System.Net.Security.NegotiateStreamPal.MakeSignature C# (CSharp) Method

        internal static int MakeSignature(SafeDeleteContext securityContext, byte[] buffer, int offset, int count, ref byte[] output)
        {
            SecPkgContext_Sizes sizes = SSPIWrapper.QueryContextAttributes(
                GlobalSSPI.SSPIAuth,
                securityContext,
                Interop.SspiCli.ContextAttribute.SECPKG_ATTR_SIZES
                ) as SecPkgContext_Sizes;

            // alloc new output buffer if not supplied or too small
            int resultSize = count + sizes.cbMaxSignature;
            if (output == null || output.Length < resultSize)
            {
                output = new byte[resultSize];
            }

            // make a copy of user data for in-place encryption
            Buffer.BlockCopy(buffer, offset, output, sizes.cbMaxSignature, count);

            // setup security buffers for ssp call
            SecurityBuffer[] securityBuffer = new SecurityBuffer[2];
            securityBuffer[0] = new SecurityBuffer(output, 0, sizes.cbMaxSignature, SecurityBufferType.SECBUFFER_TOKEN);
            securityBuffer[1] = new SecurityBuffer(output, sizes.cbMaxSignature, count, SecurityBufferType.SECBUFFER_DATA);

            // call SSP Function
            int errorCode = SSPIWrapper.MakeSignature(GlobalSSPI.SSPIAuth, securityContext, securityBuffer, 0);

            // throw if error
            if (errorCode != 0)
            {
                NetEventSource.Info($"MakeSignature threw error: {errorCode.ToString("x", NumberFormatInfo.InvariantInfo)}");
                throw new Win32Exception(errorCode);
            }

            // return signed size
            return securityBuffer[0].size + securityBuffer[1].size;
        }
    }