fuse (Was Re: early-gdm redux)

[Thorsten Leemhuis]

On 19.09.2007 09:51, Alexander Larsson wrote:
> On Wed, 2007-09-19 at 09:38 +0200, Thorsten Leemhuis wrote:
>> On 19.09.2007 09:09, Alexander Larsson wrote:
>>> On Tue, 2007-09-18 at 19:41 +0200, Thorsten Leemhuis wrote:
>>>> Thus I'm not even able to read from it:
>>>> $ dd if=/dev/sda3 bs=512K count=1 | strings
>>>> dd: opening `/dev/sda3': Permission denied
>>>> Life sucks, but that's how things are supposed to be in linux/unix land
>>>> as far as I know. But well, for fuse there seem to exist different rules:
>>>> $ mkdir ntfs
>>>> $ /sbin/mount.ntfs-3g /dev/sda3 ntfs/
>>>> $ touch ntfs/foo
>>>> $ ls -l ntfs/foo
>>>> -rwxrwxrwx 1 thl thl 0 18. Sep 19:27 ntfs/foo
>>>> Which brings me to my questions: Can somebody please explain why the
>>>> above it working? Does it mean that if I write my own malicious
>>>> fuse.ext3 userspace driver that I can mount each and every block-device
>>>> on my system and read or modify the files on it (all by using fuse)?
>>>> What if there is a small error in mount.ntfs-3g somewhere -- could it be
>>>> abused to destroy a partition on my system while being a ordinary user?
>>> Thats quite weird. [...]
>> Agreed. But I got the impression that how some users expect it to work.
>>> Is /sbin/mount.ntfs-3g setuid perhaps?
>> Yes:
>> $ ls -l /sbin/mount.ntfs-3g
>> -rwsr-xr-- 1 root fuse 40528 26. Aug 16:50 /sbin/mount.ntfs-3g
> Oh. That seems like a bad idea to me. 

+1

I tried to discuss the issue with spot (the ntfs-3g maintainer) in
#fedora-devel but he was busy and he asked me to file a bug, which I
just did:

https://bugzilla.redhat.com/show_bug.cgi?id=298651

Cu
knurd