Improve some debug messages and error codes

On a parsing error in TLS, return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE, not a crypto error code. On error paths, emit a level-1 debug message. Report the offending sizes. Downgrade an informational message's level to 3. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
misch7 · Oct 2, 2023 · 530c423 · 530c423
1 parent 6dd5b9a
commit 530c423
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Showing 2 changed files with 15 additions and 6 deletions.
diff --git a/library/ssl_tls12_server.c b/library/ssl_tls12_server.c
@@ -3718,25 +3718,31 @@ static int ssl_parse_client_key_exchange(mbedtls_ssl_context *ssl)
         psa_status_t status = PSA_ERROR_GENERIC_ERROR;
         mbedtls_ssl_handshake_params *handshake = ssl->handshake;
 
-        MBEDTLS_SSL_DEBUG_MSG(1, ("Read the peer's public key."));
+        MBEDTLS_SSL_DEBUG_MSG(3, ("Read the peer's public key."));
 
         /*
          * We must have at least two bytes (1 for length, at least 1 for data)
          */
         if (buf_len < 2) {
-            MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid buffer length"));
-            return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
+            MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid buffer length: %" MBEDTLS_PRINTF_SIZET,
+                                      buf_len));
+            return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
         }
 
         if (data_len < 1 || data_len > buf_len) {
-            MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid data length"));
-            return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
+            MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid data length: %" MBEDTLS_PRINTF_SIZET
+                                      " > %" MBEDTLS_PRINTF_SIZET,
+                                      data_len, buf_len));
+            return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
         }
 
         /* Store peer's ECDH public key. */
         MBEDTLS_SSL_DEBUG_MSG(3, ("data_len=%zu sizeof(handshake->xxdh_psa_peerkey)=%zu", data_len, sizeof(handshake->xxdh_psa_peerkey)));
         if (data_len > sizeof(handshake->xxdh_psa_peerkey)) {
-            MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid data length"));
+            MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid public key length: %" MBEDTLS_PRINTF_SIZET
+                                      " > %" MBEDTLS_PRINTF_SIZET,
+                                      data_len,
+                                      sizeof(handshake->xxdh_psa_peerkey)));
             return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
         }
         memcpy(handshake->xxdh_psa_peerkey, p, data_len);

diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
@@ -1518,6 +1518,9 @@ int mbedtls_ssl_tls13_read_public_xxdhe_share(mbedtls_ssl_context *ssl,
 
     /* Store peer's ECDH/FFDH public key. */
     if (peerkey_len > sizeof(handshake->xxdh_psa_peerkey)) {
+        MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid public key length: %u > %" MBEDTLS_PRINTF_SIZET,
+                                  (unsigned) peerkey_len,
+                                  sizeof(handshake->xxdh_psa_peerkey)));
         return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
     }
     memcpy(handshake->xxdh_psa_peerkey, p, peerkey_len);