protected void OneShotRoundtripTest(byte[] plaintext, byte[] ciphertext, PaddingMode padding, CipherMode mode, int feedbackSize = 0)
{
using (SymmetricAlgorithm alg = CreateAlgorithm())
{
int paddingSizeBytes = mode == CipherMode.CFB ? feedbackSize / 8 : alg.BlockSize / 8;
alg.Key = Key;
// Set the instance to use a different mode and padding than what will be used
// in the one-shots to test that the one shot "wins".
alg.FeedbackSize = 8;
alg.Mode = mode == CipherMode.ECB ? CipherMode.CBC : CipherMode.ECB;
alg.Padding = padding == PaddingMode.None ? PaddingMode.PKCS7 : PaddingMode.None;
byte[] encrypted = mode switch
{
CipherMode.ECB => alg.EncryptEcb(plaintext, padding),
CipherMode.CBC => alg.EncryptCbc(plaintext, IV, padding),
CipherMode.CFB => alg.EncryptCfb(plaintext, IV, padding, feedbackSize),
_ => throw new NotImplementedException(),
};
byte[] decrypted = mode switch
{
CipherMode.ECB => alg.DecryptEcb(encrypted, padding),
CipherMode.CBC => alg.DecryptCbc(encrypted, IV, padding),
CipherMode.CFB => alg.DecryptCfb(encrypted, IV, padding, feedbackSize),
_ => throw new NotImplementedException(),
};
AssertPlaintexts(plaintext, decrypted, padding);
AssertCiphertexts(encrypted, ciphertext, padding, paddingSizeBytes);
decrypted = mode switch
{
CipherMode.ECB => alg.DecryptEcb(ciphertext, padding),
CipherMode.CBC => alg.DecryptCbc(ciphertext, IV, padding),
CipherMode.CFB => alg.DecryptCfb(ciphertext, IV, padding, feedbackSize),
_ => throw new NotImplementedException(),
};
encrypted = mode switch
{
CipherMode.ECB => alg.EncryptEcb(decrypted, padding),
CipherMode.CBC => alg.EncryptCbc(decrypted, IV, padding),
CipherMode.CFB => alg.EncryptCfb(decrypted, IV, padding, feedbackSize),
_ => throw new NotImplementedException(),
};
AssertPlaintexts(plaintext, decrypted, padding);
AssertCiphertexts(ciphertext, encrypted, padding, paddingSizeBytes);
}
}
internal static void VerifyPersistedKey(
string keyName,
int plainBytesCount,
Func <string, SymmetricAlgorithm> persistedFunc,
Func <SymmetricAlgorithm> ephemeralFunc,
CipherMode cipherMode,
PaddingMode paddingMode,
int feedbackSizeInBits)
{
byte[] plainBytes = GenerateRandom(plainBytesCount);
using (SymmetricAlgorithm persisted = persistedFunc(keyName))
using (SymmetricAlgorithm ephemeral = ephemeralFunc())
{
persisted.Mode = ephemeral.Mode = cipherMode;
persisted.Padding = ephemeral.Padding = paddingMode;
if (cipherMode == CipherMode.CFB)
{
persisted.FeedbackSize = ephemeral.FeedbackSize = feedbackSizeInBits;
}
ephemeral.Key = persisted.Key;
ephemeral.GenerateIV();
persisted.IV = ephemeral.IV;
using (ICryptoTransform persistedEncryptor = persisted.CreateEncryptor())
using (ICryptoTransform persistedDecryptor = persisted.CreateDecryptor())
using (ICryptoTransform ephemeralEncryptor = ephemeral.CreateEncryptor())
{
Assert.True(
persistedEncryptor.CanTransformMultipleBlocks,
"Pre-condition: persistedEncryptor.CanTransformMultipleBlocks");
byte[] persistedEncrypted = persistedEncryptor.TransformFinalBlock(plainBytes, 0, plainBytesCount);
byte[] ephemeralEncrypted = ephemeralEncryptor.TransformFinalBlock(plainBytes, 0, plainBytesCount);
Assert.Equal(ephemeralEncrypted, persistedEncrypted);
byte[] cipherBytes = persistedEncrypted;
byte[] persistedDecrypted = persistedDecryptor.TransformFinalBlock(cipherBytes, 0,
cipherBytes.Length);
byte[] expectedBytes = plainBytes;
if (persistedDecrypted.Length > plainBytes.Length)
{
// This should only ever happen in
Assert.Equal(PaddingMode.Zeros, paddingMode);
expectedBytes = new byte[persistedDecrypted.Length];
Buffer.BlockCopy(plainBytes, 0, expectedBytes, 0, plainBytesCount);
}
Assert.Equal(expectedBytes, persistedDecrypted);
}
byte[] oneShotPersistedEncrypted = null;
byte[] oneShotEphemeralEncrypted = null;
byte[] oneShotPersistedDecrypted = null;
if (cipherMode == CipherMode.ECB)
{
oneShotPersistedEncrypted = persisted.EncryptEcb(plainBytes, paddingMode);
oneShotEphemeralEncrypted = ephemeral.EncryptEcb(plainBytes, paddingMode);
oneShotPersistedDecrypted = persisted.DecryptEcb(oneShotEphemeralEncrypted, paddingMode);
}
else if (cipherMode == CipherMode.CBC)
{
oneShotPersistedEncrypted = persisted.EncryptCbc(plainBytes, persisted.IV, paddingMode);
oneShotEphemeralEncrypted = ephemeral.EncryptCbc(plainBytes, ephemeral.IV, paddingMode);
oneShotPersistedDecrypted = persisted.DecryptCbc(oneShotEphemeralEncrypted, persisted.IV, paddingMode);
}
else if (cipherMode == CipherMode.CFB)
{
oneShotPersistedEncrypted = persisted.EncryptCfb(plainBytes, persisted.IV, paddingMode, feedbackSizeInBits);
oneShotEphemeralEncrypted = ephemeral.EncryptCfb(plainBytes, ephemeral.IV, paddingMode, feedbackSizeInBits);
oneShotPersistedDecrypted = persisted.DecryptCfb(oneShotEphemeralEncrypted, persisted.IV, paddingMode, feedbackSizeInBits);
}
if (oneShotPersistedEncrypted is not null)
{
Assert.Equal(oneShotEphemeralEncrypted, oneShotPersistedEncrypted);
if (paddingMode == PaddingMode.Zeros)
{
byte[] plainPadded = new byte[oneShotPersistedDecrypted.Length];
plainBytes.AsSpan().CopyTo(plainPadded);
Assert.Equal(plainPadded, oneShotPersistedDecrypted);
}
else
{
Assert.Equal(plainBytes, oneShotPersistedDecrypted);
}
}
}
}