From mboxrd@z Thu Jan 1 00:00:00 1970 From: serge@hallyn.com (Serge E. Hallyn) Date: Fri, 23 Jun 2017 11:00:26 -0500 Subject: [PATCH 0/3] Enable namespaced file capabilities In-Reply-To: References: <1498157989-11814-1-git-send-email-stefanb@linux.vnet.ibm.com> Message-ID: <20170623160026.GA18257@mail.hallyn.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org Quoting Amir Goldstein (amir73il at gmail.com): > On Thu, Jun 22, 2017 at 9:59 PM, Stefan Berger > wrote: > > This series of patches primary goal is to enable file capabilities > > in user namespaces without affecting the file capabilities that are > > effective on the host. This is to prevent that any unprivileged user > > on the host maps his own uid to root in a private namespace, writes > > the xattr, and executes the file with privilege on the host. > > > > We achieve this goal by writing extended attributes with a different > > name when a user namespace is used. If for example the root user > > in a user namespace writes the security.capability xattr, the name > > of the xattr that is actually written is encoded as > > security.capability at uid=1000 for root mapped to uid 1000 on the host. > > When listing the xattrs on the host, the existing security.capability > > as well as the security.capability at uid=1000 will be shown. Inside the > > namespace only 'security.capability', with the value of > > security.capability at uid=1000, is visible. > > > > Am I the only one who thinks that suffix is perhaps not the best grammar > to use for this namespace? You're the only one to have mentioned it so far. > xattrs are clearly namespaced by prefix, so it seems right to me to keep > it that way - define a new special xattr namespace "ns" and only if that > prefix exists, the @uid suffix will be parsed. > This could be either ns.security.capability at uid=1000 or > ns at uid=1000.security.capability. The latter seems more correct to me, > because then we will be able to namespace any xattr without having to > protect from "unprivileged xattr injection", i.e.: > setfattr -n "user.whatever.foo at uid=0" I like it for simplifying the parser code. One concern I have is that, since ns.* is currently not gated, one could write ns.* on an older kernel and then exploit it on a newer one. -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html