md5的C++实现

时间：2015-12-23 21:01:12 阅读：289 评论：0 收藏：0 [点我收藏+]

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一、原理

前一阵子，想知道md5的原理查了一下资料，说得基本都一样，最后让我看懂的是这两个链接：

http://blog.csdn.net/qf_study/article/details/2630903

http://baike.baidu.com/link?url=MBQj5ddK13WUItbGHutP_cEX17jZ5ou3nu_bdHYECctRKFLIikI0xrcwzv31JB2PsZHMKlFnOT94v9aMB6LzTa

用我的话说一下原理就是这样的：

先定义a、b、c、d四个变量，赋一个初值。
然后把你输入的数据按照每512位分个块，最后的512字节前448字节用部位实现，后64字节存输入的长度；
每个512位的块，分成16个组，每组也就是一个32位的变量，按照一定的算法叠加到a,b,c,d四个变量里；
算法是这样的：a=b+(a+Process P(b,c,d)+M[i]+T[k])<<s），后面的块把结果叠加到前面块的计算结果中(相当于abcd就是个全局变量)
最后算出的a,b,c,d级联到一起，就是一个128位的数，用16进制表示每个位，就是一个长度为32的字符串，也就是最终的结果；

二、MD5的源码：

http://www.cnblogs.com/ruihong/archive/2012/10/24/2736727.html (如果转载请加注源作者的链接)

经过修改之后，可以编译使用了，为了方便以后引用，记录如下：

md5.h

#ifndef _CMD5_H
#define _CMD5_H

//#pragma warning(disable:4786)

#include <string>

using namespace std;

/*!
 * Manage CMD5.
 */
class CMD5
{
private:
    #define uint8  unsigned char
    #define uint32 unsigned long int

    struct md5_context
    {
        uint32 total[2];
        uint32 state[4];
        uint8 buffer[64];
    };

    void md5_starts( struct md5_context *ctx );
    void md5_process( struct md5_context *ctx, uint8 data[64] );
    void md5_update( struct md5_context *ctx, uint8 *input, uint32 length );
    void md5_finish( struct md5_context *ctx, uint8 digest[16] );

public:
    //! construct a CMD5 from any buffer
    void GenerateMD5(unsigned char* buffer,int bufferlen);

    //! construct a CMD5
    CMD5();

    //! construct a md5src from char *
    CMD5(const char * md5src);

    //! construct a CMD5 from a 16 bytes md5
    CMD5(unsigned long* md5src);

    //! add a other md5
    CMD5 operator +(CMD5 adder);

    //! just if equal
    bool operator ==(CMD5 cmper);

    //! give the value from equer
    // void operator =(CMD5 equer);

    //! to a string
    string ToString();

    unsigned long m_data[4];
};
#endif /* md5.h */

md5.cpp

/*
 * RFC 1321 compliant CMD5 implementation,
 * by Christophe Devine <devine@cr0.net>;
 * this program is licensed under the GPL.
 */
#include "md5.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define GET_UINT32(n,b,i)                                      \
{                                                                                          (n) = (uint32) ((uint8 *) b)[(i)]                                       | (((uint32) ((uint8 *) b)[(i)+1]) <<  8)                        | (((uint32) ((uint8 *) b)[(i)+2]) << 16)                      | (((uint32) ((uint8 *) b)[(i)+3]) << 24);               }

#define PUT_UINT32(n,b,i)                                              \
{                                                                                                  (((uint8 *) b)[(i)]  ) = (uint8) (((n)      ) & 0xFF);                 (((uint8 *) b)[(i)+1]) = (uint8) (((n) >>  8) & 0xFF);          (((uint8 *) b)[(i)+2]) = (uint8) (((n) >> 16) & 0xFF);         (((uint8 *) b)[(i)+3]) = (uint8) (((n) >> 24) & 0xFF);     }

//extern pthread_mutex_t mutexMemory;

void CMD5::md5_starts( struct md5_context *ctx )
{
    ctx->total[0] = 0;
    ctx->total[1] = 0;
    ctx->state[0] = 0x67452301;
    ctx->state[1] = 0xEFCDAB89;
    ctx->state[2] = 0x98BADCFE;
    ctx->state[3] = 0x10325476;
}

void CMD5::md5_process( struct md5_context *ctx, uint8 data[64] )
{
    uint32 A, B, C, D, X[16];

    GET_UINT32( X[0],  data,  0 );
    GET_UINT32( X[1],  data,  4 );
    GET_UINT32( X[2],  data,  8 );
    GET_UINT32( X[3],  data, 12 );
    GET_UINT32( X[4],  data, 16 );
    GET_UINT32( X[5],  data, 20 );
    GET_UINT32( X[6],  data, 24 );
    GET_UINT32( X[7],  data, 28 );
    GET_UINT32( X[8],  data, 32 );
    GET_UINT32( X[9],  data, 36 );
    GET_UINT32( X[10], data, 40 );
    GET_UINT32( X[11], data, 44 );
    GET_UINT32( X[12], data, 48 );
    GET_UINT32( X[13], data, 52 );
    GET_UINT32( X[14], data, 56 );
    GET_UINT32( X[15], data, 60 );

#define S(x,n) ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)))

#define P(a,b,c,d,k,s,t)                                    \
{                                                                               a += F(b,c,d) + X[k] + t; a = S(a,s) + b;      }

    A = ctx->state[0];
    B = ctx->state[1];
    C = ctx->state[2];
    D = ctx->state[3];

#define F(x,y,z) (z ^ (x & (y ^ z)))

    P( A, B, C, D,  0,  7, 0xD76AA478 );
    P( D, A, B, C,  1, 12, 0xE8C7B756 );
    P( C, D, A, B,  2, 17, 0x242070DB );
    P( B, C, D, A,  3, 22, 0xC1BDCEEE );
    P( A, B, C, D,  4,  7, 0xF57C0FAF );
    P( D, A, B, C,  5, 12, 0x4787C62A );
    P( C, D, A, B,  6, 17, 0xA8304613 );
    P( B, C, D, A,  7, 22, 0xFD469501 );
    P( A, B, C, D,  8,  7, 0x698098D8 );
    P( D, A, B, C,  9, 12, 0x8B44F7AF );
    P( C, D, A, B, 10, 17, 0xFFFF5BB1 );
    P( B, C, D, A, 11, 22, 0x895CD7BE );
    P( A, B, C, D, 12,  7, 0x6B901122 );
    P( D, A, B, C, 13, 12, 0xFD987193 );
    P( C, D, A, B, 14, 17, 0xA679438E );
    P( B, C, D, A, 15, 22, 0x49B40821 );

#undef F

#define F(x,y,z) (y ^ (z & (x ^ y)))

    P( A, B, C, D,  1,  5, 0xF61E2562 );
    P( D, A, B, C,  6,  9, 0xC040B340 );
    P( C, D, A, B, 11, 14, 0x265E5A51 );
    P( B, C, D, A,  0, 20, 0xE9B6C7AA );
    P( A, B, C, D,  5,  5, 0xD62F105D );
    P( D, A, B, C, 10,  9, 0x02441453 );
    P( C, D, A, B, 15, 14, 0xD8A1E681 );
    P( B, C, D, A,  4, 20, 0xE7D3FBC8 );
    P( A, B, C, D,  9,  5, 0x21E1CDE6 );
    P( D, A, B, C, 14,  9, 0xC33707D6 );
    P( C, D, A, B,  3, 14, 0xF4D50D87 );
    P( B, C, D, A,  8, 20, 0x455A14ED );
    P( A, B, C, D, 13,  5, 0xA9E3E905 );
    P( D, A, B, C,  2,  9, 0xFCEFA3F8 );
    P( C, D, A, B,  7, 14, 0x676F02D9 );
    P( B, C, D, A, 12, 20, 0x8D2A4C8A );

#undef F
    
#define F(x,y,z) (x ^ y ^ z)

    P( A, B, C, D,  5,  4, 0xFFFA3942 );
    P( D, A, B, C,  8, 11, 0x8771F681 );
    P( C, D, A, B, 11, 16, 0x6D9D6122 );
    P( B, C, D, A, 14, 23, 0xFDE5380C );
    P( A, B, C, D,  1,  4, 0xA4BEEA44 );
    P( D, A, B, C,  4, 11, 0x4BDECFA9 );
    P( C, D, A, B,  7, 16, 0xF6BB4B60 );
    P( B, C, D, A, 10, 23, 0xBEBFBC70 );
    P( A, B, C, D, 13,  4, 0x289B7EC6 );
    P( D, A, B, C,  0, 11, 0xEAA127FA );
    P( C, D, A, B,  3, 16, 0xD4EF3085 );
    P( B, C, D, A,  6, 23, 0x04881D05 );
    P( A, B, C, D,  9,  4, 0xD9D4D039 );
    P( D, A, B, C, 12, 11, 0xE6DB99E5 );
    P( C, D, A, B, 15, 16, 0x1FA27CF8 );
    P( B, C, D, A,  2, 23, 0xC4AC5665 );

#undef F

#define F(x,y,z) (y ^ (x | ~z))

    P( A, B, C, D,  0,  6, 0xF4292244 );
    P( D, A, B, C,  7, 10, 0x432AFF97 );
    P( C, D, A, B, 14, 15, 0xAB9423A7 );
    P( B, C, D, A,  5, 21, 0xFC93A039 );
    P( A, B, C, D, 12,  6, 0x655B59C3 );
    P( D, A, B, C,  3, 10, 0x8F0CCC92 );
    P( C, D, A, B, 10, 15, 0xFFEFF47D );
    P( B, C, D, A,  1, 21, 0x85845DD1 );
    P( A, B, C, D,  8,  6, 0x6FA87E4F );
    P( D, A, B, C, 15, 10, 0xFE2CE6E0 );
    P( C, D, A, B,  6, 15, 0xA3014314 );
    P( B, C, D, A, 13, 21, 0x4E0811A1 );
    P( A, B, C, D,  4,  6, 0xF7537E82 );
    P( D, A, B, C, 11, 10, 0xBD3AF235 );
    P( C, D, A, B,  2, 15, 0x2AD7D2BB );
    P( B, C, D, A,  9, 21, 0xEB86D391 );

#undef F

    ctx->state[0] += A;
    ctx->state[1] += B;
    ctx->state[2] += C;
    ctx->state[3] += D;
}

void CMD5::md5_update( struct md5_context *ctx, uint8 *input, uint32 length )
{
    uint32 left, fill;

    if( ! length ) return;

    left = ( ctx->total[0] >> 3 ) & 0x3F;
    fill = 64 - left;

    ctx->total[0] += length <<  3;
    ctx->total[1] += length >> 29;

    ctx->total[0] &= 0xFFFFFFFF;
    ctx->total[1] += ctx->total[0] < length << 3;

    if( left && length >= fill )
    {
        memcpy( (void *) (ctx->buffer + left), (void *) input, fill );
        md5_process( ctx, ctx->buffer );
        length -= fill;
        input  += fill;
        left = 0;
    }

    while( length >= 64 )
    {
        md5_process( ctx, input );
        length -= 64;
        input  += 64;
    }

    if( length )
    {
        memcpy( (void *) (ctx->buffer + left), (void *) input, length );
    }
}

static uint8 md5_padding[64] =
{
 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 CMD5::md5_finish( struct md5_context *ctx, uint8 digest[16] )
{
    uint32 last, padn;
    uint8 msglen[8];

    PUT_UINT32( ctx->total[0], msglen, 0 );
    PUT_UINT32( ctx->total[1], msglen, 4 );

    last = ( ctx->total[0] >> 3 ) & 0x3F;
    padn = ( last < 56 ) ? ( 56 - last ) : ( 120 - last );

    md5_update( ctx, md5_padding, padn );
    md5_update( ctx, msglen, 8 );

    PUT_UINT32( ctx->state[0], digest,  0 );
    PUT_UINT32( ctx->state[1], digest,  4 );
    PUT_UINT32( ctx->state[2], digest,  8 );
    PUT_UINT32( ctx->state[3], digest, 12 );
}

void CMD5::GenerateMD5(unsigned char* buffer,int bufferlen)
{
    struct md5_context context;
    md5_starts (&context);
    md5_update (&context, buffer, bufferlen);
    md5_finish (&context,(unsigned char*)m_data);
}

CMD5::CMD5()
{
    for(int i=0;i<4;i++)
        m_data[i]=0;
}

CMD5::CMD5(unsigned long* md5src)
{
    memcpy(m_data,md5src,16);
}
int _httoi(const char *value)
{
  struct CHexMap
  {
    char chr;
    int value;
  };
  const int HexMapL = 16;
  CHexMap HexMap[HexMapL] =
  {
    {‘0‘, 0}, {‘1‘, 1},
    {‘2‘, 2}, {‘3‘, 3},
    {‘4‘, 4}, {‘5‘, 5},
    {‘6‘, 6}, {‘7‘, 7},
    {‘8‘, 8}, {‘9‘, 9},
    {‘a‘, 10}, {‘b‘, 11},
    {‘c‘, 12}, {‘d‘, 13},
    {‘e‘, 14}, {‘f‘, 15}
  };
  //pthread_mutex_lock(&mutexMemory);
  char *mstr = strdup(value);
  //pthread_mutex_unlock(&mutexMemory);
  char *s = mstr;
  int result = 0;
  if (*s == ‘0‘ && *(s + 1) == ‘X‘) s += 2;
  bool firsttime = true;
  while (*s != ‘/0‘)
  {
    bool found = false;
    for (int i = 0; i < HexMapL; i++)
    {
      if (*s == HexMap[i].chr)
      {
        if (!firsttime) result <<= 4;
        result |= HexMap[i].value;
        found = true;
        break;
      }
    }
    if (!found) break;
    s++;
    firsttime = false;
  }
  //pthread_mutex_lock(&mutexMemory);
  free(mstr);
  //pthread_mutex_unlock(&mutexMemory);
  return result;
}


CMD5::CMD5(const char* md5src)
{
    if (strcmp(md5src,"")==0)
    {
        for(int i=0;i<4;i++)
            m_data[i]=0;
        return;
    }
    for(int j = 0; j < 16; j++ )
    {
        char buf[10];
        strncpy(buf,md5src,2);
        md5src+=2;
        ((unsigned char*)m_data)[j] = _httoi(buf);
    }
}

CMD5 CMD5::operator +(CMD5 adder)
{
    unsigned long m_newdata[4];
    for(int i=0;i<4;i++)
        m_newdata[i]=m_data[i]^(adder.m_data[i]);
    return CMD5(m_newdata);
}

bool CMD5::operator ==(CMD5 cmper)
{
    return (memcmp(cmper.m_data ,m_data,16)==0);
}

//void CMD5::operator =(CMD5 equer)
//{
//    memcpy(m_data,equer.m_data ,16);
//}

string CMD5::ToString()
{
    char output[33];
    for(int j = 0; j < 16; j++ )
    {
        sprintf( output + j * 2, "%02x", ((unsigned char*)m_data)[j]);
    }
    return string(output);
}

main.cpp

#include <iostream>
#include "md5.h"
using namespace std;

int main()
{
    const char *text = "hello world";
    const char *text1 = "hello ";
    const char *text2 = "world";

    CMD5 iMD5;
    iMD5.GenerateMD5((unsigned char*)text, strlen(text) );
    std::string result = iMD5.ToString();
    cout<<result<<endl;
}

Makefile

COMPILER=g++

executemain : main.o md5.o
    $(COMPILER) -o executemain main.o md5.o
main.o : main.cpp md5.h
    $(COMPILER) -g -c main.cpp
md5.o : md5.h md5.cpp
    $(COMPILER) -g -c md5.cpp
clean :
    rm -f executemain main.o md5.o

三、大文件也没问题

源码中只给md5传了一个字符数组，万一是大文件怎么办？

看懂了原理，应该不难理解，都是分成512个位的块叠加，用数组多传几次是一样的效果，只是源码中把主要函数设置为私有变量，如果需要自己封装一下也可以实现，只是给大家引用一个CSDN大神的解法：http://bbs.csdn.net/topics/230085330提供个思路吧

$ cat t2.c; gcc -o t2 t2.c `pkg-config openssl --cflags --libs`; ./t2
/***************************************************************/
#include <stdio.h>
#include <openssl/md5.h>
#include <openssl/rand.h>

typedef unsigned char byte;
#define INPUT_LEN               (1024+123)

void test1( byte* input , int len , int l1 )
{
        int i;
        byte  md5[16];
        MD5_CTX ctx;
        MD5_Init( &ctx );
        for( ;len >= l1; input += l1 , len -= l1 )
                MD5_Update( &ctx , input , l1 );
        if( len )
                MD5_Update( &ctx , input , len );
        MD5_Final( md5 , &ctx );

        for( i = 0; i < 16; ++i )
                printf( "%02X " , md5[i] );
        printf( " : %d\n" , l1 );
}
int main()
{
        int     l1;
        byte    input[INPUT_LEN];
        RAND_bytes( input , sizeof( input ) );

        for( l1 = 1; l1 <= INPUT_LEN; l1 <<= 1 )
                test1( input , sizeof( input ) , l1 );
return 0;
}
/***************************************************************/
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 1
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 2
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 4
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 8
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 16
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 32
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 64
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 128
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 256
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 512
AD 84 BB AF 9C E9 5A DD 7D CB 3A 3F C8 E1 63 03  : 1024

md5的C++实现

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原文地址：http://www.cnblogs.com/bugutian/p/5071016.html

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