C与C#通讯加密之C语言DES的cbc pkcs7的实现(二）

没有想到，上个随笔的代码在POS机上出错，查了半天，如果去掉malloc和free,就没有事了。
所以，把现在的不用动态内存分配的算法记录下

/**//*
    功能：用mode = cbc , padding = pkcs7 来加密
         如果to == NULL, 则返回加密后数据的长度
    书写：evlon ,QQ:273352165
*/
int des_cbc_pkcs7_encrypt(uchar* from, int nLength,  uchar * to, uchar key[],uchar iv[])
{
    //uchar buffer[8];
    int nSize = nLength % 8 ?(nLength + 7) / 8 * 8 : nLength + 8;
    if(to == NULL)
    {
        //计算长度
        return nSize;
    }
    else
    {
        deskey(key,EN0);
        uchar preEnc[8];
        memcpy(preEnc,iv,8);
        
        //加密块
        int i=0;
        for(; i < nSize; i+=8)
        {
            uchar*     ps = from + i;
            uchar*     pd = to + i;

            if(nSize - i > 8)
            {
                //XOR
                for(int j = 0; j < 8; ++j)
                {
                    preEnc[j] ^= *(ps + j);
                }
            }
            else
            {
                //XOR
                for(int j = 0; j < nLength - i; ++j)
                {
                    preEnc[j] ^= *(ps + j);
                }

                for(int j = nLength - i; j < 8; ++j)
                {
                    preEnc[j] ^= nSize - nLength;
                }
            }

            des(preEnc,pd);

            //保存前一个输出
            memcpy(preEnc, pd,8);

        }
        return i;
    }
}



int des_cbc_pkcs7_decrypt(uchar* from, int nLength,  uchar * to, uchar key[], uchar iv[])
{

    if(nLength % 8)
        return 0;    //数据不正确


    //uchar* toBackup = to;
    //to = (uchar*)malloc(nLength);    //申请内存

    //XOR
    uchar preEnc[8],buffer[8];
    memcpy(preEnc,iv,8);

    deskey(key,DE1);

    int i = 0;
    for(; i < nLength; i+=8)
    {
        uchar*     ps = from + i;
        uchar*     pd = to + i;

        des(ps,buffer);

        //XOR
        for(int j = 0; j < 8; ++j)
        {
            buffer[j] ^= preEnc[j];
        }


        if(nLength - i > 8)
        {
            //保存前一个输出
            memcpy(preEnc, ps,8);
            memcpy(pd,buffer,sizeof(buffer));
        }
        else
        {
            //去除数据尾
            uchar chEnd = buffer[sizeof(buffer) - 1];
            if(chEnd > 0 && chEnd < 9)
            {
                //有可能是填充字符,去除掉
                for(int j = sizeof(buffer) - 1; j >= (int)(sizeof(buffer) - chEnd); --j)
                {
                    if(buffer[j] != chEnd)
                        return 0;
                }

                int nSize =nLength - chEnd;

                memcpy(pd, buffer, sizeof(buffer) - chEnd);
                
                return nLength - chEnd;

            }
            else
            {
                //数据格式不正确
                return 0;
            }
            
        }
    }

    return 0;
}