// RemoteHash returns the hash of the full protected file. This is an expensive
// operation, as the value is not chached.
func (h *Header) RemoteHash() (gocrypt.Hash, error) {
f, err := os.Open(h.AbsRemotePath())
if err != nil {
return nil, err
}
defer f.Close()
return hash.Sha256(f)
}
// Write rebuilds the protected file on disk, ensuring the contents and header
// are current with the local file
func (h *Header) Write() error {
// Get data from local file for header
localFile, err := os.Open(h.AbsLocalPath())
if err != nil {
return &ErrProtectedFile{"Unable to open local file", err}
}
defer localFile.Close()
h.contentHash, err = hash.Sha256(localFile)
if err != nil {
return &ErrProtectedFile{"Unable to get local file hash", err}
}
// Keys
h.contentKeys, err = aes.NewKeyCombo()
if err != nil {
return &ErrProtectedFile{"Failed to generate keys for file", err}
}
// Write header to temp file
headerBytes := memstream.NewCapacity(1024)
writer := bufio.NewWriter(headerBytes)
err = writer.WriteByte(1) // Version
if err != nil {
return &ErrProtectedFile{"Unable to write version", err}
}
_, err = writer.Write(h.contentKeys.CryptoKey)
if err != nil {
return &ErrProtectedFile{"Unable to write crypto key", err}
}
_, err = writer.Write(h.contentKeys.AuthKey)
if err != nil {
return &ErrProtectedFile{"Unable to write auth key", err}
}
_, err = writer.Write(h.contentHash)
if err != nil {
return &ErrProtectedFile{"Unable to write hash", err}
}
localLenBytes := gocrypt.Uint64ToBytes(uint64(len(h.LocalPath())))
_, err = writer.Write(localLenBytes)
if err != nil {
return &ErrProtectedFile{"Unable to write path length", err}
}
_, err = writer.Write([]byte(h.LocalPath()))
if err != nil {
return &ErrProtectedFile{"Unable to write local path", err}
}
if err = writer.Flush(); err != nil {
return &ErrProtectedFile{"Flushing header failed", err}
}
// Encrypt and write header to temp file
protFile, err := ioutil.TempFile("", "syncerprotfile")
if err != nil {
return &ErrProtectedFile{"Unable to create temp protected file", err}
}
defer func() {
protFile.Close()
os.Remove(protFile.Name())
}()
headerBytes.Rewind()
metakeys := h.sync.Keys()
_, _, err = aes.Encrypt(headerBytes, protFile, &metakeys)
if err != nil {
return &ErrProtectedFile{"Unable to encrypt header", err}
}
// Update length of header. Not in file, just used internally for extracting
headLen, err := protFile.Seek(0, 1)
h.headerLen = int(headLen)
if err != nil {
return &ErrProtectedFile{"Unable to determine length of header", err}
}
// Encrypt and append contents
_, err = localFile.Seek(0, 0)
if err != nil {
return &ErrProtectedFile{"Unable to return to beginning of local file", err}
}
_, _, err = aes.Encrypt(localFile, protFile, h.contentKeys)
if err != nil {
return &ErrProtectedFile{"Unable to encrypt contents", err}
}
// Move file to final location
// TODO create any needed directories?
protFile.Close()
err = moveFile(protFile.Name(), h.AbsRemotePath())
if err != nil {
return &ErrProtectedFile{"Failed to move final protected file", err}
}
return nil
}