On 14.06.2014 11:44, Rainer Jung wrote:
> On 14.06.2014 10:23, Kaspar Brand wrote:
>> On 13.06.2014 16:55, Rainer Jung wrote:
>>> Now since a long time most clients do no longer rely on the server
>>> caching the sessions. Instead they use TLS session resumption (RFC
>>> 5077).
>>
>> "without server-side state"/"stateless" is actually the important term
>> from this RFC (session resumption is a standard protocol feature).
>>
>>> Currently mod_ssl does not provide a way to control the time how long
>>> such a ticket may be used by the client. As far as I can see, there is
>>> no specific API in OpenSSL for that, but there is a general API allowing
>>> to set a session timeout that is checked whenever a session is
>>> reconstructed.
>>
>> What OpenSSL function do you have in mind? SSL_SESSION_set_timeout?
>
> I was hoping SSL_CTX_set_timeout() would do the trick.
>
>> AFAICT, t1_lib.c:tls_decrypt_ticket simply restores the (relative)
>> timeout for the SSL_SESSION, which is set to 5 minutes by default... but
>> if I'm understanding correctly, you are concerned about clients reusing
>> "old" tickets, is that correct? (If so, then I guess there's currently
>> no other way than switching to a new ticket encryption key, see also [1]).
>
> Yes that's my concern. I will give SSL_CTX_set_timeout() a try over the
> weekend.
SSL_CTX_set_timeout() seems to work pretty well. I tested with Firefox
30 as client using TLS 1.2 and verifying that the server side cache was
not used. As soon as the new timeout is over (delta to the creation time
of the session), resumption fails and a new session is created.
In addition to the usual directive management lines, the patch should be
as simple as
Index: modules/ssl/ssl_engine_init.c
===================================================================
--- modules/ssl/ssl_engine_init.c (revision 1593916)
+++ modules/ssl/ssl_engine_init.c (working copy)
@@ -1365,6 +1365,8 @@
}
#endif
+ SSL_CTX_set_timeout(sc->server->ssl_ctx, sc->server->session_timeout);
+
return APR_SUCCESS;
}
where sc->server->session_timeout is the new configuration item (if we
do not stick to the existing cache timeout).
>> Kaspar
>>
>> [1]
>> https://mail-archives.apache.org/mod_mbox/httpd-dev/201308.mbox/%3C20130821111727.GA7331%40redhat.com%3E
>> or
>> https://mail-archives.apache.org/mod_mbox/httpd-dev/201309.mbox/%3C52248C40.7070206%40opensslfoundation.com%3E
Rainer
