7 files changed, 80 insertions, 5 deletions
diff --git a/Documentation/MANPAGE.md b/Documentation/MANPAGE.md
index e20b786..1c7e7b9 100644
--- a/Documentation/MANPAGE.md
+++ b/Documentation/MANPAGE.md
@@ -19,6 +19,9 @@ SYNOPSIS
 #### Change password
 `gocryptfs -passwd [OPTIONS] CIPHERDIR`
 
+#### Check consistency
+`gocryptfs -fsck [OPTIONS] CIPHERDIR`
+
 DESCRIPTION
 ===========
 
@@ -96,6 +99,10 @@ that uses built-in Go crypto.
 
 Setting this option forces the filesystem to read-only and noexec.
 
+#### -fsck
+Check CIPHERDIR for consistency. If corruption is found, the
+exit code is 26.
+
 #### -fsname string
 Override the filesystem name (first column in df -T). Can also be
 passed as "-o fsname=" and is equivalent to libfuse's option of the
@@ -351,6 +358,7 @@ EXIT CODES
 22: password is empty (on "-init")  
 23: could not read gocryptfs.conf  
 24: could not write gocryptfs.conf (on "-init" or "-password")  
+26: fsck found errors  
 other: please check the error message
 
 SEE ALSO
diff --git a/README.md b/README.md
index 5b53061..ec8a8b6 100644
--- a/README.md
+++ b/README.md
@@ -158,6 +158,8 @@ vNEXT, in progress
   ([#218](https://github.com/rfjakob/gocryptfs/issues/218))
 * Support extended attributes (xattr) in forward mode
   ([#217](https://github.com/rfjakob/gocryptfs/issues/217))
+* Add `-fsck` function
+  ([#191](https://github.com/rfjakob/gocryptfs/issues/191))
 
 v1.4.4, 2018-03-18
 * Overwrite secrets in memory with zeros as soon as possible
diff --git a/fsck.go b/fsck.go
index 9eff72e..d1dc7e5 100644
--- a/fsck.go
+++ b/fsck.go
@@ -6,6 +6,7 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
+	"sync"
 	"syscall"
 
 	"github.com/hanwen/go-fuse/fuse"
@@ -19,17 +20,34 @@ type fsckObj struct {
 	fs *fusefrontend.FS
 	// List of corrupt files
 	corruptList []string
+	// Protects corruptList
+	corruptListLock sync.Mutex
 }
 
 func (ck *fsckObj) markCorrupt(path string) {
+	ck.corruptListLock.Lock()
 	ck.corruptList = append(ck.corruptList, path)
+	ck.corruptListLock.Unlock()
 }
 
 // Recursively check dir for corruption
 func (ck *fsckObj) dir(path string) {
 	//fmt.Printf("ck.dir %q\n", path)
 	ck.xattrs(path)
+	done := make(chan struct{})
+	go func() {
+		for {
+			select {
+			case item := <-ck.fs.CorruptItems:
+				fmt.Printf("fsck: corrupt entry in dir %q: %q\n", path, item)
+				ck.markCorrupt(filepath.Join(path, item))
+			case <-done:
+				return
+			}
+		}
+	}()
 	entries, status := ck.fs.OpenDir(path, nil)
+	done <- struct{}{}
 	if !status.Ok() {
 		ck.markCorrupt(path)
 		fmt.Printf("fsck: error opening dir %q: %v\n", path, status)
@@ -80,6 +98,19 @@ func (ck *fsckObj) file(path string) {
 	defer f.Release()
 	buf := make([]byte, fuse.MAX_KERNEL_WRITE)
 	var off int64
+	done := make(chan struct{})
+	go func() {
+		for {
+			select {
+			case item := <-ck.fs.CorruptItems:
+				fmt.Printf("fsck: corrupt file %q (inode %s)\n", path, item)
+				ck.markCorrupt(path)
+			case <-done:
+				return
+			}
+		}
+	}()
+	defer func() { done <- struct{}{} }()
 	for {
 		result, status := f.Read(buf, off)
 		if !status.Ok() {
@@ -97,7 +128,20 @@ func (ck *fsckObj) file(path string) {
 
 // Check xattrs on file/dir at path
 func (ck *fsckObj) xattrs(path string) {
+	done := make(chan struct{})
+	go func() {
+		for {
+			select {
+			case item := <-ck.fs.CorruptItems:
+				fmt.Printf("fsck: corrupt xattr name on file %q: %q\n", path, item)
+				ck.markCorrupt(path + " xattr:" + item)
+			case <-done:
+				return
+			}
+		}
+	}()
 	attrs, status := ck.fs.ListXAttr(path, nil)
+	done <- struct{}{}
 	if !status.Ok() {
 		fmt.Printf("fsck: error listing xattrs on %q: %v\n", path, status)
 		ck.markCorrupt(path)
@@ -120,19 +164,17 @@ func fsck(args *argContainer) {
 	args.allow_other = false
 	pfs, wipeKeys := initFuseFrontend(args)
 	fs := pfs.(*fusefrontend.FS)
+	fs.CorruptItems = make(chan string)
 	ck := fsckObj{
 		fs: fs,
 	}
 	ck.dir("")
 	wipeKeys()
 	if len(ck.corruptList) == 0 {
-		fmt.Printf("fsck summary: no problems found")
+		fmt.Printf("fsck summary: no problems found\n")
 		return
 	}
-	fmt.Printf("fsck summary: found %d corrupt files:\n", len(ck.corruptList))
-	for _, path := range ck.corruptList {
-		fmt.Printf("  %q\n", path)
-	}
+	fmt.Printf("fsck summary: %d corrupt files\n", len(ck.corruptList))
 	os.Exit(exitcodes.FsckErrors)
 }
 
diff --git a/internal/fusefrontend/file.go b/internal/fusefrontend/file.go
index af13170..72319e9 100644
--- a/internal/fusefrontend/file.go
+++ b/internal/fusefrontend/file.go
@@ -4,6 +4,7 @@ package fusefrontend
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"log"
 	"os"
@@ -99,6 +100,7 @@ func (f *file) readFileID() ([]byte, error) {
 		if err == io.EOF && n != 0 {
 			tlog.Warn.Printf("readFileID %d: incomplete file, got %d instead of %d bytes",
 				f.qIno.Ino, n, readLen)
+			f.fs.reportCorruptItem(fmt.Sprint(f.qIno.Ino))
 		}
 		return nil, err
 	}
diff --git a/internal/fusefrontend/fs.go b/internal/fusefrontend/fs.go
index 5f84541..8a3935f 100644
--- a/internal/fusefrontend/fs.go
+++ b/internal/fusefrontend/fs.go
@@ -38,6 +38,11 @@ type FS struct {
 	// This lock is used by openWriteOnlyFile() to block concurrent opens while
 	// it relaxes the permissions on a file.
 	openWriteOnlyLock sync.RWMutex
+	// CorruptItems is filled with file or xattr names that have been
+	// skipped (ignored) because they were corrupt. This is used by fsck
+	// to inform the user.
+	// Use the reportCorruptItem() function to push an item.
+	CorruptItems chan string
 }
 
 var _ pathfs.FileSystem = &FS{} // Verify that interface is implemented.
@@ -601,3 +606,16 @@ func (fs *FS) Access(path string, mode uint32, context *fuse.Context) (code fuse
 	}
 	return fuse.ToStatus(syscall.Access(cPath, mode))
 }
+
+func (fs *FS) reportCorruptItem(item string) {
+	if fs.CorruptItems == nil {
+		return
+	}
+	select {
+	case fs.CorruptItems <- item:
+	case <-time.After(1 * time.Second):
+		tlog.Warn.Printf("BUG: reportCorruptItem: timeout")
+		//debug.PrintStack()
+		return
+	}
+}
diff --git a/internal/fusefrontend/fs_dir.go b/internal/fusefrontend/fs_dir.go
index e13afed..089429e 100644
--- a/internal/fusefrontend/fs_dir.go
+++ b/internal/fusefrontend/fs_dir.go
@@ -326,6 +326,7 @@ func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, f
 			if err != nil {
 				tlog.Warn.Printf("OpenDir %q: invalid entry %q: Could not read .name: %v",
 					cDirName, cName, err)
+				fs.reportCorruptItem(cName)
 				errorCount++
 				continue
 			}
@@ -338,6 +339,7 @@ func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, f
 		if err != nil {
 			tlog.Warn.Printf("OpenDir %q: invalid entry %q: %v",
 				cDirName, cName, err)
+			fs.reportCorruptItem(cName)
 			if runtime.GOOS == "darwin" && cName == dsStoreName {
 				// MacOS creates lots of these files. Log the warning but don't
 				// increment errorCount - does not warrant returning EIO.
diff --git a/internal/fusefrontend/xattr.go b/internal/fusefrontend/xattr.go
index 1d628b7..faaebd4 100644
--- a/internal/fusefrontend/xattr.go
+++ b/internal/fusefrontend/xattr.go
@@ -115,6 +115,7 @@ func (fs *FS) ListXAttr(path string, context *fuse.Context) ([]string, fuse.Stat
 		name, err := fs.decryptXattrName(curName)
 		if err != nil {
 			tlog.Warn.Printf("ListXAttr: invalid xattr name %q: %v", curName, err)
+			fs.reportCorruptItem(curName)
 			continue
 		}
 		names = append(names, name)