c++ - 无效密文异常

Question

我是 cryptopp 的新手，我尝试加密和解密文件中的文本。我总是在这些行之后的内存位置 0x0012efe4 收到此错误 CryptoPP::InvalidCiphertext:

CryptoPP::StreamTransformationFilter stfDecryptor(cbcDecryption, new CryptoPP::StringSink( decryptedtext ) );
stfDecryptor.Put( reinterpret_cast<const unsigned char*>( ciphertext.c_str() ), ciphertext.length());
stfDecryptor.MessageEnd();

加解密代码:

BOOL Encryption()
{
    // Key and IV setup
    byte key[ CryptoPP::AES::DEFAULT_KEYLENGTH ], iv[ CryptoPP::AES::BLOCKSIZE ];
    memset( key, 0x00, CryptoPP::AES::DEFAULT_KEYLENGTH );
    memset( iv, 0x00, CryptoPP::AES::BLOCKSIZE );

    HW_PROFILE_INFO hwProfileInfo;
    GetCurrentHwProfile(&hwProfileInfo);

    (hwProfileInfo.szHwProfileGuid, strlen(hwProfileInfo.szHwProfileGuid), key);     
    (hwProfileInfo.szHwProfileGuid, strlen(hwProfileInfo.szHwProfileGuid), iv);

    // String and Sink setup
    string STRING;
    ifstream infile;
    infile.open ("test2.txt");

    getline(infile,STRING, '\0'); // Saves the line in STRING.
    char cFilm[1000];
    strcpy(cFilm,STRING.c_str());
    infile.close();

    std::string plaintext = cFilm;
    std::string ciphertext;
    std::string decryptedtext;

    // Dump Plain Text
    std::cout << "Plain Text (" << plaintext.size() << " bytes)" << std::endl;
    std::cout << plaintext;
    std::cout << std::endl << std::endl;

    // Create Cipher Text
    CryptoPP::AES::Encryption aesEncryption(key, CryptoPP::AES::DEFAULT_KEYLENGTH);
    CryptoPP::CBC_Mode_ExternalCipher::Encryption cbcEncryption( aesEncryption, iv );
    CryptoPP::StreamTransformationFilter stfEncryptor(cbcEncryption, new CryptoPP::StringSink( ciphertext ) );
    stfEncryptor.Put( reinterpret_cast<const unsigned char*>( plaintext.c_str() ), plaintext.length() + 1 );
    stfEncryptor.MessageEnd();

    // Dump Cipher Text
    ofstream write ("test2a.txt", ios::out | ios::binary);
    int at = ciphertext.length()+ 1;
    write.write(ciphertext.c_str(),at);
    write.close();
    ciphertext.erase();

    remove("test2.txt");
    rename("test2a.txt","c:\\test2.txt");

    return 0;
}

BOOL Decryption()
{
    // Key and IV setup
    byte key[ CryptoPP::AES::DEFAULT_KEYLENGTH ], iv[ CryptoPP::AES::BLOCKSIZE ];
    memset( key, 0x00, CryptoPP::AES::DEFAULT_KEYLENGTH );
    memset( iv, 0x00, CryptoPP::AES::BLOCKSIZE );

    HW_PROFILE_INFO hwProfileInfo;
    GetCurrentHwProfile(&hwProfileInfo);

    // String and Sink setup
    string STRING2;
    ifstream infile2;
    infile2.open ("test2.txt",ios::binary);

    getline(infile2,STRING2, '\0'); // Saves the line in STRING.
    char cFilm2[1000];
    strcpy(cFilm2,STRING2.c_str());
    infile2.close();

    std::string ciphertext (cFilm2);
    std::string decryptedtext;

    // Decrypt
    CryptoPP::AES::Decryption aesDecryption(key, CryptoPP::AES::DEFAULT_KEYLENGTH);
    CryptoPP::CBC_Mode_ExternalCipher::Decryption cbcDecryption( aesDecryption, iv );

    CryptoPP::StreamTransformationFilter stfDecryptor(cbcDecryption, new CryptoPP::StringSink( decryptedtext ) );
    stfDecryptor.Put( reinterpret_cast<const unsigned char*>( ciphertext.c_str() ), ciphertext.length());
    stfDecryptor.MessageEnd();

    // Dump Decrypted Text
    ofstream write ("test2a.txt", ios::out | ios::binary);
    write << decryptedtext;
    write.close();
    decryptedtext.erase();

    remove("test2.txt");
    rename("test2a.txt","test2.txt");

    return 0;
}

Answer 1

您的主要问题似乎是在 Decryption() 中使用带有 '\0' 定界符的 getline。这可能适用于 Encryption() 中的明文，如果它不包含空字符，但密文很可能充满了 '\0'贯穿始终。

您似乎已经正确识别出加密文件包含二进制数据，但您需要照原样读取它，例如使用 std::ifstream::read或 std::istreambuf_iterator .

我已经在下面更新了您的示例代码:

#include "windows.h"

#include <algorithm>  // for std::copy
#include <fstream>
#include <iostream>
#include <iterator>  // for std::istreambuf_iterator
#include <string>

#ifdef _MSC_VER
#  pragma warning(push)
#  pragma warning(disable: 4100 4127 4189 4244)
#endif
#include "cryptopp/aes.h"
#include "cryptopp/config.h"
#include "cryptopp/files.h"
#include "cryptopp/filters.h"
#include "cryptopp/modes.h"
#ifdef _MSC_VER
#  pragma warning(pop)
#endif

namespace {
const std::string original_file("original.txt");
const std::string encrypted_file("encrypted.txt");
const std::string decrypted_file("decrypted.txt");
const int key_size(CryptoPP::AES::DEFAULT_KEYLENGTH);
const int iv_size(CryptoPP::AES::BLOCKSIZE);
}

void GetKeyAndIv(byte* key, byte* iv) {
  HW_PROFILE_INFOA profile;
  GetCurrentHwProfileA(&profile);
  char* guid(profile.szHwProfileGuid);
  assert(std::char_traits<char>::length(guid) >= key_size + iv_size);
  // Assign first 'key_size' chars of GUID to 'key'
  std::copy(guid, guid + key_size, key);
  // Assign next 'iv_size' chars of GUID to 'iv'
  std::copy(guid + key_size, guid + key_size + iv_size, iv);
};

void Encrypt() {
  // Initialise the key and IV
  byte key[key_size] = {0}, iv[iv_size] = {0};
  GetKeyAndIv(key, iv);

  // Read the file contents to a string and output to cout.  Safest to read
  // contents as binary data, although non-printable characters shouldn't be
  // output to cout.
  std::ifstream infile(original_file.c_str(), std::ios::binary);
  const std::string plaintext((std::istreambuf_iterator<char>(infile)),
                               std::istreambuf_iterator<char>());
  infile.close();
  std::cout << "Plain Text (" << plaintext.size() << " bytes)\n"
            << plaintext << "\n\n";

  // Encrypt
  CryptoPP::AES::Encryption cipher(key, key_size);
  CryptoPP::CBC_Mode_ExternalCipher::Encryption encryption(cipher, iv);
  std::string cipher_text;
  CryptoPP::StreamTransformationFilter filter(encryption,
      new CryptoPP::StringSink(cipher_text));
  filter.Put(reinterpret_cast<const byte*>(plaintext.c_str()), plaintext.size());
  filter.MessageEnd();

  // Dump cipher text
  std::ofstream outfile(encrypted_file.c_str(), std::ios::binary);
  outfile.write(cipher_text.c_str(), cipher_text.size());
  outfile.close();
}

void Decrypt() {
  // Initialise the key and IV
  byte key[key_size] = {0}, iv[iv_size] = {0};
  GetKeyAndIv(key, iv);

  // Read the encrypted file contents to a string as binary data.
  std::ifstream infile(encrypted_file.c_str(), std::ios::binary);
  const std::string cipher_text((std::istreambuf_iterator<char>(infile)),
                                 std::istreambuf_iterator<char>());
  infile.close();

  // Decrypt
  CryptoPP::AES::Decryption cipher(key, key_size);
  CryptoPP::CBC_Mode_ExternalCipher::Decryption decryption(cipher, iv);
  std::string decrypted_test;
  CryptoPP::StreamTransformationFilter filter(decryption,
      new CryptoPP::StringSink(decrypted_test));
  filter.Put(reinterpret_cast<const byte*>(cipher_text.c_str()),
             cipher_text.size());
  filter.MessageEnd();

  // Dump decrypted text
  std::ofstream outfile(decrypted_file.c_str(), std::ios::binary);
  outfile.write(decrypted_test.c_str(), decrypted_test.size());
  outfile.close();
}

int main() {
  try {
    Encrypt();
    Decrypt();
  }
  catch(const CryptoPP::Exception& exception) {
    std::cout << "Caught exception: " << exception.what() << '\n';
    return -1;
  }
  return 0;
}

一个更直接的选择是使用 CryptoPP 的 FileSource 和 FileSink 类来避免手动读取/写入文件:

void Encrypt() {
  byte key[key_size] = {0}, iv[iv_size] = {0};
  GetKeyAndIv(key, iv);
  CryptoPP::CBC_Mode<CryptoPP::AES>::Encryption encryption;
  encryption.SetKeyWithIV(key, key_size, iv, iv_size);
  CryptoPP::FileSource file_source(original_file.c_str(), true,
    new CryptoPP::StreamTransformationFilter(encryption,
      new CryptoPP::FileSink(encrypted_file.c_str())));
}

void Decrypt() {
  byte key[key_size] = {0}, iv[iv_size] = {0};
  GetKeyAndIv(key, iv);
  CryptoPP::CBC_Mode<CryptoPP::AES>::Decryption decryption;
  decryption.SetKeyWithIV(key, key_size, iv, iv_size);
  CryptoPP::FileSource file_source(encrypted_file.c_str(), true,
    new CryptoPP::StreamTransformationFilter(decryption,
      new CryptoPP::FileSink(decrypted_file.c_str())));
}