commit 2fe35f61bf90ea0d589ce2485482356a1263c017
author Max Fillinger <max@max-fillinger.net> Fri Oct 25 00:52:24 2024 +0200
committer Max Fillinger <maximilian.fillinger@foxcrypto.com> Fri Mar 28 16:53:58 2025 +0100
tree 0b021fd4d8927fb52d5e8a1e3b65dfa9c1078c78
parent 281fb791166465ad50db97e4b0e47f51e9b2d867

Create MBEDTLS_SSL_KEYING_MATERIAL_EXPORT option

Add the option MBEDTLS_SSL_KEYING_MATERIAL_EXPORT to mbedtls_config.h
to control if the function mbedtls_ssl_export_keying_material() should
be available. By default, the option is disabled.

This is because the exporter for TLS 1.2 requires client_random and
server_random need to be stored after the handshake is complete.

Signed-off-by: Max Fillinger <max@max-fillinger.net>

include/mbedtls/ssl.h

diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 9ded4e6..8383ead 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -676,6 +676,14 @@
 /* Length in number of bytes of the TLS sequence number */
 #define MBEDTLS_SSL_SEQUENCE_NUMBER_LEN 8
 
+/* Helper to state that client_random and server_random need to be stored
+ * after the handshake is complete. This is required for context serialization
+ * and for the keying material exporter in TLS 1.2. */
+#if defined(MBEDTLS_SSL_CONTEXT_SERIALIZATION) || \
+    (defined(MBEDTLS_SSL_KEYING_MATERIAL_EXPORT) && defined(MBEDTLS_SSL_PROTO_TLS1_2))
+#define MBEDTLS_SSL_KEEP_RANDBYTES
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -5407,7 +5415,7 @@
  *
  * \return            0 on success. An SSL specific error on failure.
  */
- #if defined(MBEDTLS_SSL_CONTEXT_SERIALIZATION) || !defined(MBEDTLS_SSL_PROTO_TLS1_2)
+#if defined(MBEDTLS_SSL_KEYING_MATERIAL_EXPORT)
 int mbedtls_ssl_export_keying_material(mbedtls_ssl_context *ssl,
                                        uint8_t *out, const size_t key_len,
                                        const char *label, const size_t label_len,