Merge branch 'wip/dueno/hrr-session-id' into 'master'

handshake: don't regenerate legacy_session_id in second CH after HRR

Closes #1210

See merge request gnutls/gnutls!1411

2 files changed, 31 insertions, 9 deletions

diff --git a/lib/handshake.c b/lib/handshake.c
index 33bc7f7be6..c30703ccbd 100644
--- a/lib/handshake.c
+++ b/lib/handshake.c
@@ -2216,15 +2216,17 @@ static int send_client_hello(gnutls_session_t session, int again)
 		if (max_ver->tls13_sem &&
 		    session->internals.priorities->tls13_compat_mode &&
 		    !resuming) {
-			/* Under TLS1.3 we generate a random session ID to make
-			 * the TLS1.3 session look like a resumed TLS1.2 session */
-			ret = _gnutls_generate_session_id(session->security_parameters.
-							  session_id,
-							  &session->security_parameters.
-							  session_id_size);
-			if (ret < 0) {
-				gnutls_assert();
-				goto cleanup;
+			if (!(session->internals.hsk_flags & HSK_HRR_RECEIVED)) {
+				/* Under TLS1.3 we generate a random session ID to make
+				 * the TLS1.3 session look like a resumed TLS1.2 session */
+				ret = _gnutls_generate_session_id(session->security_parameters.
+								  session_id,
+								  &session->security_parameters.
+								  session_id_size);
+				if (ret < 0) {
+					gnutls_assert();
+					goto cleanup;
+				}
 			}
 			session_id = session->security_parameters.session_id;
 			session_id_len = session->security_parameters.session_id_size;
diff --git a/tests/tls13/hello_retry_request.c b/tests/tls13/hello_retry_request.c
index f90d4ad676..dd4506b6f9 100644
--- a/tests/tls13/hello_retry_request.c
+++ b/tests/tls13/hello_retry_request.c
@@ -69,9 +69,13 @@ static void client_log_func(int level, const char *str)
 	fprintf(stderr, "client|<%d>| %s", level, str);
 }
 
+#define HANDSHAKE_SESSION_ID_POS 34
+
 struct ctx_st {
 	unsigned hrr_seen;
 	unsigned hello_counter;
+	uint8_t session_id[32];
+	size_t session_id_len;
 };
 
 static int hello_callback(gnutls_session_t session, unsigned int htype,
@@ -84,12 +88,28 @@ static int hello_callback(gnutls_session_t session, unsigned int htype,
 		ctx->hrr_seen = 1;
 
 	if (htype == GNUTLS_HANDSHAKE_CLIENT_HELLO && post == GNUTLS_HOOK_POST) {
+		size_t session_id_len;
+		uint8_t *session_id;
+
+		assert(msg->size > HANDSHAKE_SESSION_ID_POS + 1);
+		session_id_len = msg->data[HANDSHAKE_SESSION_ID_POS];
+		session_id = &msg->data[HANDSHAKE_SESSION_ID_POS + 1];
+
 		if (ctx->hello_counter > 0) {
 			assert(msg->size > 4);
 			if (msg->data[0] != 0x03 || msg->data[1] != 0x03) {
 				fail("version is %d.%d expected 3,3\n", (int)msg->data[0], (int)msg->data[1]);
 			}
+
+			if (session_id_len != ctx->session_id_len ||
+			    memcmp(session_id, ctx->session_id, session_id_len) != 0) {
+				fail("different legacy_session_id is sent after HRR\n");
+			}
 		}
+
+		ctx->session_id_len = session_id_len;
+		memcpy(ctx->session_id, session_id, session_id_len);
+
 		ctx->hello_counter++;
 	}