package pack import ( "bytes" "context" "encoding/binary" "fmt" "io" "sync" "github.com/restic/restic/internal/debug" "github.com/restic/restic/internal/errors" "github.com/restic/restic/internal/restic" "github.com/restic/restic/internal/crypto" ) // Packer is used to create a new Pack. type Packer struct { blobs []restic.Blob bytes uint k *crypto.Key wr io.Writer m sync.Mutex } // NewPacker returns a new Packer that can be used to pack blobs together. func NewPacker(k *crypto.Key, wr io.Writer) *Packer { return &Packer{k: k, wr: wr} } // Add saves the data read from rd as a new blob to the packer. Returned is the // number of bytes written to the pack plus the pack header entry size. func (p *Packer) Add(t restic.BlobType, id restic.ID, data []byte, uncompressedLength int) (int, error) { p.m.Lock() defer p.m.Unlock() c := restic.Blob{BlobHandle: restic.BlobHandle{Type: t, ID: id}} n, err := p.wr.Write(data) c.Length = uint(n) c.Offset = p.bytes c.UncompressedLength = uint(uncompressedLength) p.bytes += uint(n) p.blobs = append(p.blobs, c) n += CalculateEntrySize(c) return n, errors.Wrap(err, "Write") } var entrySize = uint(binary.Size(restic.BlobType(0)) + 2*headerLengthSize + len(restic.ID{})) var plainEntrySize = uint(binary.Size(restic.BlobType(0)) + headerLengthSize + len(restic.ID{})) // headerEntry describes the format of header entries. It serves only as // documentation. type headerEntry struct { Type uint8 Length uint32 ID restic.ID } // compressedHeaderEntry describes the format of header entries for compressed blobs. // It serves only as documentation. type compressedHeaderEntry struct { Type uint8 Length uint32 UncompressedLength uint32 ID restic.ID } // Finalize writes the header for all added blobs and finalizes the pack. func (p *Packer) Finalize() error { p.m.Lock() defer p.m.Unlock() header, err := makeHeader(p.blobs) if err != nil { return err } encryptedHeader := make([]byte, 0, crypto.CiphertextLength(len(header))) nonce := crypto.NewRandomNonce() encryptedHeader = append(encryptedHeader, nonce...) encryptedHeader = p.k.Seal(encryptedHeader, nonce, header, nil) encryptedHeader = binary.LittleEndian.AppendUint32(encryptedHeader, uint32(len(encryptedHeader))) if err := verifyHeader(p.k, encryptedHeader, p.blobs); err != nil { return fmt.Errorf("detected data corruption while writing pack-file header: %w\nCorrupted data is either caused by hardware problems or bugs in restic. Please open an issue at https://github.com/restic/restic/issues/new/choose for further troubleshooting", err) } // append the header n, err := p.wr.Write(encryptedHeader) if err != nil { return errors.Wrap(err, "Write") } if n != len(encryptedHeader) { return errors.New("wrong number of bytes written") } p.bytes += uint(len(encryptedHeader)) return nil } func verifyHeader(k *crypto.Key, header []byte, expected []restic.Blob) error { // do not offer a way to skip the pack header verification, as pack headers are usually small enough // to not result in a significant performance impact decoded, hdrSize, err := List(k, bytes.NewReader(header), int64(len(header))) if err != nil { return fmt.Errorf("header decoding failed: %w", err) } if hdrSize != uint32(len(header)) { return fmt.Errorf("unexpected header size %v instead of %v", hdrSize, len(header)) } if len(decoded) != len(expected) { return fmt.Errorf("pack header size mismatch") } for i := 0; i < len(decoded); i++ { if decoded[i] != expected[i] { return fmt.Errorf("pack header entry mismatch got %v instead of %v", decoded[i], expected[i]) } } return nil } // HeaderOverhead returns an estimate of the number of bytes written by a call to Finalize. func (p *Packer) HeaderOverhead() int { return crypto.CiphertextLength(0) + binary.Size(uint32(0)) } // makeHeader constructs the header for p. func makeHeader(blobs []restic.Blob) ([]byte, error) { buf := make([]byte, 0, len(blobs)*int(entrySize)) for _, b := range blobs { switch { case b.Type == restic.DataBlob && b.UncompressedLength == 0: buf = append(buf, 0) case b.Type == restic.TreeBlob && b.UncompressedLength == 0: buf = append(buf, 1) case b.Type == restic.DataBlob && b.UncompressedLength != 0: buf = append(buf, 2) case b.Type == restic.TreeBlob && b.UncompressedLength != 0: buf = append(buf, 3) default: return nil, errors.Errorf("invalid blob type %v", b.Type) } var lenLE [4]byte binary.LittleEndian.PutUint32(lenLE[:], uint32(b.Length)) buf = append(buf, lenLE[:]...) if b.UncompressedLength != 0 { binary.LittleEndian.PutUint32(lenLE[:], uint32(b.UncompressedLength)) buf = append(buf, lenLE[:]...) } buf = append(buf, b.ID[:]...) } return buf, nil } // Size returns the number of bytes written so far. func (p *Packer) Size() uint { p.m.Lock() defer p.m.Unlock() return p.bytes } // Count returns the number of blobs in this packer. func (p *Packer) Count() int { p.m.Lock() defer p.m.Unlock() return len(p.blobs) } // HeaderFull returns true if the pack header is full. func (p *Packer) HeaderFull() bool { p.m.Lock() defer p.m.Unlock() return headerSize+uint(len(p.blobs)+1)*entrySize > MaxHeaderSize } // Blobs returns the slice of blobs that have been written. func (p *Packer) Blobs() []restic.Blob { p.m.Lock() defer p.m.Unlock() return p.blobs } func (p *Packer) String() string { return fmt.Sprintf("", len(p.blobs), p.bytes) } var ( // we require at least one entry in the header, and one blob for a pack file minFileSize = plainEntrySize + crypto.Extension + uint(headerLengthSize) ) const ( // size of the header-length field at the end of the file; it is a uint32 headerLengthSize = 4 // headerSize is the header's constant overhead (independent of #entries) headerSize = headerLengthSize + crypto.Extension // MaxHeaderSize is the max size of header including header-length field MaxHeaderSize = 16*1024*1024 + headerLengthSize // number of header entries to download as part of header-length request eagerEntries = 15 ) // readRecords reads up to bufsize bytes from the underlying ReaderAt, returning // the raw header, the total number of bytes in the header, and any error. // If the header contains fewer than bufsize bytes, the header is truncated to // the appropriate size. func readRecords(rd io.ReaderAt, size int64, bufsize int) ([]byte, int, error) { if bufsize > int(size) { bufsize = int(size) } b := make([]byte, bufsize) off := size - int64(bufsize) if _, err := rd.ReadAt(b, off); err != nil { return nil, 0, err } hlen := binary.LittleEndian.Uint32(b[len(b)-headerLengthSize:]) b = b[:len(b)-headerLengthSize] debug.Log("header length: %v", hlen) var err error switch { case hlen == 0: err = InvalidFileError{Message: "header length is zero"} case hlen < crypto.Extension: err = InvalidFileError{Message: "header length is too small"} case int64(hlen) > size-int64(headerLengthSize): err = InvalidFileError{Message: "header is larger than file"} case int64(hlen) > MaxHeaderSize-int64(headerLengthSize): err = InvalidFileError{Message: "header is larger than maxHeaderSize"} } if err != nil { return nil, 0, errors.Wrap(err, "readHeader") } total := int(hlen + headerLengthSize) if total < bufsize { // truncate to the beginning of the pack header b = b[len(b)-int(hlen):] } return b, total, nil } // readHeader reads the header at the end of rd. size is the length of the // whole data accessible in rd. func readHeader(rd io.ReaderAt, size int64) ([]byte, error) { debug.Log("size: %v", size) if size < int64(minFileSize) { err := InvalidFileError{Message: "file is too small"} return nil, errors.Wrap(err, "readHeader") } // assuming extra request is significantly slower than extra bytes download, // eagerly download eagerEntries header entries as part of header-length request. // only make second request if actual number of entries is greater than eagerEntries eagerSize := eagerEntries*int(entrySize) + headerSize b, c, err := readRecords(rd, size, eagerSize) if err != nil { return nil, err } if c <= eagerSize { // eager read sufficed, return what we got return b, nil } b, _, err = readRecords(rd, size, c) if err != nil { return nil, err } return b, nil } // InvalidFileError is return when a file is found that is not a pack file. type InvalidFileError struct { Message string } func (e InvalidFileError) Error() string { return e.Message } // List returns the list of entries found in a pack file and the length of the // header (including header size and crypto overhead) func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, hdrSize uint32, err error) { buf, err := readHeader(rd, size) if err != nil { return nil, 0, err } if len(buf) < crypto.CiphertextLength(0) { return nil, 0, errors.New("invalid header, too small") } hdrSize = headerLengthSize + uint32(len(buf)) nonce, buf := buf[:k.NonceSize()], buf[k.NonceSize():] buf, err = k.Open(buf[:0], nonce, buf, nil) if err != nil { return nil, 0, err } // might over allocate a bit if all blobs have EntrySize but only by a few percent entries = make([]restic.Blob, 0, uint(len(buf))/plainEntrySize) pos := uint(0) for len(buf) > 0 { entry, headerSize, err := parseHeaderEntry(buf) if err != nil { return nil, 0, err } entry.Offset = pos entries = append(entries, entry) pos += entry.Length buf = buf[headerSize:] } return entries, hdrSize, nil } func parseHeaderEntry(p []byte) (b restic.Blob, size uint, err error) { l := uint(len(p)) size = plainEntrySize if l < plainEntrySize { err = errors.Errorf("parseHeaderEntry: buffer of size %d too short", len(p)) return b, size, err } tpe := p[0] switch tpe { case 0, 2: b.Type = restic.DataBlob case 1, 3: b.Type = restic.TreeBlob default: return b, size, errors.Errorf("invalid type %d", tpe) } b.Length = uint(binary.LittleEndian.Uint32(p[1:5])) p = p[5:] if tpe == 2 || tpe == 3 { size = entrySize if l < entrySize { err = errors.Errorf("parseHeaderEntry: buffer of size %d too short", len(p)) return b, size, err } b.UncompressedLength = uint(binary.LittleEndian.Uint32(p[0:4])) p = p[4:] } copy(b.ID[:], p[:]) return b, size, nil } func CalculateEntrySize(blob restic.Blob) int { if blob.UncompressedLength != 0 { return int(entrySize) } return int(plainEntrySize) } func CalculateHeaderSize(blobs []restic.Blob) int { size := headerSize for _, blob := range blobs { size += CalculateEntrySize(blob) } return size } // Size returns the size of all packs computed by index information. // If onlyHdr is set to true, only the size of the header is returned // Note that this function only gives correct sizes, if there are no // duplicates in the index. func Size(ctx context.Context, mi restic.MasterIndex, onlyHdr bool) map[restic.ID]int64 { packSize := make(map[restic.ID]int64) mi.Each(ctx, func(blob restic.PackedBlob) { size, ok := packSize[blob.PackID] if !ok { size = headerSize } if !onlyHdr { size += int64(blob.Length) } packSize[blob.PackID] = size + int64(CalculateEntrySize(blob.Blob)) }) return packSize }