Exemplo n.º 1
0
        private unsafe bool TryLoadTicket(byte[] ticket, out byte[] sessionSecret, out Guid userToken)
        {
#if SQLCLR
            sessionSecret = null;
            userToken     = Guid.Empty;
            return(false);
#else
            State     state           = m_state;
            const int encryptedLength = 32 + 16;
            const int ticketSize      = 1 + 16 + 8 + 16 + encryptedLength + 32;

            userToken     = default(Guid);
            sessionSecret = null;

            //Ticket Structure:
            //  byte      TicketVersion = 1
            //  Guid      ServerKeyName
            //  DateTime  AuthenticationTime
            //  byte[16]  IV
            //  byte[]    Encrypted Session Data 32+16
            //  byte[32]  HMAC (Sha2-256)

            if (ticket == null || ticket.Length != ticketSize)
                return(false);

            fixed(byte *lp = ticket)
            {
                var stream = new BinaryStreamPointerWrapper(lp, ticket.Length);

                if (stream.ReadUInt8() != 1)
                {
                    return(false);
                }

                if (!state.ServerKeyName.SecureEquals(stream.ReadGuid()))
                {
                    return(false);
                }


                long currentTime = DateTime.UtcNow.Ticks;
                long issueTime   = stream.ReadInt64();


                if (issueTime <= currentTime)
                {
                    //Issue time is before current time.
                    if (currentTime - issueTime > TimeSpan.TicksPerMinute * TicketExpireTimeMinutes)
                    {
                        return(false);
                    }
                }
                else
                {
                    //For some reason, the issue time is after the current time.
                    //This could be due to a clock sync on the server after the ticket was issued.
                    //Allow up to 1 minute of clock skew
                    if (issueTime - currentTime > TimeSpan.TicksPerMinute)
                    {
                        return(false);
                    }
                }

                byte[] initializationVector = stream.ReadBytes(16);

                //Verify the signature if everything else looks good.
                //This is last because it is the most computationally complex.
                //This limits denial of service attackes.
                byte[] hmac = HMAC <Sha256Digest> .Compute(state.ServerHMACKey, ticket, 0, ticket.Length - 32);

                if (!hmac.SecureEquals(ticket, ticket.Length - 32, 32))
                {
                    return(false);
                }

                byte[] encryptedData = stream.ReadBytes(encryptedLength);
                var    aes           = new RijndaelManaged();

                aes.Key     = state.ServerEncryptionkey;
                aes.IV      = initializationVector;
                aes.Mode    = CipherMode.CBC;
                aes.Padding = PaddingMode.None;
                var decrypt = aes.CreateDecryptor();

                encryptedData = decrypt.TransformFinalBlock(encryptedData, 0, encryptedData.Length);

                sessionSecret = new byte[32];
                Array.Copy(encryptedData, 0, sessionSecret, 0, 32);
                userToken = encryptedData.ToRfcGuid(32);

                return(true);
            }
#endif
        }