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Date:      Thu, 31 May 2001 18:46:05 -0700
From:      "Crist Clark" <crist.clark@globalstar.com>
To:        "Karsten W. Rohrbach" <karsten@rohrbach.de>
Cc:        "f.johan.beisser" <jan@caustic.org>, Alex Holst <a@area51.dk>, freebsd-security@FreeBSD.ORG
Subject:   Re: Apache Software Foundation Server compromised, resecured. (fwd)
Message-ID:  <3B16F3DD.E57AF761@globalstar.com>
References:  <Pine.BSF.4.21.0105311727160.66343-100000@pogo.caustic.org> <3B16E7D9.3E9B78FF@globalstar.com> <20010601031131.K85717@mail.webmonster.de>

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"Karsten W. Rohrbach" wrote:
> 
> Crist Clark(crist.clark@globalstar.com)@2001.05.31 17:54:49 +0000:
> > *sigh*
> >
> > You cannot 'record passphrases.' RSA authentication uses public key
> > cryptography. The client, the person logging in, proves it knows a
> > secret, the private key, without ever revealing it to the server who
> > only knows the public key.
> >
> *sigh*
> 
> fopen() does not have rsa support (thank god)
> btw, the ssh-agent(1) holds the _decrypted_ key you opened with
> ssh-add(1), entering your passphrase that went via a fd from ssh-askpass
> to ssh-add.

Yep. It does. So?

> > The use of public key crypto allows you to log into potentially
> > untrusted servers without revealing your secret.
> hopping a host you got to take care of the ssh binary handling your
> auth token connecting to another - untrusted - server. thus, the binary
> is also potentially untrusted.
> also the ssh ForwardAgent option is potentially dangerous, then.
> portforwarding, too.

You misunderstand what agent forwarding is. Your private RSA key does
NOT leave your local machine. Agent forwarding means that remote requests
for the agents help will be forwarded to the local machine. When you
are logged into a remote machine and do some action that requires the
agent's help, the data is forwarded to the local agent, it does whatever
magic is done, and the result of the action is passed back along to 
the remote machine. Note, the _result of the action_ is passed along,
your private key is NOT passed to the remote server.

Read the Ylonen SSH draft, specifically the section, "The Authentication 
Agent Protocol," for details.
-- 
Crist J. Clark                                Network Security Engineer
crist.clark@globalstar.com                    Globalstar, L.P.
(408) 933-4387                                FAX: (408) 933-4926

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