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#include "SkTypes.h"
12#include "SkMD5.h"
13#include <string.h>
14
15/** MD5 basic transformation. Transforms state based on block. */
16static void transform(uint32_t state[4], const uint8_t block[64]);
17
18/** Encodes input into output (4 little endian 32 bit values). */
19static void encode(uint8_t output[16], const uint32_t input[4]);
20
21/** Encodes input into output (little endian 64 bit value). */
22static void encode(uint8_t output[8], const uint64_t input);
23
24/** Decodes input (4 little endian 32 bit values) into storage, if required. */
25static const uint32_t* decode(uint32_t storage[16], const uint8_t input[64]);
26
27SkMD5::SkMD5() : byteCount(0) {
28    // These are magic numbers from the specification.
29    this->state[0] = 0x67452301;
30    this->state[1] = 0xefcdab89;
31    this->state[2] = 0x98badcfe;
32    this->state[3] = 0x10325476;
33}
34
35void SkMD5::update(const uint8_t* input, size_t inputLength) {
36    unsigned int bufferIndex = (unsigned int)(this->byteCount & 0x3F);
37    unsigned int bufferAvailable = 64 - bufferIndex;
38
39    unsigned int inputIndex;
40    if (inputLength >= bufferAvailable) {
41        if (bufferIndex) {
42            memcpy(&this->buffer[bufferIndex], input, bufferAvailable);
43            transform(this->state, this->buffer);
44            inputIndex = bufferAvailable;
45        } else {
46            inputIndex = 0;
47        }
48
49        for (; inputIndex + 63 < inputLength; inputIndex += 64) {
50            transform(this->state, &input[inputIndex]);
51        }
52
53        bufferIndex = 0;
54    } else {
55        inputIndex = 0;
56    }
57
58    memcpy(&this->buffer[bufferIndex], &input[inputIndex], inputLength - inputIndex);
59
60    this->byteCount += inputLength;
61}
62
63void SkMD5::finish(Digest& digest) {
64    // Get the number of bits before padding.
65    uint8_t bits[8];
66    encode(bits, this->byteCount << 3);
67
68    // Pad out to 56 mod 64.
69    unsigned int bufferIndex = (unsigned int)(this->byteCount & 0x3F);
70    unsigned int paddingLength = (bufferIndex < 56) ? (56 - bufferIndex) : (120 - bufferIndex);
71    static uint8_t PADDING[64] = {
72        0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
73           0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
74           0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
75           0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
76    };
77    this->update(PADDING, paddingLength);
78
79    // Append length (length before padding, will cause final update).
80    this->update(bits, 8);
81
82    // Write out digest.
83    encode(digest.data, this->state);
84
85#if defined(SK_MD5_CLEAR_DATA)
86    // Clear state.
87    memset(this, 0, sizeof(*this));
88#endif
89}
90
91struct F { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
92    //return (x & y) | ((~x) & z);
93    return ((y ^ z) & x) ^ z; //equivelent but faster
94}};
95
96struct G { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
97    return (x & z) | (y & (~z));
98    //return ((x ^ y) & z) ^ y; //equivelent but slower
99}};
100
101struct H { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
102    return x ^ y ^ z;
103}};
104
105struct I { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
106    return y ^ (x | (~z));
107}};
108
109/** Rotates x left n bits. */
110static inline uint32_t rotate_left(uint32_t x, uint8_t n) {
111    return (x << n) | (x >> (32 - n));
112}
113
114template <typename T>
115static inline void operation(T operation, uint32_t& a, uint32_t b, uint32_t c, uint32_t d,
116                             uint32_t x, uint8_t s, uint32_t t) {
117    a = b + rotate_left(a + operation(b, c, d) + x + t, s);
118}
119
120static void transform(uint32_t state[4], const uint8_t block[64]) {
121    uint32_t a = state[0], b = state[1], c = state[2], d = state[3];
122
123    uint32_t storage[16];
124    const uint32_t* X = decode(storage, block);
125
126    // Round 1
127    operation(F(), a, b, c, d, X[ 0],  7, 0xd76aa478); // 1
128    operation(F(), d, a, b, c, X[ 1], 12, 0xe8c7b756); // 2
129    operation(F(), c, d, a, b, X[ 2], 17, 0x242070db); // 3
130    operation(F(), b, c, d, a, X[ 3], 22, 0xc1bdceee); // 4
131    operation(F(), a, b, c, d, X[ 4],  7, 0xf57c0faf); // 5
132    operation(F(), d, a, b, c, X[ 5], 12, 0x4787c62a); // 6
133    operation(F(), c, d, a, b, X[ 6], 17, 0xa8304613); // 7
134    operation(F(), b, c, d, a, X[ 7], 22, 0xfd469501); // 8
135    operation(F(), a, b, c, d, X[ 8],  7, 0x698098d8); // 9
136    operation(F(), d, a, b, c, X[ 9], 12, 0x8b44f7af); // 10
137    operation(F(), c, d, a, b, X[10], 17, 0xffff5bb1); // 11
138    operation(F(), b, c, d, a, X[11], 22, 0x895cd7be); // 12
139    operation(F(), a, b, c, d, X[12],  7, 0x6b901122); // 13
140    operation(F(), d, a, b, c, X[13], 12, 0xfd987193); // 14
141    operation(F(), c, d, a, b, X[14], 17, 0xa679438e); // 15
142    operation(F(), b, c, d, a, X[15], 22, 0x49b40821); // 16
143
144    // Round 2
145    operation(G(), a, b, c, d, X[ 1],  5, 0xf61e2562); // 17
146    operation(G(), d, a, b, c, X[ 6],  9, 0xc040b340); // 18
147    operation(G(), c, d, a, b, X[11], 14, 0x265e5a51); // 19
148    operation(G(), b, c, d, a, X[ 0], 20, 0xe9b6c7aa); // 20
149    operation(G(), a, b, c, d, X[ 5],  5, 0xd62f105d); // 21
150    operation(G(), d, a, b, c, X[10],  9,  0x2441453); // 22
151    operation(G(), c, d, a, b, X[15], 14, 0xd8a1e681); // 23
152    operation(G(), b, c, d, a, X[ 4], 20, 0xe7d3fbc8); // 24
153    operation(G(), a, b, c, d, X[ 9],  5, 0x21e1cde6); // 25
154    operation(G(), d, a, b, c, X[14],  9, 0xc33707d6); // 26
155    operation(G(), c, d, a, b, X[ 3], 14, 0xf4d50d87); // 27
156    operation(G(), b, c, d, a, X[ 8], 20, 0x455a14ed); // 28
157    operation(G(), a, b, c, d, X[13],  5, 0xa9e3e905); // 29
158    operation(G(), d, a, b, c, X[ 2],  9, 0xfcefa3f8); // 30
159    operation(G(), c, d, a, b, X[ 7], 14, 0x676f02d9); // 31
160    operation(G(), b, c, d, a, X[12], 20, 0x8d2a4c8a); // 32
161
162    // Round 3
163    operation(H(), a, b, c, d, X[ 5],  4, 0xfffa3942); // 33
164    operation(H(), d, a, b, c, X[ 8], 11, 0x8771f681); // 34
165    operation(H(), c, d, a, b, X[11], 16, 0x6d9d6122); // 35
166    operation(H(), b, c, d, a, X[14], 23, 0xfde5380c); // 36
167    operation(H(), a, b, c, d, X[ 1],  4, 0xa4beea44); // 37
168    operation(H(), d, a, b, c, X[ 4], 11, 0x4bdecfa9); // 38
169    operation(H(), c, d, a, b, X[ 7], 16, 0xf6bb4b60); // 39
170    operation(H(), b, c, d, a, X[10], 23, 0xbebfbc70); // 40
171    operation(H(), a, b, c, d, X[13],  4, 0x289b7ec6); // 41
172    operation(H(), d, a, b, c, X[ 0], 11, 0xeaa127fa); // 42
173    operation(H(), c, d, a, b, X[ 3], 16, 0xd4ef3085); // 43
174    operation(H(), b, c, d, a, X[ 6], 23,  0x4881d05); // 44
175    operation(H(), a, b, c, d, X[ 9],  4, 0xd9d4d039); // 45
176    operation(H(), d, a, b, c, X[12], 11, 0xe6db99e5); // 46
177    operation(H(), c, d, a, b, X[15], 16, 0x1fa27cf8); // 47
178    operation(H(), b, c, d, a, X[ 2], 23, 0xc4ac5665); // 48
179
180    // Round 4
181    operation(I(), a, b, c, d, X[ 0],  6, 0xf4292244); // 49
182    operation(I(), d, a, b, c, X[ 7], 10, 0x432aff97); // 50
183    operation(I(), c, d, a, b, X[14], 15, 0xab9423a7); // 51
184    operation(I(), b, c, d, a, X[ 5], 21, 0xfc93a039); // 52
185    operation(I(), a, b, c, d, X[12],  6, 0x655b59c3); // 53
186    operation(I(), d, a, b, c, X[ 3], 10, 0x8f0ccc92); // 54
187    operation(I(), c, d, a, b, X[10], 15, 0xffeff47d); // 55
188    operation(I(), b, c, d, a, X[ 1], 21, 0x85845dd1); // 56
189    operation(I(), a, b, c, d, X[ 8],  6, 0x6fa87e4f); // 57
190    operation(I(), d, a, b, c, X[15], 10, 0xfe2ce6e0); // 58
191    operation(I(), c, d, a, b, X[ 6], 15, 0xa3014314); // 59
192    operation(I(), b, c, d, a, X[13], 21, 0x4e0811a1); // 60
193    operation(I(), a, b, c, d, X[ 4],  6, 0xf7537e82); // 61
194    operation(I(), d, a, b, c, X[11], 10, 0xbd3af235); // 62
195    operation(I(), c, d, a, b, X[ 2], 15, 0x2ad7d2bb); // 63
196    operation(I(), b, c, d, a, X[ 9], 21, 0xeb86d391); // 64
197
198    state[0] += a;
199    state[1] += b;
200    state[2] += c;
201    state[3] += d;
202
203#if defined(SK_MD5_CLEAR_DATA)
204    // Clear sensitive information.
205    if (X == &storage) {
206        memset(storage, 0, sizeof(storage));
207    }
208#endif
209}
210
211static void encode(uint8_t output[16], const uint32_t input[4]) {
212    for (size_t i = 0, j = 0; i < 4; i++, j += 4) {
213        output[j  ] = (uint8_t) (input[i]        & 0xff);
214        output[j+1] = (uint8_t)((input[i] >>  8) & 0xff);
215        output[j+2] = (uint8_t)((input[i] >> 16) & 0xff);
216        output[j+3] = (uint8_t)((input[i] >> 24) & 0xff);
217    }
218}
219
220static void encode(uint8_t output[8], const uint64_t input) {
221    output[0] = (uint8_t) (input        & 0xff);
222    output[1] = (uint8_t)((input >>  8) & 0xff);
223    output[2] = (uint8_t)((input >> 16) & 0xff);
224    output[3] = (uint8_t)((input >> 24) & 0xff);
225    output[4] = (uint8_t)((input >> 32) & 0xff);
226    output[5] = (uint8_t)((input >> 40) & 0xff);
227    output[6] = (uint8_t)((input >> 48) & 0xff);
228    output[7] = (uint8_t)((input >> 56) & 0xff);
229}
230
231static inline bool is_aligned(const void *pointer, size_t byte_count) {
232    return reinterpret_cast<uintptr_t>(pointer) % byte_count == 0;
233}
234
235static const uint32_t* decode(uint32_t storage[16], const uint8_t input[64]) {
236#if defined(SK_CPU_LENDIAN) && defined(SK_CPU_FAST_UNALIGNED_ACCESS)
237   return reinterpret_cast<const uint32_t*>(input);
238#else
239#if defined(SK_CPU_LENDIAN)
240    if (is_aligned(input, 4)) {
241        return reinterpret_cast<const uint32_t*>(input);
242    }
243#endif
244    for (size_t i = 0, j = 0; j < 64; i++, j += 4) {
245        storage[i] =  ((uint32_t)input[j  ])        |
246                     (((uint32_t)input[j+1]) <<  8) |
247                     (((uint32_t)input[j+2]) << 16) |
248                     (((uint32_t)input[j+3]) << 24);
249    }
250    return storage;
251#endif
252}
253