private void UpdateLegalTagSizes(SafeBCryptAlgorithmHandle algorithm)
{
Debug.Assert(algorithm != null, "algorithm != null");
Debug.Assert(!algorithm.IsClosed && !algorithm.IsInvalid, "!algorithm.IsClosed && !algorithm.IsInvalid");
// Get the authentication tag length structure.
BCryptNative.BCRYPT_KEY_LENGTHS_STRUCT tagLengths =
BCryptNative.GetValueTypeProperty <SafeBCryptAlgorithmHandle, BCryptNative.BCRYPT_KEY_LENGTHS_STRUCT>(
algorithm,
BCryptNative.ObjectPropertyName.AuthTagLength);
// BCrypt returns the tag sizes in bytes, convert them to bits for the LegalTagSizes property
LegalTagSizesValue = new KeySizes[]
{
new KeySizes(tagLengths.dwMinLength * 8, tagLengths.dwMaxLength * 8, tagLengths.dwIncrement * 8)
};
// By default, generate the maximum authentication tag length possible for this algorithm
TagSize = tagLengths.dwMaxLength * 8;
}
internal BCryptAuthenticatedSymmetricCryptoTransform(SafeBCryptAlgorithmHandle algorithm,
byte[] key,
byte[] nonce,
byte[] authenticatedData,
byte[] tag,
bool chainingSupported)
{
Debug.Assert(algorithm != null, "algorithm != null");
Debug.Assert(!algorithm.IsClosed && !algorithm.IsInvalid, "!algorithm.IsClosed && !algorithm.IsInvalid");
if (key == null)
{
throw new ArgumentNullException("key");
}
if (tag == null)
{
throw new ArgumentNullException("tag");
}
bool initializationComplete = false;
RuntimeHelpers.PrepareConstrainedRegions();
try
{
m_algorithm = algorithm;
m_key = BCryptNative.ImportSymmetricKey(algorithm, key);
// Initialize the padding info structure.
m_authInfo = new BCryptNative.BCRYPT_AUTHENTICATED_CIPHER_MODE_INFO();
BCryptNative.InitializeAuthnenticatedCipherModeInfo(ref m_authInfo);
if (nonce != null)
{
m_authInfo.cbNonce = nonce.Length;
m_authInfo.pbNonce = Marshal.AllocCoTaskMem(m_authInfo.cbNonce);
Marshal.Copy(nonce, 0, m_authInfo.pbNonce, m_authInfo.cbNonce);
}
if (authenticatedData != null)
{
m_authInfo.cbAuthData = authenticatedData.Length;
m_authInfo.pbAuthData = Marshal.AllocCoTaskMem(m_authInfo.cbAuthData);
Marshal.Copy(authenticatedData, 0, m_authInfo.pbAuthData, m_authInfo.cbAuthData);
}
if (chainingSupported)
{
m_chainingSupported = chainingSupported;
m_authInfo.cbMacContext = tag.Length;
m_authInfo.pbMacContext = Marshal.AllocCoTaskMem(m_authInfo.cbMacContext);
BCryptNative.BCRYPT_KEY_LENGTHS_STRUCT tagLengths =
BCryptNative.GetValueTypeProperty <SafeBCryptAlgorithmHandle, BCryptNative.BCRYPT_KEY_LENGTHS_STRUCT>(
algorithm,
BCryptNative.ObjectPropertyName.AuthTagLength);
m_chainData = new byte[tagLengths.dwMaxLength];
}
else
{
m_inputBuffer = new MemoryStream();
}
m_authInfo.cbTag = tag.Length;
m_authInfo.pbTag = Marshal.AllocCoTaskMem(m_authInfo.cbTag);
Marshal.Copy(tag, 0, m_authInfo.pbTag, m_authInfo.cbTag);
// Set chaining mode if supported.
if (CanChainBlocks)
{
m_authInfo.dwFlags |= BCryptNative.AuthenticatedCipherModeInfoFlags.ChainCalls;
}
initializationComplete = true;
}
finally
{
// If we failed to complete initialization we may have already allocated some native
// resources. Clean those up before leaving the constructor.
if (!initializationComplete)
{
Dispose();
}
}
}
