1 files changed, 155 insertions, 0 deletions
diff --git a/lib/ext/ext_master_secret.c b/lib/ext/ext_master_secret.c
new file mode 100644
index 0000000..bc704e6
--- /dev/null
+++ b/lib/ext/ext_master_secret.c
@@ -0,0 +1,155 @@
+/*
+ * Copyright (C) 2014-2017 Red Hat, Inc.
+ *
+ * Author: Nikos Mavrogiannopoulos
+ *
+ * This file is part of GnuTLS.
+ *
+ * The GnuTLS is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>
+ *
+ */
+
+/* This file contains the code for the RFC7627 (ext master secret) TLS extension.
+ */
+
+#include "gnutls_int.h"
+#include "errors.h"
+#include "num.h"
+#include <hello_ext.h>
+#include <ext/ext_master_secret.h>
+
+static int _gnutls_ext_master_secret_recv_params(gnutls_session_t session,
+					  const uint8_t * data,
+					  size_t data_size);
+static int _gnutls_ext_master_secret_send_params(gnutls_session_t session,
+					  gnutls_buffer_st * extdata);
+
+const hello_ext_entry_st ext_mod_ext_master_secret = {
+	.name = "Extended Master Secret",
+	.tls_id = 23,
+	.gid = GNUTLS_EXTENSION_EXT_MASTER_SECRET,
+	.client_parse_point = GNUTLS_EXT_MANDATORY,
+	.server_parse_point = GNUTLS_EXT_MANDATORY,
+	.validity = GNUTLS_EXT_FLAG_TLS|GNUTLS_EXT_FLAG_DTLS | GNUTLS_EXT_FLAG_CLIENT_HELLO |
+		    GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO,
+	.recv_func = _gnutls_ext_master_secret_recv_params,
+	.send_func = _gnutls_ext_master_secret_send_params,
+	.pack_func = NULL,
+	.unpack_func = NULL,
+	.deinit_func = NULL,
+	.cannot_be_overriden = 1
+};
+
+#ifdef ENABLE_SSL3
+static inline unsigned have_only_ssl3_enabled(gnutls_session_t session)
+{
+	if (session->internals.priorities->protocol.num_priorities == 1 &&
+	    session->internals.priorities->protocol.priorities[0] == GNUTLS_SSL3)
+	    return 1;
+	return 0;
+}
+#endif
+
+/*
+ * In case of a server: if an EXT_MASTER_SECRET extension type is received then it
+ * sets a flag into the session security parameters.
+ *
+ */
+static int
+_gnutls_ext_master_secret_recv_params(gnutls_session_t session,
+			       const uint8_t * data, size_t _data_size)
+{
+	ssize_t data_size = _data_size;
+
+	if ((session->internals.flags & GNUTLS_NO_EXTENSIONS) ||
+	    session->internals.priorities->no_extensions ||
+	    session->internals.no_ext_master_secret != 0) {
+		return 0;
+	}
+
+	if (data_size != 0) {
+		return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
+	}
+
+#ifdef ENABLE_SSL3
+	if (session->security_parameters.entity == GNUTLS_CLIENT) {
+		const version_entry_st *ver = get_version(session);
+
+		if (unlikely(ver == NULL))
+			return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
+
+		if (ver->id != GNUTLS_SSL3)
+			session->security_parameters.ext_master_secret = 1;
+	/* do not enable ext master secret if SSL 3.0 is the only protocol supported by server */
+	} else if (!have_only_ssl3_enabled(session))
+#endif
+		session->security_parameters.ext_master_secret = 1;
+
+	return 0;
+}
+
+/* returns data_size or a negative number on failure
+ */
+static int
+_gnutls_ext_master_secret_send_params(gnutls_session_t session,
+			       gnutls_buffer_st * extdata)
+{
+	if ((session->internals.flags & GNUTLS_NO_EXTENSIONS) ||
+	    session->internals.priorities->no_extensions != 0 ||
+	    session->internals.no_ext_master_secret != 0) {
+	    session->security_parameters.ext_master_secret = 0;
+	    return 0;
+	}
+
+	/* this function sends the client extension data */
+#ifdef ENABLE_SSL3
+	if (session->security_parameters.entity == GNUTLS_CLIENT) {
+		if (have_only_ssl3_enabled(session))
+		    return 0; /* this extension isn't available for SSL 3.0 */
+
+		return GNUTLS_E_INT_RET_0;
+	} else { /* server side */
+		const version_entry_st *ver = get_version(session);
+		if (unlikely(ver == NULL))
+			return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
+
+		if (ver->id != GNUTLS_SSL3 && session->security_parameters.ext_master_secret != 0)
+			return GNUTLS_E_INT_RET_0;
+	}
+
+
+	return 0;
+#else
+	if (session->security_parameters.entity == GNUTLS_CLIENT ||
+	    session->security_parameters.ext_master_secret != 0)
+		return GNUTLS_E_INT_RET_0;
+	return 0;
+#endif
+}
+
+/**
+ * gnutls_session_ext_master_secret_status:
+ * @session: is a #gnutls_session_t type.
+ *
+ * Get the status of the extended master secret extension negotiation.
+ * This is in accordance to RFC7627. That information is also
+ * available to the more generic gnutls_session_get_flags().
+ *
+ * Returns: Non-zero if the negotiation was successful or zero otherwise.
+ **/
+unsigned gnutls_session_ext_master_secret_status(gnutls_session_t session)
+{
+	return session->security_parameters.ext_master_secret;
+}
+