Fix a race condition in ciphers handling

Similarly to the previous commit we were storing the peer offered list
of ciphers in the session. In practice there is no need for this
information to be avilable from one resumption to the next since this
list is specific to a particular handshake. Since the session object is
supposed to be immutable we should not be updating it once we have decided
to resume. The solution is to remove the session list out of the session
object.

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/9176)

4 files changed, 14 insertions, 22 deletions

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 5584a1b089..ae65014c0c 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -1160,6 +1160,7 @@ void SSL_free(SSL *s)
     sk_SSL_CIPHER_free(s->cipher_list);
     sk_SSL_CIPHER_free(s->cipher_list_by_id);
     sk_SSL_CIPHER_free(s->tls13_ciphersuites);
+    sk_SSL_CIPHER_free(s->peer_ciphers);
 
     /* Make the next call work :-) */
     if (s->session != NULL) {
@@ -2438,9 +2439,9 @@ STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *s)
 
 STACK_OF(SSL_CIPHER) *SSL_get_client_ciphers(const SSL *s)
 {
-    if ((s == NULL) || (s->session == NULL) || !s->server)
+    if ((s == NULL) || !s->server)
         return NULL;
-    return s->session->ciphers;
+    return s->peer_ciphers;
 }
 
 STACK_OF(SSL_CIPHER) *SSL_get1_supported_ciphers(SSL *s)
@@ -2579,13 +2580,12 @@ char *SSL_get_shared_ciphers(const SSL *s, char *buf, int size)
     int i;
 
     if (!s->server
-            || s->session == NULL
-            || s->session->ciphers == NULL
+            || s->peer_ciphers == NULL
             || size < 2)
         return NULL;
 
     p = buf;
-    clntsk = s->session->ciphers;
+    clntsk = s->peer_ciphers;
     srvrsk = SSL_get_ciphers(s);
     if (clntsk == NULL || srvrsk == NULL)
         return NULL;
diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index 48c7eb0e53..1b7bf111fd 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -552,7 +552,6 @@ struct ssl_session_st {
     const SSL_CIPHER *cipher;
     unsigned long cipher_id;    /* when ASN.1 loaded, this needs to be used to
                                  * load the 'cipher' structure */
-    STACK_OF(SSL_CIPHER) *ciphers; /* ciphers offered by the client */
     CRYPTO_EX_DATA ex_data;     /* application specific data */
     /*
      * These are used to make removal of session-ids more efficient and to
@@ -1135,6 +1134,7 @@ struct ssl_st {
     /* Per connection DANE state */
     SSL_DANE dane;
     /* crypto */
+    STACK_OF(SSL_CIPHER) *peer_ciphers;
     STACK_OF(SSL_CIPHER) *cipher_list;
     STACK_OF(SSL_CIPHER) *cipher_list_by_id;
     /* TLSv1.3 specific ciphersuites */
diff --git a/ssl/ssl_sess.c b/ssl/ssl_sess.c
index b7638780d0..2c3bb5cf79 100644
--- a/ssl/ssl_sess.c
+++ b/ssl/ssl_sess.c
@@ -121,7 +121,6 @@ SSL_SESSION *ssl_session_dup(SSL_SESSION *src, int ticket)
     dest->psk_identity_hint = NULL;
     dest->psk_identity = NULL;
 #endif
-    dest->ciphers = NULL;
     dest->ext.hostname = NULL;
 #ifndef OPENSSL_NO_EC
     dest->ext.ecpointformats = NULL;
@@ -175,12 +174,6 @@ SSL_SESSION *ssl_session_dup(SSL_SESSION *src, int ticket)
     }
 #endif
 
-    if (src->ciphers != NULL) {
-        dest->ciphers = sk_SSL_CIPHER_dup(src->ciphers);
-        if (dest->ciphers == NULL)
-            goto err;
-    }
-
     if (!CRYPTO_dup_ex_data(CRYPTO_EX_INDEX_SSL_SESSION,
                             &dest->ex_data, &src->ex_data)) {
         goto err;
@@ -781,7 +774,6 @@ void SSL_SESSION_free(SSL_SESSION *ss)
     OPENSSL_cleanse(ss->session_id, sizeof(ss->session_id));
     X509_free(ss->peer);
     sk_X509_pop_free(ss->peer_chain, X509_free);
-    sk_SSL_CIPHER_free(ss->ciphers);
     OPENSSL_free(ss->ext.hostname);
     OPENSSL_free(ss->ext.tick);
 #ifndef OPENSSL_NO_EC
diff --git a/ssl/statem/statem_srvr.c b/ssl/statem/statem_srvr.c
index 04a23320fc..e7e95c74e7 100644
--- a/ssl/statem/statem_srvr.c
+++ b/ssl/statem/statem_srvr.c
@@ -1921,14 +1921,14 @@ static int tls_early_post_process_client_hello(SSL *s)
                 && master_key_length > 0) {
             s->session->master_key_length = master_key_length;
             s->hit = 1;
-            s->session->ciphers = ciphers;
+            s->peer_ciphers = ciphers;
             s->session->verify_result = X509_V_OK;
 
             ciphers = NULL;
 
             /* check if some cipher was preferred by call back */
             if (pref_cipher == NULL)
-                pref_cipher = ssl3_choose_cipher(s, s->session->ciphers,
+                pref_cipher = ssl3_choose_cipher(s, s->peer_ciphers,
                                                  SSL_get_ciphers(s));
             if (pref_cipher == NULL) {
                 SSLfatal(s, SSL_AD_HANDSHAKE_FAILURE,
@@ -1939,9 +1939,9 @@ static int tls_early_post_process_client_hello(SSL *s)
 
             s->session->cipher = pref_cipher;
             sk_SSL_CIPHER_free(s->cipher_list);
-            s->cipher_list = sk_SSL_CIPHER_dup(s->session->ciphers);
+            s->cipher_list = sk_SSL_CIPHER_dup(s->peer_ciphers);
             sk_SSL_CIPHER_free(s->cipher_list_by_id);
-            s->cipher_list_by_id = sk_SSL_CIPHER_dup(s->session->ciphers);
+            s->cipher_list_by_id = sk_SSL_CIPHER_dup(s->peer_ciphers);
         }
     }
 
@@ -2041,12 +2041,12 @@ static int tls_early_post_process_client_hello(SSL *s)
 #endif
 
     /*
-     * Given s->session->ciphers and SSL_get_ciphers, we must pick a cipher
+     * Given s->peer_ciphers and SSL_get_ciphers, we must pick a cipher
      */
 
     if (!s->hit || SSL_IS_TLS13(s)) {
-        sk_SSL_CIPHER_free(s->session->ciphers);
-        s->session->ciphers = ciphers;
+        sk_SSL_CIPHER_free(s->peer_ciphers);
+        s->peer_ciphers = ciphers;
         if (ciphers == NULL) {
             SSLfatal(s, SSL_AD_INTERNAL_ERROR,
                      SSL_F_TLS_EARLY_POST_PROCESS_CLIENT_HELLO,
@@ -2253,7 +2253,7 @@ WORK_STATE tls_post_process_client_hello(SSL *s, WORK_STATE wst)
             /* In TLSv1.3 we selected the ciphersuite before resumption */
             if (!SSL_IS_TLS13(s)) {
                 cipher =
-                    ssl3_choose_cipher(s, s->session->ciphers, SSL_get_ciphers(s));
+                    ssl3_choose_cipher(s, s->peer_ciphers, SSL_get_ciphers(s));
 
                 if (cipher == NULL) {
                     SSLfatal(s, SSL_AD_HANDSHAKE_FAILURE,