System.Net.SSPIWrapper.EncryptDecryptHelper C# (CSharp) Method

        private unsafe static int EncryptDecryptHelper(OP op, SSPIInterface secModule, SafeDeleteContext context, SecurityBuffer[] input, uint sequenceNumber)
        {
            Interop.SspiCli.SecBufferDesc sdcInOut = new Interop.SspiCli.SecBufferDesc(input.Length);
            var unmanagedBuffer = new Interop.SspiCli.SecBuffer[input.Length];

            fixed (Interop.SspiCli.SecBuffer* unmanagedBufferPtr = unmanagedBuffer)
            {
                sdcInOut.pBuffers = unmanagedBufferPtr;
                GCHandle[] pinnedBuffers = new GCHandle[input.Length];
                byte[][] buffers = new byte[input.Length][];
                try
                {
                    for (int i = 0; i < input.Length; i++)
                    {
                        SecurityBuffer iBuffer = input[i];
                        unmanagedBuffer[i].cbBuffer = iBuffer.size;
                        unmanagedBuffer[i].BufferType = iBuffer.type;
                        if (iBuffer.token == null || iBuffer.token.Length == 0)
                        {
                            unmanagedBuffer[i].pvBuffer = IntPtr.Zero;
                        }
                        else
                        {
                            pinnedBuffers[i] = GCHandle.Alloc(iBuffer.token, GCHandleType.Pinned);
                            unmanagedBuffer[i].pvBuffer = Marshal.UnsafeAddrOfPinnedArrayElement(iBuffer.token, iBuffer.offset);
                            buffers[i] = iBuffer.token;
                        }
                    }

                    // The result is written in the input Buffer passed as type=BufferType.Data.
                    int errorCode;
                    switch (op)
                    {
                        case OP.Encrypt:
                            errorCode = secModule.EncryptMessage(context, ref sdcInOut, sequenceNumber);
                            break;

                        case OP.Decrypt:
                            errorCode = secModule.DecryptMessage(context, ref sdcInOut, sequenceNumber);
                            break;

                        case OP.MakeSignature:
                            errorCode = secModule.MakeSignature(context, ref sdcInOut, sequenceNumber);
                            break;

                        case OP.VerifySignature:
                            errorCode = secModule.VerifySignature(context, ref sdcInOut, sequenceNumber);
                            break;

                        default:
                            NetEventSource.Fail(null, $"Unknown OP: {op}");
                            throw NotImplemented.ByDesignWithMessage(SR.net_MethodNotImplementedException);
                    }

                    // Marshalling back returned sizes / data.
                    for (int i = 0; i < input.Length; i++)
                    {
                        SecurityBuffer iBuffer = input[i];
                        iBuffer.size = unmanagedBuffer[i].cbBuffer;
                        iBuffer.type = unmanagedBuffer[i].BufferType;

                        if (iBuffer.size == 0)
                        {
                            iBuffer.offset = 0;
                            iBuffer.token = null;
                        }
                        else
                        {
                            checked
                            {
                                // Find the buffer this is inside of.  Usually they all point inside buffer 0.
                                int j;
                                for (j = 0; j < input.Length; j++)
                                {
                                    if (buffers[j] == null)
                                    {
                                        continue;
                                    }

                                    byte* bufferAddress = (byte*)Marshal.UnsafeAddrOfPinnedArrayElement(buffers[j], 0);
                                    if ((byte*)unmanagedBuffer[i].pvBuffer >= bufferAddress &&
                                        (byte*)unmanagedBuffer[i].pvBuffer + iBuffer.size <= bufferAddress + buffers[j].Length)
                                    {
                                        iBuffer.offset = (int)((byte*)unmanagedBuffer[i].pvBuffer - bufferAddress);
                                        iBuffer.token = buffers[j];
                                        break;
                                    }
                                }

                                if (j >= input.Length)
                                {
                                    NetEventSource.Fail(null, "Output buffer out of range.");
                                    iBuffer.size = 0;
                                    iBuffer.offset = 0;
                                    iBuffer.token = null;
                                }
                            }
                        }

                        // Backup validate the new sizes.
                        if (iBuffer.offset < 0 || iBuffer.offset > (iBuffer.token == null ? 0 : iBuffer.token.Length))
                        {
                            NetEventSource.Fail(null, $"'offset' out of range.  [{iBuffer.offset}]");
                        }

                        if (iBuffer.size < 0 || iBuffer.size > (iBuffer.token == null ? 0 : iBuffer.token.Length - iBuffer.offset))
                        {
                            NetEventSource.Fail(null, $"'size' out of range.  [{iBuffer.size}]");
                        }
                    }

                    if (NetEventSource.IsEnabled && errorCode != 0)
                    {                         
                        if (errorCode == Interop.SspiCli.SEC_I_RENEGOTIATE)
                        {
                            NetEventSource.Error(null, SR.Format(SR.event_OperationReturnedSomething, op, "SEC_I_RENEGOTIATE"));
                        }
                        else
                        {
                            NetEventSource.Error(null, SR.Format(SR.net_log_operation_failed_with_error, op, $"0x{0:X}"));
                        }
                    }

                    return errorCode;
                }
                finally
                {
                    for (int i = 0; i < pinnedBuffers.Length; ++i)
                    {
                        if (pinnedBuffers[i].IsAllocated)
                        {
                            pinnedBuffers[i].Free();
                        }
                    }
                }
            }
        }