1 files changed, 84 insertions, 0 deletions
diff --git a/lib/ext/dumbfw.c b/lib/ext/dumbfw.c
new file mode 100644
index 0000000..dfd2ee0
--- /dev/null
+++ b/lib/ext/dumbfw.c
@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2013-2018 Nikos Mavrogiannopoulos
+ * Copyright (C) 2018 Red Hat, Inc.
+ * 
+ * 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/>
+ *
+ */
+
+#include "gnutls_int.h"
+#include "auth.h"
+#include "errors.h"
+#include "num.h"
+#include <ext/dumbfw.h>
+
+/* This extension adds additional padding data in the TLS client hello.
+ * There is an issue with some firewalls [0] rejecting TLS client hello
+ * data that are between 256 and 511 bytes, and this extension will
+ * make sure that client hello isn't in this range.
+ *
+ * [0]. https://www.ietf.org/mail-archive/web/tls/current/msg10423.html
+ */
+
+static int _gnutls_dumbfw_send_params(gnutls_session_t session,
+				    gnutls_buffer_st * extdata);
+
+const hello_ext_entry_st ext_mod_dumbfw = {
+	.name = "ClientHello Padding",
+	.tls_id = 21,
+	.gid = GNUTLS_EXTENSION_DUMBFW,
+	.client_parse_point = GNUTLS_EXT_APPLICATION,
+	.server_parse_point = GNUTLS_EXT_APPLICATION,
+	.validity = GNUTLS_EXT_FLAG_TLS | GNUTLS_EXT_FLAG_CLIENT_HELLO,
+	.recv_func = NULL,
+	.send_func = _gnutls_dumbfw_send_params,
+	.pack_func = NULL,
+	.unpack_func = NULL,
+	.deinit_func = NULL,
+	.cannot_be_overriden = 0
+};
+
+static int
+_gnutls_dumbfw_send_params(gnutls_session_t session,
+			 gnutls_buffer_st * extdata)
+{
+	int total_size = 0, ret;
+	uint8_t pad[257];
+	unsigned pad_size;
+	ssize_t len = extdata->length - sizeof(mbuffer_st);
+
+	if (session->security_parameters.entity == GNUTLS_SERVER ||
+	    session->internals.dumbfw == 0 ||
+	    IS_DTLS(session) != 0 ||
+	    (len < 256 || len >= 512)) {
+		return 0;
+	} else {
+		/* 256 <= extdata->length < 512 */
+		pad_size = 512 - len;
+		memset(pad, 0, pad_size);
+
+		ret =
+		    gnutls_buffer_append_data(extdata, pad,
+						       pad_size);
+		if (ret < 0)
+			return gnutls_assert_val(ret);
+
+		total_size += pad_size;
+	}
+
+	return total_size;
+}
+