[AG-TECH] AG/OpenSSH vulnerability

Stuart Levy slevy at ncsa.uiuc.edu
Mon Jan 7 20:01:14 CST 2002

It looks like the CIAC people are using some sort of
blunt-instrument approach.  The ssh1 crc32 vulnerability
is certainly serious, but there are implementations of ssh1 protocol
which *do* fix it, including:

    openssh after about 2.3, i.e. all current openssh's

The openssh web site explicitly says that they've fixed the
ssh1 crc32 problem (and others that aren't likely to affect AG users).

So I don't think there's any essential reason to disable ssh1,
*so long as* you've upgraded to one of the safe implementations,
like Bob's openssh-3.0.2 bundle.


	(details of crc32-compensation-integer-overflow hole,
	 with pointers to vendor web pages)

	(summary of ssh vulnerabilities)

	(review of openssh's status with respect to
	  assorted vulnerabilities)

There is apparently a problem in the ssh1 protocol where,
if a client doesn't know the server's host key (or can be 
tricked into believing that it's changed), that a session could
be hijacked if someone can catch your traffic and process it before
it goes to the designated server.  That could be serious, though
it's not the kind of thing that lets random people break into your AG box
from outside.


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