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Re: a few bugs ...
From: drow () FALSE ORG (Daniel Jacobowitz)
Date: Mon, 20 Mar 2000 21:00:08 -0500


On Fri, Mar 17, 2000 at 10:07:45AM +0100, Michal Zalewski wrote:
3. ntalkd from redhat distri or debian... in old version ( <=5.2rh and
<=2.0db) (I don't want to be wrong so I will not write it's version -
aleph bounced;P sic! ) it's known and patched but there wasn't
official post and it may be dangerous. There is fprintf() without
format. Another hard to exploit bug :)

Aham. According to ChangeLog:

26-Nov-1998:
        Fixed bug: the talkd announce message is passed as the format
          string to fprintf, so if it has %'s in it, we probably crash.

Announce message (assembled in ntalkd/announce.c) contains remote username
and remote hostname information, as well as some hardcoded texts like
"Talk request from...". Take a note - we're talking about fprintf, so,
assuming there's no interesting data in daemon address space (I don't
think so - it is not performing any authorization, etc, only reads utmp
entries), I don't think it might lead to anything except crash. And, as
it's started from inetd, I don't think it might have any security
implications ;)

Btw. Aleph, some time ago I described proftpd crash problem with LIST
parameter. Instead of playing with FUD, I've done some debugging and
realized it won't be _probably_ exploitable. As the result, you bounced
this post, but approved this one - for sure overFUDed ;>

Actually, it was exploitable, if you are referring to the
username-passed-in-format-string bit.  In my efforts for
crack.linuxppc.org (which I have not gotten around to writing up yet,
but will - there were a few interesting tidbits), I used that for two
tricks: to gain root access within the chroot and to disable dropping
of capabilities.

Dan

/--------------------------------\  /--------------------------------\
|       Daniel Jacobowitz        |__|        SCS Class of 2002       |
|   Debian GNU/Linux Developer    __    Carnegie Mellon University   |
|         dan () debian org         |  |       dmj+ () andrew cmu edu      |
\--------------------------------/  \--------------------------------/


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