Added implementation of keying material export (RFC 5705) (API for PRF implementation...

[BearSSL] / src / ssl / ssl_keyexport.c

diff --git a/src/ssl/ssl_keyexport.c b/src/ssl/ssl_keyexport.c
new file mode 100644 (file)
index 0000000..58e6dc3
--- /dev/null
+++ b/src/ssl/ssl_keyexport.c
@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/*
+ * Supported cipher suites that use SHA-384 for the PRF when selected
+ * for TLS 1.2. All other cipher suites are deemed to use SHA-256.
+ */
+static const uint16_t suites_sha384[] = {
+       BR_TLS_RSA_WITH_AES_256_GCM_SHA384,
+       BR_TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384,
+       BR_TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384,
+       BR_TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384,
+       BR_TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384,
+       BR_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+       BR_TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384,
+       BR_TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+       BR_TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384
+};
+
+/* see bearssl_ssl.h */
+int
+br_ssl_key_export(br_ssl_engine_context *cc,
+       void *dst, size_t len, const char *label,
+       const void *context, size_t context_len)
+{
+       br_tls_prf_seed_chunk chunks[4];
+       br_tls_prf_impl iprf;
+       size_t num_chunks, u;
+       unsigned char tmp[2];
+       int prf_id;
+
+       if (cc->application_data != 1) {
+               return 0;
+       }
+       chunks[0].data = cc->client_random;
+       chunks[0].len = sizeof cc->client_random;
+       chunks[1].data = cc->server_random;
+       chunks[1].len = sizeof cc->server_random;
+       if (context != NULL) {
+               br_enc16be(tmp, (unsigned)context_len);
+               chunks[2].data = tmp;
+               chunks[2].len = 2;
+               chunks[3].data = context;
+               chunks[3].len = context_len;
+               num_chunks = 4;
+       } else {
+               num_chunks = 2;
+       }
+       prf_id = BR_SSLPRF_SHA256;
+       for (u = 0; u < (sizeof suites_sha384) / sizeof(uint16_t); u ++) {
+               if (suites_sha384[u] == cc->session.cipher_suite) {
+                       prf_id = BR_SSLPRF_SHA384;
+               }
+       }
+       iprf = br_ssl_engine_get_PRF(cc, prf_id);
+       iprf(dst, len,
+               cc->session.master_secret, sizeof cc->session.master_secret,
+               label, num_chunks, chunks);
+       return 1;
+}