MD5信息摘要算法 C语言实现

MD5信息摘要算法（英语：MD5 Message-Digest Algorithm），一种被广泛使用的密码散列函数，可以产生出一个128位（16字节）的散列值（hash value），用于确保信息传输完整一致。
本文提供了 MD5 的C语言算法，代码如下：

1. md5.c

#include <stdio.h>
#include <memory.h>

#include "md5.h"

uint8_t PADDING[] =
{
    
    
    0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
};

void MD5Init(MD5_CTX *context)
{
    
    
    context->count[0] = 0;
    context->count[1] = 0;
    context->state[0] = 0x67452301;
    context->state[1] = 0xEFCDAB89;
    context->state[2] = 0x98BADCFE;
    context->state[3] = 0x10325476;
}

void MD5Update(MD5_CTX *context, uint8_t *input, uint32_t inputlen)
{
    
    
    uint32_t i = 0;
    uint32_t index = 0;
    uint32_t partlen = 0;

    index = (context->count[0] >> 3) & 0x3F;
    partlen = 64 - index;
    context->count[0] += inputlen << 3;

    if(context->count[0] < (inputlen << 3))
    {
    
    
        context->count[1]++;
    }
    context->count[1] += inputlen >> 29;

    if(inputlen >= partlen)
    {
    
    
        memcpy(&context->buffer[index], input,partlen);
        MD5Transform(context->state, context->buffer);

        for(i = partlen; i+64 <= inputlen; i+=64)
        {
    
    
            MD5Transform(context->state, &input[i]);
        }
        index = 0;
    }
    else
    {
    
    
        i = 0;
    }
    memcpy(&context->buffer[index], &input[i], inputlen-i);
}

void MD5Final(MD5_CTX *context, uint8_t digest[16])
{
    
    
    uint32_t index = 0,padlen = 0;
    uint8_t bits[8];

    index = (context->count[0] >> 3) & 0x3F;
    padlen = (index < 56)?(56-index):(120-index);
    MD5Encode(bits, context->count, 8);
    MD5Update(context, PADDING, padlen);
    MD5Update(context, bits, 8);
    MD5Encode(digest, context->state, 16);
}

void MD5Encode(uint8_t *output, uint32_t *input, uint32_t len)
{
    
    
    uint32_t i = 0;
    uint32_t j = 0;

    while(j < len)
    {
    
    
        output[j] = input[i] & 0xFF;
        output[j+1] = (input[i] >> 8) & 0xFF;
        output[j+2] = (input[i] >> 16) & 0xFF;
        output[j+3] = (input[i] >> 24) & 0xFF;
        i++;
        j += 4;
    }
}

void MD5Decode(uint32_t *output, uint8_t *input, uint32_t len)
{
    
    
    uint32_t i = 0;
    uint32_t j = 0;

    while(j < len)
    {
    
    
        output[i] = (input[j]) | (input[j+1] << 8) | (input[j+2] << 16) | (input[j+3] << 24);
        i++;
        j += 4;
    }
}

void MD5Transform(uint32_t state[4], uint8_t block[64])
{
    
    
    uint32_t a = state[0];
    uint32_t b = state[1];
    uint32_t c = state[2];
    uint32_t d = state[3];
    uint32_t x[64];

    MD5Decode(x,block,64);

    FF(a, b, c, d, x[ 0], 7,  0xd76aa478); /* 1 */
    FF(d, a, b, c, x[ 1], 12, 0xe8c7b756); /* 2 */
    FF(c, d, a, b, x[ 2], 17, 0x242070db); /* 3 */
    FF(b, c, d, a, x[ 3], 22, 0xc1bdceee); /* 4 */
    FF(a, b, c, d, x[ 4], 7,  0xf57c0faf); /* 5 */
    FF(d, a, b, c, x[ 5], 12, 0x4787c62a); /* 6 */
    FF(c, d, a, b, x[ 6], 17, 0xa8304613); /* 7 */
    FF(b, c, d, a, x[ 7], 22, 0xfd469501); /* 8 */
    FF(a, b, c, d, x[ 8], 7,  0x698098d8); /* 9 */
    FF(d, a, b, c, x[ 9], 12, 0x8b44f7af); /* 10 */
    FF(c, d, a, b, x[10], 17, 0xffff5bb1); /* 11 */
    FF(b, c, d, a, x[11], 22, 0x895cd7be); /* 12 */
    FF(a, b, c, d, x[12], 7,  0x6b901122); /* 13 */
    FF(d, a, b, c, x[13], 12, 0xfd987193); /* 14 */
    FF(c, d, a, b, x[14], 17, 0xa679438e); /* 15 */
    FF(b, c, d, a, x[15], 22, 0x49b40821); /* 16 */

    /* Round 2 */
    GG(a, b, c, d, x[ 1], 5,  0xf61e2562); /* 17 */
    GG(d, a, b, c, x[ 6], 9,  0xc040b340); /* 18 */
    GG(c, d, a, b, x[11], 14, 0x265e5a51); /* 19 */
    GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa); /* 20 */
    GG(a, b, c, d, x[ 5], 5,  0xd62f105d); /* 21 */
    GG(d, a, b, c, x[10], 9,  0x2441453);  /* 22 */
    GG(c, d, a, b, x[15], 14, 0xd8a1e681); /* 23 */
    GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8); /* 24 */
    GG(a, b, c, d, x[ 9], 5,  0x21e1cde6); /* 25 */
    GG(d, a, b, c, x[14], 9,  0xc33707d6); /* 26 */
    GG(c, d, a, b, x[ 3], 14, 0xf4d50d87); /* 27 */
    GG(b, c, d, a, x[ 8], 20, 0x455a14ed); /* 28 */
    GG(a, b, c, d, x[13], 5,  0xa9e3e905); /* 29 */
    GG(d, a, b, c, x[ 2], 9,  0xfcefa3f8); /* 30 */
    GG(c, d, a, b, x[ 7], 14, 0x676f02d9); /* 31 */
    GG(b, c, d, a, x[12], 20, 0x8d2a4c8a); /* 32 */

    /* Round 3 */
    HH(a, b, c, d, x[ 5], 4,  0xfffa3942); /* 33 */
    HH(d, a, b, c, x[ 8], 11, 0x8771f681); /* 34 */
    HH(c, d, a, b, x[11], 16, 0x6d9d6122); /* 35 */
    HH(b, c, d, a, x[14], 23, 0xfde5380c); /* 36 */
    HH(a, b, c, d, x[ 1], 4,  0xa4beea44); /* 37 */
    HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9); /* 38 */
    HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60); /* 39 */
    HH(b, c, d, a, x[10], 23, 0xbebfbc70); /* 40 */
    HH(a, b, c, d, x[13], 4,  0x289b7ec6); /* 41 */
    HH(d, a, b, c, x[ 0], 11, 0xeaa127fa); /* 42 */
    HH(c, d, a, b, x[ 3], 16, 0xd4ef3085); /* 43 */
    HH(b, c, d, a, x[ 6], 23,  0x4881d05); /* 44 */
    HH(a, b, c, d, x[ 9], 4,  0xd9d4d039); /* 45 */
    HH(d, a, b, c, x[12], 11, 0xe6db99e5); /* 46 */
    HH(c, d, a, b, x[15], 16, 0x1fa27cf8); /* 47 */
    HH(b, c, d, a, x[ 2], 23, 0xc4ac5665); /* 48 */

    /* Round 4 */
    II(a, b, c, d, x[ 0], 6,  0xf4292244); /* 49 */
    II(d, a, b, c, x[ 7], 10, 0x432aff97); /* 50 */
    II(c, d, a, b, x[14], 15, 0xab9423a7); /* 51 */
    II(b, c, d, a, x[ 5], 21, 0xfc93a039); /* 52 */
    II(a, b, c, d, x[12], 6,  0x655b59c3); /* 53 */
    II(d, a, b, c, x[ 3], 10, 0x8f0ccc92); /* 54 */
    II(c, d, a, b, x[10], 15, 0xffeff47d); /* 55 */
    II(b, c, d, a, x[ 1], 21, 0x85845dd1); /* 56 */
    II(a, b, c, d, x[ 8], 6,  0x6fa87e4f); /* 57 */
    II(d, a, b, c, x[15], 10, 0xfe2ce6e0); /* 58 */
    II(c, d, a, b, x[ 6], 15, 0xa3014314); /* 59 */
    II(b, c, d, a, x[13], 21, 0x4e0811a1); /* 60 */
    II(a, b, c, d, x[ 4], 6,  0xf7537e82); /* 61 */
    II(d, a, b, c, x[11], 10, 0xbd3af235); /* 62 */
    II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb); /* 63 */
    II(b, c, d, a, x[ 9], 21, 0xeb86d391); /* 64 */
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
}


/*!
 *  功   能: 字符串的 MD5 信息摘要计算
 *  param1: 指向要计算的字符串的指针
 *  param2: 要计算的字符串的长度
 *  param3: 指向存储 MD5 计算结果的指针
 *  retval: 0
 */
int compute_string_md5(uint8_t *dest_str, uint32_t dest_len, uint8_t *md5_str)
{
    
    
    MD5_CTX md5;

    // init md5
    MD5Init(&md5);

    MD5Update(&md5, dest_str, dest_len);

    MD5Final(&md5, md5_str);

    return 0;
}

2. md5.h

#ifndef _MD5_H_
#define _MD5_H_

#include <stdint.h>

typedef struct
{
    
    
    uint32_t count[2];
    uint32_t state[4];
    uint8_t buffer[64];
} MD5_CTX;


#define MD5_SIZE  (16)

#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))

#define ROTATE_LEFT(x,n) ((x << n) | (x >> (32-n)))

#define FF(a,b,c,d,x,s,ac) \
{ \
	a += F(b,c,d) + x + ac; \
	a = ROTATE_LEFT(a,s); \
	a += b; \
}

#define GG(a,b,c,d,x,s,ac) \
{ \
	a += G(b,c,d) + x + ac; \
	a = ROTATE_LEFT(a,s); \
	a += b; \
}

#define HH(a,b,c,d,x,s,ac) \
{ \
	a += H(b,c,d) + x + ac; \
	a = ROTATE_LEFT(a,s); \
	a += b; \
}

#define II(a,b,c,d,x,s,ac) \
{ \
	a += I(b,c,d) + x + ac; \
	a = ROTATE_LEFT(a,s); \
	a += b; \
}                                            

void MD5Init(MD5_CTX *context);\

void MD5Update(MD5_CTX *context, uint8_t *input, uint32_t inputlen);

void MD5Final(MD5_CTX *context, uint8_t digest[16]);

void MD5Transform(uint32_t state[4], uint8_t block[64]);

void MD5Encode(uint8_t *output, uint32_t *input, uint32_t len);

void MD5Decode(uint32_t *output, uint8_t *input, uint32_t len);

int compute_string_md5(uint8_t *dest_str, uint32_t dest_len, uint8_t *md5_str);

#endif  /* md5.h */