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cryptcheck: make reading of nonce more efficient with RangeOption #1825

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...also only calculate the required hash which will speed things up slightly.
This commit is contained in:
Nick Craig-Wood 2018-02-19 17:37:07 +00:00
parent abc736df1d
commit c99412d11e
1 changed files with 15 additions and 6 deletions
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21
backend/crypt/crypt.go
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@ -465,11 +465,17 @@ func (f *Fs) DecryptFileName(encryptedFileName string) (string, error) {
// Note that we break lots of encapsulation in this function.
func (f *Fs) ComputeHash(o *Object, src fs.Object, hashType hash.Type) (hashStr string, err error) {
// Read the nonce - opening the file is sufficient to read the nonce in
in, err := o.Open()
// use a limited read so we only read the header
in, err := o.Object.Open(&fs.RangeOption{Start: 0, End: int64(fileHeaderSize) - 1})
if err != nil {
return "", errors.Wrap(err, "failed to read nonce")
return "", errors.Wrap(err, "failed to open object to read nonce")
}
nonce := in.(*decrypter).nonce
d, err := f.cipher.(*cipher).newDecrypter(in)
if err != nil {
_ = in.Close()
return "", errors.Wrap(err, "failed to open object to read nonce")
}
nonce := d.nonce
// fs.Debugf(o, "Read nonce % 2x", nonce)
// Check nonce isn't all zeros
@ -483,8 +489,8 @@ func (f *Fs) ComputeHash(o *Object, src fs.Object, hashType hash.Type) (hashStr
fs.Errorf(o, "empty nonce read")
}
// Close in once we have read the nonce
err = in.Close()
// Close d (and hence in) once we have read the nonce
err = d.Close()
if err != nil {
return "", errors.Wrap(err, "failed to close nonce read")
}
@ -503,7 +509,10 @@ func (f *Fs) ComputeHash(o *Object, src fs.Object, hashType hash.Type) (hashStr
}
// pipe into hash
m := hash.NewMultiHasher()
m, err := hash.NewMultiHasherTypes(hash.NewHashSet(hashType))
if err != nil {
return "", errors.Wrap(err, "failed to make hasher")
}
_, err = io.Copy(m, out)
if err != nil {
return "", errors.Wrap(err, "failed to hash data")