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Re: sshd1 allows unencrypted sessions regardless of server policy
From: jmoran () IPASS NET (Joseph Moran)
Date: Wed, 15 Dec 1999 01:06:24 -0500


On Tue, 14 Dec 1999, Pavel Machek wrote:

Because passphrase-less hostkeys are 'encrypted' with cipher "none"
the code for this cipher is always compiled into the programs.  This
way the client is free to choose "none" and no server will complain.

And what? Malicious ssh client can make non-encrypted connection. But
malicious ssh client can also send carbon-copy of all communication to
www.cia.org:5000! There's no way to protect from malicious ssh
clients...

Of course, but that's no excuse for a lapse in good programming.  If the
server tells the client "here, pick from this list", it's common sense
that the server would check the client's response to see if it's valid.

That aside, this hole could be useful in a situation where Party A wants
to help Party B compromise a system without leaving a paper trail.  Party
A trojans an ssh client binary, Innocent Bystander C does an ssh
connection somewhere, and Party B sniffs the cleartext traffic.  No
evidence to point to Party B.  If instead Party A trojaned the binary to
send Party B a carbon-copy, and a white hat could extract this, then Party
B is implicated.

jm


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