NServiceBus.MessageQueueExtensions.GetPermissions C# (CSharp) Method

        static MessageQueueAccessRights GetPermissions(string formatName, string sid)
        {
            var SecurityDescriptor = new byte[100];

            var sdHandle = GCHandle.Alloc(SecurityDescriptor, GCHandleType.Pinned);
            try
            {
                int lengthNeeded;
                var mqResult = MQGetQueueSecurity(formatName,
                    DACL_SECURITY_INFORMATION,
                    sdHandle.AddrOfPinnedObject(),
                    SecurityDescriptor.Length,
                    out lengthNeeded);

                if (mqResult == MQ_ERROR_SECURITY_DESCRIPTOR_TOO_SMALL)
                {
                    sdHandle.Free();
                    SecurityDescriptor = new byte[lengthNeeded];
                    sdHandle = GCHandle.Alloc(SecurityDescriptor, GCHandleType.Pinned);
                    mqResult = MQGetQueueSecurity(formatName,
                        DACL_SECURITY_INFORMATION,
                        sdHandle.AddrOfPinnedObject(),
                        SecurityDescriptor.Length,
                        out lengthNeeded);
                }

                if (mqResult != MQ_OK)
                {
                    throw new Exception($"Unable to read the security descriptor of queue [{formatName}]");
                }

                bool daclPresent, daclDefaulted;
                IntPtr pDacl;
                var success = GetSecurityDescriptorDacl(sdHandle.AddrOfPinnedObject(),
                    out daclPresent,
                    out pDacl,
                    out daclDefaulted);

                if (!success)
                {
                    throw new Win32Exception();
                }

                var allowedAce = GetAce(pDacl, sid);

                return (MessageQueueAccessRights) allowedAce.Mask;
            }
            finally
            {
                if (sdHandle.IsAllocated)
                {
                    sdHandle.Free();
                }
            }
        }