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Merge pull request #3332 from restic/debug-1999
Merge `debug examine` to salvage damaged pack files
This commit is contained in:
Alexander Neumann
GitHub
commit
af3de702c7
@ -4,12 +4,21 @@ package main
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import (
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"context"
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"crypto/aes"
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"crypto/cipher"
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"encoding/json"
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"fmt"
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"io"
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"os"
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"runtime"
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"sort"
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"time"
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"github.com/spf13/cobra"
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"golang.org/x/sync/errgroup"
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"github.com/restic/restic/internal/backend"
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"github.com/restic/restic/internal/crypto"
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"github.com/restic/restic/internal/errors"
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"github.com/restic/restic/internal/pack"
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"github.com/restic/restic/internal/repository"
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@ -39,9 +48,17 @@ Exit status is 0 if the command was successful, and non-zero if there was any er
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},
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}
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var tryRepair bool
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var repairByte bool
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var extractPack bool
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func init() {
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cmdRoot.AddCommand(cmdDebug)
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cmdDebug.AddCommand(cmdDebugDump)
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cmdDebug.AddCommand(cmdDebugExamine)
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cmdDebugExamine.Flags().BoolVar(&extractPack, "extract-pack", false, "write blobs to the current directory")
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cmdDebugExamine.Flags().BoolVar(&tryRepair, "try-repair", false, "try to repair broken blobs with single bit flips")
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cmdDebugExamine.Flags().BoolVar(&repairByte, "repair-byte", false, "try to repair broken blobs by trying bytes")
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}
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func prettyPrintJSON(wr io.Writer, item interface{}) error {
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@ -165,3 +182,367 @@ func runDebugDump(gopts GlobalOptions, args []string) error {
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return errors.Fatalf("no such type %q", tpe)
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}
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}
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var cmdDebugExamine = &cobra.Command{
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Use: "examine pack-ID...",
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Short: "Examine a pack file",
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DisableAutoGenTag: true,
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RunE: func(cmd *cobra.Command, args []string) error {
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return runDebugExamine(globalOptions, args)
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},
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}
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func tryRepairWithBitflip(ctx context.Context, key *crypto.Key, input []byte, bytewise bool) []byte {
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if bytewise {
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Printf(" trying to repair blob by finding a broken byte\n")
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} else {
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Printf(" trying to repair blob with single bit flip\n")
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}
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ch := make(chan int)
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var wg errgroup.Group
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done := make(chan struct{})
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var fixed []byte
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var found bool
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workers := runtime.GOMAXPROCS(0)
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Printf(" spinning up %d worker functions\n", runtime.GOMAXPROCS(0))
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for i := 0; i < workers; i++ {
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wg.Go(func() error {
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// make a local copy of the buffer
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buf := make([]byte, len(input))
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copy(buf, input)
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testFlip := func(idx int, pattern byte) bool {
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// flip bits
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buf[idx] ^= pattern
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nonce, plaintext := buf[:key.NonceSize()], buf[key.NonceSize():]
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plaintext, err := key.Open(plaintext[:0], nonce, plaintext, nil)
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if err == nil {
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Printf("\n")
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Printf(" blob could be repaired by XORing byte %v with 0x%02x\n", idx, pattern)
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Printf(" hash is %v\n", restic.Hash(plaintext))
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close(done)
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found = true
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fixed = plaintext
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return true
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}
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// flip bits back
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buf[idx] ^= pattern
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return false
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}
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for i := range ch {
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if bytewise {
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for j := 0; j < 255; j++ {
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if testFlip(i, byte(j)) {
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return nil
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}
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}
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} else {
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for j := 0; j < 7; j++ {
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// flip each bit once
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if testFlip(i, (1 << uint(j))) {
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return nil
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}
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}
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}
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}
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return nil
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})
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}
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wg.Go(func() error {
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defer close(ch)
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start := time.Now()
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info := time.Now()
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for i := range input {
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select {
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case ch <- i:
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case <-done:
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Printf(" done after %v\n", time.Since(start))
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return nil
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}
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if time.Since(info) > time.Second {
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secs := time.Since(start).Seconds()
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gps := float64(i) / secs
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remaining := len(input) - i
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eta := time.Duration(float64(remaining)/gps) * time.Second
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Printf("\r%d byte of %d done (%.2f%%), %.0f byte per second, ETA %v",
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i, len(input), float32(i)/float32(len(input))*100, gps, eta)
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info = time.Now()
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}
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}
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return nil
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})
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err := wg.Wait()
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if err != nil {
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panic("all go rountines can only return nil")
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}
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if !found {
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Printf("\n blob could not be repaired\n")
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}
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return fixed
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}
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func decryptUnsigned(ctx context.Context, k *crypto.Key, buf []byte) []byte {
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// strip signature at the end
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l := len(buf)
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nonce, ct := buf[:16], buf[16:l-16]
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out := make([]byte, len(ct))
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c, err := aes.NewCipher(k.EncryptionKey[:])
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if err != nil {
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panic(fmt.Sprintf("unable to create cipher: %v", err))
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}
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e := cipher.NewCTR(c, nonce)
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e.XORKeyStream(out, ct)
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return out
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}
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func loadBlobs(ctx context.Context, repo restic.Repository, pack restic.ID, list []restic.Blob) error {
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be := repo.Backend()
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h := restic.Handle{
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Name: pack.String(),
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Type: restic.PackFile,
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}
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for _, blob := range list {
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Printf(" loading blob %v at %v (length %v)\n", blob.ID, blob.Offset, blob.Length)
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buf := make([]byte, blob.Length)
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err := be.Load(ctx, h, int(blob.Length), int64(blob.Offset), func(rd io.Reader) error {
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n, err := io.ReadFull(rd, buf)
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if err != nil {
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return fmt.Errorf("read error after %d bytes: %v", n, err)
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}
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return nil
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})
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if err != nil {
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Warnf("error read: %v\n", err)
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continue
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}
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key := repo.Key()
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nonce, plaintext := buf[:key.NonceSize()], buf[key.NonceSize():]
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plaintext, err = key.Open(plaintext[:0], nonce, plaintext, nil)
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if err != nil {
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Warnf("error decrypting blob: %v\n", err)
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var plain []byte
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if tryRepair || repairByte {
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plain = tryRepairWithBitflip(ctx, key, buf, repairByte)
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}
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var prefix string
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if plain != nil {
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id := restic.Hash(plain)
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if !id.Equal(blob.ID) {
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Printf(" repaired blob (length %v), hash is %v, ID does not match, wanted %v\n", len(plain), id, blob.ID)
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prefix = "repaired-wrong-hash-"
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} else {
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Printf(" successfully repaired blob (length %v), hash is %v, ID matches\n", len(plain), id)
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prefix = "repaired-"
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}
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} else {
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plain = decryptUnsigned(ctx, key, buf)
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prefix = "damaged-"
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}
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err = storePlainBlob(blob.ID, prefix, plain)
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if err != nil {
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return err
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}
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continue
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}
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id := restic.Hash(plaintext)
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var prefix string
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if !id.Equal(blob.ID) {
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Printf(" successfully decrypted blob (length %v), hash is %v, ID does not match, wanted %v\n", len(plaintext), id, blob.ID)
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prefix = "wrong-hash-"
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} else {
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Printf(" successfully decrypted blob (length %v), hash is %v, ID matches\n", len(plaintext), id)
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prefix = "correct-"
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}
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if extractPack {
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err = storePlainBlob(id, prefix, plaintext)
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if err != nil {
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return err
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}
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}
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}
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return nil
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}
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func storePlainBlob(id restic.ID, prefix string, plain []byte) error {
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filename := fmt.Sprintf("%s%s.bin", prefix, id)
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f, err := os.Create(filename)
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if err != nil {
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return err
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}
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_, err = f.Write(plain)
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if err != nil {
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_ = f.Close()
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return err
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}
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err = f.Close()
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if err != nil {
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return err
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}
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Printf("decrypt of blob %v stored at %v\n", id, filename)
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return nil
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}
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func runDebugExamine(gopts GlobalOptions, args []string) error {
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ids := make([]restic.ID, 0)
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for _, name := range args {
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id, err := restic.ParseID(name)
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if err != nil {
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Warnf("error: %v\n", err)
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continue
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}
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ids = append(ids, id)
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}
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if len(ids) == 0 {
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return errors.Fatal("no pack files to examine")
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}
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repo, err := OpenRepository(gopts)
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if err != nil {
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return err
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}
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if !gopts.NoLock {
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lock, err := lockRepo(gopts.ctx, repo)
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defer unlockRepo(lock)
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if err != nil {
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return err
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}
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}
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err = repo.LoadIndex(gopts.ctx)
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if err != nil {
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return err
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}
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for _, id := range ids {
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err := examinePack(gopts.ctx, repo, id)
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if err != nil {
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Warnf("error: %v\n", err)
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}
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if err == context.Canceled {
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break
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}
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}
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return nil
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}
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func examinePack(ctx context.Context, repo restic.Repository, id restic.ID) error {
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Printf("examine %v\n", id)
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h := restic.Handle{
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Type: restic.PackFile,
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Name: id.String(),
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}
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fi, err := repo.Backend().Stat(ctx, h)
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if err != nil {
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return err
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}
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Printf(" file size is %v\n", fi.Size)
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buf, err := backend.LoadAll(ctx, nil, repo.Backend(), h)
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if err != nil {
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return err
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}
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gotID := restic.Hash(buf)
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if !id.Equal(gotID) {
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Printf(" wanted hash %v, got %v\n", id, gotID)
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} else {
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Printf(" hash for file content matches\n")
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}
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Printf(" ========================================\n")
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Printf(" looking for info in the indexes\n")
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blobsLoaded := false
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// examine all data the indexes have for the pack file
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for _, idx := range repo.Index().(*repository.MasterIndex).All() {
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idxIDs, err := idx.IDs()
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if err != nil {
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idxIDs = restic.IDs{}
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}
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blobs := idx.ListPack(id)
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if len(blobs) == 0 {
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continue
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}
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Printf(" index %v:\n", idxIDs)
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// convert list of blobs to []restic.Blob
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var list []restic.Blob
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for _, b := range blobs {
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list = append(list, b.Blob)
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}
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checkPackSize(list, fi.Size)
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err = loadBlobs(ctx, repo, id, list)
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if err != nil {
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Warnf("error: %v\n", err)
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} else {
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blobsLoaded = true
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}
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}
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Printf(" ========================================\n")
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Printf(" inspect the pack itself\n")
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blobs, _, err := pack.List(repo.Key(), restic.ReaderAt(ctx, repo.Backend(), h), fi.Size)
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if err != nil {
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return fmt.Errorf("pack %v: %v", id.Str(), err)
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}
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checkPackSize(blobs, fi.Size)
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if !blobsLoaded {
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return loadBlobs(ctx, repo, id, blobs)
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}
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return nil
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}
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func checkPackSize(blobs []restic.Blob, fileSize int64) {
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// track current size and offset
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var size, offset uint64
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sort.Slice(blobs, func(i, j int) bool {
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return blobs[i].Offset < blobs[j].Offset
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})
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for _, pb := range blobs {
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Printf(" %v blob %v, offset %-6d, raw length %-6d\n", pb.Type, pb.ID, pb.Offset, pb.Length)
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if offset != uint64(pb.Offset) {
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Printf(" hole in file, want offset %v, got %v\n", offset, pb.Offset)
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}
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offset += uint64(pb.Length)
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size += uint64(pb.Length)
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}
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// compute header size, per blob: 1 byte type, 4 byte length, 32 byte id
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size += uint64(restic.CiphertextLength(len(blobs) * (1 + 4 + 32)))
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// length in uint32 little endian
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size += 4
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if uint64(fileSize) != size {
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Printf(" file sizes do not match: computed %v from index, file size is %v\n", size, fileSize)
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} else {
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Printf(" file sizes match\n")
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}
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}
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