128 lines
4.4 KiB
C++
128 lines
4.4 KiB
C++
/*
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* Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "webrtc/media/base/turnutils.h"
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#include "webrtc/base/byteorder.h"
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#include "webrtc/base/checks.h"
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#include "webrtc/p2p/base/stun.h"
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namespace cricket {
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namespace {
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const size_t kTurnChannelHeaderLength = 4;
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bool IsTurnChannelData(const uint8_t* data, size_t length) {
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return length >= kTurnChannelHeaderLength && ((*data & 0xC0) == 0x40);
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}
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bool IsTurnSendIndicationPacket(const uint8_t* data, size_t length) {
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if (length < kStunHeaderSize) {
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return false;
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}
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uint16_t type = rtc::GetBE16(data);
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return (type == TURN_SEND_INDICATION);
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}
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} // namespace
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bool UnwrapTurnPacket(const uint8_t* packet,
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size_t packet_size,
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size_t* content_position,
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size_t* content_size) {
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if (IsTurnChannelData(packet, packet_size)) {
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// Turn Channel Message header format.
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// 0 1 2 3
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// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Channel Number | Length |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | |
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// / Application Data /
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// / /
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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size_t length = rtc::GetBE16(&packet[2]);
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if (length + kTurnChannelHeaderLength > packet_size) {
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return false;
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}
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*content_position = kTurnChannelHeaderLength;
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*content_size = length;
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return true;
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}
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if (IsTurnSendIndicationPacket(packet, packet_size)) {
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// Validate STUN message length.
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const size_t stun_message_length = rtc::GetBE16(&packet[2]);
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if (stun_message_length + kStunHeaderSize != packet_size) {
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return false;
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}
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// First skip mandatory stun header which is of 20 bytes.
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size_t pos = kStunHeaderSize;
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// Loop through STUN attributes until we find STUN DATA attribute.
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while (pos < packet_size) {
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// Keep reading STUN attributes until we hit DATA attribute.
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// Attribute will be a TLV structure.
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Type | Length |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Value (variable) ....
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// The value in the length field MUST contain the length of the Value
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// part of the attribute, prior to padding, measured in bytes. Since
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// STUN aligns attributes on 32-bit boundaries, attributes whose content
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// is not a multiple of 4 bytes are padded with 1, 2, or 3 bytes of
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// padding so that its value contains a multiple of 4 bytes. The
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// padding bits are ignored, and may be any value.
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uint16_t attr_type, attr_length;
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const int kAttrHeaderLength = sizeof(attr_type) + sizeof(attr_length);
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if (packet_size < pos + kAttrHeaderLength) {
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return false;
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}
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// Getting attribute type and length.
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attr_type = rtc::GetBE16(&packet[pos]);
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attr_length = rtc::GetBE16(&packet[pos + sizeof(attr_type)]);
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pos += kAttrHeaderLength; // Skip STUN_DATA_ATTR header.
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// Checking for bogus attribute length.
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if (pos + attr_length > packet_size) {
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return false;
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}
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if (attr_type == STUN_ATTR_DATA) {
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*content_position = pos;
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*content_size = attr_length;
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return true;
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}
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pos += attr_length;
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if ((attr_length % 4) != 0) {
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pos += (4 - (attr_length % 4));
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}
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}
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// There is no data attribute present in the message.
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return false;
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}
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// This is not a TURN packet.
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*content_position = 0;
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*content_size = packet_size;
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return true;
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}
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} // namespace cricket
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