xxtea的加密和解密

xxtea.c

#include "./xxtea.h"
#include <memory.h>
#include <stdlib.h>
static void xxtea_long_encrypt(xxtea_long *v, xxtea_long len, xxtea_long *k)
{
    xxtea_long n = len - 1;
    xxtea_long z = v[n], y = v[0], p, q = 6 + 52 / (n + 1), sum = 0, e;
    if (n < 1) {
        return;
    }
    while (0 < q--) {
        sum += XXTEA_DELTA;
        e = sum >> 2 & 3;
        for (p = 0; p < n; p++) {
            y = v[p + 1];
            z = v[p] += XXTEA_MX;
        }
        y = v[0];
        z = v[n] += XXTEA_MX;
    }
}
static void xxtea_long_decrypt(xxtea_long *v, xxtea_long len, xxtea_long *k)
{
    xxtea_long n = len - 1;
    xxtea_long z = v[n], y = v[0], p, q = 6 + 52 / (n + 1), sum = q * XXTEA_DELTA, e;
    if (n < 1) {
        return;
    }
    while (sum != 0) {
        e = sum >> 2 & 3;
        for (p = n; p > 0; p--) {
            z = v[p - 1];
            y = v[p] -= XXTEA_MX;
        }
        z = v[n];
        y = v[0] -= XXTEA_MX;
        sum -= XXTEA_DELTA;
    }
}
static unsigned char *fix_key_length(unsigned char *key, xxtea_long key_len)
{
    unsigned char *tmp = (unsigned char *)malloc(16);
    memcpy(tmp, key, key_len);
    memset(tmp + key_len, '\0', 16 - key_len);
    return tmp;
}
static xxtea_long *xxtea_to_long_array(unsigned char *data, xxtea_long len, int include_length, xxtea_long *ret_len) {
    xxtea_long i, n, *result;
                                                  
    n = len >> 2;
    n = (((len & 3) == 0) ? n : n + 1);
    if (include_length) {
        result = (xxtea_long *)malloc((n + 1) << 2);
        result[n] = len;
        *ret_len = n + 1;
    } else {
        result = (xxtea_long *)malloc(n << 2);
        *ret_len = n;
    }
    memset(result, 0, n << 2);
    for (i = 0; i < len; i++) {
        result[i >> 2] |= (xxtea_long)data[i] << ((i & 3) << 3);
    }
                                                  
    return result;
}
static unsigned char *xxtea_to_byte_array(xxtea_long *data, xxtea_long len, int include_length, xxtea_long *ret_len) {
    xxtea_long i, n, m;
    unsigned char *result;
                                                  
    n = len << 2;
    if (include_length) {
        m = data[len - 1];
        if ((m < n - 7) || (m > n - 4)) return NULL;
        n = m;
    }
    result = (unsigned char *)malloc(n + 1);
    for (i = 0; i < n; i++) {
        result[i] = (unsigned char)((data[i >> 2] >> ((i & 3) << 3)) & 0xff);
    }
    result[n] = '\0';
    *ret_len = n;
                                                  
    return result;
}
static unsigned char *do_xxtea_encrypt(unsigned char *data, xxtea_long len, unsigned char *key, xxtea_long *ret_len) {
    unsigned char *result;
    xxtea_long *v, *k, v_len, k_len;
                                                  
    v = xxtea_to_long_array(data, len, 1, &v_len);
    k = xxtea_to_long_array(key, 16, 0, &k_len);
    xxtea_long_encrypt(v, v_len, k);
    result = xxtea_to_byte_array(v, v_len, 0, ret_len);
    free(v);
    free(k);
                                                  
    return result;
}
static unsigned char *do_xxtea_decrypt(unsigned char *data, xxtea_long len, unsigned char *key, xxtea_long *ret_len) {
    unsigned char *result;
    xxtea_long *v, *k, v_len, k_len;
                                                  
    v = xxtea_to_long_array(data, len, 0, &v_len);
    k = xxtea_to_long_array(key, 16, 0, &k_len);
    xxtea_long_decrypt(v, v_len, k);
    result = xxtea_to_byte_array(v, v_len, 1, ret_len);
    free(v);
    free(k);
                                                  
    return result;
}
unsigned char *xxtea_encrypt(unsigned char *data, xxtea_long data_len, unsigned char *key, xxtea_long key_len, xxtea_long *ret_length)
{
    unsigned char *result;
                                                  
    *ret_length = 0;
                                                  
    if (key_len < 16) {
        unsigned char *key2 = fix_key_length(key, key_len);
        result = do_xxtea_encrypt(data, data_len, key2, ret_length);
        free(key2);
    }
    else
    {
        result = do_xxtea_encrypt(data, data_len, key, ret_length);
    }
                                                  
    return result;
}
unsigned char *xxtea_decrypt(unsigned char *data, xxtea_long data_len, unsigned char *key, xxtea_long key_len, xxtea_long *ret_length)
{
    unsigned char *result;
                                                  
    *ret_length = 0;
                                                  
    if (key_len < 16) {
        unsigned char *key2 = fix_key_length(key, key_len);
        result = do_xxtea_decrypt(data, data_len, key2, ret_length);
        free(key2);
    }
    else
    {
        result = do_xxtea_decrypt(data, data_len, key, ret_length);
    }
                                                  
    return result;
}

xxtea.h

#ifndef XXTEA_H
#define XXTEA_H
#include <stddef.h> /* for size_t & NULL declarations */
#if defined(_MSC_VER)
typedef unsigned __int32 xxtea_long;
#else
#if defined(__FreeBSD__) && __FreeBSD__ < 5
#include <inttypes.h>
#else
#include <stdint.h>
#endif
typedef uint32_t xxtea_long;
#endif
#define XXTEA_MX (z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z)
#define XXTEA_DELTA 0x9E3779B9
unsigned char *xxtea_encrypt(unsigned char *data, xxtea_long data_len, unsigned char *key, xxtea_long key_len, xxtea_long *ret_length);
unsigned char *xxtea_decrypt(unsigned char *data, xxtea_long data_len, unsigned char *key, xxtea_long key_len, xxtea_long *ret_length);
#endif

------------------------------------------------------------

include:

extern "C" {
#include "xxtea.h"
}

用法:

unsigned long tmpSize = 0;
        unsigned char* tmpBuffer = CCFileUtils::sharedFileUtils()->getFileData(filename.c_str(), "rb", &tmpSize);
//讀取文件
        if (!tmpBuffer){
            return 1;
        }
                        
        unsigned int codeBufferSize = 0;
        unsigned char* codeBuffer = xxtea_decrypt(tmpBuffer, tmpSize, (unsigned char*)SCRIPT_KEY, sizeof(SCRIPT_KEY), &codeBufferSize); //解密
        delete[] tmpBuffer;
                        
        if (codeBuffer)
        {
        // 解密之后的真實數據
}