On Wed, Jun 10, 2020 at 08:41:29AM -0700, Casey Schaufler wrote: > > On 6/10/2020 12:59 AM, Andrei Vagin wrote: > > On Tue, Jun 09, 2020 at 06:14:27PM +0200, Christian Brauner wrote: > >> On Tue, Jun 09, 2020 at 09:06:27AM -0700, Andrei Vagin wrote: > >>> On Tue, Jun 09, 2020 at 09:44:22AM +0200, Christian Brauner wrote: > >>>> On Mon, Jun 08, 2020 at 08:42:21PM -0700, Andrei Vagin wrote: > > ... > >>>>> PTRACE_O_SUSPEND_SECCOMP is needed for C/R and it is protected by > >>>>> CAP_SYS_ADMIN too. > >>>> This is currently capable(CAP_SYS_ADMIN) (init_ns capable) why is it > >>>> safe to allow unprivileged users to suspend security policies? That > >>>> sounds like a bad idea. > > ... > >>> I don't suggest to remove or > >>> downgrade this capability check. The patch allows all c/r related > >>> operations if the current has CAP_CHECKPOINT_RESTORE. > >>> > >>> So in this case the check: > >>> if (!capable(CAP_SYS_ADMIN)) > >>> return -EPERM; > >>> > >>> will be converted in: > >>> if (!capable(CAP_SYS_ADMIN) && !capable(CAP_CHECKPOINT_RESTORE)) > >>> return -EPERM; > >> Yeah, I got that but what's the goal here? Isn't it that you want to > >> make it safe to install the criu binary with the CAP_CHECKPOINT_RESTORE > >> fscap set so that unprivileged users can restore their own processes > >> without creating a new user namespace or am I missing something? The > >> use-cases in the cover-letter make it sound like that's what this is > >> leading up to: > >>>>>> * Checkpoint/Restore in an HPC environment in combination with a resource > >>>>>> manager distributing jobs where users are always running as non-root. > >>>>>> There is a desire to provide a way to checkpoint and restore long running > >>>>>> jobs. > >>>>>> * Container migration as non-root > >>>>>> * We have been in contact with JVM developers who are integrating > >>>>>> CRIU into a Java VM to decrease the startup time. These checkpoint/restore > >>>>>> applications are not meant to be running with CAP_SYS_ADMIN. > >> But maybe I'm just misunderstanding crucial bits (likely (TM)). > > I think you understand this right. The goal is to make it possible to > > use C/R functionality for unprivileged processes. > > Y'all keep saying "unprivileged processes" when you mean > "processes with less than root privilege". A process with > CAP_CHECKPOINT_RESTORE *is* a privileged process. It would That was me being imprecise. What I mean is "unprivileged user" not "unprivileged process". It makes me a little uneasy that an unprivileged _user_ can call the criu binary with the CAP_CHECKPOINT_RESTORE fscap set and suspend seccomp of a process (Which is what my original question here was about). Maybe this is paranoia but shouldn't suspending _security_ mechanisms be kept either under CAP_SYS_ADMIN or CAP_MAC_ADMIN? Christian
