gitea/modules/lfs/content_store.go
zeripath a68db9076a
Fix race in LFS ContentStore.Put(...) (#14895)
Continuing on from #14888

The previous implementation has race whereby an incomplete upload or
hash mismatch upload can end up in the ContentStore. This PR moves the
validation into the reader so that if there is a hash error or size
mismatch the reader will return with an error instead of an io.EOF
causing the storage to abort the storage.

Signed-off-by: Andrew Thornton <art27@cantab.net>
2021-03-06 20:21:56 +00:00

161 lines
4.2 KiB
Go

// Copyright 2020 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package lfs
import (
"crypto/sha256"
"encoding/hex"
"errors"
"fmt"
"hash"
"io"
"os"
"code.gitea.io/gitea/models"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/storage"
)
var (
errHashMismatch = errors.New("Content hash does not match OID")
errSizeMismatch = errors.New("Content size does not match")
)
// ErrRangeNotSatisfiable represents an error which request range is not satisfiable.
type ErrRangeNotSatisfiable struct {
FromByte int64
}
func (err ErrRangeNotSatisfiable) Error() string {
return fmt.Sprintf("Requested range %d is not satisfiable", err.FromByte)
}
// IsErrRangeNotSatisfiable returns true if the error is an ErrRangeNotSatisfiable
func IsErrRangeNotSatisfiable(err error) bool {
_, ok := err.(ErrRangeNotSatisfiable)
return ok
}
// ContentStore provides a simple file system based storage.
type ContentStore struct {
storage.ObjectStorage
}
// Get takes a Meta object and retrieves the content from the store, returning
// it as an io.Reader. If fromByte > 0, the reader starts from that byte
func (s *ContentStore) Get(meta *models.LFSMetaObject, fromByte int64) (io.ReadCloser, error) {
f, err := s.Open(meta.RelativePath())
if err != nil {
log.Error("Whilst trying to read LFS OID[%s]: Unable to open Error: %v", meta.Oid, err)
return nil, err
}
if fromByte > 0 {
if fromByte >= meta.Size {
return nil, ErrRangeNotSatisfiable{
FromByte: fromByte,
}
}
_, err = f.Seek(fromByte, io.SeekStart)
if err != nil {
log.Error("Whilst trying to read LFS OID[%s]: Unable to seek to %d Error: %v", meta.Oid, fromByte, err)
}
}
return f, err
}
// Put takes a Meta object and an io.Reader and writes the content to the store.
func (s *ContentStore) Put(meta *models.LFSMetaObject, r io.Reader) error {
p := meta.RelativePath()
// Wrap the provided reader with an inline hashing and size checker
wrappedRd := newHashingReader(meta.Size, meta.Oid, r)
// now pass the wrapped reader to Save - if there is a size mismatch or hash mismatch then
// the errors returned by the newHashingReader should percolate up to here
written, err := s.Save(p, wrappedRd)
if err != nil {
log.Error("Whilst putting LFS OID[%s]: Failed to copy to tmpPath: %s Error: %v", meta.Oid, p, err)
return err
}
// This shouldn't happen but it is sensible to test
if written != meta.Size {
if err := s.Delete(p); err != nil {
log.Error("Cleaning the LFS OID[%s] failed: %v", meta.Oid, err)
}
return errSizeMismatch
}
return nil
}
// Exists returns true if the object exists in the content store.
func (s *ContentStore) Exists(meta *models.LFSMetaObject) (bool, error) {
_, err := s.ObjectStorage.Stat(meta.RelativePath())
if err != nil {
if os.IsNotExist(err) {
return false, nil
}
return false, err
}
return true, nil
}
// Verify returns true if the object exists in the content store and size is correct.
func (s *ContentStore) Verify(meta *models.LFSMetaObject) (bool, error) {
p := meta.RelativePath()
fi, err := s.ObjectStorage.Stat(p)
if os.IsNotExist(err) || (err == nil && fi.Size() != meta.Size) {
return false, nil
} else if err != nil {
log.Error("Unable stat file: %s for LFS OID[%s] Error: %v", p, meta.Oid, err)
return false, err
}
return true, nil
}
type hashingReader struct {
internal io.Reader
currentSize int64
expectedSize int64
hash hash.Hash
expectedHash string
}
func (r *hashingReader) Read(b []byte) (int, error) {
n, err := r.internal.Read(b)
if n > 0 {
r.currentSize += int64(n)
wn, werr := r.hash.Write(b[:n])
if wn != n || werr != nil {
return n, werr
}
}
if err != nil && err == io.EOF {
if r.currentSize != r.expectedSize {
return n, errSizeMismatch
}
shaStr := hex.EncodeToString(r.hash.Sum(nil))
if shaStr != r.expectedHash {
return n, errHashMismatch
}
}
return n, err
}
func newHashingReader(expectedSize int64, expectedHash string, reader io.Reader) *hashingReader {
return &hashingReader{
internal: reader,
expectedSize: expectedSize,
expectedHash: expectedHash,
hash: sha256.New(),
}
}