jun  9 1999),  Fabrizio Polacco
+<fpolacco () debian org>

potato & woody:
man, version 2.3.12, Wed Feb 23 00:00:00 EET 2000 (fpolacco () debian org)

It was tried setting both MANPAGER and PAGER. In each case, 4000 and 20000
were tried, and sh:<a lot of A's> command not found was echoed to stderr.

The lack of a sgid bit on /usr/bin/man is the default configuration
for both potato and woody.

Scott Lamb <slamb () oh yeah org>:

On my RedHat 6.1 system, this does NOT appear to be exploitable. The reason
is: the execution of arbitrary commands is done while processing the troff
macros: while generating the catman pages from the man pages. Merely
viewing the preformatted pages does not allow commands to be executed.

So it is not exploitable without access to the man (*.[1-9]) pages. On
RedHat 6.1, these are owned by root. Exploiting the buffer overflow in
man gives you a chance to be annoying and send nasty messages to people when
they run man, but not gain root priveleges.

Bob Billson <bob () goleader com>:

Same here on two different Linux boxen, running Debian (Slink and
Potato).

H D Moore <hdm () secureaustin com>:

I tested this on a stock RedHat 6.1 box and it wouldnt segfault unless
at least 4534 characters were in the buffer.  With some twiddling on the
command line I got it to jump to arbitrary addresses with:

$ MANPATH=`perl -e 'print "A" x 4534 . "BBBB"'`

^-- this makes jump to 0x42424242

Anyways, anyone feel like writing an exploit?

Julian Squires <tek () wiw org>:

I could equally not reproduce this on several Debian machines,
running:
man, version 2.3.10, db 2.3.1, July 12th, 1995 (G.Wilford () ee surrey ac uk)
        debian version 2.3.10-69s, (Oct 28 1999),  Fabrizio Polacco <fpolacco () debian org>

as well as:
man, version 2.3.10, db 2.3.1, July 12th, 1995 (G.Wilford () ee surrey ac uk)
        debian version 2.3.10-71, (Feb 11 2000),  Fabrizio Polacco <fpolacco () debian org>

/usr/bin/man is setuid man under debian, and I attempt with both
PAGER and MANPAGER variables, with strings up to 65536 bytes in length.

What version of man is vulnerable to this?

Marcin Owsiany <porridge () pandora info bielsko pl>:

Tested on Debian potato

ii  man-db         2.3.12         Display the on-line manual.

and slink (2.1)

ii  man-db          2.3.10-69FIX.1 Display the on-line manual.

both PAGER and MANPAGER set to a length from 400 to 40000 Bytes.
No SIGSEGV

Dylan Griffiths <Dylan_G () bigfoot com>:

Slackware Linux 7.0 is not setgid man, and the /var/man/cat directories are
owned root.root, but have the same sticky bit as the /tmp directory.
So Slackware is likely secure from any man exploits.

Kris Kennaway <kris () hub freebsd org>

FreeBSD uses the GNU man code, but it seems we fixed this (along with a
bunch of other overflows) back in '96..

From: Luca Berra <bluca () comedia it>:

this is man_db a different program than standard linux man.
past versions had bugs of their own, check bugtraq archives

Thomas Bader <thomasb () trash net>:

I could not reproduce this too. I'm using Debian GNU/Linux 2.1 .
"man --version" says:

| man, version 2.3.10, db 2.3.1, July 12th, 1995 (G.Wilford () ee surrey ac uk)
|       debian version 2.3.10-68, (Oct  6 1998),  Fabrizio Polacco <fpolacco () debian org>

And "ls -l /usr/bin/man" says:

|-rwsr-xr-x   1 man      root       119864 Oct  6  1998 /usr/bin/man

I tried the enviroments PAGER and MANPAGER, but they both didn't work.


--
Elias Levy
SecurityFocus.com
http://www.securityfocus.com/



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