How to decrypt a file in memory?-CodePudding

I'm encrypting a file this way:

#include <cryptopp/files.h>
#include <cryptopp/modes.h>
#include <cryptopp/osrng.h>
#include <cryptopp/base64.h>
#include <cryptopp/hex.h>
#include <Windows.h>
#include <iostream>
#include <fstream>


void FileEncrypt(byte key[], byte iv[]
               , const std::string& file, const std::string& dest)
{
    CTR_Mode< AES >::Encryption cipher;
    cipher.SetKeyWithIV(key, strlen((char*)key), iv, strlen((char*)iv));

    std::ifstream in{file, std::ios::binary};
    std::ofstream out{dest, std::ios::binary};

    CryptoPP::FileSource{in, true,
            new CryptoPP::StreamTransformationFilter{
            cipher, new CryptoPP::FileSink{out}}};
} 

INT main(INT argc, PCHAR* argv)
{
    std::string file = "...";
    std::string dest = "...";

    unsigned char* key[] = "p3s6v9y$B&E)H@Mc";
    unsigned char* iv[] = "VkXp2s5v8y/B?E(H";

    FileEncrypt(key, iv, file, dest);
    FileDecrypt(key, iv, file, dest);
}

I've been able to decrypt it with:

    void FileDecrypt(byte key[], byte iv[]
                   , const std::string& file, const std::string& dest)
    {
         CTR_Mode< AES >::Decryption cipher;
         cipher.SetKeyWithIV(key, strlen((char*)key), iv, strlen((char*)iv));
         
         std::ifstream in{file, std::ios::binary};
         std::ofstream out{dest, std::ios::binary};
    
         CryptoPP::FileSource{in, true,
                              new CryptoPP::StreamTransformationFilter{
                                  cipher, new CryptoPP::FileSink{out}}};
    }

But this way the decrypted file is saved to disk, how could i decrypt it on memory without saving it to disk?

I'm downloading the encrypted file from my repo, i also tried decrypting it with:

    std::string data;
    FileDownload(data, "https://github.com/..."));
    
    //...

    std::string dec;

    try {
        CTR_Mode< AES >::Decryption d;
        d.SetKeyWithIV(key, strlen((char*)key), iv, strlen((char*)iv));

        StringSource s(data, true,
            new StreamTransformationFilter(d,
            new StringSink(dec)));
    }
    catch (const CryptoPP::Exception& e)
    {
        std::cerr << e.what() << std::endl;
    }

But dec isn't returning the decrypted file correctly.

CodePudding user response：

I'm not familiar with crypto , but according to their docs, you're probably interested in using the StringSink class in place of FileSink. Note that then the output variable should be an std::string instead of an std::ofstream.

CodePudding user response：

I have been able to decode the file with:

std::string dec;

StringSource s((byte*)data.data(), raw.size(), true,
        new StreamTransformationFilter(cipher,
            new StringSink{ dec }));