Hi Tom,
very clever to bridge from the TLS negotiation to the SRP negotiation.
this isn't part of any spec/draft that I remember reading so far, have I
missed that somewhere?
My real concern is that there may be some problem using User authentication
material (name/passwd) for generating shared secret material for the secured
TLS session. This is really just a hunch or gut feeling that security is
somehow lessened by basing it on such a small amount of secret data
(name/passwd). I know that SRP uses random data and both sides generate
some data for the session that will be cleanly destroyed. I just help
thinking that this becomes less secure (though really nice and easy for use
and development and admin!) than using a client key pair. Am I way off
base?
Later,
dj
ps...so when SRP appears in a ciphersuite the telnet can the assume that the
user has been authenticated properly just by virtue of there being a secured
channel (a la TLS) - at that point the user can just be logged right in - is
that correct? very cool.... Kerberos allows auth as one name and login as
another account...that seems like it might be possible here too...I really
liked that feature. :)
--
Derek J. Browne
[EMAIL PROTECTED]
::-----Original Message-----
::From: [EMAIL PROTECTED]
::[mailto:[EMAIL PROTECTED]]On Behalf Of Tom Wu
::Sent: Sunday, March 11, 2001 11:15 PM
::To: Dj Browne
::Cc: [EMAIL PROTECTED]
::Subject: Re: TLS Based on SRP
::
::
::Dj Browne wrote:
::>
::> Also Excellent! Would this be more along the lines of adding it at the
::> application layer (telnet)?
::>
::> Rather than tying this to a particular app protocol I would
::love to see it
::> at the TLS layer so that it generates the pre-master secret directly.
::>
::> When I was thinking about this a while ago I considered doing the SRP
::> seperate from TLS and then using it to do crypto seperately in
::a bulk way
::> and not relying on TLS. Is there any strong feeling one way or the
::> other? I personally like the work Mr. Taylor has done as a
::starting point.
::
::Currently, Telnet over TLS (START_TLS) supports SRP by doing a
::"conventional" (server-cert-based or anonymous) TLS session handshake
::after the START_TLS option is negotiated, and then doing SRP
::authentication via the Telnet AUTH option. The SRP negotiation
::incorporates the TLS finished messages into its own handshake, to
::prevent MITM attacks against the TLS session, if it was anonymous or if
::the server cert was not trusted.
::
::Once SRP is supported natively as TLS ciphersuites, I will add support
::to SRP telnet/telnetd to support the use of these ciphersuites to
::identify/authenticate the user directly (similar to Kerberos V5), as
::opposed to the current approach of doing SRP separately inside a TLS
::session.
::
::I agree with you that native ciphersuite support inside TLS and OpenSSL
::is a Good Thing, since it doesn't require each app/protocol to
::incorporate subsequent SRP authentication support in its own
::app/protocol-specific way. It also provides a nice one-stop-shopping
::solution for developers who want secure password authentication plus
::transport security for their applications.
::
::Tom
::
::> Later,
::> dj
::>
::> On Sun, 11 Mar 2001, Tom Wu wrote:
::>
::> :Jeffrey Altman wrote:
::> :>
::> :> >
::> :> > hi,
::> :> >
::> :> > I recently found an IETF draft written by David Taylor
::that proposes the
::> :> > addition of a new ciphersuite.
::> :> >
::> :> > >A URL for this Internet-Draft is:
::> :> > >http://www.ietf.org/internet-drafts/draft-ietf-tls-srp-00.txt
::> :> >
::> :> >
::> :> > Has this thought come across the OpenSSL To Do list? Is
::there any comment
::> :> > on this draft?
::> :> >
::> :>
::> :> Its on my to do list.
::> :
::> :I will be doing integration work with START_TLS+SRP telnet/telnetd and
::> :doing interoperability testing.
::> :
::> :> Jeffrey Altman * Sr.Software Designer C-Kermit 7.1
::Alpha available
::> :> The Kermit Project @ Columbia University includes Secure
::Telnet and FTP
::> :> http://www.kermit-project.org/ using Kerberos, SRP, and
::> :> [EMAIL PROTECTED] OpenSSL. SSH
::soon to follow.
::> :>
::______________________________________________________________________
::> :> OpenSSL Project
http://www.openssl.org
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> :> Automated List Manager [EMAIL PROTECTED]
> :
> :
--
Tom Wu
Principal Software Engineer
Arcot Systems
(408) 969-6124
"The Borg? Sounds Swedish..."
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