Quoting Colin Walters (walters@xxxxxxxxxx): > On Wed, Mar 9, 2016, at 01:14 PM, Kees Cook wrote: > > On Mon, Mar 7, 2016 at 9:15 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > > > Hi all- > > > > > > There are several users and distros that are nervous about user > > > namespaces from an attack surface point of view. > > > > > > - RHEL and Arch have userns disabled. > > > > > > - Ubuntu requires CAP_SYS_ADMIN > > > > > > - Kees periodically proposes to upstream some sysctl to control > > > userns creation. > > > > And here's another ring0 escalation flaw, made available to > > unprivileged users because of userns: > > > > https://code.google.com/p/google-security-research/issues/detail?id=758 > > Looks like Andy won't have to eat his hat ;) > > > The change in attack surface is _substantial_. We must have a way to > > globally disable userns. > > No one would object if it was enabled but only accessible to > CAP_SYS_ADMIN though, right? This could be useful for I think that would be terrible. I'd have to expose all of CAP_SYS_ADMIN to allow use of CLONE_NEWUSER. I'd be more interested in a new CAP_NEWUSER capability. Then systems wanting to support unprivileged users doing user namespaces could set a pam module giving certain users that cap in pI, and set it on fI on their container managers. Userspace has to give access to mapped uids through /etc/subuid too, so it's not *so* huge added hurdle. Well that's not quite true - with empty subuid, users can create a userns with no mapped userids which in itself is useful for sandboxing. The biggest problem with a CAP_NEWUSER would be that it's more inherently permanent than a new sysctl. The increase in attack surface is real, but over time I'd like to think that we will have dealt with it and should be able to make CLONE_NEWUSER unprivileged. Because what we have is an implementation issue (not in user namespaces), not a design issue. And I do agree the issue is real. -serge _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
