如何从文件中读取前256位并将其存储在两个数组中

How to read first 256 bits from a file to store them in two arrays

本文关键字：存储 两个 数组 文件 读取 256位      更新时间：2023-10-16

我正在编码一个密码，密钥文件长度为256位。其中128位进入key, 128位进入IV。我明确地定义了这些数组的大小，然后读取，仍然输出我得到的是像148位设置的键，而IV具有较小的因此。最后给出堆栈粉碎错误。

int main(int argc,char *argv[]) {
    if(argc < 4 || !argv[1] || !argv[2]) {
        cout << "Usage: Encoding: " << argv[0] << " [plaintext-file] [key-file] [cipher-file]" << endl;
        cout << "Usage: Decoding: " << argv[0] << " [cipher-file] [key-file] [plaintext-file]" << endl;
        return 0;
    }
    unsigned char key[16], iv[16];
    unsigned long i;
    // read input file and size etc
    FILE* in_file = fopen(argv[1],"rb");
    if(!in_file) {
        cout << "Error opening read file" << endl;
        return 0;
    }
    fseek(in_file,0,SEEK_END);
    unsigned int msglength = ftell(in_file);
    cout << "Msglength:" << msglength << endl;
    unsigned char * mem_ptr =  (unsigned char*)malloc(msglength);
    if(!mem_ptr) {
        cout << "Error allocating memory" << endl;
        fclose(in_file);
        return 0;
    }
    rewind(in_file);
    fread(mem_ptr,1,msglength,in_file);
    fclose(in_file);
    // read keyfile etc
    FILE* key_file = fopen(argv[2],"rb");
    if(!key_file) {
        cout << "Error opening key file" << endl;
        return 0;
    }
    fseek(key_file,0,SEEK_END);
    unsigned int key_size = ftell(key_file);
    cout << "Key Size:" << key_size << endl;
    unsigned char * key_ptr = (unsigned char*)malloc(key_size);
    if(!key_ptr) {
        cout << "Error allocating memory" << endl;
        fclose(key_file);
        return 0;
    }
    rewind(key_file);
    fread(key_ptr,1,key_size,key_file);
    cout << "sizeof key"<<sizeof(key)<<"  sizeof iv" << sizeof(iv) << endl;
    for (i=0; i<256; i++) {
        if (i<128) key[i] = key_ptr[i];
        else iv[i-128] = key_ptr[i];
    }
    cout << key_ptr << endl;
    cout << "Key:" << key << endl << "IV:" << iv << endl;
}

输出
Msglength:15
Key Size:257
sizeof key16  sizeof iv16
abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678
Key:abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678
IV:abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678abcdefgh12345678
*** stack smashing detected ***: ./a.out terminated
Segmentation fault (core dumped)

你知道我哪里做错了吗?

您的key和iv的大小都是16。

unsigned char key[16], iv[16];

所以这是不好的

for (i=0; i<256; i++) {
    if (i<128) key[i] = key_ptr[i];
    else iv[i-128] = key_ptr[i];
}

你在这两个数组的末尾都写错了

您有一个缓冲区溢出:您定义key和iv为unsigned char[16]，但在您的for循环中，您尝试访问它们，如果它们是unsigned char[128]。

你是否在某些时候混淆了比特和字节?

根据这篇文章Stack Smashing实际上是gcc用来检测缓冲区溢出攻击的保护机制

and I could see 

unsigned char key[16], iv[16];

未初始化，可以考虑将它们初始化为0或NULL

也

  for (i=0;i<256;i++) {
      if (i<128) key[i] = key_ptr[i];
      else iv[i-128] = key_ptr[i];
    }

这里没有NULL终止符也许你可以看看这些来了解更多

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