commit 951b8868011366c8717e7136ba38cabf9d06cc72
author Max Fillinger <max@max-fillinger.net> Fri Oct 25 00:52:24 2024 +0200
committer Max Fillinger <maximilian.fillinger@foxcrypto.com> Wed Apr 16 11:20:50 2025 +0200
tree fd5d88aa0617bddc0c1bf625a8509184e2d25071
parent 7b52328f6c43d5030ced3500e0ee333115d8f5f3

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>

library/ssl_misc.h

diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 2925495..0fe2800 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1166,10 +1166,11 @@
     unsigned char out_cid[MBEDTLS_SSL_CID_OUT_LEN_MAX];
 #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */
 
-#if defined(MBEDTLS_SSL_CONTEXT_SERIALIZATION)
+#if defined(MBEDTLS_SSL_KEEP_RANDBYTES)
     /* We need the Hello random bytes in order to re-derive keys from the
-     * Master Secret and other session info,
-     * see ssl_tls12_populate_transform() */
+     * Master Secret and other session info and for the keying material
+     * exporter in TLS 1.2.
+     * See ssl_tls12_populate_transform() */
     unsigned char randbytes[MBEDTLS_SERVER_HELLO_RANDOM_LEN +
                             MBEDTLS_CLIENT_HELLO_RANDOM_LEN];
     /*!< ServerHello.random+ClientHello.random */

library/ssl_tls.c

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 971821a..d631420 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -8669,7 +8669,7 @@
 #endif /* MBEDTLS_SSL_SOME_SUITES_USE_CBC_ETM */
     transform->tls_version = tls_version;
 
-#if defined(MBEDTLS_SSL_CONTEXT_SERIALIZATION)
+#if defined(MBEDTLS_SSL_KEEP_RANDBYTES)
     memcpy(transform->randbytes, randbytes, sizeof(transform->randbytes));
 #endif
 
@@ -10054,8 +10054,7 @@
 }
 #endif /* MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED */
 
-
-#if defined(MBEDTLS_SSL_CONTEXT_SERIALIZATION) || !defined(MBEDTLS_SSL_PROTO_TLS1_2)
+#if defined(MBEDTLS_SSL_KEYING_MATERIAL_EXPORT)
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2)
 static int mbedtls_ssl_tls12_export_keying_material(const mbedtls_ssl_context *ssl,
@@ -10176,6 +10175,6 @@
     }
 }
 
-#endif /* defined(MBEDTLS_SSL_CONTEXT_SERIALIZATION) || !defined(MBEDTLS_SSL_PROTO_TLS1_2) */
+#endif /* defined(MBEDTLS_SSL_KEYING_MATERIAL_EXPORT) */
 
 #endif /* MBEDTLS_SSL_TLS_C */