Function loadEncryptedFileInfo

cmd/syncthing/decrypt/decrypt.go:266–293

loadEncryptedFileInfo loads the encrypted FileInfo trailer from a file on disk.

(fd fs.File)

// loadEncryptedFileInfo loads the encrypted FileInfo trailer from a file on
// disk.
func loadEncryptedFileInfo(fd fs.File) (*protocol.FileInfo, error) {
	// Seek to the size of the trailer block
	if _, err := fd.Seek(-4, io.SeekEnd); err != nil {
		return nil, err
	}
	var bs [4]byte
	if _, err := io.ReadFull(fd, bs[:]); err != nil {
		return nil, err
	}
	size := int64(binary.BigEndian.Uint32(bs[:]))

	// Seek to the start of the trailer
	if _, err := fd.Seek(-(4 + size), io.SeekEnd); err != nil {
		return nil, err
	}
	trailer := make([]byte, size)
	if _, err := io.ReadFull(fd, trailer); err != nil {
		return nil, err
	}

	var encFi bep.FileInfo
	if err := proto.Unmarshal(trailer, &encFi); err != nil {
		return nil, err
	}
	fi := protocol.FileInfoFromWire(&encFi)

	return &fi, nil
}