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fusefrontend: ensure directories without W or X perms can be deleted

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This fixed the "Permission denied" bug, but still has the problem that
the directory may be replaced behind our back. Mitigated by the fact
that we skip the workaround when running as root with -allow_other.

https://github.com/rfjakob/gocryptfs/issues/354
This commit is contained in:
Jakob Unterwurzacher 2019-01-20 14:29:28 +01:00
parent fab585ec01
commit 962c523644
1 changed files with 29 additions and 24 deletions
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45
internal/fusefrontend/fs_dir.go
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@ -151,42 +151,47 @@ func (fs *FS) Rmdir(relPath string, context *fuse.Context) (code fuse.Status) {
err = unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR)
return fuse.ToStatus(err)
}
dirfd, err := syscallcompat.Openat(parentDirFd, cName,
syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
if err == syscall.EACCES {
// We need permission to read and modify the directory
tlog.Debug.Printf("Rmdir: handling EACCESS")
// Unless we are running as root, we need read, write and execute permissions
// to handle gocryptfs.diriv.
permWorkaround := false
var origMode uint32
if !fs.args.PreserveOwner {
var st unix.Stat_t
err = syscallcompat.Fstatat(parentDirFd, cName, &st, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
tlog.Debug.Printf("Rmdir: Stat: %v", err)
return fuse.ToStatus(err)
}
if st.Mode&0700 != 0700 {
tlog.Debug.Printf("Rmdir: permWorkaround")
permWorkaround = true
// This cast is needed on Darwin, where st.Mode is uint16.
origMode := uint32(st.Mode)
origMode = uint32(st.Mode)
err = syscallcompat.FchmodatNofollow(parentDirFd, cName, origMode|0700)
if err != nil {
tlog.Debug.Printf("Rmdir: Fchmodat failed: %v", err)
tlog.Debug.Printf("Rmdir: permWorkaround: chmod failed: %v", err)
return fuse.ToStatus(err)
}
// Retry open
dirfd, err = syscallcompat.Openat(parentDirFd, cName,
}
}
dirfd, err := syscallcompat.Openat(parentDirFd, cName,
syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
// Undo the chmod if removing the directory failed
defer func() {
if code != fuse.OK {
err = syscallcompat.FchmodatNofollow(parentDirFd, cName, origMode)
if err != nil {
tlog.Warn.Printf("Rmdir: Chmod rollback failed: %v", err)
}
}
}()
}
if err != nil {
tlog.Debug.Printf("Rmdir: Open: %v", err)
return fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
// Undo the chmod if removing the directory failed. This must run before
// closing dirfd, so defer it after (defer is LIFO).
if permWorkaround {
defer func() {
if code != fuse.OK {
err = unix.Fchmod(dirfd, origMode)
if err != nil {
tlog.Warn.Printf("Rmdir: permWorkaround: rollback failed: %v", err)
}
}
}()
}
retry:
// Check directory contents
children, err := syscallcompat.Getdents(dirfd)