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 <stddef.h>
8
9 #include <string>
10
11 #include "base/check_op.h"
12 #include "base/logging.h"
13
14 namespace chrome_browser_net {
15
16 const uint32_t ProbeMessage::kVersion = 2;
17 const uint32_t ProbeMessage::kMaxNumberProbePackets = 21;
18 const uint32_t ProbeMessage::kMaxProbePacketBytes = 1500;
19 // Maximum pacing interval is 300 seconds (for testing NAT binding).
20 const uint32_t ProbeMessage::kMaxPacingIntervalMicros = 300000000;
21 const char ProbeMessage::kEncodingString[] =
22 "T\xd3?\xa5h2\x9c\x8en\xf1Q6\xbc{\xc6-4\xfa$f\xb9[\xa6\xcd@6,\xdf\xb3i-\xe6"
23 "v\x9eV\x8dXd\xd9kE\xf6=\xbeO";
24
ProbeMessage()25 ProbeMessage::ProbeMessage() {}
26
ParseInput(const std::string & input,ProbePacket * probe_packet) const27 bool ProbeMessage::ParseInput(const std::string& input,
28 ProbePacket* probe_packet) const {
29 // Encode is used for decoding here.
30 std::string input_decoded = Encode(input);
31
32 bool parse_result = probe_packet->ParseFromString(input_decoded);
33 if (!parse_result) {
34 DVLOG(1) << "ProtoBuffer string parsing error. Input size:" << input.size();
35 return false;
36 }
37 const ProbePacket_Header& header = probe_packet->header();
38 DVLOG(2) << "version " << header.version() << " checksum "
39 << header.checksum() << " type " << header.type();
40 if (header.version() != kVersion) {
41 DVLOG(1) << "Bad version number: " << header.version()
42 << " expected: " << kVersion;
43 return false;
44 }
45
46 // Checksum is computed on padding only.
47 if (probe_packet->has_padding()) {
48 DVLOG(3) << "received padding: " << probe_packet->padding();
49 uint32_t computed_checksum = Checksum(probe_packet->padding());
50 if (computed_checksum != header.checksum()) {
51 DVLOG(1) << "Checksum mismatch. Got: " << header.checksum()
52 << " expected: " << computed_checksum;
53 return false;
54 }
55 }
56
57 if (header.type() != ProbePacket_Type_HELLO_REPLY &&
58 header.type() != ProbePacket_Type_PROBE_REPLY) {
59 DVLOG(1) << "Received unknown packet type:" << header.type();
60 return false;
61 }
62 return true;
63 }
64
Checksum(const std::string & str) const65 uint32_t ProbeMessage::Checksum(const std::string& str) const {
66 uint32_t ret = 0;
67 for (std::string::const_iterator i = str.begin(); i != str.end(); ++i) {
68 ret += static_cast<uint8_t>(*i);
69 }
70 return ret;
71 }
72
GenerateProbeRequest(const ProbePacket_Token & token,uint32_t group_id,uint32_t probe_size,uint32_t pacing_interval_micros,uint32_t number_probe_packets,ProbePacket * probe_packet)73 void ProbeMessage::GenerateProbeRequest(const ProbePacket_Token& token,
74 uint32_t group_id,
75 uint32_t probe_size,
76 uint32_t pacing_interval_micros,
77 uint32_t number_probe_packets,
78 ProbePacket* probe_packet) {
79 DCHECK_LE(number_probe_packets, kMaxNumberProbePackets);
80 DCHECK_LE(probe_size, kMaxProbePacketBytes);
81 DCHECK_LE(pacing_interval_micros, kMaxPacingIntervalMicros);
82
83 SetPacketHeader(ProbePacket_Type_PROBE_REQUEST, probe_packet);
84 *(probe_packet->mutable_token()) = token;
85 probe_packet->set_group_id(group_id);
86 probe_packet->set_probe_size_bytes(probe_size);
87 probe_packet->set_pacing_interval_micros(pacing_interval_micros);
88 probe_packet->set_number_probe_packets(number_probe_packets);
89
90 // Add padding to mitigate amplification attack.
91 std::string* padding = probe_packet->mutable_padding();
92 int padding_size = probe_size - probe_packet->ByteSize();
93 padding->append(std::string(std::max(0, padding_size), 0));
94 probe_packet->mutable_header()->set_checksum(Checksum(*padding));
95 DVLOG(3) << "Request size " << probe_packet->ByteSize() << " probe size "
96 << probe_size;
97 DCHECK_LE(probe_size, static_cast<uint32_t>(probe_packet->ByteSize()));
98 }
99
SetPacketHeader(ProbePacket_Type packet_type,ProbePacket * probe_packet) const100 void ProbeMessage::SetPacketHeader(ProbePacket_Type packet_type,
101 ProbePacket* probe_packet) const {
102 ProbePacket_Header* header = probe_packet->mutable_header();
103 header->set_version(kVersion);
104 header->set_type(packet_type);
105 }
106
Encode(const std::string & input) const107 std::string ProbeMessage::Encode(const std::string& input) const {
108
109 std::string output(input.size(), 0);
110 int key_pos = 0;
111 // kEncodingString contains a ending '\0' character, excluded for encoding.
112 int key_size = sizeof(kEncodingString) - 1;
113 for (size_t i = 0; i < input.size(); ++i) {
114 output[i] = input[i] ^ kEncodingString[key_pos];
115 ++key_pos;
116 if (key_pos >= key_size)
117 key_pos = 0;
118 }
119 return output;
120 }
121
MakeEncodedPacket(const ProbePacket & probe_packet) const122 std::string ProbeMessage::MakeEncodedPacket(
123 const ProbePacket& probe_packet) const {
124 std::string output;
125 probe_packet.SerializeToString(&output);
126 return Encode(output);
127 }
128
129 } // namespace chrome_browser_net
130