Internal.Cryptography.Pal.DirectoryBasedStoreProvider.EnsureFilePermissions C# (CSharp) Method

        private static void EnsureFilePermissions(FileStream stream, uint userId)
        {
            // Verify that we're creating files with u+rw and g-rw, o-rw.
            const Interop.Sys.Permissions requiredPermissions =
                Interop.Sys.Permissions.S_IRUSR | Interop.Sys.Permissions.S_IWUSR;

            const Interop.Sys.Permissions forbiddenPermissions =
                Interop.Sys.Permissions.S_IRGRP | Interop.Sys.Permissions.S_IWGRP |
                Interop.Sys.Permissions.S_IROTH | Interop.Sys.Permissions.S_IWOTH;

            Interop.Sys.FileStatus stat;
            if (Interop.Sys.FStat(stream.SafeFileHandle, out stat) != 0)
            {
                Interop.ErrorInfo error = Interop.Sys.GetLastErrorInfo();
                throw new CryptographicException(
                    SR.Cryptography_FileStatusError,
                    new IOException(error.GetErrorMessage(), error.RawErrno));
            }

            if (stat.Uid != userId)
            {
                throw new CryptographicException(SR.Format(SR.Cryptography_OwnerNotCurrentUser, stream.Name));
            }

            if ((stat.Mode & (int)requiredPermissions) != (int)requiredPermissions ||
                (stat.Mode & (int)forbiddenPermissions) != 0)
            {
                if (Interop.Sys.FChMod(stream.SafeFileHandle, (int)requiredPermissions) < 0)
                {
                    Interop.ErrorInfo error = Interop.Sys.GetLastErrorInfo();
                    throw new CryptographicException(
                        SR.Format(SR.Cryptography_InvalidFilePermissions, stream.Name),
                        new IOException(error.GetErrorMessage(), error.RawErrno));
                }

                Debug.Assert(Interop.Sys.FStat(stream.SafeFileHandle, out stat) == 0);
                Debug.Assert((stat.Mode & (int)requiredPermissions) == (int)requiredPermissions);
                Debug.Assert((stat.Mode & (int)forbiddenPermissions) == 0);
            }
        }