SNI: avoid surplus lookup of virtual server if SNI was used.


git-svn-id: svn://svn.nginx.org/nginx/trunk@5094 73f98a42-aea0-e011-b76d-00259023448c
SNI: reset to default server if requested host was not found.

Not only this is consistent with a case without SNI, but this also
prevents abusing configurations that assume that the $host variable
is limited to one of the configured names for a server.

An example of potentially unsafe configuration:

  server {
      listen 443 ssl default_server;
      ...
  }

  server {
      listen 443;
      server_name example.com;

      location / {
          proxy_pass http://$host;
      }
  }

Note: it is possible to negotiate "example.com" by SNI, and to request
arbitrary host name that does not exist in the configuration above.


git-svn-id: svn://svn.nginx.org/nginx/trunk@5095 73f98a42-aea0-e011-b76d-00259023448c
SNI: added restriction on requesting host other than negotiated.

According to RFC 6066, client is not supposed to request a different server
name at the application layer.  Server implementations that rely upon these
names being equal must validate that a client did not send a different name
in HTTP request.  Current versions of Apache HTTP server always return 400
"Bad Request" in such cases.

There exist implementations however (e.g., SPDY) that rely on being able to
request different host names in one connection.  Given this, we only reject
requests with differing host names if verification of client certificates
is enabled in a corresponding server configuration.

An example of configuration that might not work as expected:

  server {
      listen 433 ssl default;
      return 404;
  }

  server {
      listen 433 ssl;
      server_name example.org;

      ssl_client_certificate org.cert;
      ssl_verify_client on;
  }

  server {
      listen 433 ssl;
      server_name example.com;

      ssl_client_certificate com.cert;
      ssl_verify_client on;
  }

Previously, a client was able to request example.com by presenting
a certificate for example.org, and vice versa.


git-svn-id: svn://svn.nginx.org/nginx/trunk@5096 73f98a42-aea0-e011-b76d-00259023448c