Merge pull request #7058 from yuhaoth/pr/tls13-early-data-parsing-0-rtt-data

TLS 1.3 EarlyData SRV: Parsing 0-RTT data

include/mbedtls/ssl.h

@@ -687,7 +687,6 @@ typedef enum {
     MBEDTLS_SSL_SERVER_FINISHED,
     MBEDTLS_SSL_FLUSH_BUFFERS,
     MBEDTLS_SSL_HANDSHAKE_WRAPUP,
-
     MBEDTLS_SSL_NEW_SESSION_TICKET,
     MBEDTLS_SSL_SERVER_HELLO_VERIFY_REQUEST_SENT,
     MBEDTLS_SSL_HELLO_RETRY_REQUEST,

library/ssl_tls13_server.c

@@ -1880,10 +1880,18 @@ static int ssl_tls13_postprocess_client_hello(mbedtls_ssl_context *ssl)
 #if defined(MBEDTLS_SSL_EARLY_DATA)
     /* There is enough information, update early data state. */
     ssl_tls13_update_early_data_status(ssl);
+
+    if (ssl->early_data_status == MBEDTLS_SSL_EARLY_DATA_STATUS_ACCEPTED) {
+        ret = mbedtls_ssl_tls13_compute_early_transform(ssl);
+        if (ret != 0) {
+            MBEDTLS_SSL_DEBUG_RET(
+                1, "mbedtls_ssl_tls13_compute_early_transform", ret);
+            return ret;
+        }
+    }
 #endif /* MBEDTLS_SSL_EARLY_DATA */
 
     return 0;
-
 }
 
 /*
@@ -2748,6 +2756,59 @@ static int ssl_tls13_write_certificate_verify(mbedtls_ssl_context *ssl)
 }
 #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */
 
+/*
+ * RFC 8446 section A.2
+ *
+ *                                | Send ServerHello
+ *                                | K_send = handshake
+ *                                | Send EncryptedExtensions
+ *                                | [Send CertificateRequest]
+ * Can send                       | [Send Certificate + CertificateVerify]
+ * app data                       | Send Finished
+ * after   -->                    | K_send = application
+ * here                  +--------+--------+
+ *              No 0-RTT |                 | 0-RTT
+ *                       |                 |
+ *   K_recv = handshake  |                 | K_recv = early data
+ * [Skip decrypt errors] |    +------> WAIT_EOED -+
+ *                       |    |       Recv |      | Recv EndOfEarlyData
+ *                       |    | early data |      | K_recv = handshake
+ *                       |    +------------+      |
+ *                       |                        |
+ *                       +> WAIT_FLIGHT2 <--------+
+ *                                |
+ *                       +--------+--------+
+ *               No auth |                 | Client auth
+ *                       |                 |
+ *                       |                 v
+ *                       |             WAIT_CERT
+ *                       |        Recv |       | Recv Certificate
+ *                       |       empty |       v
+ *                       | Certificate |    WAIT_CV
+ *                       |             |       | Recv
+ *                       |             v       | CertificateVerify
+ *                       +-> WAIT_FINISHED <---+
+ *                                | Recv Finished
+ *
+ *
+ * The following function handles the state changes after WAIT_FLIGHT2 in the
+ * above diagram. We are not going to receive early data related messages
+ * anymore, prepare to receive the first handshake message of the client
+ * second flight.
+ */
+static void ssl_tls13_prepare_for_handshake_second_flight(
+    mbedtls_ssl_context *ssl)
+{
+    if (ssl->handshake->certificate_request_sent) {
+        mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE);
+    } else {
+        MBEDTLS_SSL_DEBUG_MSG(2, ("skip parse certificate"));
+        MBEDTLS_SSL_DEBUG_MSG(2, ("skip parse certificate verify"));
+
+        mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_FINISHED);
+    }
+}
+
 /*
  * Handler for MBEDTLS_SSL_SERVER_FINISHED
  */
@@ -2769,20 +2830,200 @@ static int ssl_tls13_write_server_finished(mbedtls_ssl_context *ssl)
         return ret;
     }
 
-    MBEDTLS_SSL_DEBUG_MSG(1, ("Switch to handshake keys for inbound traffic"));
+#if defined(MBEDTLS_SSL_EARLY_DATA)
+    if (ssl->early_data_status == MBEDTLS_SSL_EARLY_DATA_STATUS_ACCEPTED) {
+        /* See RFC 8446 section A.2 for more information */
+        MBEDTLS_SSL_DEBUG_MSG(
+            1, ("Switch to early keys for inbound traffic. "
+                "( K_recv = early data )"));
+        mbedtls_ssl_set_inbound_transform(
+            ssl, ssl->handshake->transform_earlydata);
+        mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_END_OF_EARLY_DATA);
+        return 0;
+    }
+#endif /* MBEDTLS_SSL_EARLY_DATA */
+    MBEDTLS_SSL_DEBUG_MSG(
+        1, ("Switch to handshake keys for inbound traffic "
+            "( K_recv = handshake )"));
     mbedtls_ssl_set_inbound_transform(ssl, ssl->handshake->transform_handshake);
 
-    if (ssl->handshake->certificate_request_sent) {
+    ssl_tls13_prepare_for_handshake_second_flight(ssl);
-        mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE);
-    } else {
-        MBEDTLS_SSL_DEBUG_MSG(2, ("skip parse certificate"));
-        MBEDTLS_SSL_DEBUG_MSG(2, ("skip parse certificate verify"));
-        mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_FINISHED);
-    }
 
     return 0;
 }
 
+#if defined(MBEDTLS_SSL_EARLY_DATA)
+/*
+ * Handler for MBEDTLS_SSL_END_OF_EARLY_DATA
+ */
+#define SSL_GOT_END_OF_EARLY_DATA      0
+#define SSL_GOT_EARLY_DATA             1
+/* Coordination:
+ * Deals with the ambiguity of not knowing if the next message is an
+ * EndOfEarlyData message or an application message containing early data.
+ * Returns a negative code on failure, or
+ * - SSL_GOT_END_OF_EARLY_DATA
+ * - SSL_GOT_EARLY_DATA
+ * indicating which message is received.
+ */
+MBEDTLS_CHECK_RETURN_CRITICAL
+static int ssl_tls13_end_of_early_data_coordinate(mbedtls_ssl_context *ssl)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    if ((ret = mbedtls_ssl_read_record(ssl, 0)) != 0) {
+        MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_read_record", ret);
+        return ret;
+    }
+    ssl->keep_current_message = 1;
+
+    if (ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE        &&
+        ssl->in_msg[0]  == MBEDTLS_SSL_HS_END_OF_EARLY_DATA) {
+        MBEDTLS_SSL_DEBUG_MSG(3, ("Received an end_of_early_data message."));
+        return SSL_GOT_END_OF_EARLY_DATA;
+    }
+
+    if (ssl->in_msgtype == MBEDTLS_SSL_MSG_APPLICATION_DATA) {
+        MBEDTLS_SSL_DEBUG_MSG(3, ("Received early data"));
+        return SSL_GOT_EARLY_DATA;
+    }
+
+    MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE,
+                                 MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE);
+    return MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE;
+}
+
+MBEDTLS_CHECK_RETURN_CRITICAL
+static int ssl_tls13_parse_end_of_early_data(mbedtls_ssl_context *ssl,
+                                             const unsigned char *buf,
+                                             const unsigned char *end)
+{
+    /* RFC 8446 section 4.5
+     *
+     * struct {} EndOfEarlyData;
+     */
+    if (buf != end) {
+        MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR,
+                                     MBEDTLS_ERR_SSL_DECODE_ERROR);
+        return MBEDTLS_ERR_SSL_DECODE_ERROR;
+    }
+    return 0;
+}
+
+MBEDTLS_CHECK_RETURN_CRITICAL
+static int ssl_tls13_process_early_application_data(mbedtls_ssl_context *ssl)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    if ((ret = mbedtls_ssl_read_record(ssl, 0)) != 0) {
+        MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_read_record", ret);
+        return ret;
+    }
+
+    /*
+     * Output early data
+     *
+     * For the time being, we print received data via debug message.
+     *
+     * TODO: Remove it when `mbedtls_ssl_read_early_data` is ready.
+     */
+    ssl->in_msg[ssl->in_msglen] = 0;
+    MBEDTLS_SSL_DEBUG_MSG(3, ("\n%s", ssl->in_msg));
+
+    /* RFC 8446 section 4.6.1
+     *
+     * A server receiving more than max_early_data_size bytes of 0-RTT data
+     * SHOULD terminate the connection with an "unexpected_message" alert.
+     *
+     * TODO: Add received data size check here.
+     */
+
+    return 0;
+}
+
+/*
+ * RFC 8446 section A.2
+ *
+ *                                | Send ServerHello
+ *                                | K_send = handshake
+ *                                | Send EncryptedExtensions
+ *                                | [Send CertificateRequest]
+ * Can send                       | [Send Certificate + CertificateVerify]
+ * app data                       | Send Finished
+ * after   -->                    | K_send = application
+ * here                  +--------+--------+
+ *              No 0-RTT |                 | 0-RTT
+ *                       |                 |
+ *   K_recv = handshake  |                 | K_recv = early data
+ * [Skip decrypt errors] |    +------> WAIT_EOED -+
+ *                       |    |       Recv |      | Recv EndOfEarlyData
+ *                       |    | early data |      | K_recv = handshake
+ *                       |    +------------+      |
+ *                       |                        |
+ *                       +> WAIT_FLIGHT2 <--------+
+ *                                |
+ *                       +--------+--------+
+ *               No auth |                 | Client auth
+ *                       |                 |
+ *                       |                 v
+ *                       |             WAIT_CERT
+ *                       |        Recv |       | Recv Certificate
+ *                       |       empty |       v
+ *                       | Certificate |    WAIT_CV
+ *                       |             |       | Recv
+ *                       |             v       | CertificateVerify
+ *                       +-> WAIT_FINISHED <---+
+ *                                | Recv Finished
+ *
+ * The function handles actions and state changes from 0-RTT to WAIT_FLIGHT2 in
+ * the above diagram.
+ */
+MBEDTLS_CHECK_RETURN_CRITICAL
+static int ssl_tls13_process_end_of_early_data(mbedtls_ssl_context *ssl)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    MBEDTLS_SSL_DEBUG_MSG(2, ("=> ssl_tls13_process_end_of_early_data"));
+
+    MBEDTLS_SSL_PROC_CHK_NEG(ssl_tls13_end_of_early_data_coordinate(ssl));
+
+    if (ret == SSL_GOT_END_OF_EARLY_DATA) {
+        unsigned char *buf;
+        size_t buf_len;
+
+        MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_tls13_fetch_handshake_msg(
+                                 ssl, MBEDTLS_SSL_HS_END_OF_EARLY_DATA,
+                                 &buf, &buf_len));
+
+        MBEDTLS_SSL_PROC_CHK(ssl_tls13_parse_end_of_early_data(
+                                 ssl, buf, buf + buf_len));
+
+        MBEDTLS_SSL_DEBUG_MSG(
+            1, ("Switch to handshake keys for inbound traffic"
+                "( K_recv = handshake )"));
+        mbedtls_ssl_set_inbound_transform(
+            ssl, ssl->handshake->transform_handshake);
+
+        MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_add_hs_msg_to_checksum(
+                                 ssl, MBEDTLS_SSL_HS_END_OF_EARLY_DATA,
+                                 buf, buf_len));
+
+        ssl_tls13_prepare_for_handshake_second_flight(ssl);
+
+    } else if (ret == SSL_GOT_EARLY_DATA) {
+        MBEDTLS_SSL_PROC_CHK(ssl_tls13_process_early_application_data(ssl));
+    } else {
+        MBEDTLS_SSL_DEBUG_MSG(1, ("should never happen"));
+        ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
+        goto cleanup;
+    }
+
+cleanup:
+    MBEDTLS_SSL_DEBUG_MSG(2, ("<= ssl_tls13_process_end_of_early_data"));
+    return ret;
+}
+#endif /* MBEDTLS_SSL_EARLY_DATA */
+
 /*
  * Handler for MBEDTLS_SSL_CLIENT_FINISHED
  */
@@ -3207,6 +3448,12 @@ int mbedtls_ssl_tls13_handshake_server_step(mbedtls_ssl_context *ssl)
             ret = ssl_tls13_write_server_finished(ssl);
             break;
 
+#if defined(MBEDTLS_SSL_EARLY_DATA)
+        case MBEDTLS_SSL_END_OF_EARLY_DATA:
+            ret = ssl_tls13_process_end_of_early_data(ssl);
+            break;
+#endif /* MBEDTLS_SSL_EARLY_DATA */
+
         case MBEDTLS_SSL_CLIENT_FINISHED:
             ret = ssl_tls13_process_client_finished(ssl);
             break;

tests/opt-testcases/tls13-misc.sh

@@ -513,12 +513,12 @@ requires_all_configs_enabled MBEDTLS_SSL_EARLY_DATA MBEDTLS_SSL_SESSION_TICKETS
                              MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE
 requires_any_configs_enabled MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ENABLED \
                              MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL_ENABLED
-run_test "TLS 1.3 G->m: EarlyData: feature is enabled, fail." \
+run_test "TLS 1.3 G->m: EarlyData: feature is enabled, good." \
          "$P_SRV force_version=tls13 debug_level=4 max_early_data_size=$EARLY_DATA_INPUT_LEN" \
          "$G_NEXT_CLI localhost --priority=NORMAL:-VERS-ALL:+VERS-TLS1.3:+GROUP-ALL:+KX-ALL \
                       -d 10 -r --earlydata $EARLY_DATA_INPUT " \
-         1 \
+         0 \
          -s "ClientHello: early_data(42) extension exists."                 \
          -s "EncryptedExtensions: early_data(42) extension exists."         \
          -s "NewSessionTicket: early_data(42) extension does not exist."    \
-         -s "Last error was: -29056 - SSL - Verification of the message MAC failed"
+         -s "$( tail -1 $EARLY_DATA_INPUT )"