crypto++ Sending IV to another Function but i get an error: StreamTransformationFilter: invalid PKCS #7 block padding found

Question

测试程序使用 crypto++ 加密，然后它发送 iv 和消息作为 IV::EncryptedMessage。

我能够加密，但在解密时出现填充错误 #7，我已经搜索了几个小时，但无论如何都找不到将 std::string IV 传递给 crypto++。

我认为我的错误出在 decc 函数中，我在其中使用了 hexdecode?

string encc(string plain) {
    using namespace CryptoPP;

    AutoSeededRandomPool prng;


    SecByteBlock iv(AES::BLOCKSIZE);
    std::string sKey = "UltraSecretKeyPhrase";
    SecByteBlock key((const unsigned char*)(sKey.data()), sKey.size());
    prng.GenerateBlock(iv, iv.size());
    std::string cipher, recovered;

    try
    {
        CBC_Mode< AES >::Encryption e;
        e.SetKeyWithIV(key, key.size(), iv);

        StringSource s(plain, true,
            new StreamTransformationFilter(e,
                new StringSink(cipher)
            ) 
        ); 
    }
    catch (const Exception& e)
    {
        exit(1);
    }

    string ciphertxt, ivString;

    HexEncoder encoder(new FileSink(std::cout));
    encoder.Detach(new StringSink(ivString));
    encoder.Put(iv, iv.size());
    encoder.MessageEnd();

    encoder.Detach(new StringSink(ciphertxt));
    encoder.Put((const byte*)&cipher[0], cipher.size());
    encoder.MessageEnd();

    string toSend = ivString + "::" + ciphertxt;
    return toSend;
}

string decc(string toDec) {
    using namespace CryptoPP;

    std::string sKey = "UltraSecretKeyPhrase";
    SecByteBlock key((const unsigned char*)(sKey.data()), sKey.size());
    
    
    std::string recovered;
    string str1 = "::";

   
    size_t found = toDec.find(str1);
    if (found != string::npos) {

        std::string sIv = toDec.substr(0, found);
        std::string encMessage = toDec.substr(found + 2, toDec.length());
        
        cout << endl << "IV: " << sIv << endl << "Encoded Msg: " << encMessage << endl;
        
        string iv;
        HexDecoder decoder;

        decoder.Attach(new StringSink(iv));
        decoder.Put((byte*)sIv.data(), sIv.size());
        decoder.MessageEnd();
        try
        {
            CBC_Mode< AES >::Decryption d;
            d.SetKeyWithIV(key.data(), key.size(), (byte *)iv.data(), AES::BLOCKSIZE);

            StringSource s(encMessage, true,
                new StreamTransformationFilter(d,
                    new StringSink(recovered)
                )
            );
            return recovered;
        }
        catch (const Exception& e)
        {
            std::cerr << e.what() << std::endl;
            exit(1);
        }
    }
    else return NULL;
}

int main(){
    string hh = encc("this is encoded");
    cout << hh << endl;
    string gg = decc(hh);
    cout << gg << endl;
    return 0;
}

似乎无法为 google 使用正确的词:)

Answer 1

你有一个解码错误，你应该写 toDec.substr(found + 2, toDec.length() - (found + 2)) 而不是 toDec.substr(found + 2, toDec.length())，因为 .substr() 接受符号的数量，而不是结束位置。

也许还有其他错误，但这肯定会破坏解码过程，因为加密消息中存在乱码。

你也可以只使用toDec.substr(found + 2)，即不指定计数，如果没有指定第二个参数，则子字符串一直取到字符串的末尾。

Answer 2

我解码了 IV 的十六进制，但从未解码实际的加密消息。我发smh后当然看到了...

这是一个 crypto++ 编码和解码函数的功能示例，适合任何正在寻找它的人。


string encc(string plain) {
    using namespace CryptoPP;

    AutoSeededRandomPool prng;


    SecByteBlock iv(AES::BLOCKSIZE);
    std::string sKey = "UltraSecretKeyPhrase";
    SecByteBlock key((const unsigned char*)(sKey.data()), sKey.size());
    prng.GenerateBlock(iv, iv.size());
    std::string cipher, recovered;

    try
    {
        CBC_Mode< AES >::Encryption e;
        e.SetKeyWithIV(key, key.size(), iv);

        StringSource s(plain, true,
            new StreamTransformationFilter(e,
                new StringSink(cipher)
            ) 
        ); 
    }
    catch (const Exception& e)
    {
        exit(1);
    }

    string ciphertxt, ivString;

    HexEncoder encoder(new FileSink(std::cout));
    encoder.Detach(new StringSink(ivString));
    encoder.Put(iv, iv.size());
    encoder.MessageEnd();

    encoder.Detach(new StringSink(ciphertxt));
    encoder.Put((const byte*)&cipher[0], cipher.size());
    encoder.MessageEnd();

    string toSend = ivString + "::" + ciphertxt;
    return toSend;
}

string decc(string toDec) {
    using namespace CryptoPP;

    std::string sKey = "UltraSecretKeyPhrase";
    SecByteBlock key((const unsigned char*)(sKey.data()), sKey.size());
    
    
    std::string recovered;
    string str1 = "::";

   
    size_t found = toDec.find(str1);
    if (found != string::npos) {

        std::string sIv = toDec.substr(0, found);
        std::string encMessageHex = toDec.substr(found + 2);
        
        cout << endl << "IV: " << sIv << endl << "Encoded Msg: " << encMessageHex << endl;
        
        string iv, encMessage;
        HexDecoder decoder, msgDecoder;

        decoder.Attach(new StringSink(iv));
        decoder.Put((byte*)sIv.data(), sIv.size());
        decoder.MessageEnd();
        // Forgot to decode encrypted message hex. added here
        decoder.Attach(new StringSink(encMessage));
        decoder.Put((byte*)encMessageHex.data(), encMessageHex.size());
        decoder.MessageEnd();
        try
        {
            CBC_Mode< AES >::Decryption d;
            d.SetKeyWithIV(key.data(), key.size(), (byte *)iv.data(), AES::BLOCKSIZE);

            StringSource s(encMessage, true,
                new StreamTransformationFilter(d,
                    new StringSink(recovered)
                )
            );
            return recovered;
        }
        catch (const Exception& e)
        {
            std::cerr << e.what() << std::endl;
            exit(1);
        }
    }
    else return NULL;
}

int main(){
    string hh = encc("this is encoded");
    cout << hh << endl;
    string gg = decc(hh);
    cout << gg << endl;
    return 0;
}

crypto++ Sending IV to another Function but i get an error: StreamTransformationFilter: invalid PKCS #7 block padding found

crypto++ Sending IV to another Function but i get an error: StreamTransformationFilter: invalid PKCS #7 block padding found

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