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 writing setuid binaries that expose some of the features, but e.g. not CAP_NET_ADMIN. Andy's suggestion of having this be a per-namespace setting makes sense to me. Currently some container tools that do use userns are by default denying it to be recursive (Sandstorm.io and Docker 1.10 at least) by using a seccomp filter on clone(). If we had this setting that filter wouldn't be necessary, and would solve the issue that seccomp filters aren't robust against the kernel adding new API, e.g. a new CLONE_NEWUSER_NONEWPRIVS which might enable chroot() but not CAP_NET_ADMIN. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
