Introduce ticket support. To enable them it is enough to set a positive

lifetime with tls_config_set_session_lifetime(). This enables tickets
and uses an internal automatic rekeying mode for the ticket keys.

If multiple processes are involved the following functions can be used to make
tickets work accross all instances:
- tls_config_set_session_id() sets the session identifier
- tls_config_add_ticket_key() adds an encryption and authentication key

For now only the last 4 keys added will be used (unless they are too old).
If tls_config_add_ticket_key() is used the caller must ensure to add new keys
regularly. It is best to do this 4 times per session lifetime (which is also
the ticket key lifetime).

Since tickets break PFS it is best to minimize the session lifetime according
to needs.

With a lot of help, input and OK beck@, jsing@

1 files changed, 23 insertions, 1 deletions

diff --git a/src/lib/libtls/tls_internal.h b/src/lib/libtls/tls_internal.h
index 1db186a05f..3650ca9462 100644
--- a/src/lib/libtls/tls_internal.h
+++ b/src/lib/libtls/tls_internal.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls_internal.h,v 1.50 2016/11/05 15:13:26 beck Exp $ */
+/* $OpenBSD: tls_internal.h,v 1.51 2017/01/24 01:48:05 claudio Exp $ */
 /*
  * Copyright (c) 2014 Jeremie Courreges-Anglas <jca@openbsd.org>
  * Copyright (c) 2014 Joel Sing <jsing@openbsd.org>
@@ -53,6 +53,22 @@ struct tls_keypair {
         size_t key_len;
 };
 
+#define TLS_MIN_SESSION_TIMEOUT (4)
+#define TLS_MAX_SESSION_TIMEOUT (24 * 60 * 60)
+
+#define TLS_NUM_TICKETS                         4
+#define TLS_TICKET_NAME_SIZE                    16
+#define TLS_TICKET_AES_SIZE                     32
+#define TLS_TICKET_HMAC_SIZE                    16
+
+struct tls_ticket_key {
+        /* The key_name must be 16 bytes according to -lssl */
+        unsigned char   key_name[TLS_TICKET_NAME_SIZE];
+        unsigned char   aes_key[TLS_TICKET_AES_SIZE];
+        unsigned char   hmac_key[TLS_TICKET_HMAC_SIZE];
+        time_t          time;
+};
+
 struct tls_config {
         struct tls_error error;
 
@@ -70,6 +86,11 @@ struct tls_config {
         char *ocsp_staple;
         size_t ocsp_staple_len;
         uint32_t protocols;
+        unsigned char session_id[TLS_MAX_SESSION_ID_LENGTH];
+        int session_lifetime;
+        struct tls_ticket_key ticket_keys[TLS_NUM_TICKETS];
+        uint32_t ticket_keyrev;
+        int ticket_autorekey;
         int verify_cert;
         int verify_client;
         int verify_depth;
@@ -171,6 +192,7 @@ int tls_handshake_server(struct tls *ctx);
 
 int tls_config_load_file(struct tls_error *error, const char *filetype,
     const char *filename, char **buf, size_t *len);
+int tls_config_ticket_autorekey(struct tls_config *config);
 int tls_host_port(const char *hostport, char **host, char **port);
 
 int tls_set_cbs(struct tls *ctx,