public static byte[] Decrypt(byte[] bytes, Dictionary <ulong, Smb2CryptoInfo> cryptoInfoTable, Smb2Role role)
{
// Client: If the size of the message received from the server is not greater than the size of SMB2 TRANSFORM_HEADER as specified, the client MUST discard the message.
// Server: If the size of the message received from the client is not greater than the size of the SMB2 TRANSFORM_HEADER, the server MUST disconnect the connection.
int minimumLength = Marshal.SizeOf(typeof(Transform_Header));
if (bytes.Length < minimumLength)
{
throw new InvalidOperationException(
String.Format(
"Too less data for encrypted message. Expected length more than {0}, actual {1}.",
minimumLength,
bytes.Length
)
);
}
Transform_Header transformHeader = Smb2Utility.UnmarshalStructure <Transform_Header>(bytes);
// Client: If the Flags/EncryptionAlgorithm in the SMB2 TRANSFORM_HEADER is not 0x0001, the client MUST discard the message.
// Server: If the Flags/EncryptionAlgorithm in the SMB2 TRANSFORM_HEADER is not 0x0001, the server MUST disconnect the connection.
if (transformHeader.Flags != TransformHeaderFlags.Encrypted)
{
throw new InvalidOperationException(
String.Format(
"Flags/EncryptionAlgorithm field is invalid for encrypted message. Expected value 0x0001, actual {0}.",
(ushort)transformHeader.Flags
)
);
}
if (transformHeader.SessionId == 0 || !cryptoInfoTable.ContainsKey(transformHeader.SessionId))
{
throw new InvalidOperationException("Invalid SessionId in TRANSFORM_HEADER.");
}
Smb2CryptoInfo cryptoInfo = cryptoInfoTable[transformHeader.SessionId];
using (var bcrypt = new BCryptAlgorithm("AES"))
{
int nonceLength = 0;
BCryptCipherMode mode = BCryptCipherMode.NotAvailable;
GetCryptoParams(cryptoInfo, CryptoOperationType.Decrypt, out mode, out nonceLength);
bcrypt.Mode = mode;
bcrypt.Key = role == Smb2Role.Server ? cryptoInfo.ServerInKey : cryptoInfo.ServerOutKey;
return(bcrypt.Decrypt(bytes.Skip(52).ToArray(), transformHeader.Nonce.ToByteArray().Take(nonceLength).ToArray(), bytes.Skip(20).Take(32).ToArray(), transformHeader.Signature));
}
}
public static byte[] Decrypt(byte[] bytes, Dictionary <ulong, Smb2CryptoInfo> cryptoInfoTable, Smb2Role role, out Transform_Header transformHeader)
{
var encryptedPacket = new Smb2EncryptedPacket();
int consumedLen;
int expectedLen;
encryptedPacket.FromBytes(bytes, out consumedLen, out expectedLen);
transformHeader = encryptedPacket.Header;
// For client: If the Flags/EncryptionAlgorithm in the SMB2 TRANSFORM_HEADER is not 0x0001, the client MUST discard the message.
// For server: If the Flags/EncryptionAlgorithm in the SMB2 TRANSFORM_HEADER is not 0x0001, the server MUST disconnect the connection.
if (transformHeader.Flags != TransformHeaderFlags.Encrypted)
{
throw new InvalidOperationException(
String.Format(
"Flags/EncryptionAlgorithm field is invalid for encrypted message. Expected value 0x0001, actual {0}.",
(ushort)transformHeader.Flags
)
);
}
if (transformHeader.SessionId == 0 || !cryptoInfoTable.ContainsKey(transformHeader.SessionId))
{
throw new InvalidOperationException("Invalid SessionId in TRANSFORM_HEADER.");
}
Smb2CryptoInfo cryptoInfo = cryptoInfoTable[transformHeader.SessionId];
using (var bcrypt = new BCryptAlgorithm("AES"))
{
int nonceLength = 0;
BCryptCipherMode mode = BCryptCipherMode.NotAvailable;
GetCryptoParams(cryptoInfo, CryptoOperationType.Decrypt, out mode, out nonceLength);
bcrypt.Mode = mode;
bcrypt.Key = role == Smb2Role.Server ? cryptoInfo.ServerInKey : cryptoInfo.ServerOutKey;
// Auth data is Transform_Header start from Nonce, excluding ProtocolId and Signature.
var authData = Smb2Utility.MarshalStructure(transformHeader).Skip((int)Marshal.OffsetOf <Transform_Header>("Nonce")).ToArray();
return(bcrypt.Decrypt(encryptedPacket.EncryptdData, transformHeader.Nonce.ToByteArray().Take(nonceLength).ToArray(), authData, transformHeader.Signature));
}
}
public static byte[] Decrypt(byte[] bytes, Dictionary <ulong, Smb2CryptoInfo> cryptoInfoTable, Smb2Role role)
{
Transform_Header transformHeader = Smb2Utility.UnmarshalStructure <Transform_Header>(bytes);
if (transformHeader.SessionId == 0 || !cryptoInfoTable.ContainsKey(transformHeader.SessionId))
{
throw new InvalidOperationException("Invalid SessionId in TRANSFORM_HEADER.");
}
Smb2CryptoInfo cryptoInfo = cryptoInfoTable[transformHeader.SessionId];
using (var bcrypt = new BCryptAlgorithm("AES"))
{
int nonceLength = 0;
BCryptCipherMode mode = BCryptCipherMode.NotAvailable;
GetCryptoParams(cryptoInfo, CryptoOperationType.Decrypt, out mode, out nonceLength);
bcrypt.Mode = mode;
bcrypt.Key = role == Smb2Role.Server ? cryptoInfo.ServerInKey : cryptoInfo.ServerOutKey;
return(bcrypt.Decrypt(bytes.Skip(52).ToArray(), transformHeader.Nonce.ToByteArray().Take(nonceLength).ToArray(), bytes.Skip(20).Take(32).ToArray(), transformHeader.Signature));
}
}
private static void GetCryptoParams(Smb2CryptoInfo cryptoInfo, CryptoOperationType operationType, out BCryptCipherMode mode, out int nonceLength)
{
if (cryptoInfo.CipherId == EncryptionAlgorithm.ENCRYPTION_AES128_CCM)
{
mode = BCryptCipherMode.CCM;
nonceLength = Smb2Consts.AES128CCM_Nonce_Length;
}
else if (cryptoInfo.CipherId == EncryptionAlgorithm.ENCRYPTION_AES128_GCM)
{
mode = BCryptCipherMode.GCM;
nonceLength = Smb2Consts.AES128GCM_Nonce_Length;
}
else
{
throw new InvalidOperationException(String.Format(
"No valid encryption algorithm is set in Smb2CryptoInfo when trying to {0}", operationType));
}
}
private static byte[] Encrypt(ulong sessionId, Smb2CryptoInfo cryptoInfo, Smb2Role role, Smb2Packet originalPacket)
{
Packet_Header header;
if (originalPacket is Smb2SinglePacket)
{
header = (originalPacket as Smb2SinglePacket).Header;
}
else
{
header = (originalPacket as Smb2CompoundPacket).Packets[0].Header;
}
// Encrypt all messages after session setup if global encryption enabled.
// Encrypt all messages after tree connect if global encryption disabled but share encryption enabled.
if ((cryptoInfo.EnableSessionEncryption ||
(cryptoInfo.EnableTreeEncryption.Contains(header.TreeId) &&
header.Command != Smb2Command.TREE_CONNECT
)
)
)
{
using (var bcrypt = new BCryptAlgorithm("AES"))
{
byte[] originalBinary = originalPacket.ToBytes();
Transform_Header transformHeader = new Transform_Header
{
ProtocolId = Smb2Consts.ProtocolIdInTransformHeader,
OriginalMessageSize = (uint)originalBinary.Length,
SessionId = sessionId,
Signature = new byte[16]
};
if (cryptoInfo.Dialect == DialectRevision.Smb311)
{
transformHeader.Flags = TransformHeaderFlags.Encrypted;
}
else
{
transformHeader.EncryptionAlgorithm = EncryptionAlgorithm.ENCRYPTION_AES128_CCM;
}
byte[] tag;
int nonceLength = 0;
BCryptCipherMode mode = BCryptCipherMode.NotAvailable;
GetCryptoParams(cryptoInfo, CryptoOperationType.Encrypt, out mode, out nonceLength);
bcrypt.Mode = mode;
bcrypt.Key = role == Smb2Role.Server ? cryptoInfo.ServerOutKey : cryptoInfo.ServerInKey;
// The reserved field (5 bytes for CCM, 4 bytes for GCM) must be set to zero.
byte[] nonce = new byte[16];
Buffer.BlockCopy(Guid.NewGuid().ToByteArray(), 0, nonce, 0, nonceLength);
transformHeader.Nonce = new Guid(nonce);
byte[] output = bcrypt.Encrypt(
originalBinary,
transformHeader.Nonce.ToByteArray().Take(nonceLength).ToArray(),
// Use the fields including and after Nonce field as auth data
Smb2Utility.MarshalStructure(transformHeader).Skip(20).ToArray(),
// Signature is 16 bytes in length
16,
out tag);
transformHeader.Signature = tag;
return(Smb2Utility.MarshalStructure(transformHeader).Concat(output).ToArray());
}
}
// Return null if the message is not required to be encrypted.
return(null);
}
private static void GetCryptoParams(Smb2CryptoInfo cryptoInfo, CryptoOperationType operationType, out BCryptCipherMode mode, out int nonceLength)
{
if (cryptoInfo.CipherId == EncryptionAlgorithm.ENCRYPTION_AES128_CCM)
{
mode = BCryptCipherMode.CCM;
nonceLength = Smb2Consts.AES128CCM_Nonce_Length;
}
else if (cryptoInfo.CipherId == EncryptionAlgorithm.ENCRYPTION_AES128_GCM)
{
mode = BCryptCipherMode.GCM;
nonceLength = Smb2Consts.AES128GCM_Nonce_Length;
}
else
{
throw new InvalidOperationException(String.Format(
"No valid encryption algorithm is set in Smb2CryptoInfo when trying to {0}", operationType));
}
}
