[PATCH] SSL: ssl_session_tickets directive

[Dirkjan Bussink]

# HG changeset patch
# User Dirkjan Bussink <d.bussink at gmail.com>
# Date 1389366760 -3600
# Node ID d049b0ea00a388c142627f10a0ee01c5b1bedc43
# Parent  4aa64f6950313311e0d322a2af1788edeb7f036c
SSL: ssl_session_tickets directive.

This adds support so it's possible to explicitly disable SSL Session
Tickets. In order to have good Forward Secrecy support either the
session ticket key has to be reloaded by using nginx' binary upgrade
process or using an external key file and reloading the configuration.
This directive adds another possibility to have good support by
disabling session tickets altogether.

If session tickets are enabled and the process lives for a long a time,
an attacker can grab the session ticket from the process and use that to
decrypt any traffic that occured during the entire lifetime of the
process.

diff -r 4aa64f695031 -r d049b0ea00a3 src/http/modules/ngx_http_ssl_module.c
--- a/src/http/modules/ngx_http_ssl_module.c	Sat Jan 04 03:32:22 2014 +0400
+++ b/src/http/modules/ngx_http_ssl_module.c	Fri Jan 10 16:12:40 2014 +0100
@@ -160,6 +160,13 @@
       0,
       NULL },
 
+    { ngx_string("ssl_session_tickets"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, session_tickets),
+      NULL },
+
     { ngx_string("ssl_session_ticket_key"),
       NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_str_array_slot,
@@ -436,6 +443,7 @@
     sscf->verify_depth = NGX_CONF_UNSET_UINT;
     sscf->builtin_session_cache = NGX_CONF_UNSET;
     sscf->session_timeout = NGX_CONF_UNSET;
+    sscf->session_tickets = NGX_CONF_UNSET;
     sscf->session_ticket_keys = NGX_CONF_UNSET_PTR;
     sscf->stapling = NGX_CONF_UNSET;
     sscf->stapling_verify = NGX_CONF_UNSET;
@@ -644,6 +652,14 @@
         return NGX_CONF_ERROR;
     }
 
+    ngx_conf_merge_value(conf->session_tickets, prev->session_tickets, 1);
+
+#ifdef SSL_OP_NO_TICKET
+    if (!conf->session_tickets) {
+        SSL_CTX_set_options(conf->ssl.ctx, SSL_OP_NO_TICKET);
+    }
+#endif
+
     ngx_conf_merge_ptr_value(conf->session_ticket_keys,
                          prev->session_ticket_keys, NULL);
 
diff -r 4aa64f695031 -r d049b0ea00a3 src/http/modules/ngx_http_ssl_module.h
--- a/src/http/modules/ngx_http_ssl_module.h	Sat Jan 04 03:32:22 2014 +0400
+++ b/src/http/modules/ngx_http_ssl_module.h	Fri Jan 10 16:12:40 2014 +0100
@@ -44,6 +44,7 @@
 
     ngx_shm_zone_t                 *shm_zone;
 
+    ngx_flag_t                      session_tickets;
     ngx_array_t                    *session_ticket_keys;
 
     ngx_flag_t                      stapling;
diff -r 4aa64f695031 -r d049b0ea00a3 src/mail/ngx_mail_ssl_module.c
--- a/src/mail/ngx_mail_ssl_module.c	Sat Jan 04 03:32:22 2014 +0400
+++ b/src/mail/ngx_mail_ssl_module.c	Fri Jan 10 16:12:40 2014 +0100
@@ -116,6 +116,13 @@
       0,
       NULL },
 
+    { ngx_string("ssl_session_tickets"),
+      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_MAIL_SRV_CONF_OFFSET,
+      offsetof(ngx_mail_ssl_conf_t, session_tickets),
+      NULL },
+
     { ngx_string("ssl_session_ticket_key"),
       NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_str_array_slot,
@@ -191,6 +198,7 @@
     scf->prefer_server_ciphers = NGX_CONF_UNSET;
     scf->builtin_session_cache = NGX_CONF_UNSET;
     scf->session_timeout = NGX_CONF_UNSET;
+    scf->session_tickets = NGX_CONF_UNSET;
     scf->session_ticket_keys = NGX_CONF_UNSET_PTR;
 
     return scf;
@@ -339,6 +347,15 @@
         return NGX_CONF_ERROR;
     }
 
+    ngx_conf_merge_value(conf->session_tickets,
+                         prev->session_tickets, 1);
+
+#ifdef SSL_OP_NO_TICKET
+    if (!conf->session_tickets) {
+        SSL_CTX_set_options(conf->ssl.ctx, SSL_OP_NO_TICKET);
+    }
+#endif
+
     ngx_conf_merge_ptr_value(conf->session_ticket_keys,
                          prev->session_ticket_keys, NULL);
 
diff -r 4aa64f695031 -r d049b0ea00a3 src/mail/ngx_mail_ssl_module.h
--- a/src/mail/ngx_mail_ssl_module.h	Sat Jan 04 03:32:22 2014 +0400
+++ b/src/mail/ngx_mail_ssl_module.h	Fri Jan 10 16:12:40 2014 +0100
@@ -41,6 +41,7 @@
 
     ngx_shm_zone_t  *shm_zone;
 
+    ngx_flag_t       session_tickets;
     ngx_array_t     *session_ticket_keys;
 
     u_char          *file;