纯C实现MD5加密

序

    真是天下文章一大抄，国内的牛人们在抄国外的开源项目，而小白们就在抄这些牛人的博客。在写这篇文章的时候，上网查了一下，才发现已经有很多牛人用中文翻译了类似的PHP的md5源码。

   

我从php源码5.2.17中提取并封装的MD5类代码如下：

zmd5.h

/*
 这个类是通用MD5加密 by Dewei 2013-10-21
 用法：	
 #include "zmd5.h"
 std::string out = ZMD5::MD5("你好");
*/

#ifndef ZMD5_H
#define ZMD5_H
#include <string>
class ZMD5
{
public:
	ZMD5(){};
	~ZMD5(){};
	//计算原字符串的MD5值并返回
	static std::string MD5(std::string str_src);

private:
	/* MD5 context. */
	typedef struct {
		unsigned int state[4];				/* state (ABCD) */
		unsigned int count[2];				/* number of bits, modulo 2^64 (lsb first) */
		unsigned char buffer[64];	        /* input buffer */
	} MD5_CTX;

	static void make_digest_ex(char *md5str, unsigned char *digest, int len);
	static void MD5Init(MD5_CTX *);
	static void MD5Update(MD5_CTX *, const unsigned char *, unsigned int);
	static void MD5Final(unsigned char[16], MD5_CTX *);

	static void MD5Transform(unsigned int[4], const unsigned char[64]);
	static void Encode(unsigned char *, unsigned int *, unsigned int);
	static void Decode(unsigned int *, const unsigned char *, unsigned int);

 };//class ZMD5 end 
#endif

 zmd5.cc

#include "zmd5.h"

/* {{{ 计算原字符串的MD5值并返回 */
std::string ZMD5::MD5(std::string str_src)
{
	std::string str_out;
	str_out.resize(33);
	char md5str[33] = {0};
	const unsigned char *src = (const unsigned char*)str_src.c_str();
	int num_len = str_src.length();
	MD5_CTX context;
	unsigned char digest[16] = {0};
	
	md5str[0] = '\0';
	MD5Init(&context);
	MD5Update(&context, src, num_len);
	MD5Final(digest, &context);
	make_digest_ex(md5str, digest, 16);
	str_out = md5str;
	return str_out;
}
/* }}} */

void ZMD5::make_digest_ex(char *md5str, unsigned char *digest, int len)
{
	static const char hexits[17] = "0123456789abcdef";
	int i;

	for (i = 0; i < len; i++) {
		md5str[i * 2]       = hexits[digest[i] >> 4];
		md5str[(i * 2) + 1] = hexits[digest[i] &  0x0F];
	}
	md5str[len * 2] = '\0';
}
/*
 * The remaining code is the reference MD5 code (md5c.c) from rfc1321
 */
/* MD5C.C - RSA Data Security, Inc., MD5 message-digest algorithm
 */

/* Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
   rights reserved.

   License to copy and use this software is granted provided that it
   is identified as the "RSA Data Security, Inc. MD5 Message-Digest
   Algorithm" in all material mentioning or referencing this software
   or this function.

   License is also granted to make and use derivative works provided
   that such works are identified as "derived from the RSA Data
   Security, Inc. MD5 Message-Digest Algorithm" in all material
   mentioning or referencing the derived work.

   RSA Data Security, Inc. makes no representations concerning either
   the merchantability of this software or the suitability of this
   software for any particular purpose. It is provided "as is"
   without express or implied warranty of any kind.

   These notices must be retained in any copies of any part of this
   documentation and/or software.
 */

/* 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



static unsigned char 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
};

/* 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) + (unsigned int)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define GG(a, b, c, d, x, s, ac) { \
 (a) += G ((b), (c), (d)) + (x) + (unsigned int)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define HH(a, b, c, d, x, s, ac) { \
 (a) += H ((b), (c), (d)) + (x) + (unsigned int)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define II(a, b, c, d, x, s, ac) { \
 (a) += I ((b), (c), (d)) + (x) + (unsigned int)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }

/* {{{ MD5Init
 * MD5 initialization. Begins an MD5 operation, writing a new context.
 */
void ZMD5::MD5Init(MD5_CTX * context)
{
	context->count[0] = context->count[1] = 0;
	/* Load magic initialization constants.
	 */
	context->state[0] = 0x67452301;
	context->state[1] = 0xefcdab89;
	context->state[2] = 0x98badcfe;
	context->state[3] = 0x10325476;
}
/* }}} */

/* {{{ MD5Update
   MD5 block update operation. Continues an MD5 message-digest
   operation, processing another message block, and updating the
   context.
 */
void ZMD5::MD5Update(MD5_CTX * context, const unsigned char *input,
			   unsigned int inputLen)
{
	unsigned int i, index, partLen;

	/* Compute number of bytes mod 64 */
	index = (unsigned int) ((context->count[0] >> 3) & 0x3F);

	/* Update number of bits */
	if ((context->count[0] += ((unsigned int) inputLen << 3))
		< ((unsigned int) inputLen << 3))
		context->count[1]++;
	context->count[1] += ((unsigned int) inputLen >> 29);

	partLen = 64 - index;

	/* Transform as many times as possible.
	 */
	if (inputLen >= partLen) {
		memcpy
			((unsigned char*) & context->buffer[index], (unsigned char*) input, partLen);
		MD5Transform(context->state, context->buffer);

		for (i = partLen; i + 63 < inputLen; i += 64)
			MD5Transform(context->state, &input[i]);

		index = 0;
	} else
		i = 0;

	/* Buffer remaining input */
	memcpy
		((unsigned char*) & context->buffer[index], (unsigned char*) & input[i],
		 inputLen - i);
}
/* }}} */

/* {{{ MD5Final
   MD5 finalization. Ends an MD5 message-digest operation, writing the
   the message digest and zeroizing the context.
 */
void ZMD5::MD5Final(unsigned char digest[16], MD5_CTX * context)
{
	unsigned char bits[8];
	unsigned int index, padLen;

	/* Save number of bits */
	Encode(bits, context->count, 8);

	/* Pad out to 56 mod 64.
	 */
	index = (unsigned int) ((context->count[0] >> 3) & 0x3f);
	padLen = (index < 56) ? (56 - index) : (120 - index);
	MD5Update(context, PADDING, padLen);

	/* Append length (before padding) */
	MD5Update(context, bits, 8);

	/* Store state in digest */
	Encode(digest, context->state, 16);

	/* Zeroize sensitive information.
	 */
	memset((unsigned char*) context, 0, sizeof(*context));
}
/* }}} */

/* {{{ MD5Transform
 * MD5 basic transformation. Transforms state based on block.
 */
void ZMD5::MD5Transform(unsigned int state[4], const unsigned char block[64])
{
	unsigned int a = state[0], b = state[1], c = state[2], d = state[3], x[16];

	Decode(x, block, 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;

	/* Zeroize sensitive information. */
	memset((unsigned char*) x, 0, sizeof(x));
}
/* }}} */

/* {{{ Encode
   Encodes input (unsigned int) into output (unsigned char). Assumes len is
   a multiple of 4.
 */
void ZMD5::Encode(unsigned char *output, unsigned int *input, unsigned int len)
{
	unsigned int i, j;

	for (i = 0, j = 0; j < len; i++, j += 4) {
		output[j] = (unsigned char) (input[i] & 0xff);
		output[j + 1] = (unsigned char) ((input[i] >> 8) & 0xff);
		output[j + 2] = (unsigned char) ((input[i] >> 16) & 0xff);
		output[j + 3] = (unsigned char) ((input[i] >> 24) & 0xff);
	}
}
/* }}} */

/* {{{ Decode
   Decodes input (unsigned char) into output (unsigned int). Assumes len is
   a multiple of 4.
 */
void ZMD5::Decode(unsigned int *output, const unsigned char *input, unsigned int len)
{
	unsigned int i, j;

	for (i = 0, j = 0; j < len; i++, j += 4)
		output[i] = ((unsigned int) input[j]) | (((unsigned int) input[j + 1]) << 8) |
			(((unsigned int) input[j + 2]) << 16) | (((unsigned int) input[j + 3]) << 24);
}
/* }}} */