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Re: [TLS] comment on draft-kinnear-tls-client-net-address

David Schinazi <dschinazi.ietf@gmail.com> Mon, 25 March 2019 16:02 UTC

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From: David Schinazi <dschinazi.ietf@gmail.com>
Date: Mon, 25 Mar 2019 17:02:34 +0100
Message-ID: <CAPDSy+5=RuSZ5n+hAdQdkaArfM1Zap4Ngz8LZkMy3seb7iwXYw@mail.gmail.com>
To: Hubert Kario <hkario@redhat.com>
Cc: tls@ietf.org
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Subject: Re: [TLS] comment on draft-kinnear-tls-client-net-address
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Ah, I see - thanks. In other words, the proposal requires trusting the
server and the reply comes before the identity of the server has been
authenticated.

David

On Mon, Mar 25, 2019 at 4:54 PM Hubert Kario <hkario@redhat.com> wrote:

> On Monday, 25 March 2019 15:09:21 CET David Schinazi wrote:
> > Hi Hubert,
> >
> > Can you elaborate on how "TLS is a providing integrity and authenticity
> to
> > the IP address information"? In my understanding, TLS only provides
> > integrity and authenticity to a byte stream, not to how your byte stream
> is
> > being transported over the network.
>
> my point is that EncryptedExtensions, while encrypted and integrity
> protected
> on record layer level, are _not yet_ bound to any identity, so an attacker
> can
> trivially reply to any non-PSK ClientHello with a ServerHello of its own
> and
> then he'll be able to generate arbitrary encrypted EncryptedExtensions
> message
>
> the forgery will be noticed only after the CertificateVerify is processed
>
> > Thanks,
> > David
> >
> > On Mon, Mar 25, 2019 at 12:31 PM Hubert Kario <hkario@redhat.com> wrote:
> > > I wanted to rise one comment on the IETF session, but we ran out of
> time:
> > >
> > > given that TLS is a providing integrity and authenticity to the IP
> address
> > > information, shouldn't the protocol require the client to perform the
> full
> > > handshake and only then request information from the server? I.e. make
> it
> > > a
> > > post-handshake messages, like KeyUpdate, rather than an extension.
> > >
> > > I worry that some clients may short-circuit processing and do the
> > > handshake
> > > only up to EncryptedExtensions, without processing CertificateVerify or
> > > Finished (in case of PSK), and in result expose themselves to MitM
> > > attacks.
> > > --
> > > Regards,
> > > Hubert Kario
> > > Senior Quality Engineer, QE BaseOS Security team
> > > Web: www.cz.redhat.com
> > > Red Hat Czech s.r.o., Purkyňova 115, 612 00  Brno, Czech
> > > Republic_______________________________________________
> > > TLS mailing list
> > > TLS@ietf.org
> > > https://www.ietf.org/mailman/listinfo/tls
>
>
> --
> Regards,
> Hubert Kario
> Senior Quality Engineer, QE BaseOS Security team
> Web: www.cz.redhat.com
> Red Hat Czech s.r.o., Purkyňova 115, 612 00  Brno, Czech Republic

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