MD5的常见实现由RFC1321给出。 MD5Update函数接收指向chars的指针的位置。
我的架构，一个SHARC ADSP-21371，不是字节可压缩的，这意味着：
sizeof(int32_t) == 1
因此我无法真正使用此算法。我需要包含一些复杂性来解压每个int32_t数据。
是否有替代解决方案，我可以开箱即用，如果可能的话兼容C99或C11？
答案 0 :(得分：2)
我最终为一个八位位组可寻址架构实现了MD5，这里是一个DSP SHARC（ADSP-21371）。
#ifndef MD5_H
#define MD5_H
#include <stdlib.h>
#include <stdint.h>
typedef struct {
uint32_t state[4]; //!< State (ABCD)
uint64_t count; //!< Number of bits
uint32_t buffer[16]; //!< Input buffer
} md5_context_t;
void md5_init(md5_context_t*);
void md5_update(md5_context_t*, uint32_t*, size_t);
void md5_final(md5_context_t*);
#endif /* MD5_H */
/**
* This is a custom implementation for MD5 hash algorithm derived from RFC1321
* https://www.ietf.org/rfc/rfc1321.txt
*
* The original implementation requires a octet-addressable processor which is not
* the case of the SHARC. Thus the implementation must me modified to support this
* processor.
*
* It comes with a limitation when the input buffer is not a multple of 32-bits.
* At the end of the the message, a padding is inserted starting with 0x80. If the
* message is 0x12345678, the beginning of the 64-bytes buffer will be:
*
* 0x012345678
* 0x000000080
* 0x000000000
* ...
*
* If the input message is 0x78 0x56 0x34 0x12 0xAA, the input buffer should be:
*
* 0x012345678
* 0x0000080AA
* 0x000000000
* ...
*
* Which will not be the case in this implementation because the given size to md5_update
* is expressed in sizeof(long) which is 32-bits wide on a SHARC architecture.
*/
#include "md5.h"
#include <string.h>
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21
static uint32_t padding[16] = {
[0] = 0x80, [1 ... sizeof(padding) / sizeof(uint32_t) - 2] = 0};
/**
* F, G, H and I are basic MD5 functions.
*/
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))
/**
* ROTATE_LEFT rotates x left n bits.
*/
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
/**
* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
* Rotation is separate from addition to prevent recomputation.
*/
#define FF(a, b, c, d, x, s, ac) { \
(a) += F ((b), (c), (d)) + (x) + (uint32_t)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
(a) += G ((b), (c), (d)) + (x) + (uint32_t)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
(a) += H ((b), (c), (d)) + (x) + (uint32_t)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
(a) += I ((b), (c), (d)) + (x) + (uint32_t)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
/**
* MD5 basic transformation. Transforms state based on block.
*/
static void md5_transform(uint32_t state[4], uint32_t x[16])
{
uint32_t a = state[0];
uint32_t b = state[1];
uint32_t c = state[2];
uint32_t d = state[3];
// Round 1
FF(a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
FF(d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
FF(c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
FF(b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
FF(a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
FF(d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
FF(c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
FF(b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
FF(a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
FF(d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */
// Round 2
GG(a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
GG(d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
GG(b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
GG(a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
GG(d, a, b, c, x[10], S22, 0x02441453); /* 22 */
GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
GG(b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
GG(a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
GG(c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
GG(b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
GG(d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
GG(c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */
// Round 3
HH(a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
HH(d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
HH(a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
HH(d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
HH(c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
HH(d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
HH(c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
HH(b, c, d, a, x[ 6], S34, 0x04881d05); /* 44 */
HH(a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
HH(b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */
// Round 4
II(a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
II(d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
II(b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
II(d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
II(b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
II(a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
II(c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
II(a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
II(c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
II(b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */
state[0] += a;
state[1] += b;
state[2] += c;
state[3] += d;
}
/**
* MD5 block update operation. Continues an MD5 message-digest
* operation, processing another message block, and updating the
* context.
*/
void md5_update(md5_context_t *context, uint32_t* input, size_t length)
{
size_t size = 0;
size_t index = (context->count >> 5) & 0xF; // Modulo 16
size_t part_len = 16 - index;
context->count += length << 5; // Update number of bits
// Transform as many times as possible.
if (length >= part_len) {
memcpy(&context->buffer[index], input, sizeof(uint32_t) * part_len);
md5_transform(context->state, context->buffer);
for (size_t size = part_len; size + 15 < length; size += 16)
md5_transform(context->state, &input[size]);
index = 0;
}
// Buffer remaining input
memcpy(&context->buffer[index], &input[size], sizeof(uint32_t) * (length - size));
}
/**
* MD5 finalization. Ends an MD5 message-digest operation, writing the
* the message digest and zeroizing the context.
*/
void md5_final(md5_context_t *context)
{
int64_t count = context->count; // Count before padding
// Pad out to 56 mod 64 bytes.
size_t index = (context->count >> 5) & 0xf;
size_t padLen = index < 14 ? 14 - index : 30 - index;
md5_update(context, padding, padLen);
md5_update(context, &((uint32_t*)(&count))[1], 1);
md5_update(context, &((uint32_t*)(&count))[0], 1);
}
/**
* MD5 initialization. Begins an MD5 operation, writing a new context.
*/
void md5_init(md5_context_t *context)
{
context->count = 0;
context->state[0] = 0x67452301;
context->state[1] = 0xefcdab89;
context->state[2] = 0x98badcfe;
context->state[3] = 0x10325476;
}