C++ MD5的源码实例详解

C++ MD5源码：

md5.h:

#ifndef MD5_H
#define MD5_H

#include <string>
#include <fstream>

/* Type define */
typedef unsigned char byte;
typedef unsigned int uint32;

using std::string;
using std::ifstream;

/* MD5 declaration. */
class MD5 {
public:
 MD5();
 MD5(const void *input, size_t length);
 MD5(const string &str);
 MD5(ifstream &in);
 void update(const void *input, size_t length);
 void update(const string &str);
 void update(ifstream &in);
 const byte* digest();
 string toString();
 void reset();
private:
 void update(const byte *input, size_t length);
 void final();
 void transform(const byte block[64]);
 void encode(const uint32 *input, byte *output, size_t length);
 void decode(const byte *input, uint32 *output, size_t length);
 string bytesToHexString(const byte *input, size_t length);

 /* class uncopyable */
 MD5(const MD5&);
 MD5& operator=(const MD5&);
private:
 uint32 _state[4]; /* state (ABCD) */
 uint32 _count[2]; /* number of bits, modulo 2^64 (low-order word first) */
 byte _buffer[64]; /* input buffer */
 byte _digest[16]; /* message digest */
 bool _finished; /* calculate finished ? */

 static const byte PADDING[64]; /* padding for calculate */
 static const char HEX[16];
 static const size_t BUFFER_SIZE = 1024;
};

#endif/*MD5_H*/

md5.cpp:

#include "md5.h"

using namespace std;

/* Constants for MD5Transform routine. */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21


/* F, G, H and I are basic MD5 functions.
*/
#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)))

/* ROTATE_LEFT rotates x left n bits.
*/
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
Rotation is separate from addition to prevent recomputation.
*/
#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); \
}


const byte MD5::PADDING[64] = { 0x80 };
const char MD5::HEX[16] = {
 '0', '1', '2', '3',
 '4', '5', '6', '7',
 '8', '9', 'a', 'b',
 'c', 'd', 'e', 'f'
};

/* Default construct. */
MD5::MD5() {
 reset();
}

/* Construct a MD5 object with a input buffer. */
MD5::MD5(const void *input, size_t length) {
 reset();
 update(input, length);
}

/* Construct a MD5 object with a string. */
MD5::MD5(const string &str) {
 reset();
 update(str);
}

/* Construct a MD5 object with a file. */
MD5::MD5(ifstream &in) {
 reset();
 update(in);
}

/* Return the message-digest */
const byte* MD5::digest() {
 if (!_finished) {
 _finished = true;
 final();
 }
 return _digest;
}

/* Reset the calculate state */
void MD5::reset() {

 _finished = false;
 /* reset number of bits. */
 _count[0] = _count[1] = 0;
 /* Load magic initialization constants. */
 _state[0] = 0x67452301;
 _state[1] = 0xefcdab89;
 _state[2] = 0x98badcfe;
 _state[3] = 0x10325476;
}

/* Updating the context with a input buffer. */
void MD5::update(const void *input, size_t length) {
 update((const byte*)input, length);
}

/* Updating the context with a string. */
void MD5::update(const string &str) {
 update((const byte*)str.c_str(), str.length());
}

/* Updating the context with a file. */
void MD5::update(ifstream &in) {

 if (!in)
 return;

 std::streamsize length;
 char buffer[BUFFER_SIZE];
 while (!in.eof()) {
 in.read(buffer, BUFFER_SIZE);
 length = in.gcount();
 if (length > 0)
  update(buffer, length);
 }
 in.close();
}

/* MD5 block update operation. Continues an MD5 message-digest
operation, processing another message block, and updating the
context.
*/
void MD5::update(const byte *input, size_t length) {

 uint32 i, index, partLen;

 _finished = false;

 /* Compute number of bytes mod 64 */
 index = (uint32)((_count[0] >> 3) & 0x3f);

 /* update number of bits */
 if((_count[0] += ((uint32)length << 3)) < ((uint32)length << 3))
 _count[1]++;
 _count[1] += ((uint32)length >> 29);

 partLen = 64 - index;

 /* transform as many times as possible. */
 if(length >= partLen) {

 memcpy(&_buffer[index], input, partLen);
 transform(_buffer);

 for (i = partLen; i + 63 < length; i += 64)
  transform(&input[i]);
 index = 0;

 } else {
 i = 0;
 }

 /* Buffer remaining input */
 memcpy(&_buffer[index], &input[i], length-i);
}

/* MD5 finalization. Ends an MD5 message-_digest operation, writing the
the message _digest and zeroizing the context.
*/
void MD5::final() {

 byte bits[8];
 uint32 oldState[4];
 uint32 oldCount[2];
 uint32 index, padLen;

 /* Save current state and count. */
 memcpy(oldState, _state, 16);
 memcpy(oldCount, _count, 8);

 /* Save number of bits */
 encode(_count, bits, 8);

 /* Pad out to 56 mod 64. */
 index = (uint32)((_count[0] >> 3) & 0x3f);
 padLen = (index < 56) ? (56 - index) : (120 - index);
 update(PADDING, padLen);

 /* Append length (before padding) */
 update(bits, 8);

 /* Store state in digest */
 encode(_state, _digest, 16);

 /* Restore current state and count. */
 memcpy(_state, oldState, 16);
 memcpy(_count, oldCount, 8);
}

/* MD5 basic transformation. Transforms _state based on block. */
void MD5::transform(const byte block[64]) {

 uint32 a = _state[0], b = _state[1], c = _state[2], d = _state[3], x[16];

 decode(block, x, 64);

 /* Round 1 */
 FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
 FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
 FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
 FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
 FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
 FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
 FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
 FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
 FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
 FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
 FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
 FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
 FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
 FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
 FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
 FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

 /* Round 2 */
 GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
 GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
 GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
 GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
 GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
 GG (d, a, b, c, x[10], S22, 0x2441453); /* 22 */
 GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
 GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
 GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
 GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
 GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
 GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
 GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
 GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
 GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
 GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

 /* Round 3 */
 HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
 HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
 HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
 HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
 HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
 HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
 HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
 HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
 HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
 HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
 HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
 HH (b, c, d, a, x[ 6], S34, 0x4881d05); /* 44 */
 HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
 HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
 HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
 HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

 /* Round 4 */
 II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
 II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
 II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
 II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
 II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
 II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
 II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
 II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
 II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
 II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
 II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
 II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
 II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
 II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
 II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
 II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

 _state[0] += a;
 _state[1] += b;
 _state[2] += c;
 _state[3] += d;
}

/* Encodes input (ulong) into output (byte). Assumes length is
a multiple of 4.
*/
void MD5::encode(const uint32 *input, byte *output, size_t length) {

 for(size_t i=0, j=0; j<length; i++, j+=4) {
 output[j]= (byte)(input[i] & 0xff);
 output[j+1] = (byte)((input[i] >> 8) & 0xff);
 output[j+2] = (byte)((input[i] >> 16) & 0xff);
 output[j+3] = (byte)((input[i] >> 24) & 0xff);
 }
}

/* Decodes input (byte) into output (ulong). Assumes length is
a multiple of 4.
*/
void MD5::decode(const byte *input, uint32 *output, size_t length) {

 for(size_t i=0, j=0; j<length; i++, j+=4) {
 output[i] = ((uint32)input[j]) | (((uint32)input[j+1]) << 8) |
  (((uint32)input[j+2]) << 16) | (((uint32)input[j+3]) << 24);
 }
}

/* Convert byte array to hex string. */
string MD5::bytesToHexString(const byte *input, size_t length) {
 string str;
 str.reserve(length << 1);
 for(size_t i = 0; i < length; i++) {
 int t = input[i];
 int a = t / 16;
 int b = t % 16;
 str.append(1, HEX[a]);
 str.append(1, HEX[b]);
 }
 return str;
}

/* Convert digest to string value */
string MD5::toString() {
 return bytesToHexString(digest(), 16);
}

测试文件test.cpp:

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

using namespace std;

void PrintMD5(const string &str, MD5 &md5) {
 cout << "MD5(\"" << str << "\") = " << md5.toString() << endl;
}

string FileDigest(const string &file) {

 ifstream in(file.c_str(), ios::binary);
 if (!in)
 return "";

 MD5 md5;
 std::streamsize length;
 char buffer[1024];
 while (!in.eof()) {
 in.read(buffer, 1024);
 length = in.gcount();
 if (length > 0)
  md5.update(buffer, length);
 }
 in.close();
 return md5.toString();
}

int main() {

 cout << MD5("abc").toString() << endl;
 cout << MD5(ifstream("D:\\test.txt")).toString() << endl;
 cout << MD5(ifstream("D:\\test.exe", ios::binary)).toString() << endl;
 cout << FileDigest("D:\\test.exe") << endl;

 MD5 md5;
 md5.update("");
 PrintMD5("", md5);

 md5.update("a");
 PrintMD5("a", md5);

 md5.update("bc");
 PrintMD5("abc", md5);

 md5.update("defghijklmnopqrstuvwxyz");
 PrintMD5("abcdefghijklmnopqrstuvwxyz", md5);

 md5.reset();
 md5.update("message digest");
 PrintMD5("message digest", md5);

 md5.reset();
 md5.update(ifstream("D:\\test.txt"));
 PrintMD5("D:\\test.txt", md5);
 return 0;
}

类MD5封装了与MD5相关的操作,其有

4个构造函数:

MD5();          //默认构造函数
MD5(const void *input, size_t length);   //输入内存地址与长度信息的构造函数
MD5(const string &str);      //输入字符串的构造函数
MD5(ifstream &in);       //输入流的构造函数
3个Update函数:
void update(const void *input, size_t length); //往MD5对象内添加内存块
void update(const string &str);    //添加字符串
void update(ifstream &in);     //添加流

const byte* digest();       //计算MD5码,并返回指向它的指针
string toString();       //计算MD5,并返回其对应的字符串
void reset();        //重置,

test.cpp文件内的main函数描述了MD5类的用法。

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