From e99e8417137a713348d2797ba813bcefe0c3984d Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Fri, 11 Dec 2015 19:54:53 +0100
Subject: Rmdir: handle creating and removing unreadable directories

This patch also splits off Mkdir and Rmdir into its own file.

Fixes issue #8, thanks to @diseq for the bug report.
---
 pathfs_frontend/fs_dir.go | 151 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 151 insertions(+)
 create mode 100644 pathfs_frontend/fs_dir.go

(limited to 'pathfs_frontend/fs_dir.go')

diff --git a/pathfs_frontend/fs_dir.go b/pathfs_frontend/fs_dir.go
new file mode 100644
index 0000000..95257bb
--- /dev/null
+++ b/pathfs_frontend/fs_dir.go
@@ -0,0 +1,151 @@
+package pathfs_frontend
+
+import (
+	"os"
+	"path/filepath"
+	"syscall"
+	"fmt"
+
+	"github.com/hanwen/go-fuse/fuse"
+	"github.com/rfjakob/gocryptfs/cryptfs"
+)
+
+func (fs *FS) Mkdir(relPath string, mode uint32, context *fuse.Context) (code fuse.Status) {
+	if fs.isFiltered(relPath) {
+		return fuse.EPERM
+	}
+	encPath, err := fs.getBackingPath(relPath)
+	if err != nil {
+		return fuse.ToStatus(err)
+	}
+	if !fs.args.DirIV {
+		return fuse.ToStatus(os.Mkdir(encPath, os.FileMode(mode)))
+	}
+
+	// We need write and execute permissions to create gocryptfs.diriv
+	origMode := mode
+	mode = mode | 0300
+
+	// The new directory may take the place of an older one that is still in the cache
+	fs.CryptFS.DirIVCacheEnc.Clear()
+	// Create directory
+	fs.dirIVLock.Lock()
+	defer fs.dirIVLock.Unlock()
+	err = os.Mkdir(encPath, os.FileMode(mode))
+	if err != nil {
+		return fuse.ToStatus(err)
+	}
+	// Create gocryptfs.diriv inside
+	err = cryptfs.WriteDirIV(encPath)
+	if err != nil {
+		// This should not happen
+		cryptfs.Warn.Printf("Mkdir: WriteDirIV failed: %v\n", err)
+		err2 := syscall.Rmdir(encPath)
+		if err2 != nil {
+			cryptfs.Warn.Printf("Mkdir: Rmdir rollback failed: %v\n", err2)
+		}
+		return fuse.ToStatus(err)
+	}
+
+	// Set permissions back to what the user wanted
+	if origMode != mode {
+		err = os.Chmod(encPath, os.FileMode(origMode))
+		if err != nil {
+			cryptfs.Warn.Printf("Mkdir: Chmod failed: %v\n", err)
+		}
+	}
+
+	return fuse.OK
+}
+
+func (fs *FS) Rmdir(name string, context *fuse.Context) (code fuse.Status) {
+	encPath, err := fs.getBackingPath(name)
+	if err != nil {
+		return fuse.ToStatus(err)
+	}
+	if !fs.args.DirIV {
+		return fuse.ToStatus(syscall.Rmdir(encPath))
+	}
+
+	// If the directory is not empty besides gocryptfs.diriv, do not even
+	// attempt the dance around gocryptfs.diriv.
+	fd, err := os.Open(encPath)
+	if perr, ok := err.(*os.PathError); ok && perr.Err == syscall.EACCES {
+		// We need permission to read and modify the directory
+		cryptfs.Debug.Printf("Rmdir: handling EACCESS\n")
+		fi, err2 := os.Stat(encPath)
+		if err2 != nil {
+			cryptfs.Debug.Printf("Rmdir: Stat: %v\n", err2)
+			return fuse.ToStatus(err2)
+		}
+		origMode := fi.Mode()
+		newMode := origMode | 0700
+		err2 = os.Chmod(encPath, newMode)
+		if err2 != nil {
+			cryptfs.Debug.Printf("Rmdir: Chmod failed: %v\n", err2)
+			return fuse.ToStatus(err)
+		}
+		defer func () {
+			if code != fuse.OK {
+				// Undo the chmod if removing the directory failed
+				err3 := os.Chmod(encPath, origMode)
+				if err3 != nil {
+					cryptfs.Warn.Printf("Rmdir: Chmod rollback failed: %v\n", err2)
+				}
+			}
+		}()
+		// Retry open
+		fd, err = os.Open(encPath)
+	}
+	if err != nil {
+		cryptfs.Debug.Printf("Rmdir: Open: %v\n", err)
+		return fuse.ToStatus(err)
+	}
+	list, err := fd.Readdirnames(10)
+	fd.Close()
+	if err != nil {
+		cryptfs.Debug.Printf("Rmdir: Readdirnames: %v\n", err)
+		return fuse.ToStatus(err)
+	}
+	if len(list) > 1 {
+		return fuse.ToStatus(syscall.ENOTEMPTY)
+	} else if len(list) == 0 {
+		cryptfs.Warn.Printf("Rmdir: gocryptfs.diriv missing, allowing deletion\n")
+		return fuse.ToStatus(syscall.Rmdir(encPath))
+	}
+
+	// Move "gocryptfs.diriv" to the parent dir as "gocryptfs.diriv.rmdir.XYZ"
+	dirivPath := filepath.Join(encPath, cryptfs.DIRIV_FILENAME)
+	parentDir := filepath.Dir(encPath)
+	tmpName := fmt.Sprintf("gocryptfs.diriv.rmdir.%d", cryptfs.RandUint64())
+	tmpDirivPath := filepath.Join(parentDir, tmpName)
+	cryptfs.Debug.Printf("Rmdir: Renaming %s to %s\n", cryptfs.DIRIV_FILENAME, tmpDirivPath)
+	// The directory is in an inconsistent state between rename and rmdir. Protect against
+	// concurrent readers.
+	fs.dirIVLock.Lock()
+	defer fs.dirIVLock.Unlock()
+	err = os.Rename(dirivPath, tmpDirivPath)
+	if err != nil {
+		cryptfs.Warn.Printf("Rmdir: Renaming %s to %s failed: %v\n", cryptfs.DIRIV_FILENAME, tmpDirivPath, err)
+		return fuse.ToStatus(err)
+	}
+	// Actual Rmdir
+	err = syscall.Rmdir(encPath)
+	if err != nil {
+		// This can happen if another file in the directory was created in the
+		// meantime, undo the rename
+		err2 := os.Rename(tmpDirivPath, dirivPath)
+		if err2 != nil {
+			cryptfs.Warn.Printf("Rmdir: Rename rollback failed: %v\n", err2)
+		}
+		return fuse.ToStatus(err)
+	}
+	// Delete "gocryptfs.diriv.rmdir.INODENUMBER"
+	err = syscall.Unlink(tmpDirivPath)
+	if err != nil {
+		cryptfs.Warn.Printf("Rmdir: Could not clean up %s: %v\n", tmpName, err)
+	}
+	// The now-deleted directory may have been in the DirIV cache. Clear it.
+	fs.CryptFS.DirIVCacheEnc.Clear()
+	return fuse.OK
+}
-- 
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