QQ通讯协议里的TEA加解密算法

 

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <string.h>
#include <time.h>

//#define CRYPT_ONE_BYTE

typedef char int8 ;
typedef unsigned char uint8 ;
typedef short int16 ;
typedef unsigned short uint16 ;
typedef long int32 ;
typedef unsigned long uint32 ;

typedef struct tagTEACTX
{
    uint8 buf[8] ;
    uint8 bufPre[8] ;
    const uint8 *pKey ; //指向16字节的key
    uint8 *pCrypt ;
    uint8 *pCryptPre ;
} TEACTX, *LPTEACTX ;

uint16 Host2NetShort(uint16 usHost)
{
    const uint16 us = 0x1234 ;
    return ((uint8 *)&us)[0] == 0x12 ? usHost : ((usHost>>8) | (usHost<<8)) ;
}

uint16 Net2HostShort(uint16 usNet)
{
    return Host2NetShort(usNet) ;
}

uint32 Host2NetLong(uint32 ulHost)
{
    const uint16 us = 0x1234 ;
    return ((uint8 *)&us)[0] == 0x12 ? ulHost : (((ulHost>>8) & 0xFF00) |
        ((ulHost<<8) & 0xFF0000) | (ulHost<<24) | (ulHost>>24)) ;
}

uint32 Net2HostLong(uint32 ulHost)
{
    return Host2NetLong(ulHost) ;
}

//TEA加密。v明文8字节。k密钥16字节。w密文输出8字节。
void EnCipher(const uint32 *const v, const uint32 *const k, uint32 *const w)
{
    register uint32
        y     = Host2NetLong(v[0]),
        z     = Host2NetLong(v[1]),
        a     = Host2NetLong(k[0]),
        b     = Host2NetLong(k[1]),
        c     = Host2NetLong(k[2]),
        d     = Host2NetLong(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] = Net2HostLong(y);
    w[1] = Net2HostLong(z);
}

//TEA解密。v密文8字节。k密钥16字节。w明文输出8字节。
void DeCipher(const uint32 *const v, const uint32 *const k, uint32 *const w)
{
    register uint32
        y     = Host2NetLong(v[0]),
        z     = Host2NetLong(v[1]),
        a     = Host2NetLong(k[0]),
        b     = Host2NetLong(k[1]),
        c     = Host2NetLong(k[2]),
        d     = Host2NetLong(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] = Net2HostLong(y);
    w[1] = Net2HostLong(z);
}

uint32 Random(void)
{
    return (uint32)rand();
    //return 0xdead ;
}

//每次8字节加密
static void EncryptEach8Bytes(TEACTX *pCtx)
{
#ifdef CRYPT_ONE_BYTE
    uint32 i ;
    uint8 *pPlain8, *pPlainPre8, *pCrypt8, *pCryptPre8 ;
    pPlain8 = (uint8 *)pCtx->buf ;
    pPlainPre8 = (uint8 *)pCtx->bufPre ;
    pCrypt8 = (uint8 *)pCtx->pCrypt ;
    pCryptPre8 = (uint8 *)pCtx->pCryptPre ;
    //本轮明文与上一轮的密文异或
    for(i=0; i<8; i++)
        pPlain8[i] ^= pCryptPre8[i] ;
    //再对异或后的明文加密
    EnCipher((uint32 *)pPlain8, (uint32 *)pCtx->pKey, (uint32 *)pCrypt8) ;
    //将加密后的密文与上一轮的明文(其实是上一轮明文与上上轮密文异或结果)异或
    for(i=0; i<8; i++)
        pCrypt8[i] ^= pPlainPre8[i] ;
    //
    for(i=0; i<8; i++)
        pPlainPre8[i] = pPlain8[i] ;
#else
    uint32 *pPlain8, *pPlainPre8, *pCrypt8, *pCryptPre8 ;
    pPlain8 = (uint32 *)pCtx->buf ;
    pPlainPre8 = (uint32 *)pCtx->bufPre ;
    pCrypt8 = (uint32 *)pCtx->pCrypt ;
    pCryptPre8 = (uint32 *)pCtx->pCryptPre ;
    pPlain8[0] ^= pCryptPre8[0] ;
    pPlain8[1] ^= pCryptPre8[1] ;
    EnCipher(pPlain8, (const uint32 *)pCtx->pKey, pCrypt8) ;
    pCrypt8[0] ^= pPlainPre8[0] ;
    pCrypt8[1] ^= pPlainPre8[1] ;
    pPlainPre8[0] = pPlain8[0] ;
    pPlainPre8[1] = pPlain8[1] ;
#endif
    pCtx->pCryptPre = pCtx->pCrypt ;
    pCtx->pCrypt += 8 ;
}

//加密。pPlain指向待加密的明文。ulPlainLen明文长度。pKey密钥16字节。
//pOut指向密文输出缓冲区。pOutLen输入输出参数，指示输出缓冲区长度、密文长度。
uint32 Encrypt(TEACTX *pCtx, const uint8 *pPlain, uint32 ulPlainLen,
    const uint8 *pKey, uint8 *pOut, uint32 *pOutLen)
{
    uint32 ulPos, ulPadding, ulOut ;
    const uint8 *p ;
    if(pPlain == NULL || ulPlainLen == 0 || pOutLen == NULL)
        return 0 ;
    //计算需要填充的字节数
    //整个加密流程下来，不管明文长度多少，填充10个字节是固定的，
    //然后再根据明文的长度计算还需要填充的字节数。
    ulPos = (8 - ((ulPlainLen + 10) & 0x07)) & 0x07 ;
    //计算加密后的长度
    ulOut = 1 + ulPos + 2 + ulPlainLen + 7 ;
    if(*pOutLen < ulOut)
    {
        *pOutLen = ulOut ;
        return 0 ;
    }
    *pOutLen = ulOut ;
    memset(pCtx, 0, sizeof(TEACTX)) ;
    pCtx->pCrypt = pOut ;
    pCtx->pCryptPre = pCtx->bufPre ;
    pCtx->pKey = pKey ;
    //buf[0]的最低3bit位等于所填充的长度
    pCtx->buf[0] = (uint8)((Random() & 0xF8) | ulPos) ;
    //用随机数填充上面计算得到的填充长度(每个字节填充的内容是一样的)。
    //这里填充的起始位置是&buf[1]。
    memset(pCtx->buf+1, (uint8)Random(), ulPos++) ;
    //至少再填充两字节
    for(ulPadding=0; ulPadding<2; ulPadding++)
    {
        if(ulPos == 8)
        {
            EncryptEach8Bytes(pCtx) ;
            ulPos = 0 ;
        }
        pCtx->buf[ulPos++] = (uint8)Random() ;
    }
    p = pPlain ;
    while(ulPlainLen > 0)
    {
        if(ulPos == 8)
        {
            EncryptEach8Bytes(pCtx) ;
            ulPos = 0 ;
        }
        pCtx->buf[ulPos++] = *(p++) ;
        ulPlainLen-- ;
    }
    //末尾再添加7字节0后加密，在解密过程的时候可以用来判断key是否正确。
    for(ulPadding=0; ulPadding<7; ulPadding++)
        pCtx->buf[ulPos++] = 0x00 ;
    //
    EncryptEach8Bytes(pCtx) ;
    return ulOut ;
}

//每次8字节进行解密
static void DecryptEach8Bytes(TEACTX *pCtx)
{
#ifdef CRYPT_ONE_BYTE
    uint32 i ;
    uint8 bufTemp[8] ;
    uint8 *pBuf8, *pBufPre8, *pCrypt8, *pCryptPre8 ;
    pBuf8 = (uint8 *)pCtx->buf ;
    pBufPre8 = (uint8 *)pCtx->bufPre ;
    pCrypt8 = (uint8 *)pCtx->pCrypt ;
    pCryptPre8 = (uint8 *)pCtx->pCryptPre ;
    //当前的密文与前一轮明文(实际是前一轮明文与前前轮密文异或结果)异或
    for(i=0; i<8; i++)
        bufTemp[i] = pCrypt8[i] ^ pBufPre8[i] ;
    //异或后的结果再解密(解密后得到当前名文与前一轮密文异或的结果，并非真正明文)
    DeCipher((uint32 *)bufTemp, (uint32 *)pCtx->pKey, (uint32 *)pBufPre8) ;
    //解密后的结果与前一轮的密文异或，得到真正的明文
    for(i=0; i<8; i++)
        pBuf8[i] = pBufPre8[i] ^ pCryptPre8[i] ;
#else
    uint32 bufTemp[2] ;
    uint32 *pBuf8, *pBufPre8, *pCrypt8, *pCryptPre8 ;
    pBuf8 = (uint32 *)pCtx->buf ;
    pBufPre8 = (uint32 *)pCtx->bufPre ;
    pCrypt8 = (uint32 *)pCtx->pCrypt ;
    pCryptPre8 = (uint32 *)pCtx->pCryptPre ;
    bufTemp[0] = pCrypt8[0] ^ pBufPre8[0] ;
    bufTemp[1] = pCrypt8[1] ^ pBufPre8[1] ;
    DeCipher(bufTemp, (const uint32 *)pCtx->pKey, pBufPre8) ;
    pBuf8[0] = pBufPre8[0] ^ pCryptPre8[0] ;
    pBuf8[1] = pBufPre8[1] ^ pCryptPre8[1] ;
#endif
    pCtx->pCryptPre = pCtx->pCrypt ;
    pCtx->pCrypt += 8 ;
}

//解密。pCipher指向待解密密文。ulCipherLen密文长度。pKey密钥16字节。
//pOut指向明文输出缓冲区。pOutLen输入输出参数，指示输出缓冲区长度、明文长度。
uint32 Decrypt(TEACTX *pCtx, const uint8 *pCipher, uint32 ulCipherLen,
    const uint8 *pKey, uint8 *pOut, uint32 *pOutLen)
{
    uint32 ulPos, ulPadding, ulOut, ul ;
    // 待解密的数据长度最少16字节，并且长度满足是8的整数倍。
    if(pCipher == NULL || pOutLen == NULL ||
            ulCipherLen < 16 || (ulCipherLen & 0x07) != 0)
        return 0 ;
    // 先解密头8字节，以便获取第一轮加密时填充的长度。
    DeCipher((const uint32 *)pCipher, (const uint32 *)pKey, (uint32 *)pCtx->bufPre) ;
    for(ul=0; ul<8; ul++)
        pCtx->buf[ul] = pCtx->bufPre[ul] ;
    ulPos = pCtx->buf[0] & 0x07 ; //第一轮加密时填充的长度
    if(ulPos > 1)
    {
        for(ulOut=2; ulOut<=ulPos; ulOut++)
        {
            if(pCtx->buf[1] != pCtx->buf[ulOut])
            {
                *pOutLen = 0 ;
                return 0 ; //解密失败
            }
        }
    }
    ulOut = ulCipherLen - ulPos - 10 ;
    if(ulPos + 10 > ulCipherLen || *pOutLen < ulOut)
        return 0 ;
    pCtx->pCryptPre = (uint8 *)pCipher ;
    pCtx->pCrypt = (uint8 *)pCipher + 8 ;
    ulPos++ ;
    for(ulPadding=0; ulPadding<2; ulPadding++)
    {
        if(ulPos == 8)
        {
            DecryptEach8Bytes(pCtx) ;
            ulPos = 0 ;
        }
        ulPos++ ;
    }
    //
    for(ul=0; ul<ulOut; ul++)
    {
        if(ulPos == 8)
        {
            DecryptEach8Bytes(pCtx) ;
            ulPos = 0 ;
        }
        pOut[ul] = pCtx->buf[ulPos] ;
        ulPos++ ;
    }
    //
    for(ulPadding=0; ulPadding<7; ulPadding++)
    {
        if(ulPos < 8)
        {
            if(pCtx->buf[ulPos] != 0x00)
            {
                *pOutLen = 0 ;
                return 0 ;
            }
        }
        ulPos++ ;
    }
    *pOutLen = ulOut ;
    return 1 ;
}

void PrintBuffer(const uint8 *buf, uint32 ulLen)
{
    uint32 i ;
    for(i=0; i<ulLen; i++)
    {
        printf("%.2X ", buf[i]) ;
        if((i+1) % 16 == 0)
            putchar('\n') ;
    }
    if((ulLen & 0x0F) != 0)
        putchar('\n') ;
}

int main(void)
{
    const char *pPK[][2] =
    {
        //明文--密钥
        {"tea", "123456789abcdef"},
        {"tea", "123456789abcdef"},
        {"123456",  "password1234567"},
        {"AABBCCD", "aabbccddeeffggh"},
        {"Hello World 你好世界！", "aabbccddeeffggh"}
    } ;
    TEACTX ctx ;
    uint8 bufEnc[512], bufDec[512] ;
    uint32 ulEnc, ulDec, ulRet ;
    int i ;
    for(i=0; i<sizeof(pPK)/sizeof(pPK[0]); i++)
    {
        printf("明文：%s\n密钥：%s\n", pPK[i][0], pPK[i][1]) ;
        ulEnc = sizeof(bufEnc) ;
        Encrypt(&ctx, (const uint8 *)pPK[i][0], strlen(pPK[i][0])+1,
                (const uint8 *)pPK[i][1], (uint8 *)bufEnc, &ulEnc) ;
        printf("密文：\n") ;
        PrintBuffer(bufEnc, ulEnc) ;
        ulDec = sizeof(bufDec) ;
        ulRet = Decrypt(&ctx, bufEnc, ulEnc, (const uint8 *)pPK[i][1],
                (uint8 *)bufDec, &ulDec) ;
        if(ulRet != 0)
            printf("解密后明文：%s\n", bufDec) ;
        else
            printf("解密失败！\n") ;
        putchar('\n') ;
    }
    return 0 ;
}