Re: [TLS] TLS Proxy Server Extension
"Kemp, David P." <DPKemp@missi.ncsc.mil> Wed, 03 August 2011 20:55 UTC
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Date: Wed, 03 Aug 2011 16:55:57 -0400
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From: "Kemp, David P." <DPKemp@missi.ncsc.mil>
To: David McGrew <mcgrew@cisco.com>, mrex@sap.com
Cc: tls@ietf.org
Subject: Re: [TLS] TLS Proxy Server Extension
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--- Begin Message ---From: David McGrew > On Aug 1, 2011, at 9:15 AM, Martin Rex wrote: >> If the proxy terminates the clients >> TLS connection and establishes a new connection to the real server, >> then it will have to impersonate the real server to the client > > No, that's not right, at least not if "impersonate" is meant in the > cryptographic sense. If "impersonate" is meant in the sense that a > proxy can modify the traffic passing through it, then yes, that is a > goal for the system; it is a requirement if TLS is to be used to > protect communications when an HTTP proxy is present (for many types > of proxies). A TLS connection between S and C provides integrity protection (which by definition is impossible without authentication): C knows that data it receives is identical to that sent by S. How do you propose to define roles that extend integrity properties to a three-party protocol? C must know that data it receives from S is sent by S, with no insertions or deletions. And that data it receives from P was sent by P with no insertions or deletions. "Modifying" traffic is fundamentally incompatible with data integrity - the concept is meaningless. There must be either two independent unmodifiable data streams between C and S and between C and P, or there must be a single stream between C and P, where C trusts P to be the data provider without knowing or caring where P got the data in the first place. That is what is meant by impersonation. In an application protocol it would be appropriate to tag sections of data that have different properties and originated from different sources - think chat room, or a portion-marked word document. TLS claims to protect an application-independent data stream - I have no idea how you define semantics of a 3-party "session" without becoming application-specific. Dave--- End Message ---
- [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Yngve N. Pettersen
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension Adam Langley
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension Adam Langley
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Matt McCutchen
- [TLS] Certificate pins vs. MITM proxies Matt McCutchen
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension Matt McCutchen
- Re: [TLS] TLS Proxy Server Extension Matt McCutchen
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension Marsh Ray
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension Marsh Ray
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension Marsh Ray
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Marsh Ray
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension Marsh Ray
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension Anders Rundgren
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension Ken Peirce
- Re: [TLS] TLS Proxy Server Extension Peter Gutmann
- Re: [TLS] TLS Proxy Server Extension Matt McCutchen
- Re: [TLS] TLS Proxy Server Extension Martin Rex
- Re: [TLS] TLS Proxy Server Extension Joshua Davies
- Re: [TLS] TLS Proxy Server Extension Yoav Nir
- Re: [TLS] TLS Proxy Server Extension Ken Peirce
- Re: [TLS] TLS Proxy Server Extension Philip Gladstone
- Re: [TLS] TLS Proxy Server Extension Kemp, David P.
- Re: [TLS] TLS Proxy Server Extension David McGrew
- Re: [TLS] TLS Proxy Server Extension Ralph Holz