AES/CTR 使用 Crypto++ 解密意外停止？

Question

我正在尝试使用 Crypto++ 库 对字节数组 (vector<unsigned char>) 进行 AES 加密和解密。加密工作正常。

我的函数生成一个随机 IV 并将其放在加密数据的前面。解密当然是读IV。我修改了 this 答案中的代码，因此它适用于我的矢量和 CTR/No 填充。

程序在第stfDecryptor.Put(...)行崩溃。一开始我以为数据或IV读取不正确，但检查后发现并非如此。

我希望我在这里犯了一个非常明显的错误。

谢谢大家:)

Class 来电：

//The code is not clean, i want to get it working first and then clean it up. 
auto key = Helper::RandomBytes(16); //returns "byte Array" with random Bytes
auto data = Helper::UTF8String2ByteArray("HELLO WORLD!");
auto encrypted = AESCrypt::encrypt(key, data);
cout << Helper::ByteArray2HexString(key);
cout << "\r\n";
cout << Helper::ByteArray2HexString(data);
cout << "\r\n";
cout << Helper::ByteArray2HexString(encrypted);
cout << "\r\n";    
auto decrypted = AESCrypt::decrypt(key, encrypted);
auto clear = Helper::ByteArray2UTF8String(decrypted);

Class:

vector<unsigned char> AESCrypt::encrypt(vector<unsigned char> key_, vector<unsigned char> data)
{
    vector<unsigned char> iv_ = Helper::RandomBytes(16); //returns "byte Array" with random Bytes

    byte key[AES::DEFAULT_KEYLENGTH], iv[AES::BLOCKSIZE];

    for (size_t i = 0; i < AES::DEFAULT_KEYLENGTH; i++)
        key[i] = key_[i];
    for (size_t i = 0; i < iv_.size(); i++)
        iv[i] = iv_[i];

    AES::Encryption aesEncryption(key, AES::DEFAULT_KEYLENGTH);
    CTR_Mode_ExternalCipher::Encryption ctrEncryption(aesEncryption, iv);

    vector<unsigned char> encrypted;
    StreamTransformationFilter stfEncryptor(
        ctrEncryption,
        new VectorSink(encrypted),
        BlockPaddingSchemeDef::NO_PADDING);

    stfEncryptor.Put((const byte*)data.data(), data.size());
    stfEncryptor.MessageEnd();

    vector<unsigned char> output(encrypted.size() + 16);

    for (size_t i = 0; i < 16; i++)
        output[i] = iv[i];
    for (size_t i = 0; i < encrypted.size(); i++)
        output[16 + i] = encrypted[i];

    return output;
}

vector<unsigned char> AESCrypt::decrypt(vector<unsigned char> key_, vector<unsigned char> data_)
{    
    byte key[AES::DEFAULT_KEYLENGTH], iv[AES::BLOCKSIZE];
    for (size_t i = 0; i < AES::DEFAULT_KEYLENGTH; i++)
        key[i] = key_[i];
    for (size_t i = 0; i < 16; i++)
        iv[i] = data_[i];

    vector<unsigned char> data(data_.size() - 16);
    for (size_t i = 0; i < data.size(); i++)
    {
        data[i] = data_[16 + i];
    }

    AES::Decryption aesDecryption(key, AES::DEFAULT_KEYLENGTH);
    CTR_Mode_ExternalCipher::Decryption ctrDecryption(aesDecryption, iv);

    vector<unsigned char> decrypted;
    StreamTransformationFilter stfDecryptor(
        ctrDecryption,
        new VectorSink(decrypted),
        BlockPaddingSchemeDef::NO_PADDING);

    stfDecryptor.Put((const byte*)data.data(), data.size()); //this is where it crashes
    stfDecryptor.MessageEnd();

    return decrypted;

}

这是 CallStack 的图片：

这是它在 Crypto++ 库中停止的行：

CRYPTOPP_ASSERT(m_cipher->IsForwardTransformation());

Answer 1

This is the line where it stopps inside the CryptoPP Libary:
CRYPTOPP_ASSERT(m_cipher->IsForwardTransformation());

计数器模式（CTR）对加密和解密都使用正向变换。 "Forward transformation"表示加密。 IV/counter加密生成密钥流，然后与明文或密文进行异或运算

你应该改变这个：

AES::Decryption aesDecryption(key, AES::DEFAULT_KEYLENGTH);
CTR_Mode_ExternalCipher::Decryption ctrDecryption(aesDecryption, iv);

为此：

AES::Encryption aesDecryption(key, AES::DEFAULT_KEYLENGTH);
CTR_Mode_ExternalCipher::Decryption ctrDecryption(aesDecryption, iv);

通知计数器模式解密使用加密器。

wiki 有一个计数器模式的例子，我们把这个问答作为外部密码例子的一部分。另请参阅 Crypto++ wiki 上的 CTR Mode。

这是复制器。

$ cat test.cxx
#include "cryptlib.h"
#include "secblock.h"
#include "filters.h"
#include "modes.h"
#include "aes.h"

#include <iostream>
#include <string>

int main (int argc, char* argv[])
{
    using namespace CryptoPP;

    SecByteBlock key(16), iv(16);
    std::memset(key, 0xff, key.size());
    std::memset( iv, 0x88,  iv.size());

    std::string message, encrypted, decrypted;
    message = "Now is the time for all good men "
        "to come to the aide of their country.";

    AES::Encryption aesEncryption(key, key.size());
    CTR_Mode_ExternalCipher::Encryption ctrEncryption(aesEncryption, iv);

    StreamTransformationFilter stfEncryptor(
        ctrEncryption, new StringSink(encrypted));

    stfEncryptor.Put((const byte*)&message[0], message.size());
    stfEncryptor.MessageEnd();

    AES::Encryption aesDecryption(key, key.size());
    CTR_Mode_ExternalCipher::Decryption ctrDecryption(aesDecryption, iv);

    StreamTransformationFilter stfDecryptor(
        ctrDecryption, new StringSink(decrypted));

    stfDecryptor.Put((const byte*)&encrypted[0], encrypted.size());
    stfDecryptor.MessageEnd();

    std::cout << "Message: " << message << std::endl;
    std::cout << "Recovered: " << decrypted << std::endl;

    return 0;
}

并且：

$ g++ -g2 -O1 test.cxx ./libcryptopp.a -o test.exe
$ ./test.exe
Message: Now is the time for all good men to come to the aide of their country.
Recovered: Now is the time for all good men to come to the aide of their country.

StreamTransformationFilter stfEncryptor(
    ctrEncryption,
    new VectorSink(encrypted),
    BlockPaddingSchemeDef::NO_PADDING);

对于计数器模式，不需要BlockPaddingSchemeDef::NO_PADDING。这是计数器模式的默认值。

虽然不明显，但在手册 BlockPaddingScheme 的文档中有说明：

DEFAULT_PADDING means PKCS_PADDING if cipher.MandatoryBlockSize() > 1 && cipher.MinLastBlockSize() == 0, which holds for ECB or CBC mode. Otherwise, NO_PADDING for modes like OFB, CFB, CTR, CBC-CTS.

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