mirror of
https://github.com/mumble-voip/grumble.git
synced 2025-12-19 21:59:59 -08:00
84 lines
2.5 KiB
Go
84 lines
2.5 KiB
Go
// Copyright (c) 2011-2013 The Grumble Authors
|
|
// The use of this source code is goverened by a BSD-style
|
|
// license that can be found in the LICENSE-file.
|
|
|
|
package blobstore
|
|
|
|
import (
|
|
"bytes"
|
|
"crypto/sha1"
|
|
"encoding/hex"
|
|
"hash"
|
|
"io"
|
|
)
|
|
|
|
// EOFHashMismatchError signals that a blobReader reached EOF, but that
|
|
// the calculated hash did not match the given blob key. This signals
|
|
// a successful read of the blob, but that the on-disk content is
|
|
// corrupted in some fashion.
|
|
type EOFHashMismatchError struct {
|
|
// Sum represents that was calculated during the read operation.
|
|
Sum []byte
|
|
}
|
|
|
|
func (hme EOFHashMismatchError) Error() string {
|
|
return "blobstore: EOF hash mismatch"
|
|
}
|
|
|
|
// blobReader implements an io.ReadCloser that reads a blob from disk
|
|
// and hashes all incoming data to ensure integrity. On EOF, it matches
|
|
// its calculated hash with the given blob key in order to detect data
|
|
// corruption.
|
|
//
|
|
// If a mismatch is detected on EOF, the blobReader will return
|
|
// the error ErrEOFHashMismatch instead of a regular io.EOF error.
|
|
type blobReader struct {
|
|
rc io.ReadCloser
|
|
sum []byte
|
|
hash hash.Hash
|
|
}
|
|
|
|
// newBlobReader returns a new blobReader reading from rc.
|
|
// The rc is expected to be a blobstore entry identified by
|
|
// the given key. (The blobstore is content addressible, and
|
|
// a blob's key represents the SHA1 of its content).
|
|
func newBlobReader(rc io.ReadCloser, key string) (*blobReader, error) {
|
|
sum, err := hex.DecodeString(key)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return &blobReader{rc, sum, sha1.New()}, nil
|
|
}
|
|
|
|
// Read implements the Read method of io.ReadCloser.
|
|
// This Read implementation passes on read calls to the
|
|
// wrapper io.ReadCloser and hashes all read content.
|
|
// When EOF is reached, the sum of the streaming hash
|
|
// hash is calculated and compared to the blob key given
|
|
// in newBlobReader. If the calculated hash does not match
|
|
// the blob key, the special error ErrEOFHashMismatch is
|
|
// returned to signal EOF, while also signalling a hash
|
|
// mismatch.
|
|
func (r *blobReader) Read(b []byte) (int, error) {
|
|
n, err := r.rc.Read(b)
|
|
_, werr := r.hash.Write(b[:n])
|
|
if werr != nil {
|
|
return 0, werr
|
|
}
|
|
if err != io.EOF {
|
|
return n, err
|
|
}
|
|
// Match the calculated digest with the expected
|
|
// digest on EOF.
|
|
calcSum := r.hash.Sum(nil)
|
|
if !bytes.Equal(r.sum, calcSum) {
|
|
return 0, EOFHashMismatchError{Sum: calcSum}
|
|
}
|
|
return n, io.EOF
|
|
}
|
|
|
|
// Close implements the Close method of io.ReadCloser.
|
|
// This Close method simply closes the wrapped io.ReadCloser.
|
|
func (r *blobReader) Close() error {
|
|
return r.rc.Close()
|
|
}
|