【发布时间】：2015-03-25 22:30:31
【问题描述】：
我正在尝试使用 OpenSSL 兼容格式在 Win OS 中加密 (aes-128-cbc)，并在 Linux OS 上使用 Poco::Crypto 进行解密，Poco::Crypto 是 OpenSSL 的包装器。 我正在使用密码和盐。
挖掘 Stack Overflow、OpenSSL 和 Poco 我发现：
1) 需要从 Win 端（我使用 C# 方法）创建一个标题为 "Salted__1.....8" 字节的文件，其中 1..8 字节是以随机模式生成盐。标头字节总数 = 16。事实上 OpenSSL 函数 EVP_BytesToKey(..) 从标头中提取的盐生成密钥。我将所有字节（头 + 盐 + 加密）保存在一个文件中。
我要感谢 Antanas Veiverys 在https://antanas.veiverys.com/encrypt-data-with-net-decrypt-with-openssl/ 上提供的代码。我使用他的类如下（sn-p）：
public static class AESEncryption
{
private static byte[] randomBytes(int size)
{
byte[] array = new byte[size];
new Random().NextBytes(array);
return array;
}
/// Encrypt a string
public static string Encrypt(string plainText, string password)
{
byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
byte[] encryptedBytes = Encrypt(plainTextBytes, password);
return Convert.ToBase64String(encryptedBytes);
}
public static byte[] Encrypt(byte[] plainTextBytes, string password)
{
byte[] salt = randomBytes(8);
// if salt is same during every encryption, same key is used. May be useful for testing, must not be used in production code
//salt = new byte[8]; //set {0,0...}
byte[] passwordBytes = Encoding.UTF8.GetBytes(password);
MD5 md5 = MD5.Create();
int preKeyLength = password.Length + salt.Length;
byte[] preKey = new byte[preKeyLength];
Buffer.BlockCopy(passwordBytes, 0, preKey, 0, passwordBytes.Length);
Buffer.BlockCopy(salt, 0, preKey, passwordBytes.Length, salt.Length);
byte[] key = md5.ComputeHash(preKey);
int preIVLength = key.Length + preKeyLength;
byte[] preIV = new byte[preIVLength];
Buffer.BlockCopy(key, 0, preIV, 0, key.Length);
Buffer.BlockCopy(preKey, 0, preIV, key.Length, preKey.Length);
byte[] iv = md5.ComputeHash(preIV);
md5.Clear();
md5 = null;
//debug
Console.WriteLine("Key:");
foreach(byte b in key){
Console.WriteLine("Hex: {0:X}", b);
}
Console.WriteLine("--------------------");
AesManaged aes = new AesManaged();
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
aes.KeySize = 128;
aes.BlockSize = 128;
aes.Key = key;
aes.IV = iv;
byte[] encrypted = null;
using (ICryptoTransform Encryptor = aes.CreateEncryptor())
{
using (MemoryStream MemStream = new MemoryStream())
{
using (CryptoStream CryptoStream = new CryptoStream(MemStream, Encryptor, CryptoStreamMode.Write))
{
CryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
CryptoStream.FlushFinalBlock();
encrypted = MemStream.ToArray();
CryptoStream.Close();
}
MemStream.Close();
}
}
aes.Clear();
int resultLength = encrypted.Length + 8 + 8;
byte[] salted = Encoding.UTF8.GetBytes("Salted__");
byte[] result = new byte[resultLength];
Buffer.BlockCopy(salted, 0, result, 0, salted.Length);
Buffer.BlockCopy(salt, 0, result, 8, salt.Length);
Buffer.BlockCopy(encrypted, 0, result, 16, encrypted.Length);
return result;
}
2）此时，要在 Poco 中创建正确的键，我必须将 ItererationCount = 1 而不是 2000 设置为默认值：
CipherKeyImpl
{
const std::string & name,
const std::string & passphrase,
const std::string & salt,
int iterationCount = 2000
);
这样，我将从头文件中提取盐，生成密钥并尝试使用以下代码解密：
ifstream myfile(FILE_TO_DECRYPT, ios::binary);
//get the length
myfile.seekg(0, myfile.end);
int length = myfile.tellg();
myfile.seekg(0, myfile.beg);
//read the encrypted file
char buffer = new char[lenght]();
myfile.read(buffer, lenght);
//get the salt from the header
string toDecrypt(buffer);
string salt = toDecrypt.substr(8, 8); //the salt is 8 bytes start from 8th in header in OpenSSL
//decode
CipherFactory& factory = CipherFactory::defaultFactory();
Chipher key("aes-128-cbc", PASSWORD, salt, 1);
//key is well generated!
unique_ptr<Cipher> uptrCipher(factory.createCipher(key));
string decrypted = uptrChiper->decryptString(toDecrypt, Cipher::ENC_BASE64);
我检查了 salt 和 key 是否正常：它们与我在 C# 代码中使用的相同。
最后一行产生错误："EVP_DecryptFinal_ex: wrong final block length."
我不明白我错在哪里。任何帮助表示赞赏。
【问题讨论】：
标签： c# c++ cryptography openssl poco