From 6291b230807ddfe8de1cfe90def5c016a9375e9e Mon Sep 17 00:00:00 2001
From: Ronald Cron <ronald.cron@arm.com>
Date: Wed, 8 Mar 2023 15:51:25 +0100
Subject: [PATCH] tls: Add logic in handshake step to enable server version
 negotiation

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
---
 library/ssl_tls.c          | 21 +++++++++++----------
 library/ssl_tls12_server.c | 37 ++++++++++++++++++++++---------------
 2 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 6a7fa96d8..811d63d09 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -3883,22 +3883,23 @@ int mbedtls_ssl_handshake_step(mbedtls_ssl_context *ssl)
 #endif
         }
     }
-#endif
+#endif /* MBEDTLS_SSL_CLI_C */
+
 #if defined(MBEDTLS_SSL_SRV_C)
     if (ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER) {
-#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
-        if (mbedtls_ssl_conf_is_tls13_only(ssl->conf)) {
+#if defined(MBEDTLS_SSL_PROTO_TLS1_2) && defined(MBEDTLS_SSL_PROTO_TLS1_3)
+        if (ssl->tls_version == MBEDTLS_SSL_VERSION_TLS1_3) {
             ret = mbedtls_ssl_tls13_handshake_server_step(ssl);
-        }
-#endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
-
-#if defined(MBEDTLS_SSL_PROTO_TLS1_2)
-        if (mbedtls_ssl_conf_is_tls12_only(ssl->conf)) {
+        } else {
             ret = mbedtls_ssl_handshake_server_step(ssl);
         }
-#endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
-    }
+#elif defined(MBEDTLS_SSL_PROTO_TLS1_2)
+        ret = mbedtls_ssl_handshake_server_step(ssl);
+#else
+        ret = mbedtls_ssl_tls13_handshake_server_step(ssl);
 #endif
+    }
+#endif /* MBEDTLS_SSL_SRV_C */
 
     if (ret != 0) {
         /* handshake_step return error. And it is same
diff --git a/library/ssl_tls12_server.c b/library/ssl_tls12_server.c
index 656c40d5b..b781adcb7 100644
--- a/library/ssl_tls12_server.c
+++ b/library/ssl_tls12_server.c
@@ -920,12 +920,15 @@ read_record_header:
      * If renegotiating, then the input was read with mbedtls_ssl_read_record(),
      * otherwise read it ourselves manually in order to support SSLv2
      * ClientHello, which doesn't use the same record layer format.
+     * Otherwise in a scenario of TLS 1.3/TLS 1.2 version negotiation, the
+     * ClientHello has been already fully fetched by the TLS 1.3 code and the
+     * flag ssl->keep_current_message is raised.
      */
     renegotiating = 0;
 #if defined(MBEDTLS_SSL_RENEGOTIATION)
     renegotiating = (ssl->renego_status != MBEDTLS_SSL_INITIAL_HANDSHAKE);
 #endif
-    if (!renegotiating) {
+    if (!renegotiating && !ssl->keep_current_message) {
         if ((ret = mbedtls_ssl_fetch_input(ssl, 5)) != 0) {
             /* No alert on a read error. */
             MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_fetch_input", ret);
@@ -1000,24 +1003,28 @@ read_record_header:
     } else
 #endif
     {
-        if (msg_len > MBEDTLS_SSL_IN_CONTENT_LEN) {
-            MBEDTLS_SSL_DEBUG_MSG(1, ("bad client hello message"));
-            return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER;
-        }
+        if (ssl->keep_current_message) {
+            ssl->keep_current_message = 0;
+        } else {
+            if (msg_len > MBEDTLS_SSL_IN_CONTENT_LEN) {
+                MBEDTLS_SSL_DEBUG_MSG(1, ("bad client hello message"));
+                return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER;
+            }
 
-        if ((ret = mbedtls_ssl_fetch_input(ssl,
-                                           mbedtls_ssl_in_hdr_len(ssl) + msg_len)) != 0) {
-            MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_fetch_input", ret);
-            return ret;
-        }
+            if ((ret = mbedtls_ssl_fetch_input(ssl,
+                                               mbedtls_ssl_in_hdr_len(ssl) + msg_len)) != 0) {
+                MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_fetch_input", ret);
+                return ret;
+            }
 
-        /* Done reading this record, get ready for the next one */
+            /* Done reading this record, get ready for the next one */
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
-        if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) {
-            ssl->next_record_offset = msg_len + mbedtls_ssl_in_hdr_len(ssl);
-        } else
+            if (ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM) {
+                ssl->next_record_offset = msg_len + mbedtls_ssl_in_hdr_len(ssl);
+            } else
 #endif
-        ssl->in_left = 0;
+            ssl->in_left = 0;
+        }
     }
 
     buf = ssl->in_msg;