1 files changed, 242 insertions, 0 deletions
diff --git a/lib/extv.c b/lib/extv.c
new file mode 100644
index 0000000..0c0c46f
--- /dev/null
+++ b/lib/extv.c
@@ -0,0 +1,242 @@
+/*
+ * Copyright (C) 2017-2018 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/>
+ *
+ */
+
+#include "gnutls_int.h"
+#include "hello_ext.h"
+#include "errors.h"
+#include "extv.h"
+
+/* Iterates through all extensions found, and calls the cb()
+ * function with their data */
+int _gnutls_extv_parse(void *ctx,
+		       gnutls_ext_raw_process_func cb,
+		       const uint8_t * data, int data_size)
+{
+	int next, ret;
+	int pos = 0;
+	uint16_t tls_id;
+	const uint8_t *sdata;
+	uint16_t size;
+
+	if (data_size == 0)
+		return 0;
+
+	DECR_LENGTH_RET(data_size, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
+	next = _gnutls_read_uint16(data);
+	pos += 2;
+
+	DECR_LENGTH_RET(data_size, next, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
+
+	if (next == 0 && data_size == 0) /* field is present, but has zero length? Ignore it. */
+		return 0;
+	else if (data_size > 0) /* forbid unaccounted data */
+		return gnutls_assert_val(GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
+
+	do {
+		DECR_LENGTH_RET(next, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
+		tls_id = _gnutls_read_uint16(&data[pos]);
+		pos += 2;
+
+		DECR_LENGTH_RET(next, 2, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
+		size = _gnutls_read_uint16(&data[pos]);
+		pos += 2;
+
+		DECR_LENGTH_RET(next, size, GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
+		sdata = &data[pos];
+		pos += size;
+
+		ret = cb(ctx, tls_id, sdata, size);
+		if (ret < 0)
+			return gnutls_assert_val(ret);
+	}
+	while (next > 2);
+
+	/* forbid leftovers */
+	if (next > 0)
+		return gnutls_assert_val(GNUTLS_E_UNEXPECTED_EXTENSIONS_LENGTH);
+
+	return 0;
+}
+
+#define HANDSHAKE_SESSION_ID_POS (34)
+/**
+ * gnutls_ext_raw_parse:
+ * @ctx: a pointer to pass to callback function
+ * @cb: callback function to process each extension found
+ * @data: TLS extension data
+ * @flags: should be zero or %GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO or %GNUTLS_EXT_RAW_FLAG_DTLS_CLIENT_HELLO
+ *
+ * This function iterates through the TLS extensions as passed in
+ * @data, passing the individual extension data to callback. The
+ * @data must conform to Extension extensions<0..2^16-1> format.
+ *
+ * If flags is %GNUTLS_EXT_RAW_TLS_FLAG_CLIENT_HELLO then this function
+ * will parse the extension data from the position, as if the packet in
+ * @data is a client hello (without record or handshake headers) -
+ * as provided by gnutls_handshake_set_hook_function().
+ *
+ * The return value of the callback will be propagated.
+ *
+ * Returns: %GNUTLS_E_SUCCESS on success, or an error code. On unknown
+ *   flags it returns %GNUTLS_E_INVALID_REQUEST.
+ *
+ * Since: 3.6.3
+ **/
+int gnutls_ext_raw_parse(void *ctx, gnutls_ext_raw_process_func cb,
+			 const gnutls_datum_t *data, unsigned int flags)
+{
+	if (flags & GNUTLS_EXT_RAW_FLAG_TLS_CLIENT_HELLO) {
+		size_t size = data->size;
+		size_t len;
+		uint8_t *p = data->data;
+
+		DECR_LEN(size, HANDSHAKE_SESSION_ID_POS);
+
+		if (p[0] != 0x03)
+			return gnutls_assert_val(GNUTLS_E_UNSUPPORTED_VERSION_PACKET);
+
+		p += HANDSHAKE_SESSION_ID_POS;
+
+		/* skip session id */
+		DECR_LEN(size, 1);
+		len = p[0];
+		p++;
+		DECR_LEN(size, len);
+		p += len;
+
+		/* CipherSuites */
+		DECR_LEN(size, 2);
+		len = _gnutls_read_uint16(p);
+		p += 2;
+		DECR_LEN(size, len);
+		p += len;
+
+		/* legacy_compression_methods */
+		DECR_LEN(size, 1);
+		len = p[0];
+		p++;
+		DECR_LEN(size, len);
+		p += len;
+
+		if (size == 0)
+			return gnutls_assert_val(GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);
+
+		return _gnutls_extv_parse(ctx, cb, p, size);
+	} else if (flags & GNUTLS_EXT_RAW_FLAG_DTLS_CLIENT_HELLO) {
+		size_t size = data->size;
+		size_t len;
+		uint8_t *p = data->data;
+
+		DECR_LEN(size, HANDSHAKE_SESSION_ID_POS);
+
+		if (p[0] != 254)
+			return gnutls_assert_val(GNUTLS_E_UNSUPPORTED_VERSION_PACKET);
+
+		p += HANDSHAKE_SESSION_ID_POS;
+
+		/* skip session id */
+		DECR_LEN(size, 1);
+		len = p[0];
+		p++;
+		DECR_LEN(size, len);
+		p += len;
+
+		/* skip cookie */
+		DECR_LEN(size, 1);
+		len = p[0];
+		p++;
+		DECR_LEN(size, len);
+		p += len;
+
+		/* CipherSuites */
+		DECR_LEN(size, 2);
+		len = _gnutls_read_uint16(p);
+		p += 2;
+		DECR_LEN(size, len);
+		p += len;
+
+		/* legacy_compression_methods */
+		DECR_LEN(size, 1);
+		len = p[0];
+		p++;
+		DECR_LEN(size, len);
+		p += len;
+
+		if (size == 0)
+			return gnutls_assert_val(GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE);
+
+		return _gnutls_extv_parse(ctx, cb, p, size);
+	}
+
+	if (flags != 0)
+		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
+
+	return _gnutls_extv_parse(ctx, cb, data->data, data->size);
+}
+
+/* Returns:
+ *  * On success the number of bytes appended (always positive), or zero if not sent
+ *  * On failure, a negative error code.
+ */
+int _gnutls_extv_append(gnutls_buffer_st *buf,
+			uint16_t tls_id,
+		        void *ctx,
+		        int (*cb)(void *ctx, gnutls_buffer_st *buf))
+{
+	int size_pos, appended, ret;
+	size_t size_prev;
+
+	ret = _gnutls_buffer_append_prefix(buf, 16, tls_id);
+	if (ret < 0)
+		return gnutls_assert_val(ret);
+
+	size_pos = buf->length;
+	ret = _gnutls_buffer_append_prefix(buf, 16, 0);
+	if (ret < 0)
+		return gnutls_assert_val(ret);
+
+	size_prev = buf->length;
+	ret = cb(ctx, buf);
+	if (ret < 0 && ret != GNUTLS_E_INT_RET_0) {
+		return gnutls_assert_val(ret);
+	}
+
+	/* returning GNUTLS_E_INT_RET_0 means to send an empty
+	 * extension of this type.
+	 */
+	appended = buf->length - size_prev;
+
+	if (appended > 0 || ret == GNUTLS_E_INT_RET_0) {
+		if (ret == GNUTLS_E_INT_RET_0)
+			appended = 0;
+
+		/* write the real size */
+		_gnutls_write_uint16(appended,
+				     &buf->data[size_pos]);
+	} else if (appended == 0) {
+		buf->length -= 4;	/* reset type and size */
+		return 0;
+	}
+
+	return appended + 4;
+}
+