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@ -1,12 +1,19 @@
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using System;
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using System.IO;
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using System.Linq;
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using System.Security.Cryptography;
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using System.Text;
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namespace Ombi.Helpers
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{
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public static class StringCipher
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public class StringCipher
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{
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// This constant determines the number of iterations for the password bytes generation function.
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private const int DerivationIterations = 1000;
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// This constant is used to determine the keysize of the encryption algorithm in bits.
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// We divide this by 8 within the code below to get the equivalent number of bytes.
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private const int Keysize = 256;
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/// <summary>
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/// Decrypts the specified cipher text.
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/// </summary>
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@ -15,32 +22,39 @@ namespace Ombi.Helpers
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/// <returns></returns>
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public static string Decrypt(string cipherText, string passPhrase)
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{
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var fullCipher = Convert.FromBase64String(cipherText);
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var iv = new byte[16];
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var cipher = new byte[16];
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Buffer.BlockCopy(fullCipher, 0, iv, 0, iv.Length);
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Buffer.BlockCopy(fullCipher, iv.Length, cipher, 0, iv.Length);
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var key = Encoding.UTF8.GetBytes(passPhrase);
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// Get the complete stream of bytes that represent:
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// [32 bytes of Salt] + [32 bytes of IV] + [n bytes of CipherText]
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var cipherTextBytesWithSaltAndIv = Convert.FromBase64String(cipherText);
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// Get the saltbytes by extracting the first 32 bytes from the supplied cipherText bytes.
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var saltStringBytes = cipherTextBytesWithSaltAndIv.Take(Keysize / 8).ToArray();
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// Get the IV bytes by extracting the next 32 bytes from the supplied cipherText bytes.
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var ivStringBytes = cipherTextBytesWithSaltAndIv.Skip(Keysize / 8).Take(Keysize / 8).ToArray();
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// Get the actual cipher text bytes by removing the first 64 bytes from the cipherText string.
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var cipherTextBytes = cipherTextBytesWithSaltAndIv.Skip((Keysize / 8) * 2).Take(cipherTextBytesWithSaltAndIv.Length - ((Keysize / 8) * 2)).ToArray();
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using (var aesAlg = Aes.Create())
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using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
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{
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using (var decryptor = aesAlg.CreateDecryptor(key, iv))
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var keyBytes = password.GetBytes(Keysize / 8);
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var aes = Aes.Create();
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using (var symmetricKey = new RijndaelManaged())
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{
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string result;
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using (var msDecrypt = new MemoryStream(cipher))
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symmetricKey.BlockSize = 256;
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symmetricKey.Mode = CipherMode.CBC;
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symmetricKey.Padding = PaddingMode.PKCS7;
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using (var decryptor = symmetricKey.CreateDecryptor(keyBytes, ivStringBytes))
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{
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using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
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using (var memoryStream = new MemoryStream(cipherTextBytes))
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{
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using (var srDecrypt = new StreamReader(csDecrypt))
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using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
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{
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result = srDecrypt.ReadToEnd();
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var plainTextBytes = new byte[cipherTextBytes.Length];
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var decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
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memoryStream.Close();
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cryptoStream.Close();
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return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
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}
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}
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}
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return result;
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}
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}
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}
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@ -53,33 +67,54 @@ namespace Ombi.Helpers
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/// <returns></returns>
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public static string Encrypt(string plainText, string passPhrase)
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{
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var key = Encoding.UTF8.GetBytes(passPhrase);
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using (var aesAlg = Aes.Create())
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// Salt and IV is randomly generated each time, but is preprended to encrypted cipher text
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// so that the same Salt and IV values can be used when decrypting.
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var saltStringBytes = Generate256BitsOfRandomEntropy();
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var ivStringBytes = Generate256BitsOfRandomEntropy();
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var plainTextBytes = Encoding.UTF8.GetBytes(plainText);
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using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
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{
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using (var encryptor = aesAlg.CreateEncryptor(key, aesAlg.IV))
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var keyBytes = password.GetBytes(Keysize / 8);
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using (var symmetricKey = new RijndaelManaged())
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{
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using (var msEncrypt = new MemoryStream())
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symmetricKey.BlockSize = 256;
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symmetricKey.Mode = CipherMode.CBC;
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symmetricKey.Padding = PaddingMode.PKCS7;
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using (var encryptor = symmetricKey.CreateEncryptor(keyBytes, ivStringBytes))
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{
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using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
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using (var swEncrypt = new StreamWriter(csEncrypt))
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using (var memoryStream = new MemoryStream())
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{
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swEncrypt.Write(plainText);
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using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
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{
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cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
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cryptoStream.FlushFinalBlock();
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// Create the final bytes as a concatenation of the random salt bytes, the random iv bytes and the cipher bytes.
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var cipherTextBytes = saltStringBytes;
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cipherTextBytes = cipherTextBytes.Concat(ivStringBytes).ToArray();
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cipherTextBytes = cipherTextBytes.Concat(memoryStream.ToArray()).ToArray();
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memoryStream.Close();
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cryptoStream.Close();
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return Convert.ToBase64String(cipherTextBytes);
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}
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}
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var iv = aesAlg.IV;
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var decryptedContent = msEncrypt.ToArray();
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var result = new byte[iv.Length + decryptedContent.Length];
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Buffer.BlockCopy(iv, 0, result, 0, iv.Length);
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Buffer.BlockCopy(decryptedContent, 0, result, iv.Length, decryptedContent.Length);
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return Convert.ToBase64String(result);
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}
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}
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}
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}
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/// <summary>
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/// Generate256s the bits of random entropy.
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/// </summary>
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/// <returns></returns>
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private static byte[] Generate256BitsOfRandomEntropy()
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{
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var randomBytes = new byte[32]; // 32 Bytes will give us 256 bits.
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using (var rngCsp = new RNGCryptoServiceProvider())
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{
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// Fill the array with cryptographically secure random bytes.
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rngCsp.GetBytes(randomBytes);
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}
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return randomBytes;
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}
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}
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}
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tidusjar
8 years ago