restic/internal/backend/utils.go

77 lines
2.1 KiB
Go

package backend
import (
"bytes"
"context"
"encoding/hex"
"fmt"
"io"
"github.com/minio/sha256-simd"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
)
func verifyContentMatchesName(s string, data []byte) (bool, error) {
if len(s) != hex.EncodedLen(sha256.Size) {
return false, fmt.Errorf("invalid length for ID: %q", s)
}
b, err := hex.DecodeString(s)
if err != nil {
return false, fmt.Errorf("invalid ID: %s", err)
}
var id [sha256.Size]byte
copy(id[:], b)
hashed := sha256.Sum256(data)
return id == hashed, nil
}
// LoadAll reads all data stored in the backend for the handle into the given
// buffer, which is truncated. If the buffer is not large enough or nil, a new
// one is allocated.
func LoadAll(ctx context.Context, buf []byte, be Backend, h Handle) ([]byte, error) {
retriedInvalidData := false
err := be.Load(ctx, h, 0, 0, func(rd io.Reader) error {
// make sure this is idempotent, in case an error occurs this function may be called multiple times!
wr := bytes.NewBuffer(buf[:0])
_, cerr := io.Copy(wr, rd)
if cerr != nil {
return cerr
}
buf = wr.Bytes()
// retry loading damaged data only once. If a file fails to download correctly
// the second time, then it is likely corrupted at the backend. Return the data
// to the caller in that case to let it decide what to do with the data.
if !retriedInvalidData && h.Type != ConfigFile {
if matches, err := verifyContentMatchesName(h.Name, buf); err == nil && !matches {
debug.Log("retry loading broken blob %v", h)
retriedInvalidData = true
return errors.Errorf("loadAll(%v): invalid data returned", h)
}
}
return nil
})
if err != nil {
return nil, err
}
return buf, nil
}
// LimitedReadCloser wraps io.LimitedReader and exposes the Close() method.
type LimitedReadCloser struct {
io.Closer
io.LimitedReader
}
// LimitReadCloser returns a new reader wraps r in an io.LimitedReader, but also
// exposes the Close() method.
func LimitReadCloser(r io.ReadCloser, n int64) *LimitedReadCloser {
return &LimitedReadCloser{Closer: r, LimitedReader: io.LimitedReader{R: r, N: n}}
}