dtls 1.3: allow rtx interval to be less than a second

Author: julek-wolfssl

src/dtls13.c

@@ -110,7 +110,9 @@ typedef struct Dtls13RecordPlaintextHeader {
    supported. */
 #define DTLS13_UNIFIED_HEADER_SIZE 5
 #define DTLS13_MIN_CIPHERTEXT 16
-#define DTLS13_MIN_RTX_INTERVAL 1
+#ifndef DTLS13_MIN_RTX_INTERVAL
+#define DTLS13_MIN_RTX_INTERVAL 1000
+#endif
 
 #ifndef NO_WOLFSSL_CLIENT
 WOLFSSL_METHOD* wolfDTLSv1_3_client_method_ex(void* heap)
@@ -1570,21 +1572,24 @@ static int Dtls13RtxSendBuffered(WOLFSSL* ssl)
     int isLast;
     int sendSz;
 #ifndef NO_ASN_TIME
+#ifdef WOLFSSL_32BIT_MILLI_TIME
     word32 now;
+#else
+    sword64 now;
+#endif
 #endif
     int ret;
 
     WOLFSSL_ENTER("Dtls13RtxSendBuffered");
 
 #ifndef NO_ASN_TIME
-    now = LowResTimer();
+    now = TimeNowInMilliseconds();
     if (now - ssl->dtls13Rtx.lastRtx < DTLS13_MIN_RTX_INTERVAL) {
 #ifdef WOLFSSL_DEBUG_TLS
         WOLFSSL_MSG("Avoid too fast retransmission");
 #endif /* WOLFSSL_DEBUG_TLS */
         return 0;
     }
-
     ssl->dtls13Rtx.lastRtx = now;
 #endif
 

src/tls13.c

@@ -1665,7 +1665,7 @@ int DeriveTls13Keys(WOLFSSL* ssl, int secret, int side, int store)
     return ret;
 }
 
-#if (defined(HAVE_SESSION_TICKET) || !defined(NO_PSK))
+#if defined(HAVE_SESSION_TICKET) || !defined(NO_PSK) || defined(WOLFSSL_DTLS13)
 #ifdef WOLFSSL_32BIT_MILLI_TIME
 #ifndef NO_ASN_TIME
 #if defined(USER_TICKS)
@@ -2264,7 +2264,7 @@ int DeriveTls13Keys(WOLFSSL* ssl, int secret, int side, int store)
      */
 #endif /* !NO_ASN_TIME */
 #endif /* WOLFSSL_32BIT_MILLI_TIME */
-#endif /* HAVE_SESSION_TICKET || !NO_PSK */
+#endif /* HAVE_SESSION_TICKET || !NO_PSK || WOLFSSL_DTLS13 */
 
 /* Add record layer header to message.
  *

tests/api/test_dtls.c

@@ -2489,3 +2489,80 @@ int test_dtls_mtu_split_messages(void)
     return TEST_SKIPPED;
 #endif
 }
+
+/* Test DTLS 1.3 minimum retransmission interval. This test calls
+ * wolfSSL_dtls_got_timeout() to simulate timeouts and verify that
+ * retransmissions are spaced at least DTLS13_MIN_RTX_INTERVAL apart.
+ */
+int test_dtls13_min_rtx_interval(void)
+{
+    EXPECT_DECLS;
+#if defined(HAVE_MANUAL_MEMIO_TESTS_DEPENDENCIES) && \
+    defined(WOLFSSL_DTLS13) && !defined(DTLS13_MIN_RTX_INTERVAL) && \
+    !defined(NO_ASN_TIME)
+    /* We don't want to test when DTLS13_MIN_RTX_INTERVAL is defined because
+     * it may be too low to trigger reliably in a test. The default value is
+     * 1 second which is sufficient for testing here. */
+    WOLFSSL_CTX *ctx_c = NULL, *ctx_s = NULL;
+    WOLFSSL *ssl_c = NULL, *ssl_s = NULL;
+    struct test_memio_ctx test_ctx;
+    int c_msg_count = 0;
+
+    XMEMSET(&test_ctx, 0, sizeof(test_ctx));
+
+    /* Setup DTLS 1.3 contexts */
+    ExpectIntEQ(test_memio_setup(&test_ctx, &ctx_c, &ctx_s, &ssl_c, &ssl_s,
+                    wolfDTLSv1_3_client_method, wolfDTLSv1_3_server_method), 0);
+
+    /* CH0 */
+    ExpectIntEQ(wolfSSL_connect(ssl_c), -1);
+    ExpectIntEQ(wolfSSL_get_error(ssl_c, -1), SSL_ERROR_WANT_READ);
+
+    /* HRR */
+    ExpectIntEQ(wolfSSL_accept(ssl_s), -1);
+    ExpectIntEQ(wolfSSL_get_error(ssl_s, -1), SSL_ERROR_WANT_READ);
+
+    /* CH1 */
+    ExpectIntEQ(wolfSSL_connect(ssl_c), -1);
+    ExpectIntEQ(wolfSSL_get_error(ssl_c, -1), SSL_ERROR_WANT_READ);
+
+    /* SH ... FINISHED */
+    ExpectIntEQ(wolfSSL_accept(ssl_s), -1);
+    ExpectIntEQ(wolfSSL_get_error(ssl_s, -1), SSL_ERROR_WANT_READ);
+
+    /* We should have SH ... FINISHED messages in the buffer */
+    ExpectIntGE(test_ctx.c_msg_count, 2);
+
+    /* Drop everything */
+    test_memio_clear_buffer(&test_ctx, 1);
+
+    /* First timeout. This one should trigger a retransmission */
+    if (wolfSSL_dtls13_use_quick_timeout(ssl_s))
+        ExpectIntEQ(wolfSSL_dtls_got_timeout(ssl_s), WOLFSSL_SUCCESS);
+    ExpectIntEQ(wolfSSL_dtls_got_timeout(ssl_s), WOLFSSL_SUCCESS);
+    /* Save the message count to make sure no new messages are sent */
+    ExpectIntGE(c_msg_count = test_ctx.c_msg_count, 2);
+
+    /* Second timeout. This one should not trigger a retransmission */
+    if (wolfSSL_dtls13_use_quick_timeout(ssl_s))
+        ExpectIntEQ(wolfSSL_dtls_got_timeout(ssl_s), WOLFSSL_SUCCESS);
+    ExpectIntEQ(wolfSSL_dtls_got_timeout(ssl_s), WOLFSSL_SUCCESS);
+    /* This is the critical check. The message count should not increase
+     * after the second timeout. DTLS13_MIN_RTX_INTERVAL should have blocked
+     * retransmission here. */
+    ExpectIntEQ(c_msg_count, test_ctx.c_msg_count);
+
+    /* Now complete the handshake. We didn't clear the first retransmission
+     * so the handshake should proceed without issues. */
+    ExpectIntEQ(test_memio_do_handshake(ssl_c, ssl_s, 10, NULL), 0);
+
+    /* Cleanup */
+    wolfSSL_free(ssl_c);
+    wolfSSL_CTX_free(ctx_c);
+    wolfSSL_free(ssl_s);
+    wolfSSL_CTX_free(ctx_s);
+    return EXPECT_RESULT();
+#else
+    return TEST_SKIPPED;
+#endif
+}

tests/api/test_dtls.h

@@ -49,6 +49,7 @@ int test_dtls_memio_wolfio(void);
 int test_dtls_memio_wolfio_stateless(void);
 int test_dtls_mtu_fragment_headroom(void);
 int test_dtls_mtu_split_messages(void);
+int test_dtls13_min_rtx_interval(void);
 
 #define TEST_DTLS_DECLS                                                        \
         TEST_DECL_GROUP("dtls", test_dtls12_basic_connection_id),              \
@@ -77,5 +78,6 @@ int test_dtls_mtu_split_messages(void);
         TEST_DECL_GROUP("dtls", test_dtls_memio_wolfio),                       \
         TEST_DECL_GROUP("dtls", test_dtls_mtu_fragment_headroom),              \
         TEST_DECL_GROUP("dtls", test_dtls_mtu_split_messages),                 \
-        TEST_DECL_GROUP("dtls", test_dtls_memio_wolfio_stateless)
+        TEST_DECL_GROUP("dtls", test_dtls_memio_wolfio_stateless),             \
+        TEST_DECL_GROUP("dtls", test_dtls13_min_rtx_interval)
 #endif /* TESTS_API_DTLS_H */

wolfssl/internal.h

@@ -5773,7 +5773,11 @@ typedef struct Dtls13Rtx {
     Dtls13RtxRecord *rtxRecords;
     Dtls13RtxRecord **rtxRecordTailPtr;
     Dtls13RecordNumber *seenRecords;
+#ifdef WOLFSSL_32BIT_MILLI_TIME
     word32 lastRtx;
+#else
+    sword64 lastRtx;
+#endif
     byte triggeredRtxs; /* Unused? */
     byte sendAcks;
     byte retransmit;
@@ -6825,7 +6829,8 @@ WOLFSSL_LOCAL word32 MacSize(const WOLFSSL* ssl);
 
     WOLFSSL_LOCAL void WriteSEQ(WOLFSSL* ssl, int verifyOrder, byte* out);
 
-#if defined(WOLFSSL_TLS13) && (defined(HAVE_SESSION_TICKET) || !defined(NO_PSK))
+#if defined(WOLFSSL_TLS13) && (defined(HAVE_SESSION_TICKET) || \
+        !defined(NO_PSK) || defined(WOLFSSL_DTLS13))
 #ifdef WOLFSSL_32BIT_MILLI_TIME
     WOLFSSL_LOCAL word32 TimeNowInMilliseconds(void);
 #else