Implement Maximum Fragment Length TLS extension.

[openssl.git] / ssl / statem / extensions_srvr.c

diff --git a/ssl/statem/extensions_srvr.c b/ssl/statem/extensions_srvr.c
index 8183ea574c920f951152fc6f4c2cd23310eb8dda..1b56fa1b88d9aac46c66fceaa7aca97d155002af 100644 (file)
--- a/ssl/statem/extensions_srvr.c
+++ b/ssl/statem/extensions_srvr.c
@@ -139,6 +139,40 @@ int tls_parse_ctos_server_name(SSL *s, PACKET *pkt, unsigned int context,
     return 1;
 }
 
+int tls_parse_ctos_maxfragmentlen(SSL *s, PACKET *pkt, unsigned int context,
+                                  X509 *x, size_t chainidx, int *al)
+{
+    unsigned int value;
+
+    if (PACKET_remaining(pkt) != 1 || !PACKET_get_1(pkt, &value)) {
+        *al = TLS1_AD_DECODE_ERROR;
+        return 0;
+    }
+
+    /* Received |value| should be a valid max-fragment-length code. */
+    if (!IS_MAX_FRAGMENT_LENGTH_EXT_VALID(value)) {
+        *al = SSL_AD_ILLEGAL_PARAMETER;
+        return 0;
+    }
+
+    /*
+     * RFC 6066:  The negotiated length applies for the duration of the session
+     * including session resumptions.
+     * We should receive the same code as in resumed session !
+     */
+    if (s->hit && s->session->ext.max_fragment_len_mode != value) {
+        *al = SSL_AD_ILLEGAL_PARAMETER;
+        return 0;
+    }
+
+    /*
+     * Store it in session, so it'll become binding for us
+     * and we'll include it in a next Server Hello.
+     */
+    s->session->ext.max_fragment_len_mode = value;
+    return 1;
+}
+
 #ifndef OPENSSL_NO_SRP
 int tls_parse_ctos_srp(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
                        size_t chainidx, int *al)
@@ -499,8 +533,8 @@ int tls_parse_ctos_key_share(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
 #ifndef OPENSSL_NO_TLS1_3
     unsigned int group_id;
     PACKET key_share_list, encoded_pt;
-    const uint16_t *clntcurves, *srvrcurves;
-    size_t clnt_num_curves, srvr_num_curves;
+    const uint16_t *clntgroups, *srvrgroups;
+    size_t clnt_num_groups, srvr_num_groups;
     int found = 0;
 
     if (s->hit && (s->ext.psk_kex_mode & TLSEXT_KEX_MODE_FLAG_KE_DHE) == 0)
@@ -519,11 +553,11 @@ int tls_parse_ctos_key_share(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
         return 0;
     }
 
-    /* Get our list of supported curves */
-    tls1_get_supported_groups(s, &srvrcurves, &srvr_num_curves);
-    /* Get the clients list of supported curves. */
-    tls1_get_peer_groups(s, &clntcurves, &clnt_num_curves);
-    if (clnt_num_curves == 0) {
+    /* Get our list of supported groups */
+    tls1_get_supported_groups(s, &srvrgroups, &srvr_num_groups);
+    /* Get the clients list of supported groups. */
+    tls1_get_peer_groups(s, &clntgroups, &clnt_num_groups);
+    if (clnt_num_groups == 0) {
         /*
          * This can only happen if the supported_groups extension was not sent,
          * because we verify that the length is non-zero when we process that
@@ -553,14 +587,14 @@ int tls_parse_ctos_key_share(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
             continue;
 
         /* Check if this share is in supported_groups sent from client */
-        if (!check_in_list(s, group_id, clntcurves, clnt_num_curves, 0)) {
+        if (!check_in_list(s, group_id, clntgroups, clnt_num_groups, 0)) {
             *al = SSL_AD_ILLEGAL_PARAMETER;
             SSLerr(SSL_F_TLS_PARSE_CTOS_KEY_SHARE, SSL_R_BAD_KEY_SHARE);
             return 0;
         }
 
         /* Check if this share is for a group we can use */
-        if (!check_in_list(s, group_id, srvrcurves, srvr_num_curves, 1)) {
+        if (!check_in_list(s, group_id, srvrgroups, srvr_num_groups, 1)) {
             /* Share not suitable */
             continue;
         }
@@ -844,6 +878,29 @@ EXT_RETURN tls_construct_stoc_server_name(SSL *s, WPACKET *pkt,
     return EXT_RETURN_SENT;
 }
 
+/* Add/include the server's max fragment len extension into ServerHello */
+EXT_RETURN tls_construct_stoc_maxfragmentlen(SSL *s, WPACKET *pkt,
+                                             unsigned int context, X509 *x,
+                                             size_t chainidx, int *al)
+{
+    if (!USE_MAX_FRAGMENT_LENGTH_EXT(s->session))
+        return EXT_RETURN_NOT_SENT;
+
+    /*-
+     * 4 bytes for this extension type and extension length
+     * 1 byte for the Max Fragment Length code value.
+     */
+    if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_max_fragment_length)
+        || !WPACKET_start_sub_packet_u16(pkt)
+        || !WPACKET_put_bytes_u8(pkt, s->session->ext.max_fragment_len_mode)
+        || !WPACKET_close(pkt)) {
+        SSLerr(SSL_F_TLS_CONSTRUCT_STOC_MAXFRAGMENTLEN, ERR_R_INTERNAL_ERROR);
+        return EXT_RETURN_FAIL;
+    }
+
+    return EXT_RETURN_SENT;
+}
+
 #ifndef OPENSSL_NO_EC
 EXT_RETURN tls_construct_stoc_ec_pt_formats(SSL *s, WPACKET *pkt,
                                             unsigned int context, X509 *x,