1 /*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "ChecksumCalculator.h"
18
19 #include <string.h>
20
21 // Checklist when implementing new protocol:
22 // 1. update CHECKSUMHELPER_MAX_VERSION
23 // 2. update ChecksumCalculator::Sizes enum
24 // 3. update checksumByteSize()
25 // 4. update addBuffer, writeChecksum, resetChecksum, validate
26
27 // change CHECKSUMHELPER_MAX_VERSION when you want to update the protocol version
28 #define CHECKSUMHELPER_MAX_VERSION 1
29
30 // utility macros to create checksum string at compilation time
31 #define CHECKSUMHELPER_VERSION_STR_PREFIX "ANDROID_EMU_CHECKSUM_HELPER_v"
32 #define CHECKSUMHELPER_MACRO_TO_STR(x) #x
33 #define CHECKSUMHELPER_MACRO_VAL_TO_STR(x) CHECKSUMHELPER_MACRO_TO_STR(x)
34
35 static const uint32_t kMaxVersion = CHECKSUMHELPER_MAX_VERSION;
36 static const char* kMaxVersionStrPrefix = CHECKSUMHELPER_VERSION_STR_PREFIX;
37 static const char* kMaxVersionStr = CHECKSUMHELPER_VERSION_STR_PREFIX CHECKSUMHELPER_MACRO_VAL_TO_STR(CHECKSUMHELPER_MAX_VERSION);
38
39 #undef CHECKSUMHELPER_MAX_VERSION
40 #undef CHECKSUMHELPER_VERSION_STR_PREFIX
41 #undef CHECKSUMHELPER_MACRO_TO_STR
42 #undef CHECKSUMHELPER_MACRO_VAL_TO_STR
43
getMaxVersion()44 uint32_t ChecksumCalculator::getMaxVersion() {return kMaxVersion;}
getMaxVersionStr()45 const char* ChecksumCalculator::getMaxVersionStr() {return kMaxVersionStr;}
getMaxVersionStrPrefix()46 const char* ChecksumCalculator::getMaxVersionStrPrefix() {return kMaxVersionStrPrefix;}
47
setVersion(uint32_t version)48 bool ChecksumCalculator::setVersion(uint32_t version) {
49 if (version > kMaxVersion) { // unsupported version
50 LOG_CHECKSUMHELPER("%s: ChecksumCalculator Set Unsupported version Version %d\n",
51 __FUNCTION__, m_version);
52 return false;
53 }
54 if (m_isEncodingChecksum) { // setVersion is called in the middle of encoding checksums
55 LOG_CHECKSUMHELPER("%s: called between addBuffer and writeChecksum\n",
56 __FUNCTION__);
57 return false;
58 }
59 m_version = version;
60 LOG_CHECKSUMHELPER("%s: ChecksumCalculator Set Version %d\n", __FUNCTION__,
61 m_version);
62 return true;
63 }
64
checksumByteSize() const65 size_t ChecksumCalculator::checksumByteSize() const {
66 switch (m_version) {
67 case 0:
68 return 0;
69 case 1:
70 return sizeof(uint32_t) + sizeof(m_numWrite);
71 default:
72 return 0;
73 }
74 }
75
ChecksumCalculator()76 ChecksumCalculator::ChecksumCalculator()
77 : m_version(0)
78 , m_numRead(0)
79 , m_numWrite(0)
80 , m_isEncodingChecksum(false)
81 , m_v1BufferTotalLength(0)
82 {
83 }
84
addBuffer(const void * buf,size_t packetLen)85 void ChecksumCalculator::addBuffer(const void* buf, size_t packetLen) {
86 m_isEncodingChecksum = true;
87 switch (m_version) {
88 case 1:
89 m_v1BufferTotalLength += packetLen;
90 break;
91 }
92 }
93
writeChecksum(void * outputChecksum,size_t outputChecksumLen)94 bool ChecksumCalculator::writeChecksum(void* outputChecksum, size_t outputChecksumLen) {
95 if (outputChecksumLen < checksumByteSize()) return false;
96 char *checksumPtr = (char *)outputChecksum;
97 switch (m_version) {
98 case 1: { // protocol v1 is to reverse the packetLen and write it at the end
99 uint32_t val = computeV1Checksum();
100 memcpy(checksumPtr, &val, sizeof(val));
101 memcpy(checksumPtr+sizeof(val), &m_numWrite, sizeof(m_numWrite));
102 break;
103 }
104 }
105 resetChecksum();
106 m_numWrite++;
107 return true;
108 }
109
resetChecksum()110 void ChecksumCalculator::resetChecksum() {
111 switch (m_version) {
112 case 1:
113 m_v1BufferTotalLength = 0;
114 break;
115 }
116 m_isEncodingChecksum = false;
117 }
118
validate(const void * expectedChecksum,size_t expectedChecksumLen)119 bool ChecksumCalculator::validate(const void* expectedChecksum, size_t expectedChecksumLen) {
120 size_t checksumSize = checksumByteSize();
121 if (expectedChecksumLen != checksumSize) {
122 m_numRead++;
123 resetChecksum();
124 return false;
125 }
126 bool isValid;
127 switch (m_version) {
128 case 1: {
129 const uint32_t val = computeV1Checksum();
130 isValid = 0 == memcmp(&val, expectedChecksum, sizeof(val)) &&
131 0 == memcmp(&m_numRead,
132 static_cast<const char*>(expectedChecksum) +
133 sizeof(val),
134 sizeof(m_numRead));
135
136 break;
137 }
138 default:
139 isValid = true; // No checksum is a valid checksum.
140 break;
141 }
142 m_numRead++;
143 resetChecksum();
144 return isValid;
145 }
146
computeV1Checksum()147 uint32_t ChecksumCalculator::computeV1Checksum() {
148 uint32_t revLen = m_v1BufferTotalLength;
149 revLen = (revLen & 0xffff0000) >> 16 | (revLen & 0x0000ffff) << 16;
150 revLen = (revLen & 0xff00ff00) >> 8 | (revLen & 0x00ff00ff) << 8;
151 revLen = (revLen & 0xf0f0f0f0) >> 4 | (revLen & 0x0f0f0f0f) << 4;
152 revLen = (revLen & 0xcccccccc) >> 2 | (revLen & 0x33333333) << 2;
153 revLen = (revLen & 0xaaaaaaaa) >> 1 | (revLen & 0x55555555) << 1;
154 return revLen;
155 }
156