Add support for the age_add field

Update SSL_SESSION to store the age_add and use it where needed.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2259)

ssl/ssl_asn1.c

diff --git a/ssl/ssl_asn1.c b/ssl/ssl_asn1.c
index 401aeb5..ced6a51 100644
--- a/ssl/ssl_asn1.c
+++ b/ssl/ssl_asn1.c
@@ -55,6 +55,7 @@
     long verify_result;
     ASN1_OCTET_STRING *tlsext_hostname;
     long tlsext_tick_lifetime_hint;
+    long tlsext_tick_age_add;
     ASN1_OCTET_STRING *tlsext_tick;
 #ifndef OPENSSL_NO_PSK
     ASN1_OCTET_STRING *psk_identity_hint;
@@ -89,7 +90,8 @@
 #ifndef OPENSSL_NO_SRP
     ASN1_EXP_OPT(SSL_SESSION_ASN1, srp_username, ASN1_OCTET_STRING, 12),
 #endif
-    ASN1_EXP_OPT(SSL_SESSION_ASN1, flags, ZLONG, 13)
+    ASN1_EXP_OPT(SSL_SESSION_ASN1, flags, ZLONG, 13),
+    ASN1_EXP_OPT(SSL_SESSION_ASN1, tlsext_tick_age_add, ZLONG, 14)
 } static_ASN1_SEQUENCE_END(SSL_SESSION_ASN1)
 
 IMPLEMENT_STATIC_ASN1_ENCODE_FUNCTIONS(SSL_SESSION_ASN1)
@@ -190,6 +192,7 @@
     }
     if (in->ext.tick_lifetime_hint > 0)
         as.tlsext_tick_lifetime_hint = in->ext.tick_lifetime_hint;
+    as.tlsext_tick_age_add = in->ext.tick_age_add;
 #ifndef OPENSSL_NO_PSK
     ssl_session_sinit(&as.psk_identity_hint, &psk_identity_hint,
                       in->psk_identity_hint);
@@ -326,6 +329,7 @@
 #endif
 
     ret->ext.tick_lifetime_hint = as->tlsext_tick_lifetime_hint;
+    ret->ext.tick_age_add = as->tlsext_tick_age_add;
     if (as->tlsext_tick) {
         ret->ext.tick = as->tlsext_tick->data;
         ret->ext.ticklen = as->tlsext_tick->length;

ssl/ssl_locl.h

diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index 7e5246c..e9bb445 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -574,6 +574,7 @@
         size_t ticklen;      /* Session ticket length */
         /* Session lifetime hint in seconds */
         unsigned long tick_lifetime_hint;
+        uint32_t tick_age_add;
         int tick_identity;
     } ext;
 # ifndef OPENSSL_NO_SRP

ssl/statem/extensions_clnt.c

diff --git a/ssl/statem/extensions_clnt.c b/ssl/statem/extensions_clnt.c
index c6a8124..366462e 100644
--- a/ssl/statem/extensions_clnt.c
+++ b/ssl/statem/extensions_clnt.c
@@ -694,6 +694,11 @@
     now = (uint32_t)time(NULL);
     ages = now - (uint32_t)s->session->time;
 
+    if (s->session->ext.tick_lifetime_hint < ages) {
+        /* Ticket is too old. Ignore it. */
+        return 1;
+    }
+
     /*
      * Calculate age in ms. We're just doing it to nearest second. Should be
      * good enough.
@@ -708,7 +713,11 @@
         return 1;
     }
 
-    /* TODO(TLS1.3): Obfuscate the age here */
+    /*
+     * Obfuscate the age. Overflow here is fine, this addition is supposed to
+     * be mod 2^32.
+     */
+    agems += s->session->ext.tick_age_add;
 
     cipher = ssl3_get_cipher_by_id(s->session->cipher_id);
     if (cipher == NULL) {

ssl/statem/statem_clnt.c

diff --git a/ssl/statem/statem_clnt.c b/ssl/statem/statem_clnt.c
index d5d622c..3bcd590 100644
--- a/ssl/statem/statem_clnt.c
+++ b/ssl/statem/statem_clnt.c
@@ -48,6 +48,7 @@
  */
 
 #include <stdio.h>
+#include <time.h>
 #include "../ssl_locl.h"
 #include "statem_locl.h"
 #include <openssl/buffer.h>
@@ -2195,12 +2196,12 @@
 {
     int al;
     unsigned int ticklen;
-    unsigned long ticket_lifetime_hint, add_age;
+    unsigned long ticket_lifetime_hint, age_add;
     unsigned int sess_len;
     RAW_EXTENSION *exts = NULL;
 
     if (!PACKET_get_net_4(pkt, &ticket_lifetime_hint)
-        || (SSL_IS_TLS13(s) && !PACKET_get_net_4(pkt, &add_age))
+        || (SSL_IS_TLS13(s) && !PACKET_get_net_4(pkt, &age_add))
         || !PACKET_get_net_2(pkt, &ticklen)
         || (!SSL_IS_TLS13(s) && PACKET_remaining(pkt) != ticklen)
         || (SSL_IS_TLS13(s) && (ticklen == 0
@@ -2243,6 +2244,12 @@
         s->session = new_sess;
     }
 
+    /*
+     * Technically the cast to long here is not guaranteed by the C standard -
+     * but we use it elsewhere, so this should be ok.
+     */
+    s->session->time = (long)time(NULL);
+
     OPENSSL_free(s->session->ext.tick);
     s->session->ext.tick = NULL;
     s->session->ext.ticklen = 0;
@@ -2259,6 +2266,7 @@
     }
 
     s->session->ext.tick_lifetime_hint = ticket_lifetime_hint;
+    s->session->ext.tick_age_add = age_add;
     s->session->ext.ticklen = ticklen;
 
     if (SSL_IS_TLS13(s)) {

ssl/statem/statem_srvr.c

diff --git a/ssl/statem/statem_srvr.c b/ssl/statem/statem_srvr.c
index 20e521a..98171b9 100644
--- a/ssl/statem/statem_srvr.c
+++ b/ssl/statem/statem_srvr.c
@@ -3250,6 +3250,12 @@
         uint32_t age_add;
     } age_add_u;
 
+    if (SSL_IS_TLS13(s)) {
+        if (RAND_bytes(age_add_u.age_add_c, sizeof(age_add_u)) <= 0)
+            goto err;
+        s->session->ext.tick_age_add = age_add_u.age_add;
+    }
+
     /* get session encoding length */
     slen_full = i2d_SSL_SESSION(s->session, NULL);
     /*
@@ -3341,10 +3347,6 @@
                sizeof(tctx->ext.tick_key_name));
     }
 
-    if (SSL_IS_TLS13(s) && RAND_bytes(age_add_u.age_add_c,
-                                      sizeof(age_add_u)) <= 0)
-        goto err;
-
     /*
      * Ticket lifetime hint (advisory only): We leave this unspecified
      * for resumed session (for simplicity), and guess that tickets for