Full Disclosure mailing list archives
Re: No Subject (re: openssh exploit code?)
From: Valdis.Kletnieks () vt edu
Date: Tue, 21 Oct 2003 10:34:29 -0400
On Tue, 21 Oct 2003 00:22:53 PDT, mitch_hurrison () ziplip com said:
As far as it being "easy" to exploit. No it isn't. You have to abuse a lesser issue, a memory leak to be more precise, to get a heap layout that will allow you to survive the initial memset without landing in bad memory. Now without going into details anyone who manages to survive the initial memset should be able to debug the crash to the point of exploitation. This is managable on atleast Linux IA32 systems.
On Tue, 21 Oct 2003 09:21:26 +0200, Michal Zalewski said:
While I'd hate to take sides on the OpenSSH vulnerability, this alone is not a problem. On little endian machines, other than overwriting (zeroing) variables, you can also benefit from partial pointer overwrite, something you really should be aware of before getting in such a flame war. By zeroing least significant bytes of certain user pointers on the heap, or by overwriting certain malloc structures, it is possible to trigger writes to other, somewhat controlled areas of the heap whenever the pointer is written or freed, spoof contents when it is read, etc.
This makes it (sometimes) possible to point the code to a buffer created previously, for which you control the contents, and can follow the same procedure, now controlling the entire pointer (or pursue other,> application-specific vectors), triggering writes to stack or such, at which point, you are home.
These paragraphs do more to convince me that the exploit is possible than all the rest of the flame war put together. Thanks, both of you.
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- Re: No Subject (re: openssh exploit code?), (continued)
- Re: No Subject (re: openssh exploit code?) Paul Schmehl (Oct 20)
- Re: No Subject (re: openssh exploit code?) security snot (Oct 21)
- Re: No Subject (re: openssh exploit code?) John Sage (Oct 21)
- Re: No Subject (re: openssh exploit code?) madsaxon (Oct 21)
- Re: No Subject (re: openssh exploit code?) Paul Schmehl (Oct 20)
- Re: No Subject (re: openssh exploit code?) mitch_hurrison (Oct 21)
- Re: No Subject (re: openssh exploit code?) Anders B Jansson (Oct 21)
- Re: No Subject (re: openssh exploit code?) S . f . Stover (Oct 21)
- Re: No Subject (re: openssh exploit code?) Jason Coombs (Oct 21)
- Re: No Subject (re: openssh exploit code?) morning_wood (Oct 21)
- Re: No Subject (re: openssh exploit code?) Jason Coombs (Oct 21)
- Re: No Subject (re: openssh exploit code?) Valdis . Kletnieks (Oct 21)
- Re: No Subject (re: openssh exploit code?) Peter Busser (Oct 22)
- RE: No Subject (re: openssh exploit code?) Schmehl, Paul L (Oct 21)
- RE: No Subject (re: openssh exploit code?) Schmehl, Paul L (Oct 21)
- RE: No Subject (re: openssh exploit code?) Brent J. Nordquist (Oct 21)
- RE: No Subject (re: openssh exploit code?) mitch_hurrison (Oct 21)
- RE: No Subject (re: openssh exploit code?) Schmehl, Paul L (Oct 21)
- RE: No Subject (re: openssh exploit code?) Montana Tenor (Oct 21)
- RE: No Subject (re: openssh exploit code?) Ted Unangst (Oct 21)
- Re: No Subject (re: openssh exploit code?) Benjamin Krueger (Oct 21)
- Re: No Subject (re: openssh exploit code?) Shawn McMahon (Oct 22)
- RE: No Subject (re: openssh exploit code?) Montana Tenor (Oct 21)