Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (Transport Layer
Simon Josefsson <simon@josefsson.org> Thu, 01 October 2009 10:59 UTC
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From: Simon Josefsson <simon@josefsson.org>
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Date: Thu, 01 Oct 2009 13:00:34 +0200
In-Reply-To: <200909301454.n8UEsEFw007520@fs4113.wdf.sap.corp> (Martin Rex's message of "Wed, 30 Sep 2009 16:54:14 +0200 (MEST)")
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Cc: tls@ietf.org
Subject: Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (Transport Layer
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Martin Rex <Martin.Rex@sap.com> writes: > Blumenthal, Uri wrote: >> >> In my understanding, TLS-established server_name should be >> enforced by the server. >> >> And Martin - I couldn't disagree more with you. The whole point of >> using TLS is to enforce who can access what. So the client makes sure >> he accesses the right server, the server makes sure he grants access >> to the right pages on the right virtual host. And if your server >> doesn't do that - please kindly tell me what commercial or >> freeware product it is included in, so I can avoid buying or >> using it in the future. > > There seems to be a significant misunderstanding. > > The Host header field of an HTTP request is a detail of an > application protocol. The hostname conveyed by the TLS extension > server name indication (SNI) happens at a competely different > protocol layer. > > The difference becomes obvious when you add reverse proxies > into the picture (those which terminate the TLS wrapping). > > Conceptually, the Host: header field of a HTTP request is > part of the URL. If a reverse proxy perform URL rewriting, > it may as well have to rewrite Host: header fields. That > depends entirely on the backend architecture of each > particular software installation. > > > Whether or not an application may want to make consistency > checks between a Host: Header field and a hostname received > via SNI at the specific point of the backend architecture > where TLS was terminated depends entirely on the backend > architecture, and is an application issue. I believe this wording in RFC 4366bis makes it a TLS issue: If the server_name is established in the TLS session handshake, the client SHOULD NOT attempt to request a different server name at the application layer. I believe there are two options: 1) Either remove all requirements on application behaviour from 4366bis (including the text above) and explicitly defer such discussions to other documents. 2) Add the text I proposed to make servers actually validate proper client behaviour. I went for 2) assuming that the text above was intentional, but I share your arguments for going with approach 1). /Simon
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Blumenthal, Uri
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Blumenthal, Uri
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Martin Rex
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Simon Josefsson
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Joseph Salowey (jsalowey)
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Peter Saint-Andre
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Simon Josefsson
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Blumenthal, Uri
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Martin Rex