[nginx] SSL: ssl_session_tickets directive.

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/d049b0ea00a3
branches:  
changeset: 5503:d049b0ea00a3
user:      Dirkjan Bussink <d.bussink at gmail.com>
date:      Fri Jan 10 16:12:40 2014 +0100
description:
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.

diffstat:

 src/http/modules/ngx_http_ssl_module.c |  16 ++++++++++++++++
 src/http/modules/ngx_http_ssl_module.h |   1 +
 src/mail/ngx_mail_ssl_module.c         |  17 +++++++++++++++++
 src/mail/ngx_mail_ssl_module.h         |   1 +
 4 files changed, 35 insertions(+), 0 deletions(-)

diffs (103 lines):

diff --git a/src/http/modules/ngx_http_ssl_module.c b/src/http/modules/ngx_http_ssl_module.c
--- 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_comma
       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 
     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 *
         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
--- 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
--- 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_comma
       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, 
         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
--- 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;