Add copy functionality

Add a copy command to copy snapshots between repositories. It allows the user
to specify a destination repository, password, password-file, password-command
or key-hint to supply the necessary details to open the destination repository.

You need to supply a list of snapshots to copy, snapshots which already exist
in the destination repository will be skipped.

Note, when using the network this becomes rather slow, as it needs to read the
blocks, decrypt them using the source key, then encrypt them again using the
destination key before finally writing them out to the destination repository.

changelog/unreleased/issue-323

@@ -0,0 +1,13 @@
+Enhancement: Add command for copying snapshots between repositories
+
+We've added a copy command, allowing you to copy snapshots from one
+repository to another.
+
+Note that this process will have to read (download) and write (upload) the
+entire snapshot(s) due to the different encryption keys used on the source
+and destination repository. Also, the transferred files are not re-chunked,
+which may break deduplication between files already stored in the
+destination repo and files copied there using this command.
+
+https://github.com/restic/restic/issues/323
+https://github.com/restic/restic/pull/2606

cmd/restic/cmd_copy.go

@@ -0,0 +1,203 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/restic/restic/internal/debug"
+	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/restic"
+
+	"github.com/spf13/cobra"
+)
+
+var cmdCopy = &cobra.Command{
+	Use:   "copy [flags] [snapshotID ...]",
+	Short: "Copy snapshots from one repository to another",
+	Long: `
+The "copy" command copies one or more snapshots from one repository to another
+repository. Note that this will have to read (download) and write (upload) the
+entire snapshot(s) due to the different encryption keys on the source and
+destination, and that transferred files are not re-chunked, which may break
+their deduplication.
+`,
+	RunE: func(cmd *cobra.Command, args []string) error {
+		return runCopy(copyOptions, globalOptions, args)
+	},
+}
+
+// CopyOptions bundles all options for the copy command.
+type CopyOptions struct {
+	Repo            string
+	PasswordFile    string
+	PasswordCommand string
+	KeyHint         string
+	Hosts           []string
+	Tags            restic.TagLists
+	Paths           []string
+}
+
+var copyOptions CopyOptions
+
+func init() {
+	cmdRoot.AddCommand(cmdCopy)
+
+	f := cmdCopy.Flags()
+	f.StringVarP(&copyOptions.Repo, "repo2", "", os.Getenv("RESTIC_REPOSITORY2"), "destination repository to copy snapshots to (default: $RESTIC_REPOSITORY2)")
+	f.StringVarP(&copyOptions.PasswordFile, "password-file2", "", os.Getenv("RESTIC_PASSWORD_FILE2"), "read the destination repository password from a file (default: $RESTIC_PASSWORD_FILE2)")
+	f.StringVarP(&copyOptions.KeyHint, "key-hint2", "", os.Getenv("RESTIC_KEY_HINT2"), "key ID of key to try decrypting the destination repository first (default: $RESTIC_KEY_HINT2)")
+	f.StringVarP(&copyOptions.PasswordCommand, "password-command2", "", os.Getenv("RESTIC_PASSWORD_COMMAND2"), "specify a shell command to obtain a password for the destination repository (default: $RESTIC_PASSWORD_COMMAND2)")
+
+	f.StringArrayVarP(&copyOptions.Hosts, "host", "H", nil, "only consider snapshots for this `host`, when no snapshot ID is given (can be specified multiple times)")
+	f.Var(&copyOptions.Tags, "tag", "only consider snapshots which include this `taglist`, when no snapshot ID is given")
+	f.StringArrayVar(&copyOptions.Paths, "path", nil, "only consider snapshots which include this (absolute) `path`, when no snapshot ID is given")
+}
+
+func runCopy(opts CopyOptions, gopts GlobalOptions, args []string) error {
+	if opts.Repo == "" {
+		return errors.Fatal("Please specify a destination repository location (--repo2)")
+	}
+	var err error
+	dstGopts := gopts
+	dstGopts.Repo = opts.Repo
+	dstGopts.PasswordFile = opts.PasswordFile
+	dstGopts.PasswordCommand = opts.PasswordCommand
+	dstGopts.KeyHint = opts.KeyHint
+	dstGopts.password, err = resolvePassword(dstGopts, "RESTIC_PASSWORD2")
+	if err != nil {
+		return err
+	}
+	dstGopts.password, err = ReadPassword(dstGopts, "enter password for destination repository: ")
+	if err != nil {
+		return err
+	}
+
+	ctx, cancel := context.WithCancel(gopts.ctx)
+	defer cancel()
+
+	srcRepo, err := OpenRepository(gopts)
+	if err != nil {
+		return err
+	}
+
+	dstRepo, err := OpenRepository(dstGopts)
+	if err != nil {
+		return err
+	}
+
+	srcLock, err := lockRepo(srcRepo)
+	defer unlockRepo(srcLock)
+	if err != nil {
+		return err
+	}
+
+	dstLock, err := lockRepo(dstRepo)
+	defer unlockRepo(dstLock)
+	if err != nil {
+		return err
+	}
+
+	debug.Log("Loading source index")
+	if err := srcRepo.LoadIndex(ctx); err != nil {
+		return err
+	}
+
+	debug.Log("Loading destination index")
+	if err := dstRepo.LoadIndex(ctx); err != nil {
+		return err
+	}
+
+	for sn := range FindFilteredSnapshots(ctx, srcRepo, opts.Hosts, opts.Tags, opts.Paths, args) {
+		Verbosef("snapshot %s of %v at %s)\n", sn.ID().Str(), sn.Paths, sn.Time)
+		Verbosef("  copy started, this may take a while...\n")
+
+		if err := copyTree(ctx, srcRepo, dstRepo, *sn.Tree); err != nil {
+			return err
+		}
+		debug.Log("tree copied")
+
+		if err = dstRepo.Flush(ctx); err != nil {
+			return err
+		}
+		debug.Log("flushed packs")
+
+		err = dstRepo.SaveIndex(ctx)
+		if err != nil {
+			debug.Log("error saving index: %v", err)
+			return err
+		}
+		debug.Log("saved index")
+
+		// save snapshot
+		sn.Parent = nil   // Parent does not have relevance in the new repo.
+		sn.Original = nil // Original does not have relevance in the new repo.
+		newID, err := dstRepo.SaveJSONUnpacked(ctx, restic.SnapshotFile, sn)
+		if err != nil {
+			return err
+		}
+		Verbosef("snapshot %s saved\n", newID.Str())
+	}
+	return nil
+}
+
+func copyTree(ctx context.Context, srcRepo, dstRepo restic.Repository, treeID restic.ID) error {
+	tree, err := srcRepo.LoadTree(ctx, treeID)
+	if err != nil {
+		return fmt.Errorf("LoadTree(%v) returned error %v", treeID.Str(), err)
+	}
+	// Do we already have this tree blob?
+	if !dstRepo.Index().Has(treeID, restic.TreeBlob) {
+		newTreeID, err := dstRepo.SaveTree(ctx, tree)
+		if err != nil {
+			return fmt.Errorf("SaveTree(%v) returned error %v", treeID.Str(), err)
+		}
+		// Assurance only.
+		if newTreeID != treeID {
+			return fmt.Errorf("SaveTree(%v) returned unexpected id %s", treeID.Str(), newTreeID.Str())
+		}
+	}
+
+	// TODO: keep only one (big) buffer around.
+	// TODO: parellize this stuff, likely only needed inside a tree.
+
+	for _, entry := range tree.Nodes {
+		// If it is a directory, recurse
+		if entry.Type == "dir" && entry.Subtree != nil {
+			if err := copyTree(ctx, srcRepo, dstRepo, *entry.Subtree); err != nil {
+				return err
+			}
+		}
+		// Copy the blobs for this file.
+		for _, blobID := range entry.Content {
+			// Do we already have this data blob?
+			if dstRepo.Index().Has(blobID, restic.DataBlob) {
+				continue
+			}
+			debug.Log("Copying blob %s\n", blobID.Str())
+			size, found := srcRepo.LookupBlobSize(blobID, restic.DataBlob)
+			if !found {
+				return fmt.Errorf("LookupBlobSize(%v) failed", blobID)
+			}
+			buf := restic.NewBlobBuffer(int(size))
+			n, err := srcRepo.LoadBlob(ctx, restic.DataBlob, blobID, buf)
+			if err != nil {
+				return fmt.Errorf("LoadBlob(%v) returned error %v", blobID, err)
+			}
+			if n != len(buf) {
+				return fmt.Errorf("wrong number of bytes read, want %d, got %d", len(buf), n)
+			}
+
+			newBlobID, err := dstRepo.SaveBlob(ctx, restic.DataBlob, buf, blobID)
+			if err != nil {
+				return fmt.Errorf("SaveBlob(%v) returned error %v", blobID, err)
+			}
+			// Assurance only.
+			if newBlobID != blobID {
+				return fmt.Errorf("SaveBlob(%v) returned unexpected id %s", blobID.Str(), newBlobID.Str())
+			}
+		}
+	}
+
+	return nil
+}

cmd/restic/global.go

@@ -274,7 +274,7 @@ func Exitf(exitcode int, format string, args ...interface{}) {
 }
 
 // resolvePassword determines the password to be used for opening the repository.
-func resolvePassword(opts GlobalOptions) (string, error) {
+func resolvePassword(opts GlobalOptions, envStr string) (string, error) {
 	if opts.PasswordFile != "" && opts.PasswordCommand != "" {
 		return "", errors.Fatalf("Password file and command are mutually exclusive options")
 	}
@@ -299,7 +299,7 @@ func resolvePassword(opts GlobalOptions) (string, error) {
 		return strings.TrimSpace(string(s)), errors.Wrap(err, "Readfile")
 	}
 
-	if pwd := os.Getenv("RESTIC_PASSWORD"); pwd != "" {
+	if pwd := os.Getenv(envStr); pwd != "" {
 		return pwd, nil
 	}
 

cmd/restic/main.go

@@ -54,7 +54,7 @@ directories in an encrypted repository stored on different backends.
 		if c.Name() == "version" {
 			return nil
 		}
-		pwd, err := resolvePassword(globalOptions)
+		pwd, err := resolvePassword(globalOptions, "RESTIC_PASSWORD")
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "Resolving password failed: %v\n", err)
 			Exit(1)