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.

4 files changed, 35 insertions, 0 deletions

diff --git a/src/http/modules/ngx_http_ssl_module.c b/src/http/modules/ngx_http_ssl_module.c
index a0d258c8a..593111ca6 100644
--- a/src/http/modules/ngx_http_ssl_module.c
+++ b/src/http/modules/ngx_http_ssl_module.c
@@ -160,6 +160,13 @@ static ngx_command_t  ngx_http_ssl_commands[] = {
       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 @@ ngx_http_ssl_create_srv_conf(ngx_conf_t *cf)
     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 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
         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 --git a/src/http/modules/ngx_http_ssl_module.h b/src/http/modules/ngx_http_ssl_module.h
index e72b921ac..ec2c62f6f 100644
--- a/src/http/modules/ngx_http_ssl_module.h
+++ b/src/http/modules/ngx_http_ssl_module.h
@@ -44,6 +44,7 @@ typedef struct {
 
     ngx_shm_zone_t                 *shm_zone;
 
+    ngx_flag_t                      session_tickets;
     ngx_array_t                    *session_ticket_keys;
 
     ngx_flag_t                      stapling;
diff --git a/src/mail/ngx_mail_ssl_module.c b/src/mail/ngx_mail_ssl_module.c
index 94c015700..fe88f48e4 100644
--- a/src/mail/ngx_mail_ssl_module.c
+++ b/src/mail/ngx_mail_ssl_module.c
@@ -116,6 +116,13 @@ static ngx_command_t  ngx_mail_ssl_commands[] = {
       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 @@ ngx_mail_ssl_create_conf(ngx_conf_t *cf)
     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 @@ ngx_mail_ssl_merge_conf(ngx_conf_t *cf, void *parent, void *child)
         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 --git a/src/mail/ngx_mail_ssl_module.h b/src/mail/ngx_mail_ssl_module.h
index 54e057721..bef0e515a 100644
--- a/src/mail/ngx_mail_ssl_module.h
+++ b/src/mail/ngx_mail_ssl_module.h
@@ -41,6 +41,7 @@ typedef struct {
 
     ngx_shm_zone_t  *shm_zone;
 
+    ngx_flag_t       session_tickets;
     ngx_array_t     *session_ticket_keys;
 
     u_char          *file;