Bug 1017769 - Make the CONNECT Host header the same as the Request-URI. r=mcmanus

It's possible to construct a request where the Host header differs from
the authority in the URL, for example in an extension with
nsIHttpChannel and setRequestHeader. MakeConnectString generates a
host:port string for the CONNECT Request-Line, but peeks into the
tunneled request in order to copy the Host header to the proxy request.

Instead, use the same host:port string for Host as is used in the
Request-URI, to avoid revealing the plaintext of the Host header outside
of the tunnel.

netwerk/protocol/http/nsHttpConnection.cpp

@@ -1759,14 +1759,11 @@ nsHttpConnection::MakeConnectString(nsAHttpTransaction *trans,
     request->SetHeader(nsHttp::Proxy_Connection, NS_LITERAL_CSTRING("keep-alive"));
     request->SetHeader(nsHttp::Connection, NS_LITERAL_CSTRING("keep-alive"));
 
-    const char *val = trans->RequestHead()->PeekHeader(nsHttp::Host);
-    if (val) {
     // all HTTP/1.1 requests must include a Host header (even though it
     // may seem redundant in this case; see bug 82388).
-        request->SetHeader(nsHttp::Host, nsDependentCString(val));
-    }
+    request->SetHeader(nsHttp::Host, result);
 
-    val = trans->RequestHead()->PeekHeader(nsHttp::Proxy_Authorization);
+    const char *val = trans->RequestHead()->PeekHeader(nsHttp::Proxy_Authorization);
     if (val) {
         // we don't know for sure if this authorization is intended for the
         // SSL proxy, so we add it just in case.