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1 /*
2  * Copyright 2012 Google Inc.
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  *
7  * The following code is based on the description in RFC 1321.
8  * http://www.ietf.org/rfc/rfc1321.txt
9  */
10 
11 //The following macros can be defined to affect the MD5 code generated.
12 //SK_MD5_CLEAR_DATA causes all intermediate state to be overwritten with 0's.
13 //SK_CPU_LENDIAN allows 32 bit <=> 8 bit conversions without copies (if alligned).
14 //SK_CPU_FAST_UNALIGNED_ACCESS allows 32 bit <=> 8 bit conversions without copies if SK_CPU_LENDIAN.
15 
16 #include "SkMD5.h"
17 #include <string.h>
18 
19 /** MD5 basic transformation. Transforms state based on block. */
20 static void transform(uint32_t state[4], const uint8_t block[64]);
21 
22 /** Encodes input into output (4 little endian 32 bit values). */
23 static void encode(uint8_t output[16], const uint32_t input[4]);
24 
25 /** Encodes input into output (little endian 64 bit value). */
26 static void encode(uint8_t output[8], const uint64_t input);
27 
28 /** Decodes input (4 little endian 32 bit values) into storage, if required. */
29 static const uint32_t* decode(uint32_t storage[16], const uint8_t input[64]);
30 
SkMD5()31 SkMD5::SkMD5() : byteCount(0) {
32     // These are magic numbers from the specification.
33     this->state[0] = 0x67452301;
34     this->state[1] = 0xefcdab89;
35     this->state[2] = 0x98badcfe;
36     this->state[3] = 0x10325476;
37 }
38 
write(const void * buf,size_t inputLength)39 bool SkMD5::write(const void* buf, size_t inputLength) {
40     const uint8_t* input = reinterpret_cast<const uint8_t*>(buf);
41     unsigned int bufferIndex = (unsigned int)(this->byteCount & 0x3F);
42     unsigned int bufferAvailable = 64 - bufferIndex;
43 
44     unsigned int inputIndex;
45     if (inputLength >= bufferAvailable) {
46         if (bufferIndex) {
47             memcpy(&this->buffer[bufferIndex], input, bufferAvailable);
48             transform(this->state, this->buffer);
49             inputIndex = bufferAvailable;
50         } else {
51             inputIndex = 0;
52         }
53 
54         for (; inputIndex + 63 < inputLength; inputIndex += 64) {
55             transform(this->state, &input[inputIndex]);
56         }
57 
58         bufferIndex = 0;
59     } else {
60         inputIndex = 0;
61     }
62 
63     memcpy(&this->buffer[bufferIndex], &input[inputIndex], inputLength - inputIndex);
64 
65     this->byteCount += inputLength;
66     return true;
67 }
68 
finish(Digest & digest)69 void SkMD5::finish(Digest& digest) {
70     // Get the number of bits before padding.
71     uint8_t bits[8];
72     encode(bits, this->byteCount << 3);
73 
74     // Pad out to 56 mod 64.
75     unsigned int bufferIndex = (unsigned int)(this->byteCount & 0x3F);
76     unsigned int paddingLength = (bufferIndex < 56) ? (56 - bufferIndex) : (120 - bufferIndex);
77     static uint8_t PADDING[64] = {
78         0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
79            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
80            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
81            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
82     };
83     (void)this->write(PADDING, paddingLength);
84 
85     // Append length (length before padding, will cause final update).
86     (void)this->write(bits, 8);
87 
88     // Write out digest.
89     encode(digest.data, this->state);
90 
91 #if defined(SK_MD5_CLEAR_DATA)
92     // Clear state.
93     memset(this, 0, sizeof(*this));
94 #endif
95 }
96 
operator ()F97 struct F { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
98     //return (x & y) | ((~x) & z);
99     return ((y ^ z) & x) ^ z; //equivelent but faster
100 }};
101 
operator ()G102 struct G { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
103     return (x & z) | (y & (~z));
104     //return ((x ^ y) & z) ^ y; //equivelent but slower
105 }};
106 
operator ()H107 struct H { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
108     return x ^ y ^ z;
109 }};
110 
operator ()I111 struct I { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
112     return y ^ (x | (~z));
113 }};
114 
115 /** Rotates x left n bits. */
rotate_left(uint32_t x,uint8_t n)116 static inline uint32_t rotate_left(uint32_t x, uint8_t n) {
117     return (x << n) | (x >> (32 - n));
118 }
119 
120 template <typename T>
operation(T operation,uint32_t & a,uint32_t b,uint32_t c,uint32_t d,uint32_t x,uint8_t s,uint32_t t)121 static inline void operation(T operation, uint32_t& a, uint32_t b, uint32_t c, uint32_t d,
122                              uint32_t x, uint8_t s, uint32_t t) {
123     a = b + rotate_left(a + operation(b, c, d) + x + t, s);
124 }
125 
transform(uint32_t state[4],const uint8_t block[64])126 static void transform(uint32_t state[4], const uint8_t block[64]) {
127     uint32_t a = state[0], b = state[1], c = state[2], d = state[3];
128 
129     uint32_t storage[16];
130     const uint32_t* X = decode(storage, block);
131 
132     // Round 1
133     operation(F(), a, b, c, d, X[ 0],  7, 0xd76aa478); // 1
134     operation(F(), d, a, b, c, X[ 1], 12, 0xe8c7b756); // 2
135     operation(F(), c, d, a, b, X[ 2], 17, 0x242070db); // 3
136     operation(F(), b, c, d, a, X[ 3], 22, 0xc1bdceee); // 4
137     operation(F(), a, b, c, d, X[ 4],  7, 0xf57c0faf); // 5
138     operation(F(), d, a, b, c, X[ 5], 12, 0x4787c62a); // 6
139     operation(F(), c, d, a, b, X[ 6], 17, 0xa8304613); // 7
140     operation(F(), b, c, d, a, X[ 7], 22, 0xfd469501); // 8
141     operation(F(), a, b, c, d, X[ 8],  7, 0x698098d8); // 9
142     operation(F(), d, a, b, c, X[ 9], 12, 0x8b44f7af); // 10
143     operation(F(), c, d, a, b, X[10], 17, 0xffff5bb1); // 11
144     operation(F(), b, c, d, a, X[11], 22, 0x895cd7be); // 12
145     operation(F(), a, b, c, d, X[12],  7, 0x6b901122); // 13
146     operation(F(), d, a, b, c, X[13], 12, 0xfd987193); // 14
147     operation(F(), c, d, a, b, X[14], 17, 0xa679438e); // 15
148     operation(F(), b, c, d, a, X[15], 22, 0x49b40821); // 16
149 
150     // Round 2
151     operation(G(), a, b, c, d, X[ 1],  5, 0xf61e2562); // 17
152     operation(G(), d, a, b, c, X[ 6],  9, 0xc040b340); // 18
153     operation(G(), c, d, a, b, X[11], 14, 0x265e5a51); // 19
154     operation(G(), b, c, d, a, X[ 0], 20, 0xe9b6c7aa); // 20
155     operation(G(), a, b, c, d, X[ 5],  5, 0xd62f105d); // 21
156     operation(G(), d, a, b, c, X[10],  9,  0x2441453); // 22
157     operation(G(), c, d, a, b, X[15], 14, 0xd8a1e681); // 23
158     operation(G(), b, c, d, a, X[ 4], 20, 0xe7d3fbc8); // 24
159     operation(G(), a, b, c, d, X[ 9],  5, 0x21e1cde6); // 25
160     operation(G(), d, a, b, c, X[14],  9, 0xc33707d6); // 26
161     operation(G(), c, d, a, b, X[ 3], 14, 0xf4d50d87); // 27
162     operation(G(), b, c, d, a, X[ 8], 20, 0x455a14ed); // 28
163     operation(G(), a, b, c, d, X[13],  5, 0xa9e3e905); // 29
164     operation(G(), d, a, b, c, X[ 2],  9, 0xfcefa3f8); // 30
165     operation(G(), c, d, a, b, X[ 7], 14, 0x676f02d9); // 31
166     operation(G(), b, c, d, a, X[12], 20, 0x8d2a4c8a); // 32
167 
168     // Round 3
169     operation(H(), a, b, c, d, X[ 5],  4, 0xfffa3942); // 33
170     operation(H(), d, a, b, c, X[ 8], 11, 0x8771f681); // 34
171     operation(H(), c, d, a, b, X[11], 16, 0x6d9d6122); // 35
172     operation(H(), b, c, d, a, X[14], 23, 0xfde5380c); // 36
173     operation(H(), a, b, c, d, X[ 1],  4, 0xa4beea44); // 37
174     operation(H(), d, a, b, c, X[ 4], 11, 0x4bdecfa9); // 38
175     operation(H(), c, d, a, b, X[ 7], 16, 0xf6bb4b60); // 39
176     operation(H(), b, c, d, a, X[10], 23, 0xbebfbc70); // 40
177     operation(H(), a, b, c, d, X[13],  4, 0x289b7ec6); // 41
178     operation(H(), d, a, b, c, X[ 0], 11, 0xeaa127fa); // 42
179     operation(H(), c, d, a, b, X[ 3], 16, 0xd4ef3085); // 43
180     operation(H(), b, c, d, a, X[ 6], 23,  0x4881d05); // 44
181     operation(H(), a, b, c, d, X[ 9],  4, 0xd9d4d039); // 45
182     operation(H(), d, a, b, c, X[12], 11, 0xe6db99e5); // 46
183     operation(H(), c, d, a, b, X[15], 16, 0x1fa27cf8); // 47
184     operation(H(), b, c, d, a, X[ 2], 23, 0xc4ac5665); // 48
185 
186     // Round 4
187     operation(I(), a, b, c, d, X[ 0],  6, 0xf4292244); // 49
188     operation(I(), d, a, b, c, X[ 7], 10, 0x432aff97); // 50
189     operation(I(), c, d, a, b, X[14], 15, 0xab9423a7); // 51
190     operation(I(), b, c, d, a, X[ 5], 21, 0xfc93a039); // 52
191     operation(I(), a, b, c, d, X[12],  6, 0x655b59c3); // 53
192     operation(I(), d, a, b, c, X[ 3], 10, 0x8f0ccc92); // 54
193     operation(I(), c, d, a, b, X[10], 15, 0xffeff47d); // 55
194     operation(I(), b, c, d, a, X[ 1], 21, 0x85845dd1); // 56
195     operation(I(), a, b, c, d, X[ 8],  6, 0x6fa87e4f); // 57
196     operation(I(), d, a, b, c, X[15], 10, 0xfe2ce6e0); // 58
197     operation(I(), c, d, a, b, X[ 6], 15, 0xa3014314); // 59
198     operation(I(), b, c, d, a, X[13], 21, 0x4e0811a1); // 60
199     operation(I(), a, b, c, d, X[ 4],  6, 0xf7537e82); // 61
200     operation(I(), d, a, b, c, X[11], 10, 0xbd3af235); // 62
201     operation(I(), c, d, a, b, X[ 2], 15, 0x2ad7d2bb); // 63
202     operation(I(), b, c, d, a, X[ 9], 21, 0xeb86d391); // 64
203 
204     state[0] += a;
205     state[1] += b;
206     state[2] += c;
207     state[3] += d;
208 
209 #if defined(SK_MD5_CLEAR_DATA)
210     // Clear sensitive information.
211     if (X == &storage) {
212         memset(storage, 0, sizeof(storage));
213     }
214 #endif
215 }
216 
encode(uint8_t output[16],const uint32_t input[4])217 static void encode(uint8_t output[16], const uint32_t input[4]) {
218     for (size_t i = 0, j = 0; i < 4; i++, j += 4) {
219         output[j  ] = (uint8_t) (input[i]        & 0xff);
220         output[j+1] = (uint8_t)((input[i] >>  8) & 0xff);
221         output[j+2] = (uint8_t)((input[i] >> 16) & 0xff);
222         output[j+3] = (uint8_t)((input[i] >> 24) & 0xff);
223     }
224 }
225 
encode(uint8_t output[8],const uint64_t input)226 static void encode(uint8_t output[8], const uint64_t input) {
227     output[0] = (uint8_t) (input        & 0xff);
228     output[1] = (uint8_t)((input >>  8) & 0xff);
229     output[2] = (uint8_t)((input >> 16) & 0xff);
230     output[3] = (uint8_t)((input >> 24) & 0xff);
231     output[4] = (uint8_t)((input >> 32) & 0xff);
232     output[5] = (uint8_t)((input >> 40) & 0xff);
233     output[6] = (uint8_t)((input >> 48) & 0xff);
234     output[7] = (uint8_t)((input >> 56) & 0xff);
235 }
236 
is_aligned(const void * pointer,size_t byte_count)237 static inline bool is_aligned(const void *pointer, size_t byte_count) {
238     return reinterpret_cast<uintptr_t>(pointer) % byte_count == 0;
239 }
240 
decode(uint32_t storage[16],const uint8_t input[64])241 static const uint32_t* decode(uint32_t storage[16], const uint8_t input[64]) {
242 #if defined(SK_CPU_LENDIAN) && defined(SK_CPU_FAST_UNALIGNED_ACCESS)
243    return reinterpret_cast<const uint32_t*>(input);
244 #else
245 #if defined(SK_CPU_LENDIAN)
246     if (is_aligned(input, 4)) {
247         return reinterpret_cast<const uint32_t*>(input);
248     }
249 #endif
250     for (size_t i = 0, j = 0; j < 64; i++, j += 4) {
251         storage[i] =  ((uint32_t)input[j  ])        |
252                      (((uint32_t)input[j+1]) <<  8) |
253                      (((uint32_t)input[j+2]) << 16) |
254                      (((uint32_t)input[j+3]) << 24);
255     }
256     return storage;
257 #endif
258 }
259