C语言计算MD5

计算MD5这种很标准的东西，一般直接使用别人写好的了就行，本文主要针对写好的接口测试一下如何使用的问题。

下面是MD5的实现
md5.h

#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 MD5Init(MD5_CTX *context);  
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen);  
void MD5Final(MD5_CTX *context,unsigned char digest[16]);  
void MD5Transform(unsigned int state[4],unsigned char block[64]);  
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len);  
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len); 
#endif

md5.c

#include <string.h>
#include "md5.h" 


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};  

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


    GG(a, b, c, d, x[ 1], 5, 0xf61e2562);   
    GG(d, a, b, c, x[ 6], 9, 0xc040b340);   
    GG(c, d, a, b, x[11], 14, 0x265e5a51);   
    GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);   
    GG(a, b, c, d, x[ 5], 5, 0xd62f105d);   
    GG(d, a, b, c, x[10], 9,  0x2441453);   
    GG(c, d, a, b, x[15], 14, 0xd8a1e681);   
    GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);   
    GG(a, b, c, d, x[ 9], 5, 0x21e1cde6);   
    GG(d, a, b, c, x[14], 9, 0xc33707d6);   
    GG(c, d, a, b, x[ 3], 14, 0xf4d50d87);   
    GG(b, c, d, a, x[ 8], 20, 0x455a14ed);   
    GG(a, b, c, d, x[13], 5, 0xa9e3e905);   
    GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8);   
    GG(c, d, a, b, x[ 7], 14, 0x676f02d9);   
    GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);   


    HH(a, b, c, d, x[ 5], 4, 0xfffa3942);   
    HH(d, a, b, c, x[ 8], 11, 0x8771f681);   
    HH(c, d, a, b, x[11], 16, 0x6d9d6122);   
    HH(b, c, d, a, x[14], 23, 0xfde5380c);   
    HH(a, b, c, d, x[ 1], 4, 0xa4beea44);   
    HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);   
    HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60);   
    HH(b, c, d, a, x[10], 23, 0xbebfbc70);   
    HH(a, b, c, d, x[13], 4, 0x289b7ec6);   
    HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);   
    HH(c, d, a, b, x[ 3], 16, 0xd4ef3085);   
    HH(b, c, d, a, x[ 6], 23,  0x4881d05);   
    HH(a, b, c, d, x[ 9], 4, 0xd9d4d039);   
    HH(d, a, b, c, x[12], 11, 0xe6db99e5);   
    HH(c, d, a, b, x[15], 16, 0x1fa27cf8);   
    HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);   


    II(a, b, c, d, x[ 0], 6, 0xf4292244);   
    II(d, a, b, c, x[ 7], 10, 0x432aff97);   
    II(c, d, a, b, x[14], 15, 0xab9423a7);   
    II(b, c, d, a, x[ 5], 21, 0xfc93a039);   
    II(a, b, c, d, x[12], 6, 0x655b59c3);   
    II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);   
    II(c, d, a, b, x[10], 15, 0xffeff47d);   
    II(b, c, d, a, x[ 1], 21, 0x85845dd1);   
    II(a, b, c, d, x[ 8], 6, 0x6fa87e4f);   
    II(d, a, b, c, x[15], 10, 0xfe2ce6e0);   
    II(c, d, a, b, x[ 6], 15, 0xa3014314);   
    II(b, c, d, a, x[13], 21, 0x4e0811a1);   
    II(a, b, c, d, x[ 4], 6, 0xf7537e82);   
    II(d, a, b, c, x[11], 10, 0xbd3af235);   
    II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb);   
    II(b, c, d, a, x[ 9], 21, 0xeb86d391);   
    state[0] += a;  
    state[1] += b;  
    state[2] += c;  
    state[3] += d;  
}

下面是测试程序, 主要依次调用MD5Init， MD5Update，MD5Final三个函数就行了

/************************************************************
Copyright (C), 2017, Leon, All Rights Reserved.
FileName: test_md5.c
Description: MD5函数测试
Author: Leon
Version: 1.0
Date: 
Function:

History:
<author>    <time>  <version>   <description>
 Leon
************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include "md5.h"

/* md5函数测试 */
int main(int argc, char *argv[])
{
    struct stat st;
    unsigned char digest[16] = {0};
    MD5_CTX context;
    int i = 0;

    if(argc < 2)
        return;

    MD5Init(&context);

    if(-1 == stat(argv[1], &st))
    {
        /* 文件不存在则计算参数字符串的MD5 */
        MD5Update(&context, argv[1], strlen(argv[1]));
    }
    else
    {
        /* 计算文件MD5 */
        FILE *fp = fopen(argv[1], "r");
        char *data = NULL;
        int ret = 0;

        if(!fp)
        {
            perror("fopen");
            exit(-1);
        }

        data = malloc(st.st_size);
        if(!data)
        {
            perror("malloc");
            exit(-1);
        }
        ret = fread(data, 1, st.st_size, fp);
        if(ret != st.st_size)
        {
            perror("fread");
            exit(-1);
        } 
        MD5Update(&context, data, st.st_size);
        fclose(fp);
        free(data);
    }
    MD5Final(&context, digest);

    /* 打印MD5值 */
    printf("md5: ");
    for(i = 0; i < 16; i++)
    {
        printf("%02x", digest[i]);
    }
    printf("\n");
    return 0;
}

执行结果与openssl结果对比是一致的：

测试结果：
root@ubuntu:online_upgrade# ./a.out 123.txt 
md5: 86109d400f0ed29e840b47ed72777c84
root@ubuntu:online_upgrade# openssl md5 123.txt
MD5(123.txt)= 86109d400f0ed29e840b47ed72777c84

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