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>

library/ssl_misc.h

diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index e51a3df..596e7bc 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1118,10 +1118,11 @@
     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 e4450b6..c20a68d 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -7746,7 +7746,7 @@
 #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
 
@@ -8930,8 +8930,7 @@
 }
 #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,
@@ -9052,6 +9051,6 @@
     }
 }
 
-#endif /* defined(MBEDTLS_SSL_CONTEXT_SERIALIZATION) || !defined(MBEDTLS_SSL_PROTO_TLS1_2) */
+#endif /* defined(MBEDTLS_SSL_KEYING_MATERIAL_EXPORT) */
 
 #endif /* MBEDTLS_SSL_TLS_C */