MD5工具

一、工具的使用

参考这个链接即可：https://www.cnblogs.com/miracle-luna/p/11967246.html

二、源码及编译

2.1 源码

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

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#include <memory.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};
 
/********************************************************
* 名    称: MD5Init()
* 功    能: 初始化MD5结构体
* 入口参数: 
   context：要初始化的MD5结构体 
* 出口参数: 无
*********************************************************/                      
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;
}
 
/*********************************************************
* 名    称: MD5Update()
* 功    能: 将要加密的信息传递给初始化过的MD5结构体，无返回值
* 入口参数: 
    context：初始化过了的MD5结构体 
    input：需要加密的信息，可以任意长度
    inputLen：指定input的长度
* 出口参数: 无
*********************************************************/
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);
}
 
/*********************************************************
* 名    称: MD5Update()
* 功    能: 将加密结果存储到digest，无返回值
* 入口参数: 
    context：初始化过了的MD5结构体
    digest ：加密过的结果
* 出口参数: 无
*********************************************************/
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); /* 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;
}

md5_test.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include "md5.h"
 
int calc_md5(char *filename,char *dest)
{
    int i;
    int filelen=0;
    int read_len;
    char temp[8]={0};
    char hexbuf[128]={0};
    unsigned char decrypt[16]={0};
    unsigned char decrypt32[64]={0};
    char fw_path[128];
 
    MD5_CTX md5;
 
    int fdf;
 
    fdf=open(filename,O_RDWR);
    if(fdf<0)
    {
        printf("%s not exist\n",filename);
        return -1;
    }
 
    MD5Init(&md5);
    while(1)
    {
        read_len=read(fdf,hexbuf,sizeof(hexbuf));
        if(read_len<0)
        {
            close(fdf);
            return -1;
        }
        if(read_len == 0)
        {
            break;
        }
        filelen+=read_len;
        MD5Update(&md5,(unsigned char *)hexbuf,read_len);
    }
 
    MD5Final(&md5,decrypt);
    strcpy((char *)decrypt32,"");
 
    for(i=0;i<16;i++)
    {
        sprintf(temp,"%02x",decrypt[i]);
        strcat((char *)decrypt32,temp);
    }
    strcpy(dest,decrypt32);
 
    printf("%s md5:%s len=%d\n",filename,dest,filelen);
    close(fdf);
 
    return filelen;
}
 
int main(int argc,char *argv[])
{
    int ret;
    int filelen;
    char md5_str[64]={0};
    char cmd[256]={0};
 
    filelen=calc_md5(argv[1],md5_str);
    if(filelen<0)
    {
        printf("calc_md5 fail\n");
        return -1;
    }
 
    return 0;
}

2.2 编译

1	`gcc md5_test.c md5.c -o my_md5`

2.3 运行

./my_md5 md5_test.c
 
md5_test.c md5:xxxxxxxxxxxxxxxxxxxxxxxx len=xxxx

三、定制

上面计算的md5 和linux 系统自带的工具是一样的，但是有时候，我们不想和系统的一样，用户约定两者之间的通信，变成一种加密技术，那么我们可以约定一个加密因子，来实现。

我们在计算md5 的时候，修改一下计算对象的某些特定字节，这样，计算的md5值就和系统的不一样，对方也可以使用同样的方法来计算md5值，然后进行比对，如果是一样，代表通信是内容是没有篡改过的。

char salt_ramdom[128] = { 0x80 };
bool add_ramdom = true;
 
strcpy(salt_ramdom, "xxxxxxxxx");
 
while (1)
{
        read_len=read(fdf,hexbuf,sizeof(hexbuf));
        if(read_len<0)
        {
                close(fdf);
                return -1;
        }
        if(read_len == 0)
        {
                break;
        }
 
        if (add_ramdom)
        {
                //printf("ramdom is:%s\n",salt_ramdom);
                while (salt_ramdom[nIndex] != 0x00)
                {
                        //printf("ramdom[%d]=%c\n",nIndex,salt_ramdom[nIndex]);
                        hexbuf[nIndex] ^= salt_ramdom[nIndex];
                        nIndex++;
                }
 
                add_ramdom = false;
        }
 
        filelen += read_len;
 
        MD5Update(&md5, (unsigned char*)hexbuf, read_len);
}