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);
}
