Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (Transport Layer
Martin Rex <Martin.Rex@sap.com> Mon, 28 September 2009 21:20 UTC
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From: Martin Rex <Martin.Rex@sap.com>
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To: simon@josefsson.org
Date: Mon, 28 Sep 2009 23:21:37 +0200
In-Reply-To: <87ab0lskpf.fsf@mocca.josefsson.org> from "Simon Josefsson" at Sep 23, 9 06:13:32 pm
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Cc: ietf@ietf.org, tls@ietf.org
Subject: Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (Transport Layer
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Simon Josefsson wrote: > > One attack could works like this: > > 1) Client establish an client-authenticated HTTPS session with a TLS SNI > for blog.example.org and sends a HTTP GET with a Host: header for > internal-website.example.org. > > 2) The server TLS code authenticate and authorize the client (using the > certificate) for use with the blog.example.org domain. The server HTTP > code serves the internal-website.example.org web page to the client. > > This system would be insecure but still compliant with RFC 4366bis as > far as I can tell, which seems suboptimal. Adding a requirement for > servers to check for this attack would solve the problem. I do not see why you consider this a vulnerability in the _server_! This is exactly how virtual hosting works. Virtual hosting does NOT seperate content. And neither will the use of TLS provide any such content seperation. The use or non-use of server name indication does not make a difference. Server Name Indication is a feature for the _client_ side, and was invented to accomodate virtual hosting when HTTP over TLS is used and the client performs weak server endpoint identification that is suggested by rfc-2818, section 3.1. If you can coerce a Browser into sending a Host: header field different to the host that is used for server endpoint identification, then this might possibly be considered a problem in the *client*. When using Reverse Proxies with re-encryption, there may be a by-design difference in the SNI as supplied by the client (matching the hostname of the reverse proxy) and the host header field that the backend server is going to see/use. -Martin
- [TLS] Last Call: draft-ietf-tls-rfc4366-bis (Tran… The IESG
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Simon Josefsson
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Dean Anderson
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Eric Rescorla
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Pasi.Eronen
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Peter Sylvester
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Martin Rex
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Michael D'Errico
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Martin Rex
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Michael D'Errico
- Re: [TLS] Last Call: draft-ietf-tls-rfc4366-bis (… Joseph Salowey (jsalowey)
- 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 (… Blumenthal, Uri