1 // Copyright 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "chrome/browser/net/probe_message.h"
6
7 #include <string>
8
9 #include "base/logging.h"
10
11 namespace chrome_browser_net {
12
13 const uint32 ProbeMessage::kVersion = 2;
14 const uint32 ProbeMessage::kMaxNumberProbePackets = 21;
15 const uint32 ProbeMessage::kMaxProbePacketBytes = 1500;
16 // Maximum pacing interval is 300 seconds (for testing NAT binding).
17 const uint32 ProbeMessage::kMaxPacingIntervalMicros = 300000000;
18 const char ProbeMessage::kEncodingString[] =
19 "T\xd3?\xa5h2\x9c\x8en\xf1Q6\xbc{\xc6-4\xfa$f\xb9[\xa6\xcd@6,\xdf\xb3i-\xe6"
20 "v\x9eV\x8dXd\xd9kE\xf6=\xbeO";
21
ProbeMessage()22 ProbeMessage::ProbeMessage() {}
23
ParseInput(const std::string & input,ProbePacket * probe_packet) const24 bool ProbeMessage::ParseInput(const std::string& input,
25 ProbePacket* probe_packet) const {
26 // Encode is used for decoding here.
27 std::string input_decoded = Encode(input);
28
29 bool parse_result = probe_packet->ParseFromString(input_decoded);
30 if (!parse_result) {
31 DVLOG(1) << "ProtoBuffer string parsing error. Input size:" << input.size();
32 return false;
33 }
34 const ProbePacket_Header& header = probe_packet->header();
35 DVLOG(2) << "version " << header.version() << " checksum "
36 << header.checksum() << " type " << header.type();
37 if (header.version() != kVersion) {
38 DVLOG(1) << "Bad version number: " << header.version()
39 << " expected: " << kVersion;
40 return false;
41 }
42
43 // Checksum is computed on padding only.
44 if (probe_packet->has_padding()) {
45 DVLOG(3) << "received padding: " << probe_packet->padding();
46 uint32 computed_checksum = Checksum(probe_packet->padding());
47 if (computed_checksum != header.checksum()) {
48 DVLOG(1) << "Checksum mismatch. Got: " << header.checksum()
49 << " expected: " << computed_checksum;
50 return false;
51 }
52 }
53
54 if (header.type() != ProbePacket_Type_HELLO_REPLY &&
55 header.type() != ProbePacket_Type_PROBE_REPLY) {
56 DVLOG(1) << "Received unknown packet type:" << header.type();
57 return false;
58 }
59 return true;
60 }
61
Checksum(const std::string & str) const62 uint32 ProbeMessage::Checksum(const std::string& str) const {
63 uint32 ret = 0;
64 for (std::string::const_iterator i = str.begin(); i != str.end(); ++i) {
65 ret += static_cast<uint8>(*i);
66 }
67 return ret;
68 }
69
GenerateProbeRequest(const ProbePacket_Token & token,uint32 group_id,uint32 probe_size,uint32 pacing_interval_micros,uint32 number_probe_packets,ProbePacket * probe_packet)70 void ProbeMessage::GenerateProbeRequest(const ProbePacket_Token& token,
71 uint32 group_id,
72 uint32 probe_size,
73 uint32 pacing_interval_micros,
74 uint32 number_probe_packets,
75 ProbePacket* probe_packet) {
76 DCHECK_LE(number_probe_packets, kMaxNumberProbePackets);
77 DCHECK_LE(probe_size, kMaxProbePacketBytes);
78 DCHECK_LE(pacing_interval_micros, kMaxPacingIntervalMicros);
79
80 SetPacketHeader(ProbePacket_Type_PROBE_REQUEST, probe_packet);
81 *(probe_packet->mutable_token()) = token;
82 probe_packet->set_group_id(group_id);
83 probe_packet->set_probe_size_bytes(probe_size);
84 probe_packet->set_pacing_interval_micros(pacing_interval_micros);
85 probe_packet->set_number_probe_packets(number_probe_packets);
86
87 // Add padding to mitigate amplification attack.
88 std::string* padding = probe_packet->mutable_padding();
89 int padding_size = probe_size - probe_packet->ByteSize();
90 padding->append(std::string(std::max(0, padding_size), 0));
91 probe_packet->mutable_header()->set_checksum(Checksum(*padding));
92 DVLOG(3) << "Request size " << probe_packet->ByteSize() << " probe size "
93 << probe_size;
94 DCHECK_LE(probe_size, static_cast<uint32>(probe_packet->ByteSize()));
95 }
96
SetPacketHeader(ProbePacket_Type packet_type,ProbePacket * probe_packet) const97 void ProbeMessage::SetPacketHeader(ProbePacket_Type packet_type,
98 ProbePacket* probe_packet) const {
99 ProbePacket_Header* header = probe_packet->mutable_header();
100 header->set_version(kVersion);
101 header->set_type(packet_type);
102 }
103
Encode(const std::string & input) const104 std::string ProbeMessage::Encode(const std::string& input) const {
105
106 std::string output(input.size(), 0);
107 int key_pos = 0;
108 // kEncodingString contains a ending '\0' character, excluded for encoding.
109 int key_size = sizeof(kEncodingString) - 1;
110 for (size_t i = 0; i < input.size(); ++i) {
111 output[i] = input[i] ^ kEncodingString[key_pos];
112 ++key_pos;
113 if (key_pos >= key_size)
114 key_pos = 0;
115 }
116 return output;
117 }
118
MakeEncodedPacket(const ProbePacket & probe_packet) const119 std::string ProbeMessage::MakeEncodedPacket(
120 const ProbePacket& probe_packet) const {
121 std::string output;
122 probe_packet.SerializeToString(&output);
123 return Encode(output);
124 }
125
126 } // namespace chrome_browser_net
127