From d7d8d14e953a13f8c236d6eba2f268de67584980 Mon Sep 17 00:00:00 2001
From: Sean Parkinson <sean@wolfssl.com>
Date: Fri, 7 Jun 2024 10:00:33 +1000
Subject: [PATCH] TLS: wrong TLS version in alert after ClientHello

Ignore protocol version being less than expected when received directly
after ClientHello.
Protocol version negotiation hasn't taken place and a lower version can
be sent to cover minimum supported protocol version.
---
 src/internal.c | 15 ++++++++++++++-
 tests/api.c    | 29 +++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/internal.c b/src/internal.c
index 3620954ff1..95e50a11c4 100644
--- a/src/internal.c
+++ b/src/internal.c
@@ -11456,7 +11456,20 @@ static int GetRecordHeader(WOLFSSL* ssl, word32* inOutIdx,
             }
         }
 #endif /* WOLFSSL_DTLS13 */
-        else {
+        /* Don't care about protocol version being lower than expected on alerts
+         * sent back before version negotitation. */
+        else if (!(ssl->options.side == WOLFSSL_CLIENT_END &&
+                            ssl->options.connectState == CLIENT_HELLO_SENT &&
+                            rh->type == alert &&
+                            rh->pvMajor == ssl->version.major &&
+        #ifdef WOLFSSL_DTLS
+                            ((ssl->options.dtls && rh->pvMinor == DTLS_MINOR) ||
+                             (!ssl->options.dtls &&
+                              rh->pvMinor < ssl->version.minor))
+        #else
+                            rh->pvMinor < ssl->version.minor
+        #endif
+                   )) {
             WOLFSSL_MSG("SSL version error");
             WOLFSSL_ERROR_VERBOSE(VERSION_ERROR);
             return VERSION_ERROR;              /* only use requested version */
diff --git a/tests/api.c b/tests/api.c
index da7adf82ff..abb7cdcac9 100644
--- a/tests/api.c
+++ b/tests/api.c
@@ -70460,6 +70460,34 @@ static int test_dtls_no_extensions(void)
     return EXPECT_RESULT();
 }
 
+static int test_tls_alert_no_server_hello(void)
+{
+    EXPECT_DECLS;
+#if defined(HAVE_MANUAL_MEMIO_TESTS_DEPENDENCIES) && !defined(WOLFSSL_NO_TLS12)
+    WOLFSSL *ssl_c = NULL;
+    WOLFSSL_CTX *ctx_c = NULL;
+    struct test_memio_ctx test_ctx;
+    unsigned char alert_msg[] = { 0x15, 0x03, 0x01, 0x00, 0x02, 0x02, 0x28 };
+
+    XMEMSET(&test_ctx, 0, sizeof(test_ctx));
+    ssl_c = NULL;
+    ctx_c = NULL;
+
+    ExpectIntEQ(test_memio_setup(&test_ctx, &ctx_c, NULL, &ssl_c, NULL,
+        wolfTLSv1_2_client_method, NULL), 0);
+
+    XMEMCPY(test_ctx.c_buff, alert_msg, sizeof(alert_msg));
+    test_ctx.c_len = sizeof(alert_msg);
+
+    ExpectIntEQ(wolfSSL_connect(ssl_c), -1);
+    ExpectIntEQ(wolfSSL_get_error(ssl_c, -1), FATAL_ERROR);
+
+    wolfSSL_free(ssl_c);
+    wolfSSL_CTX_free(ctx_c);
+#endif
+    return EXPECT_RESULT();
+}
+
 static int test_TLSX_CA_NAMES_bad_extension(void)
 {
     EXPECT_DECLS;
@@ -74037,6 +74065,7 @@ TEST_CASE testCases[] = {
     TEST_DECL(test_dtls_ipv6_check),
     TEST_DECL(test_wolfSSL_SCR_after_resumption),
     TEST_DECL(test_dtls_no_extensions),
+    TEST_DECL(test_tls_alert_no_server_hello),
     TEST_DECL(test_TLSX_CA_NAMES_bad_extension),
     TEST_DECL(test_dtls_1_0_hvr_downgrade),
     TEST_DECL(test_session_ticket_no_id),