v2api: fsck: use a temporary mount

Directly accessing the Nodes does not work properly,
as there is no way to attach a newly LOOKUPped Node
to the tree. This means Path() does not work.

Use an actual mount instead and walk the tree.

3 files changed, 135 insertions, 98 deletions

diff --git a/fsck.go b/fsck.go
index 671d5d0..6d9ca4a 100644
--- a/fsck.go
+++ b/fsck.go
@@ -3,23 +3,27 @@ package main
 import (
 	"bytes"
 	"fmt"
-	"log"
+	"io"
+	"io/ioutil"
 	"os"
+	"os/signal"
 	"path/filepath"
 	"strings"
 	"sync"
 	"syscall"
 
-	"github.com/hanwen/go-fuse/v2/fs"
 	"github.com/hanwen/go-fuse/v2/fuse"
 
 	"github.com/rfjakob/gocryptfs/internal/exitcodes"
 	"github.com/rfjakob/gocryptfs/internal/fusefrontend"
+	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
 type fsckObj struct {
 	rootNode *fusefrontend.RootNode
+	// mnt is the mountpoint of the temporary mount
+	mnt string
 	// List of corrupt files
 	corruptList []string
 	// List of skipped files
@@ -30,6 +34,8 @@ type fsckObj struct {
 	watchDone chan struct{}
 	// Inode numbers of hard-linked files (Nlink > 1) that we have already checked
 	seenInodes map[uint64]struct{}
+	// abort the running fsck operation? Checked in a few long-running loops.
+	abort bool
 }
 
 func runsAsRoot() bool {
@@ -48,6 +54,10 @@ func (ck *fsckObj) markSkipped(path string) {
 	ck.listLock.Unlock()
 }
 
+func (ck *fsckObj) abs(relPath string) (absPath string) {
+	return filepath.Join(ck.mnt, relPath)
+}
+
 // Watch for mitigated corruptions that occur during OpenDir()
 func (ck *fsckObj) watchMitigatedCorruptionsOpenDir(path string) {
 	for {
@@ -62,40 +72,45 @@ func (ck *fsckObj) watchMitigatedCorruptionsOpenDir(path string) {
 }
 
 // Recursively check dir for corruption
-func (ck *fsckObj) dir(n *fusefrontend.Node) {
-	path := n.Path()
-	tlog.Debug.Printf("ck.dir %q\n")
-	ck.xattrs(n)
+func (ck *fsckObj) dir(relPath string) {
+	tlog.Debug.Printf("ck.dir %q\n", relPath)
+	ck.xattrs(relPath)
 	// Run OpenDir and catch transparently mitigated corruptions
-	go ck.watchMitigatedCorruptionsOpenDir(path)
-	entries, errno := n.Readdir(nil)
+	go ck.watchMitigatedCorruptionsOpenDir(relPath)
+	f, err := os.Open(ck.abs(relPath))
 	ck.watchDone <- struct{}{}
-	// Also catch non-mitigated corruptions
-	if errno != 0 {
-		fmt.Printf("fsck: error opening dir %q: %v\n", n, errno)
-		if errno == syscall.EACCES && !runsAsRoot() {
-			ck.markSkipped(path)
+	if err != nil {
+		fmt.Printf("fsck: error opening dir %q: %v\n", relPath, err)
+		if err == os.ErrPermission && !runsAsRoot() {
+			ck.markSkipped(relPath)
 		} else {
-			ck.markCorrupt(path)
+			ck.markCorrupt(relPath)
 		}
 		return
 	}
-	for entries.HasNext() {
-		entry, errno := entries.Next()
-		if errno != 0 {
-			fmt.Printf("fsck: dirstream error: %v\n", errno)
-			break
+	go ck.watchMitigatedCorruptionsOpenDir(relPath)
+	entries, err := f.Readdirnames(0)
+	ck.watchDone <- struct{}{}
+	if err != nil {
+		fmt.Printf("fsck: error reading dir %q: %v\n", relPath, err)
+		ck.markCorrupt(relPath)
+		return
+	}
+	for _, entry := range entries {
+		if ck.abort {
+			return
 		}
-		if entry.Name == "." || entry.Name == ".." {
+		if entry == "." || entry == ".." {
 			continue
 		}
-		tmp, errno := n.Lookup(nil, entry.Name, &fuse.EntryOut{})
-		if errno != 0 {
-			ck.markCorrupt(filepath.Join(path, entry.Name))
+		nextPath := filepath.Join(relPath, entry)
+		var st syscall.Stat_t
+		err := syscall.Lstat(ck.abs(nextPath), &st)
+		if err != nil {
+			ck.markCorrupt(filepath.Join(relPath, entry))
 			continue
 		}
-		nextPath := tmp.Operations().(*fusefrontend.Node)
-		filetype := entry.Mode & syscall.S_IFMT
+		filetype := st.Mode & syscall.S_IFMT
 		//fmt.Printf("  %q %x\n", entry.Name, entry.Mode)
 		switch filetype {
 		case syscall.S_IFDIR:
@@ -112,12 +127,11 @@ func (ck *fsckObj) dir(n *fusefrontend.Node) {
 	}
 }
 
-func (ck *fsckObj) symlink(n *fusefrontend.Node) {
-	_, errno := n.Readlink(nil)
-	if errno != 0 {
-		path := n.Path()
-		ck.markCorrupt(path)
-		fmt.Printf("fsck: error reading symlink %q: %v\n", path, errno)
+func (ck *fsckObj) symlink(relPath string) {
+	_, err := os.Readlink(ck.abs(relPath))
+	if err != nil {
+		ck.markCorrupt(relPath)
+		fmt.Printf("fsck: error reading symlink %q: %v\n", relPath, err)
 	}
 }
 
@@ -135,55 +149,55 @@ func (ck *fsckObj) watchMitigatedCorruptionsRead(path string) {
 }
 
 // Check file for corruption
-func (ck *fsckObj) file(n *fusefrontend.Node) {
-	path := n.Path()
-	tlog.Debug.Printf("ck.file %q\n", path)
-	var attr fuse.AttrOut
-	errno := n.Getattr(nil, nil, &attr)
-	if errno != 0 {
-		ck.markCorrupt(path)
-		fmt.Printf("fsck: error stating file %q: %v\n", path, errno)
+func (ck *fsckObj) file(relPath string) {
+	tlog.Debug.Printf("ck.file %q\n", relPath)
+	var st syscall.Stat_t
+	err := syscall.Lstat(ck.abs(relPath), &st)
+	if err != nil {
+		ck.markCorrupt(relPath)
+		fmt.Printf("fsck: error stating file %q: %v\n", relPath, err)
 		return
 	}
-	if attr.Nlink > 1 {
+	if st.Nlink > 1 {
 		// Due to hard links, we may have already checked this file.
-		if _, ok := ck.seenInodes[attr.Ino]; ok {
-			tlog.Debug.Printf("ck.file : skipping %q (inode number %d already seen)\n", path, attr.Ino)
+		if _, ok := ck.seenInodes[st.Ino]; ok {
+			tlog.Debug.Printf("ck.file : skipping %q (inode number %d already seen)\n", relPath, st.Ino)
 			return
 		}
-		ck.seenInodes[attr.Ino] = struct{}{}
+		ck.seenInodes[st.Ino] = struct{}{}
 	}
-	ck.xattrs(n)
-	tmp, _, errno := n.Open(nil, syscall.O_RDONLY)
-	if errno != 0 {
-		fmt.Printf("fsck: error opening file %q: %v\n", path, errno)
-		if errno == syscall.EACCES && !runsAsRoot() {
-			ck.markSkipped(path)
+	ck.xattrs(relPath)
+	f, err := os.Open(ck.abs(relPath))
+	if err != nil {
+		fmt.Printf("fsck: error opening file %q: %v\n", relPath, err)
+		if err == os.ErrPermission && !runsAsRoot() {
+			ck.markSkipped(relPath)
 		} else {
-			ck.markCorrupt(path)
+			ck.markCorrupt(relPath)
 		}
 		return
 	}
-	f := tmp.(*fusefrontend.File2)
-	defer f.Release(nil)
+	defer f.Close()
 	// 128 kiB of zeros
 	allZero := make([]byte, fuse.MAX_KERNEL_WRITE)
 	buf := make([]byte, fuse.MAX_KERNEL_WRITE)
 	var off int64
 	// Read() through the whole file and catch transparently mitigated corruptions
-	go ck.watchMitigatedCorruptionsRead(path)
+	go ck.watchMitigatedCorruptionsRead(relPath)
 	defer func() { ck.watchDone <- struct{}{} }()
 	for {
+		if ck.abort {
+			return
+		}
 		tlog.Debug.Printf("ck.file: read %d bytes from offset %d\n", len(buf), off)
-		result, errno := f.Read(nil, buf, off)
-		if errno != 0 {
-			ck.markCorrupt(path)
-			fmt.Printf("fsck: error reading file %q (inum %d): %v\n", path, inum(f), errno)
+		n, err := f.ReadAt(buf, off)
+		if err != nil && err != io.EOF {
+			ck.markCorrupt(relPath)
+			fmt.Printf("fsck: error reading file %q (inum %d): %v\n", relPath, inum(f), err)
 			return
 		}
-		n := result.Size()
 		// EOF
-		if n == 0 {
+		if err == io.EOF {
 			return
 		}
 		off += int64(n)
@@ -192,7 +206,8 @@ func (ck *fsckObj) file(n *fusefrontend.Node) {
 		data := buf[:n]
 		if bytes.Equal(data, allZero) {
 			tlog.Debug.Printf("ck.file: trying to skip file hole\n")
-			nextOff, err := f.SeekData(off)
+			const SEEK_DATA = 3
+			nextOff, err := syscall.Seek(int(f.Fd()), off, SEEK_DATA)
 			if err == nil {
 				off = nextOff
 			}
@@ -214,35 +229,25 @@ func (ck *fsckObj) watchMitigatedCorruptionsListXAttr(path string) {
 }
 
 // Check xattrs on file/dir at path
-func (ck *fsckObj) xattrs(n *fusefrontend.Node) {
+func (ck *fsckObj) xattrs(relPath string) {
 	// Run ListXAttr() and catch transparently mitigated corruptions
-	path := n.Path()
-	go ck.watchMitigatedCorruptionsListXAttr(path)
-	listBuf := make([]byte, 1024*1024)
-	cnt, errno := n.Listxattr(nil, listBuf)
+	go ck.watchMitigatedCorruptionsListXAttr(relPath)
+	attrs, err := syscallcompat.Llistxattr(ck.abs(relPath))
 	ck.watchDone <- struct{}{}
-	// Also catch non-mitigated corruptions
-	if errno != 0 {
-		fmt.Printf("fsck: error listing xattrs on %q: %v\n", path, errno)
-		ck.markCorrupt(path)
-		return
-	}
-	if cnt == 0 {
+	if err != nil {
+		fmt.Printf("fsck: error listing xattrs on %q: %v\n", relPath, err)
+		ck.markCorrupt(relPath)
 		return
 	}
-	// Drop final trailing NULL byte
-	cnt--
-	listBuf = listBuf[:cnt]
-	attrs := bytes.Split(listBuf, []byte{0})
+	// Try to read all xattr values
 	for _, a := range attrs {
-		getBuf := make([]byte, 1024*1024)
-		_, errno := n.Getxattr(nil, string(a), getBuf)
-		if errno != 0 {
-			fmt.Printf("fsck: error reading xattr %q from %q: %v\n", a, path, errno)
-			if errno == syscall.EACCES && !runsAsRoot() {
-				ck.markSkipped(path)
+		_, err := syscallcompat.Lgetxattr(ck.abs(relPath), a)
+		if err != nil {
+			fmt.Printf("fsck: error reading xattr %q from %q: %v\n", a, relPath, err)
+			if err == syscall.EACCES && !runsAsRoot() {
+				ck.markSkipped(relPath)
 			} else {
-				ck.markCorrupt(path)
+				ck.markCorrupt(relPath)
 			}
 		}
 	}
@@ -254,21 +259,45 @@ func fsck(args *argContainer) {
 		os.Exit(exitcodes.Usage)
 	}
 	args.allow_other = false
-	pfs, wipeKeys := initFuseFrontend(args)
-	opts := fs.Options{
-		// Enable go-fuse warnings
-		Logger: log.New(os.Stderr, "go-fuse: ", 0),
+	var err error
+	args.mountpoint, err = ioutil.TempDir("", "gocryptfs.fsck.")
+	if err != nil {
+		tlog.Fatal.Printf("fsck: TmpDir: %v", err)
+		os.Exit(exitcodes.MountPoint)
 	}
-	fs.NewNodeFS(pfs, &opts)
+	pfs, wipeKeys := initFuseFrontend(args)
 	rn := pfs.(*fusefrontend.RootNode)
 	rn.MitigatedCorruptions = make(chan string)
 	ck := fsckObj{
+		mnt:        args.mountpoint,
 		rootNode:   rn,
 		watchDone:  make(chan struct{}),
 		seenInodes: make(map[uint64]struct{}),
 	}
-	ck.dir(&rn.Node)
+	// Mount
+	srv := initGoFuse(pfs, args)
+	// Handle SIGINT & SIGTERM
+	ch := make(chan os.Signal, 1)
+	signal.Notify(ch, os.Interrupt)
+	signal.Notify(ch, syscall.SIGTERM)
+	go func() {
+		<-ch
+		ck.abort = true
+	}()
+	defer func() {
+		err = srv.Unmount()
+		if err != nil {
+			tlog.Warn.Printf("failed to unmount %q: %v", ck.mnt, err)
+		}
+	}()
+	// Recursively check the root dir
+	ck.dir("")
+	// Report results
 	wipeKeys()
+	if ck.abort {
+		tlog.Info.Printf("fsck: aborted")
+		return
+	}
 	if len(ck.corruptList) == 0 && len(ck.skippedList) == 0 {
 		tlog.Info.Printf("fsck summary: no problems found\n")
 		return
@@ -294,8 +323,12 @@ func (s sortableDirEntries) Less(i, j int) bool {
 	return strings.Compare(s[i].Name, s[j].Name) < 0
 }
 
-func inum(f *fusefrontend.File2) uint64 {
-	var a fuse.AttrOut
-	f.Getattr(nil, &a)
-	return a.Ino
+func inum(f *os.File) uint64 {
+	var st syscall.Stat_t
+	err := syscall.Fstat(int(f.Fd()), &st)
+	if err != nil {
+		tlog.Warn.Printf("inum: fstat failed: %v", err)
+		return 0
+	}
+	return st.Ino
 }
diff --git a/mount.go b/mount.go
index 693d0c0..e8fa720 100644
--- a/mount.go
+++ b/mount.go
@@ -221,7 +221,7 @@ func setOpenFileLimit() {
 	}
 }
 
-// initFuseFrontend - initialize gocryptfs/fusefrontend
+// initFuseFrontend - initialize gocryptfs/internal/fusefrontend
 // Calls os.Exit on errors
 func initFuseFrontend(args *argContainer) (rootNode fs.InodeEmbedder, wipeKeys func()) {
 	var err error
@@ -326,6 +326,9 @@ func initFuseFrontend(args *argContainer) (rootNode fs.InodeEmbedder, wipeKeys f
 	return rootNode, func() { cCore.Wipe() }
 }
 
+// initGoFuse calls into go-fuse to mount `rootNode` on `args.mountpoint`.
+// The mountpoint is ready to use when the functions returns.
+// On error, it calls os.Exit and does not return.
 func initGoFuse(rootNode fs.InodeEmbedder, args *argContainer) *fuse.Server {
 	var fuseOpts *fs.Options
 	sec := time.Second
diff --git a/tests/fsck/fsck_test.go b/tests/fsck/fsck_test.go
index f56e21c..3aaba9e 100644
--- a/tests/fsck/fsck_test.go
+++ b/tests/fsck/fsck_test.go
@@ -6,6 +6,7 @@ import (
 	"os/exec"
 	"runtime"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -98,8 +99,8 @@ func TestTerabyteFile(t *testing.T) {
 	pDir := cDir + ".mnt"
 	test_helpers.MountOrFatal(t, cDir, pDir, "-extpass", "echo test")
 	defer test_helpers.UnmountErr(pDir)
-	exabyteFile := pDir + "/exabyteFile"
-	fd, err := os.Create(exabyteFile)
+	veryBigFile := pDir + "/veryBigFile"
+	fd, err := os.Create(veryBigFile)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -119,8 +120,8 @@ func TestTerabyteFile(t *testing.T) {
 	cmd.Stdout = os.Stdout
 	cmd.Start()
 	timer := time.AfterFunc(10*time.Second, func() {
-		cmd.Process.Kill()
-		t.Fatalf("timeout")
+		t.Error("timeout, sending SIGINT")
+		syscall.Kill(cmd.Process.Pid, syscall.SIGINT)
 	})
 	cmd.Wait()
 	timer.Stop()