Implemented WebDAV server to browse repositories

cmd/restic/cmd_webdav.go

@@ -0,0 +1,429 @@
+package main
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"os"
+	"path"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/spf13/cobra"
+	"golang.org/x/net/webdav"
+
+	"github.com/restic/restic/internal/bloblru"
+	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/restic"
+	"github.com/restic/restic/internal/walker"
+)
+
+var cmdWebdav = &cobra.Command{
+	Use:   "webdav [flags] address:port",
+	Short: "Serve the repository via WebDAV",
+	Long: `
+The "webdav" command serves the repository via WebDAV. This is a
+read-only mount.
+
+Snapshot Directories
+====================
+
+If you need a different template for directories that contain snapshots,
+you can pass a time template via --time-template and path templates via
+--path-template.
+
+Example time template without colons:
+
+    --time-template "2006-01-02_15-04-05"
+
+You need to specify a sample format for exactly the following timestamp:
+
+    Mon Jan 2 15:04:05 -0700 MST 2006
+
+For details please see the documentation for time.Format() at:
+  https://godoc.org/time#Time.Format
+
+For path templates, you can use the following patterns which will be replaced:
+    %i by short snapshot ID
+    %I by long snapshot ID
+    %u by username
+    %h by hostname
+    %t by tags
+    %T by timestamp as specified by --time-template
+
+The default path templates are:
+    "ids/%i"
+    "snapshots/%T"
+    "hosts/%h/%T"
+    "tags/%t/%T"
+
+EXIT STATUS
+===========
+
+Exit status is 0 if the command was successful, and non-zero if there was any error.
+`,
+	DisableAutoGenTag: true,
+	RunE: func(cmd *cobra.Command, args []string) error {
+		return runWebServer(cmd.Context(), webdavOptions, globalOptions, args)
+	},
+}
+
+type WebdavOptions struct {
+	restic.SnapshotFilter
+	TimeTemplate  string
+	PathTemplates []string
+}
+
+var webdavOptions WebdavOptions
+
+func init() {
+	cmdRoot.AddCommand(cmdWebdav)
+	cmdFlags := cmdWebdav.Flags()
+	initMultiSnapshotFilter(cmdFlags, &webdavOptions.SnapshotFilter, true)
+	cmdFlags.StringArrayVar(&webdavOptions.PathTemplates, "path-template", nil, "set `template` for path names (can be specified multiple times)")
+	cmdFlags.StringVar(&webdavOptions.TimeTemplate, "snapshot-template", time.RFC3339, "set `template` to use for snapshot dirs")
+}
+
+func runWebServer(ctx context.Context, opts WebdavOptions, gopts GlobalOptions, args []string) error {
+
+	if len(args) == 0 {
+		return errors.Fatal("wrong number of parameters")
+	}
+
+	bindAddress := args[0]
+
+	if strings.Index(bindAddress, "http://") == 0 {
+		bindAddress = bindAddress[7:]
+	}
+
+	// PathTemplates and TimeTemplate are ignored for now because `fuse.snapshots_dir(struct)`
+	// is not accessible when building on Windows and it would be ridiculous to duplicate the
+	// code. It should be shared, somehow.
+
+	ctx, repo, unlock, err := openWithReadLock(ctx, gopts, gopts.NoLock)
+	if err != nil {
+		return err
+	}
+	defer unlock()
+
+	snapshotLister, err := restic.MemorizeList(ctx, repo, restic.SnapshotFile)
+	if err != nil {
+		return err
+	}
+
+	bar := newIndexProgress(gopts.Quiet, gopts.JSON)
+	err = repo.LoadIndex(ctx, bar)
+	if err != nil {
+		return err
+	}
+
+	davFS := &webdavFS{
+		repo: repo,
+		root: webdavFSNode{
+			name:     "",
+			mode:     0555 | os.ModeDir,
+			modTime:  time.Now(),
+			children: make(map[string]*webdavFSNode),
+		},
+		snapshots: make(map[string]*restic.Snapshot),
+		blobCache: bloblru.New(64 << 20),
+	}
+
+	for sn := range FindFilteredSnapshots(ctx, snapshotLister, repo, &webdavOptions.SnapshotFilter, args[1:]) {
+		snID := sn.ID().Str()
+		davFS.root.children[snID] = &webdavFSNode{
+			name:     snID,
+			mode:     0555 | os.ModeDir,
+			modTime:  sn.Time,
+			children: make(map[string]*webdavFSNode),
+		}
+		davFS.snapshots[snID] = sn
+	}
+
+	wd := &webdav.Handler{
+		FileSystem: davFS,
+		LockSystem: webdav.NewMemLS(),
+	}
+
+	Printf("Now serving the repository at http://%s\n", bindAddress)
+	Printf("Tree contains %d snapshots\n", len(davFS.root.children))
+	Printf("When finished, quit with Ctrl-c here.\n")
+
+	return http.ListenAndServe(bindAddress, wd)
+}
+
+type webdavFS struct {
+	repo      restic.Repository
+	root      webdavFSNode
+	snapshots map[string]*restic.Snapshot
+	blobCache *bloblru.Cache
+}
+
+// Implements os.FileInfo
+type webdavFSNode struct {
+	name    string
+	mode    os.FileMode
+	modTime time.Time
+	size    int64
+
+	node     *restic.Node
+	children map[string]*webdavFSNode
+}
+
+func (f *webdavFSNode) Name() string       { return f.name }
+func (f *webdavFSNode) Size() int64        { return f.size }
+func (f *webdavFSNode) Mode() os.FileMode  { return f.mode }
+func (f *webdavFSNode) ModTime() time.Time { return f.modTime }
+func (f *webdavFSNode) IsDir() bool        { return f.mode.IsDir() }
+func (f *webdavFSNode) Sys() interface{}   { return nil }
+
+func mountSnapshot(ctx context.Context, fs *webdavFS, mountPoint string, sn *restic.Snapshot) {
+	Printf("Mounting snapshot %s at %s\n", sn.ID().Str(), mountPoint)
+	// FIXME: Need a mutex here...
+	// FIXME: All this walking should be done dynamically when the client asks for a folder...
+	walker.Walk(ctx, fs.repo, *sn.Tree, walker.WalkVisitor{
+		ProcessNode: func(parentTreeID restic.ID, nodepath string, node *restic.Node, err error) error {
+			if err != nil || node == nil {
+				return err
+			}
+			dir, wdNode, err := fs.find(mountPoint + "/" + nodepath)
+			if err != nil || dir == nil {
+				Printf("Found a leaf before the branch was created (parent not found %s)!\n", nodepath)
+				return walker.ErrSkipNode
+			}
+			if wdNode != nil {
+				Printf("Walked through a file that already exists in the tree!!! (%s: %s)\n", node.Type, nodepath)
+				return walker.ErrSkipNode
+			}
+			if dir.children == nil {
+				dir.children = make(map[string]*webdavFSNode)
+			}
+			dir.children[node.Name] = &webdavFSNode{
+				name:    node.Name,
+				mode:    node.Mode,
+				modTime: node.ModTime,
+				size:    int64(node.Size),
+				node:    node,
+			}
+			dir.size = int64(len(dir.children))
+			return nil
+		},
+	})
+}
+
+func (fs *webdavFS) find(fullname string) (*webdavFSNode, *webdavFSNode, error) {
+	fullname = strings.Trim(path.Clean("/"+fullname), "/")
+	if fullname == "" {
+		return nil, &fs.root, nil
+	}
+
+	parts := strings.Split(fullname, "/")
+	dir := &fs.root
+
+	for dir != nil {
+		part := parts[0]
+		parts = parts[1:]
+		if len(parts) == 0 {
+			return dir, dir.children[part], nil
+		}
+		dir = dir.children[part]
+	}
+
+	return nil, nil, os.ErrNotExist
+}
+
+func (fs *webdavFS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
+	Printf("OpenFile %s\n", name)
+
+	// Client can only read
+	if flag&(os.O_WRONLY|os.O_RDWR) != 0 {
+		return nil, os.ErrPermission
+	}
+
+	_, node, err := fs.find(name)
+	if err != nil {
+		return nil, err
+	}
+	if node == nil {
+		return nil, os.ErrNotExist
+	}
+	return &openFile{node: node, fs: fs}, nil
+}
+
+func (fs *webdavFS) Stat(ctx context.Context, name string) (os.FileInfo, error) {
+	_, node, err := fs.find(name)
+	if err != nil {
+		return nil, err
+	}
+	if node == nil {
+		return nil, os.ErrNotExist
+	}
+	return node, nil
+}
+
+func (fs *webdavFS) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
+	return os.ErrPermission
+}
+
+func (fs *webdavFS) RemoveAll(ctx context.Context, name string) error {
+	return os.ErrPermission
+}
+
+func (fs *webdavFS) Rename(ctx context.Context, oldName, newName string) error {
+	return os.ErrPermission
+}
+
+type openFile struct {
+	node   *webdavFSNode
+	fs     *webdavFS
+	cursor int64
+
+	initialized bool
+	// cumsize[i] holds the cumulative size of blobs[:i].
+	children []os.FileInfo
+	cumsize  []uint64
+}
+
+func (f *openFile) getBlobAt(ctx context.Context, i int) (blob []byte, err error) {
+	blob, ok := f.fs.blobCache.Get(f.node.node.Content[i])
+	if ok {
+		return blob, nil
+	}
+
+	blob, err = f.fs.repo.LoadBlob(ctx, restic.DataBlob, f.node.node.Content[i], nil)
+	if err != nil {
+		return nil, err
+	}
+
+	f.fs.blobCache.Add(f.node.node.Content[i], blob)
+
+	return blob, nil
+}
+
+func (f *openFile) Read(p []byte) (int, error) {
+	Printf("Read %s %d %d\n", f.node.name, f.cursor, len(p))
+	if f.node.IsDir() || f.cursor < 0 {
+		return 0, os.ErrInvalid
+	}
+	if f.cursor >= f.node.Size() {
+		return 0, io.EOF
+	}
+
+	// We wait until the first read before we do anything because WebDAV clients tend to open
+	// everything and do nothing...
+	if !f.initialized {
+		var bytes uint64
+		cumsize := make([]uint64, 1+len(f.node.node.Content))
+		for i, id := range f.node.node.Content {
+			size, found := f.fs.repo.LookupBlobSize(id, restic.DataBlob)
+			if !found {
+				return 0, errors.Errorf("id %v not found in repository", id)
+			}
+			bytes += uint64(size)
+			cumsize[i+1] = bytes
+		}
+		if bytes != f.node.node.Size {
+			Printf("sizes do not match: node.Size %d != size %d", bytes, f.node.Size())
+		}
+		f.cumsize = cumsize
+		f.initialized = true
+	}
+
+	offset := uint64(f.cursor)
+	remainingBytes := uint64(len(p))
+	readBytes := 0
+
+	if offset+remainingBytes > uint64(f.node.Size()) {
+		remainingBytes = uint64(f.node.Size()) - remainingBytes
+	}
+
+	// Skip blobs before the offset
+	startContent := -1 + sort.Search(len(f.cumsize), func(i int) bool {
+		return f.cumsize[i] > offset
+	})
+	offset -= f.cumsize[startContent]
+
+	for i := startContent; remainingBytes > 0 && i < len(f.cumsize)-1; i++ {
+		blob, err := f.getBlobAt(context.TODO(), i)
+		if err != nil {
+			return 0, err
+		}
+
+		if offset > 0 {
+			blob = blob[offset:]
+			offset = 0
+		}
+
+		copied := copy(p, blob)
+		remainingBytes -= uint64(copied)
+		readBytes += copied
+
+		p = p[copied:]
+	}
+
+	f.cursor += int64(readBytes)
+	return readBytes, nil
+}
+
+func (f *openFile) Readdir(count int) ([]os.FileInfo, error) {
+	Printf("Readdir %s %d %d\n", f.node.name, f.cursor, count)
+	if !f.node.IsDir() || f.cursor < 0 {
+		return nil, os.ErrInvalid
+	}
+
+	// We wait until the first read before we do anything because WebDAV clients tend to open
+	// everything and do nothing...
+	if !f.initialized {
+		// It's a snapshot, mount it
+		if f.node != &f.fs.root && f.node.node == nil && len(f.children) == 0 {
+			mountSnapshot(context.TODO(), f.fs, "/"+f.node.name, f.fs.snapshots[f.node.name])
+		}
+		children := make([]os.FileInfo, 0, len(f.node.children))
+		for _, c := range f.node.children {
+			children = append(children, c)
+		}
+		f.children = children
+		f.initialized = true
+	}
+
+	if count <= 0 {
+		return f.children, nil
+	}
+	if f.cursor >= f.node.Size() {
+		return nil, io.EOF
+	}
+	start := f.cursor
+	f.cursor += int64(count)
+	if f.cursor > f.node.Size() {
+		f.cursor = f.node.Size()
+	}
+	return f.children[start:f.cursor], nil
+}
+
+func (f *openFile) Seek(offset int64, whence int) (int64, error) {
+	Printf("Seek %s %d %d\n", f.node.name, offset, whence)
+	switch whence {
+	case io.SeekStart:
+		f.cursor = offset
+	case io.SeekCurrent:
+		f.cursor += offset
+	case io.SeekEnd:
+		f.cursor = f.node.Size() - offset
+	default:
+		return 0, os.ErrInvalid
+	}
+	return f.cursor, nil
+}
+
+func (f *openFile) Stat() (os.FileInfo, error) {
+	return f.node, nil
+}
+
+func (f *openFile) Write(p []byte) (int, error) {
+	return 0, os.ErrPermission
+}
+
+func (f *openFile) Close() error {
+	return nil
+}