Fix a race condition in supported groups handling

In TLSv1.3 the supported groups can be negotiated each time a handshake
occurs, regardless of whether we are resuming or not. We should not store
the supported groups information in the session because session objects
can be shared between multiple threads and we can end up with race
conditions. For most users this won't be seen because, by default, we
use stateless tickets in TLSv1.3 which don't get shared. However if you
use SSL_OP_NO_TICKET (to get stateful tickets in TLSv1.3) then this can
happen.

The answer is to move the supported the supported group information into
the SSL object instead.
Reviewed-by: NTomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/9176)

ssl/s3_lib.c

@@ -3601,8 +3601,8 @@ long ssl3_ctrl(SSL *s, int cmd, long larg, void *parg)
 
             if (!s->session)
                 return 0;
-            clist = s->session->ext.supportedgroups;
-            clistlen = s->session->ext.supportedgroups_len;
+            clist = s->ext.peer_supportedgroups;
+            clistlen = s->ext.peer_supportedgroups_len;
             if (parg) {
                 size_t i;
                 int *cptr = parg;

ssl/ssl_lib.c

@@ -1179,6 +1179,7 @@ void SSL_free(SSL *s)
 #ifndef OPENSSL_NO_EC
     OPENSSL_free(s->ext.ecpointformats);
     OPENSSL_free(s->ext.supportedgroups);
+    OPENSSL_free(s->ext.peer_supportedgroups);
 #endif                          /* OPENSSL_NO_EC */
     sk_X509_EXTENSION_pop_free(s->ext.ocsp.exts, X509_EXTENSION_free);
 #ifndef OPENSSL_NO_OCSP

ssl/ssl_locl.h

@@ -566,9 +566,7 @@ struct ssl_session_st {
         size_t ecpointformats_len;
         unsigned char *ecpointformats; /* peer's list */
 # endif                         /* OPENSSL_NO_EC */
-        size_t supportedgroups_len;
-        uint16_t *supportedgroups; /* peer's list */
-    /* RFC4507 info */
+        /* RFC4507 info */
         unsigned char *tick; /* Session ticket */
         size_t ticklen;      /* Session ticket length */
         /* Session lifetime hint in seconds */
@@ -1304,6 +1302,11 @@ struct ssl_st {
         size_t supportedgroups_len;
         /* our list */
         uint16_t *supportedgroups;
+
+        size_t peer_supportedgroups_len;
+         /* peer's list */
+        uint16_t *peer_supportedgroups;
+
         /* TLS Session Ticket extension override */
         TLS_SESSION_TICKET_EXT *session_ticket;
         /* TLS Session Ticket extension callback */
@@ -2240,8 +2243,8 @@ static ossl_inline int ssl_has_cert(const SSL *s, int idx)
 static ossl_inline void tls1_get_peer_groups(SSL *s, const uint16_t **pgroups,
                                              size_t *pgroupslen)
 {
-    *pgroups = s->session->ext.supportedgroups;
-    *pgroupslen = s->session->ext.supportedgroups_len;
+    *pgroups = s->ext.peer_supportedgroups;
+    *pgroupslen = s->ext.peer_supportedgroups_len;
 }
 
 # ifndef OPENSSL_UNIT_TEST

ssl/ssl_sess.c

@@ -125,7 +125,6 @@ SSL_SESSION *ssl_session_dup(SSL_SESSION *src, int ticket)
     dest->ext.hostname = NULL;
 #ifndef OPENSSL_NO_EC
     dest->ext.ecpointformats = NULL;
-    dest->ext.supportedgroups = NULL;
 #endif
     dest->ext.tick = NULL;
     dest->ext.alpn_selected = NULL;
@@ -201,14 +200,6 @@ SSL_SESSION *ssl_session_dup(SSL_SESSION *src, int ticket)
         if (dest->ext.ecpointformats == NULL)
             goto err;
     }
-    if (src->ext.supportedgroups) {
-        dest->ext.supportedgroups =
-            OPENSSL_memdup(src->ext.supportedgroups,
-                           src->ext.supportedgroups_len
-                                * sizeof(*src->ext.supportedgroups));
-        if (dest->ext.supportedgroups == NULL)
-            goto err;
-    }
 #endif
 
     if (ticket != 0 && src->ext.tick != NULL) {
@@ -797,9 +788,6 @@ void SSL_SESSION_free(SSL_SESSION *ss)
     OPENSSL_free(ss->ext.ecpointformats);
     ss->ext.ecpointformats = NULL;
     ss->ext.ecpointformats_len = 0;
-    OPENSSL_free(ss->ext.supportedgroups);
-    ss->ext.supportedgroups = NULL;
-    ss->ext.supportedgroups_len = 0;
 #endif                          /* OPENSSL_NO_EC */
 #ifndef OPENSSL_NO_PSK
     OPENSSL_free(ss->psk_identity_hint);

ssl/statem/extensions_srvr.c

@@ -962,12 +962,12 @@ int tls_parse_ctos_supported_groups(SSL *s, PACKET *pkt, unsigned int context,
     }
 
     if (!s->hit || SSL_IS_TLS13(s)) {
-        OPENSSL_free(s->session->ext.supportedgroups);
-        s->session->ext.supportedgroups = NULL;
-        s->session->ext.supportedgroups_len = 0;
+        OPENSSL_free(s->ext.peer_supportedgroups);
+        s->ext.peer_supportedgroups = NULL;
+        s->ext.peer_supportedgroups_len = 0;
         if (!tls1_save_u16(&supported_groups_list,
-                           &s->session->ext.supportedgroups,
-                           &s->session->ext.supportedgroups_len)) {
+                           &s->ext.peer_supportedgroups,
+                           &s->ext.peer_supportedgroups_len)) {
             SSLfatal(s, SSL_AD_INTERNAL_ERROR,
                      SSL_F_TLS_PARSE_CTOS_SUPPORTED_GROUPS,
                      ERR_R_INTERNAL_ERROR);