On Sat, Jul 03, 2021 at 12:59:28PM +0200, John Wood wrote:
Hi,
On Fri, Jul 02, 2021 at 05:08:09PM +0000, Alexander Lobakin wrote:
On the other hand, it leaves a potentional window for attackers to perform brute force from xattr-incapable filesystems. So at the end of the day I think that the current implementation (a strong rejection of such filesystems) is way more secure than having a fallback I proposed.
I've been thinking more about this: that the Brute LSM depends on xattr support and I don't like this part. I want that brute force attacks can be detected and mitigated on every system (with minimal dependencies). So, now I am working in a solution without this drawback. I have some ideas but I need to work on it.
I have been coding and testing a bit my ideas but:
Trying to track the applications faults info using kernel memory ends up in an easy to abuse system (denied of service due to large amount of memory in use) :(
So, I continue with the v8 idea: xattr to track application crashes info.
I'm planning to make a patch which will eliminate such weird rootfs type selection and just always use more feature-rich tmpfs if it's compiled in. So, as an alternative, you could add it to your series as a preparatory change and just add a Kconfig dependency on CONFIG_TMPFS && CONFIG_TMPFS_XATTR to CONFIG_SECURITY_FORK_BRUTE without messing with any fallbacks at all. What do you think?
Great. But I hope this patch will not be necessary for Brute LSM :)
My words are no longer valid ;)
Thanks, John Wood