c++ - 加密/解密期间 Crypto++ 显式销毁？

Question

我编写了一些包装函数来使用 crypto++ 加密/解密文件。我尝试查看维基，但可以找到我的答案。我想知道是否需要显式销毁创建的对象？

我在 wiki 中发现传递给函数的某些对象会为您销毁，但没有我确切使用的示例，所以我只是想确定一下。

   CryptoPP::AutoSeededRandomPool prng;
   //Key generation
   byte key[AES::DEFAULT_KEYLENGTH];
   prng.GenerateBlock(key, sizeof(key));
   //IV generation
   byte iv[AES::BLOCKSIZE];
   prng.GenerateBlock(iv, sizeof(iv));



   //print key
   encoded.clear();
   StringSource(key, sizeof(key), true, new HexEncoder(new StringSink(encoded)));
   cout << "key: " << encoded << endl;
   cout << "Size of key: " << sizeof(key) << endl;

   //print iv
   encoded.clear();
   StringSource(iv, sizeof(iv), true, new HexEncoder(new StringSink(encoded)));
   cout << "iv: " << encoded << endl;
   cout << "Size of iv: " << sizeof(iv) << endl;

   //See function below
   encrypt_file(inFile, outFile, key, iv, err); 

   inFile.close();
   outFile.close();

在这个函数中，字节数组由于某种原因被截断

加密文件

    bool encrypt_file(std::ifstream& inFile,
       std::ofstream& outFile,
       const byte* key, const byte* iv,
       std::string& errMsg)
    {
       std::string encoded;
       //print key
       encoded.clear();
       StringSource(key, sizeof(key), true, new HexEncoder(new StringSink(encoded)));
       cout << "key: " << encoded << endl;
       cout << "Size of key: " << sizeof(key) << endl;

       //print iv
       encoded.clear();
       StringSource(iv, sizeof(iv), true, new HexEncoder(new StringSink(encoded)));
       cout << "iv: " << encoded << endl;
       cout << "Size of iv: " << sizeof(iv) << endl;
       try {
          CryptoPP::CBC_Mode<CryptoPP::AES>::Encryption e;
          e.SetKeyWithIV(key, sizeof(key), iv);
          CryptoPP::FileSource(inFile, true, new CryptoPP::StreamTransformationFilter(e, new CryptoPP::FileSink(outFile)));
          inFile.close();
          outFile.close();
       }
       catch (CryptoPP::Exception& e) {
          errMsg = e.GetWhat();
          return false;
       }
       return true;
    }

输出:

key: 6574D7BDFD0DD3BC59CD3846D4A196A8
Size of key: 16
iv: 1B4ED692F91A32246B41F63F6B8C6EAA
Size of iv: 16
key: 6574D7BDFD0DD3BC
Size of key: 8
iv: 1B4ED692F91A3224
Size of iv: 8

Answer 1

不，你不知道。您创建的对象具有 automatic storage duration ，这意味着它们的析构函数将在其作用域结束时自动调用。此外，您通过 new 传递的参数将归 Crypto++ 对象所有，它们相应的析构函数将为您释放内存。它们属于sink 或filter 类别，事实证明您也传递了所有权。有关详细信息，请参阅:

https://www.cryptopp.com/wiki/Pipelining#Ownership

基本上是这样的( super 简化的例子):

#include <iostream>

struct Foo{};

class X
{
    Foo *p_;
public:
    X(Foo* p): p_(p) {}
    // we'd also need a copy ctor and copy assignment operator, ignored here
    ~X()
    {
        std::cout << "Releasing the memory...\n";
        delete p_;
    }
};

int main()
{
    X x(new Foo()); // sinking, no memory leak
}

Live on Coliru

我不得不说，这是迄今为止我最不喜欢的软件设计风格。人们可以使用模板和混入来实现类似的事情(阅读关于 policy based design 的内容)，而无需指针在没有明确所有权的情况下四处 float 。