pack: move to repository package

internal/repository/pack/pack.go

@@ -0,0 +1,407 @@
+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 {
+		//nolint:revive // ignore linter warnings about error message spelling
+		return fmt.Errorf("Detected data corruption while writing pack-file header: %w\nCorrupted data is either caused by hardware issues or software bugs. 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("<Packer %d blobs, %d bytes>", 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 short"}
+	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 short"}
+		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 short")
+	}
+
+	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.ListBlobser, onlyHdr bool) (map[restic.ID]int64, error) {
+	packSize := make(map[restic.ID]int64)
+
+	err := mi.ListBlobs(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, err
+}