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From Peter Crowther <>
Subject RE: HTTPS and Virtual Hosts
Date Mon, 22 Sep 2008 09:22:54 GMT
> From: André Warnier []
> As I remember from reading about this a while ago, there is/was a
> fundamental incompatibility between the HTTP Virtual Host
> mechanism, and
> HTTPS/SSL, in the sense that there is some egg-and-chicken problem
> involved, which roughly goes like this :
> - the client connects to the host and requests an encrypted connection
> to a certain hostname

Almost.  The client connects to the host on a given IP address and port, which requires an
encrypted connection.  No hostname is transferred at this point, as encryption must happen

> - the host and client negociate the encryption (based or not
> on the name of the host)

Based on the certificate that the host sends to the client as part of negotiating the encryption.
 That certificate contains the common name of the host (or occasionally a wildcard name such
as *  The client should be suspicious if the common name in the certificate
does not match the hostname the client thinks it sent the request to.

Therefore, the host cannot know to which virtual host the client wishes to connect when it
sends the certificate.

Therefore, the host cannot send the "right" certificate unless all requests to a given hostname
and port are designed to use the same certificate.

Therefore, virtual hosting using SSL is a problem.

> Is the above, very roughly and approximatively still a valid
> explanation
> of what happens, or is it totally wrong, or has something changed
> in-between that I am unaware of ?

It's close, but the problem occurs at an earlier step than you outline :-).

                - Peter

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