QQTEA加密解密实现

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crypt.h

/**
 * The QQ2003C protocol plugin
 *
 * for gaim
 *
 * Copyright © 2004 Puzzlebird
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 **************************************************
 * Reorganized by Minmin <[email protected]>, 2005-3-27
 **************************************************
 */

#ifndef Crypt_H
#define Crypt_H

#define DECRYPT 0x00
#define ENCRYPT 0x01

#include "Wingdefines.h"

class Crypt
{
public:
	Crypt();
	~Crypt();

	static void encrypt( unsigned char* instr, int32 instrlen, unsigned char* key,
				unsigned char*  outstr, int32* outstrlen_ptr);

	static int decrypt(unsigned char* instr, int32 instrlen, unsigned char* key,
				unsigned char*  outstr, int32* outstrlen_ptr);

private:
	static int rand(void);
	static void teaEncipher(unsigned int *const v, const unsigned int *const k,
				unsigned int *const w);
	static void teaDecipher(unsigned int *const v, const unsigned int *const k,
				unsigned int *const w);

	static int qq_crypt ( unsigned char   flag,  unsigned char*  instr,  int32  instrlen,
				unsigned char*  key, unsigned char*  outstr, int32* outstrlen_ptr);
};

#endif

crypt.cpp

/**
 * The QQ2003C protocol plugin
 *
 * for gaim
 *
 * Copyright © 2004 Puzzlebird
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 **************************************************
 * Reorganized by Minmin <[email protected]>, 2005-3-27
 **************************************************
 */

#include "crypt.h"

#include <string.h>
#ifdef _WIN32
#include <winsock.h>
#else
#include <arpa/inet.h>
#endif
#include <cstring>

Crypt::Crypt()
{
}

Crypt::~Crypt()
{
}

void Crypt::teaEncipher(unsigned int *const v, const unsigned int *const k,
			unsigned int *const w)
{
	register unsigned int
		y     = ntohl(v[0]),
		z     = ntohl(v[1]),
		a     = ntohl(k[0]),
		b     = ntohl(k[1]),
		c     = ntohl(k[2]),
		d     = ntohl(k[3]),
		n     = 0x10,       /* do encrypt 16 (0x10) times */
		sum   = 0,
		delta = 0x9E3779B9; /*  0x9E3779B9 - 0x100000000 = -0x61C88647 */

	while (n-- > 0) {
		sum += delta;
		y += ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
		z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
	}

	w[0] = htonl(y); w[1] = htonl(z);
}
void Crypt::teaDecipher(unsigned int *const v, const unsigned int *const k,
			unsigned int *const w)
{
	register unsigned int
		y     = ntohl(v[0]),
		z     = ntohl(v[1]),
		a     = ntohl(k[0]),
		b     = ntohl(k[1]),
		c     = ntohl(k[2]),
		d     = ntohl(k[3]),
		n     = 0x10,
		sum   = 0xE3779B90,
		/* why this ? must be related with n value*/
		delta = 0x9E3779B9;

	/* sum = delta<<5, in general sum = delta * n */
	while (n-- > 0) {
		z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
		y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
		sum -= delta;
	}

	w[0] = htonl(y); w[1] = htonl(z);
}

void Crypt::encrypt( unsigned char* instr, int32 instrlen, unsigned char* key,
			unsigned char*  outstr, int32* outstrlen_ptr)
{
	unsigned char
		plain[8],         /* plain text buffer*/
		plain_pre_8[8],   /* plain text buffer, previous 8 bytes*/
		* crypted,        /* crypted text*/
		* crypted_pre_8,  /* crypted test, previous 8 bytes*/
		* inp;            /* current position in instr*/
	int
		pos_in_byte = 1,  /* loop in the byte */
		is_header=1,      /* header is one byte*/
		count=0,          /* number of bytes being crypted*/
		padding = 0;      /* number of padding stuff*/

	//void encrypt_every_8_byte (void);

	
	/*** we encrypt every eight byte ***/
#define encrypt_every_8_byte()  \
	{\
	for(pos_in_byte=0; pos_in_byte<8; pos_in_byte++) {\
	if(is_header) { plain[pos_in_byte] ^= plain_pre_8[pos_in_byte]; }\
			else { plain[pos_in_byte] ^= crypted_pre_8[pos_in_byte]; }\  //待加密单元等于明文与前面已加密的8字节异或（交织算法第一步）
	} /* prepare plain text*/\
	teaEncipher( (unsigned int *) plain,\
	(unsigned int *) key, \
	(unsigned int *) crypted);   /* encrypt it*/\        //TEA加密
	\
	for(pos_in_byte=0; pos_in_byte<8; pos_in_byte++) {\  
	crypted[pos_in_byte] ^= plain_pre_8[pos_in_byte]; \  //密文等于加密后的数据与前一单元待加密的数据异或 （交织算法第二步）
	} \
	memcpy(plain_pre_8, plain, 8);     /* prepare next*/\
	\
	crypted_pre_8   =   crypted;       /* store position of previous 8 byte*/\
	crypted         +=  8;             /* prepare next output*/\
	count           +=  8;             /* outstrlen increase by 8*/\
	pos_in_byte     =   0;             /* back to start*/\
	is_header       =   0;             /* and exit header*/\
	}/* encrypt_every_8_byte*/

	
	pos_in_byte = (instrlen + 0x0a) % 8; /* header padding decided by instrlen*/
	if (pos_in_byte) {
		pos_in_byte = 8 - pos_in_byte;  //求出要padding多少字节
	}
	plain[0] = (rand() & 0xf8) | pos_in_byte; //头部第一个字节

	memset(plain+1, rand()&0xff, pos_in_byte++); //padding n 个字节
	memset(plain_pre_8, 0x00, sizeof(plain_pre_8)); //前8个字节清零

	crypted = crypted_pre_8 = outstr;

	padding = 1; /* pad some stuff in header*/    //pad 2 bytes
	while (padding <= 2) { /* at most two byte */
		if(pos_in_byte < 8) { plain[pos_in_byte++] = rand() & 0xff; padding ++; }
		if(pos_in_byte == 8){ encrypt_every_8_byte(); }
	}

	inp = instr;
	while (instrlen > 0) {
		if (pos_in_byte < 8) { plain[pos_in_byte++] = *(inp++); instrlen --; } //复制明文至待加密数据区
		if (pos_in_byte == 8){ encrypt_every_8_byte(); } //满8个字节则加密
	}

	padding = 1; /* pad some stuff in tailer*/           //pad 7 bytes 00
	while (padding <= 7) { /* at most sever byte*/
		if (pos_in_byte < 8) { plain[pos_in_byte++] = 0x00; padding ++; }
		if (pos_in_byte == 8){ encrypt_every_8_byte(); }
	}

	*outstrlen_ptr = count;

}

int Crypt::rand(void)
{
	/* it can be the real random seed function*/
	return 0xdead; /* override with number, convenient for debug*/
}

int Crypt::decrypt( unsigned char* instr, int32 instrlen, unsigned char* key,
			unsigned char*  outstr, int32* outstrlen_ptr)
{
	unsigned char
		decrypted[8], m[8],
		* crypt_buff,
		* crypt_buff_pre_8,
		* outp;
	int
		count,           //明文数据长度
		context_start,  //长度临时变量
		pos_in_byte,
		padding;

#define decrypt_every_8_byte()  {\  
	bool bNeedRet = false;\
	for (pos_in_byte = 0; pos_in_byte < 8; pos_in_byte ++ ) {\ 
		if (context_start + pos_in_byte >= instrlen) \
		{\
			bNeedRet = true;\
			break;\
		}\
		decrypted[pos_in_byte] ^= crypt_buff[pos_in_byte];\ //待解密单元等于前面已解密单元与下一个待解密单元异或
	}\
	if( !bNeedRet ) { \
		teaDecipher( (unsigned int *) decrypted, \
		(unsigned int *) key, \
		(unsigned int *) decrypted);\    //解密
	\
		context_start +=  8;\
		crypt_buff    +=  8;\
		pos_in_byte   =   0;\
	}\
}/* decrypt_every_8_byte*/

	/* at least 16 bytes and %8 == 0*/
	if ((instrlen % 8) || (instrlen < 16)) return 0;
	/* get information from header*/
	teaDecipher( (unsigned int *) instr,
		(unsigned int *) key,
		(unsigned int *) decrypted);   //解出头部，然后decrypted缓冲区就有初值了
	pos_in_byte = decrypted[0] & 0x7;
	count = instrlen - pos_in_byte - 10; /* this is the plaintext length*/
	/* return if outstr buffer is not large enought or error plaintext length*/
	if (*outstrlen_ptr < count || count < 0) return 0;

	memset(m, 0, 8);
	crypt_buff_pre_8 = m;
	*outstrlen_ptr = count;   /* everything is ok! set return string length*/

	crypt_buff = instr + 8;   /* address of real data start */
	context_start = 8;        /* context is at the second 8 byte*/
	pos_in_byte ++;           /* start of paddng stuffv*/

	padding = 1;              /* at least one in header*/
	while (padding <= 2) {    /* there are 2 byte padding stuff in header*/
		if (pos_in_byte < 8) {  /* bypass the padding stuff, none sense data*/
			pos_in_byte ++; padding ++;
		}
		if (pos_in_byte == 8) {
			crypt_buff_pre_8 = instr;
			//if (! decrypt_every_8_byte()) return 0;
			decrypt_every_8_byte();
		}
	}/* while*/

	outp = outstr;
	while(count !=0) {
		if (pos_in_byte < 8) {
			*outp = crypt_buff_pre_8[pos_in_byte] ^ decrypted[pos_in_byte]; //输出明文等于前一个密文单元数据异或当前解密后单元
			outp ++;
			count --;
			pos_in_byte ++;
		}
		if (pos_in_byte == 8) {
			crypt_buff_pre_8 = crypt_buff - 8;
			//if (! decrypt_every_8_byte()) return 0;
			decrypt_every_8_byte();
		}
	}/* while*/

	for (padding = 1; padding < 8; padding ++) {
		if (pos_in_byte < 8) {
			if (crypt_buff_pre_8[pos_in_byte] ^ decrypted[pos_in_byte]) return 0; //若是和0异或的话则说明已解密完毕了
			pos_in_byte ++;
		}
		if (pos_in_byte == 8 ) {
			crypt_buff_pre_8 = crypt_buff;
			//if (! decrypt_every_8_byte()) return 0;
			decrypt_every_8_byte();
		}
	}/* for*/
	return 1;

}


int Crypt::qq_crypt ( unsigned char   flag,  unsigned char*  instr,  int32  instrlen,
			unsigned char*  key, unsigned char*  outstr, int32* outstrlen_ptr)
{
	if (flag == DECRYPT)
		return decrypt(instr, instrlen, key, outstr, outstrlen_ptr);
	else
		if (flag == ENCRYPT)
			encrypt(instr, instrlen, key, outstr, outstrlen_ptr);

	return 1; /* flag must be DECRYPT or ENCRYPT*/
}/* qq_crypt*/