1 files changed, 98 insertions, 0 deletions
diff --git a/lib/ext/record_size_limit.c b/lib/ext/record_size_limit.c
new file mode 100644
index 0000000000..bb8d0c4d97
--- /dev/null
+++ b/lib/ext/record_size_limit.c
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2018 Red Hat, Inc.
+ *
+ * Author: Daiki Ueno
+ *
+ * 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 <http://www.gnu.org/licenses/>
+ *
+ */
+
+/* This file contains the code for the Record Size Limit TLS extension.
+ */
+
+#include "gnutls_int.h"
+#include "errors.h"
+#include "num.h"
+#include <hello_ext.h>
+#include <ext/record_size_limit.h>
+
+static int _gnutls_record_size_limit_recv_params(gnutls_session_t session,
+						 const uint8_t * data,
+						 size_t data_size);
+static int _gnutls_record_size_limit_send_params(gnutls_session_t session,
+						 gnutls_buffer_st * extdata);
+
+const hello_ext_entry_st ext_mod_record_size_limit = {
+	.name = "Record Size Limit",
+	.tls_id = 28,
+	.gid = GNUTLS_EXTENSION_RECORD_SIZE_LIMIT,
+	.parse_type = GNUTLS_EXT_TLS,
+	.validity = GNUTLS_EXT_FLAG_TLS | GNUTLS_EXT_FLAG_DTLS | GNUTLS_EXT_FLAG_CLIENT_HELLO |
+		    GNUTLS_EXT_FLAG_EE,
+	.recv_func = _gnutls_record_size_limit_recv_params,
+	.send_func = _gnutls_record_size_limit_send_params
+};
+
+static int
+_gnutls_record_size_limit_recv_params(gnutls_session_t session,
+				      const uint8_t * data, size_t _data_size)
+{
+	ssize_t new_size;
+	ssize_t data_size = _data_size;
+
+	DECR_LEN(data_size, 2);
+	new_size = _gnutls_read_uint16(data);
+
+	/* protocol error */
+	if (new_size < 64)
+		return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);
+
+	/* we do not want to accept sizes less than our minimum */
+	if (new_size < MIN_RECORD_SIZE)
+		return 0;
+
+	session->internals.hsk_flags |= HSK_RECORD_SIZE_LIMIT_NEGOTIATED;
+
+	/* if a larger record size limit than the protocol limit is
+	 * provided by the peer, ignore it and stick to the default */
+	if (unlikely(new_size > DEFAULT_MAX_RECORD_SIZE))
+		return gnutls_assert_val(0);
+
+	session->security_parameters.max_record_send_size = new_size;
+	session->security_parameters.max_record_recv_size = new_size;
+
+	return 0;
+}
+
+/* returns data_size or a negative number on failure
+ */
+static int
+_gnutls_record_size_limit_send_params(gnutls_session_t session,
+				      gnutls_buffer_st * extdata)
+{
+	int ret;
+
+	assert(session->security_parameters.max_record_send_size >= 64 &&
+	       session->security_parameters.max_record_send_size <=
+	       DEFAULT_MAX_RECORD_SIZE);
+
+	ret = _gnutls_buffer_append_prefix(extdata, 16,
+					   session->security_parameters.max_record_send_size);
+	if (ret < 0)
+		return gnutls_assert_val(ret);
+
+	return 2;
+}