C语言写的md5函数

水深无声 2022-12-08 12:56 155阅读 0赞

网上关于C/C++的md5函数很多，我下载后包装了一个简单的。代码和测试用例如下：  
下面只是C语言实现的针对字符串的MD5处理，如果要处理二进制数据，稍作改进就可以了。  
在C++编程里，还可以将函数改进为返回string类型对象的方式，来避免使用字符数组接收数据。

#ifndef MD5_H
    #define MD5_H
    
    typedef struct
    { 
      unsigned int count[2];
      unsigned int state[4];
      unsigned char buffer[64];
    } MD5_CTX;
    
    #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 md5(unsigned char *data, char hex[36]);
    #endif

#include <stdio.h>
    #include <string.h>
    #include "md5.h"
    
    static unsigned char 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
                              };
    
    static 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;
    }
    
    static void MD5Encode(unsigned char *output, unsigned int *input, unsigned int len)
    { 
        unsigned int i = 0, 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;
        }
    }
    
    static void MD5Decode(unsigned int *output, unsigned char *input, unsigned int len)
    { 
        unsigned int i = 0, j = 0;
        while (j < len)
        { 
            output[i] = (input[j]) |
                        (input[j + 1] << 8) |
                        (input[j + 2] << 16) |
                        (input[j + 3] << 24);
            i++;
            j += 4;
        }
    }
    
    static void MD5Transform(unsigned int state[4], unsigned char block[64])
    { 
        unsigned int a = state[0];
        unsigned int b = state[1];
        unsigned int c = state[2];
        unsigned int d = state[3];
        unsigned int 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;
    }
    
    
    static void MD5Update(MD5_CTX *context, unsigned char *input, unsigned int inputlen)
    { 
        unsigned int i = 0, index = 0, 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);
    }
    
    static void MD5Final(MD5_CTX *context, unsigned char digest[16])
    { 
        unsigned int index = 0, padlen = 0;
        unsigned char 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);
    }
    
    extern void md5(unsigned char *data, char hex[36])
    { 
    	int i;
    	unsigned char decrypt[16];
    	MD5_CTX md5;
    	MD5Init(&md5);
    	MD5Update(&md5, data, strlen((char *)data));
    	MD5Final(&md5, decrypt);
    	for (i = 0; i < 16; i++)
    	{ 
    		snprintf(hex+i*2, 3, "%02x", decrypt[i]);
    	}
    	hex[32] = 0;
    }

#include <stdio.h>
    #include "md5.h"
    
    int main(int argc, char *argv[])
    { 
    	char hex[36];
    	unsigned char *str = (unsigned char *)argv[1];
    	md5(str, hex);
    	printf("str: %s\nhex: %s\n", str, hex);
    	return 0;
    }

下载后在linux上编译gcc -o test test.c md5.c，然后运行：./test admin即可：  
![在这里插入图片描述][20200919120043664.png_pic_center]

[20200919120043664.png_pic_center]: /images/20221123/70ec32c3e321424f9b98d04f21442ff0.png