bugtraq - Re: from bugtraq: HP-UX 11.0 /usr/bin/kermit (fwd)

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Message-ID: <CMM.0.91.0.1051902713.fdc@watsol>
Date: Fri, 2 May 2003 15:11:53 EDT
From: Frank da Cruz <fdc@...umbia.edu>
To: frank goossens <frank@...gonet.be>
Subject: Re: from bugtraq: HP-UX 11.0 /usr/bin/kermit (fwd)


> don't know if you have been involved already..
> 
No, this is the first I've seen of it; thanks for sending it along.

On Fri, 2 May 2003 19:49:03 +0300 bt@...fi.lt wrote to
bugtraq@...urityfocus.com:

> Hi!
> 
> There are many buffer overflows in kermit on HP-UX 11.0 . I am sure it is
> vulnerable in other HP-UX versions, too, since "C-Kermit 6.0.192, 6 Sep 96,
> for HP-UX 10.00" is installed in HP-UX 11.0 by default.
> 
These were fixed for C-Kermit 8.0 long ago.  The current release of C-Kermit
is 8.0.209.  As far as I know, HP ships C-Kermit 8.0.200 or later with all
HP-UX 11.xx's.  I suspect anybody who has "C-Kermit 6.0.192, 6 Sep 96, for
HP-UX 10.00" on HP-UX 11.00 or later must have upgraded their HP-UX version
without also upgrading Kermit.  If you have an older version of C-Kermit on
ANY release of HP-UX all the way back to 5.21, you can get the current
release here:

  http://www.columbia.edu/kermit/ckermit.html

> /usr/bin/kermit is setuid to bin and setgrp to daemon, so upon succesfull
> exploitation, local user could get these priviledges.
> 
The setuid/setgid are required for all HP-UX programs that access serial 
ports.

> Example of on simple buffer overflow in kermit :
> $ /usr/bin/kermit -C "ask `perl -e 'print "A" x 120'`"
> Executing /usr/share/lib/kermit/ckermit.ini for UNIX...
> Good Evening.
> Segmentation fault (core dumped)
> 
The syntax for the ASK command requires a variable name after the word ASK.
Anyway, try it in C-Kermit 8.0:

  /usr/bin/kermit -C "ask foo `perl -e 'print "A" x 800'`"

If you increase 800 to some bigger number, the string is properly cut off
at the end of the ASK prompt buffer.

> There are more kermit commands that are unchecked of correct parameter
> length: askq,define, assign, getc. Several of them use the same vulnerable
> function "doask". I am SURE that these are not all vulnerabilities in
> kermit.
> 
A thorough buffer-overflow / memory-leak audit was performed for
C-Kermit 8.0 in early-mid 2000, and it was in public Alpha test before
the end of 2000.

> one more thing (I am not sure if it is exploitable,but anyway):
> [/home/xxxxxxxxxx] C-Kermit>set alarm %:%:%
> Floating point exception (core dumped)
> 
> Solution - take off setuid bits form /usr/bin/kermit.
>  
Solution: use current version.

> In my opinion, patching kermit against these(and maybe many more)
> vulnerabilities is not an option, since source of C-kermit 6.0.192 is
> publicly available, and it is very buggy.
> 
C-Kermit is maintained by the Kermit Project.  Users don't have to "patch"
it.  If you give a HELP command, it says (among other things):

  Type SUPPORT to learn how to get technical support.

Then if you give a SUPPORT command it tells you how to report problems.

> I tried to contact security-alert@...com, but i got error message "Client
> host rejected: Access denied" (spam?).
>
This topic was hashed over three years ago in Linux Bugtraq; C-Kermit 8.0
was released and furnished to HP in 2001.

Frank da Cruz
The Kermit Project
Columbia University
612 West 115th Street
New York NY  10025-7799
USA
Email: fdc@...umbia.edu
http://www.columbia.edu/kermit/