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