linux-kernel - Re: [PATCH 2/2] file capabilities: accomodate >32 bit capabilities

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 10 May 2007 13:01:27 -0700
From:	Andreas Dilger <adilger@...sterfs.com>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Andrew Morton <akpm@...ux-foundation.org>,
	jeffschroeder@...puter.org, Chris Wright <chrisw@...s-sol.org>,
	Karl MacMillan <kmacmillan@...talrootkit.com>,
	KaiGai Kohei <kaigai@...gai.gr.jp>
Subject: Re: [PATCH 2/2] file capabilities: accomodate >32 bit capabilities

On May 08, 2007  16:49 -0500, Serge E. Hallyn wrote:
> Quoting Andreas Dilger (adilger@...sterfs.com):
> > One of the important use cases I can see today is the ability to
> > split the heavily-overloaded e.g. CAP_SYS_ADMIN into much more fine
> > grained attributes.
> 
> Sounds plausible, though it suffers from both making capabilities far
> more cumbersome (i.e. finding the right capability for what you wanted
> to do) and backward compatibility.  Perhaps at that point we should
> introduce security.capabilityv2 xattrs.  A binary can then carry
> security.capability=CAP_SYS_ADMIN=p, and
> security.capabilityv2=cap_may_clone_mntns=p.

Well, the overhead of each EA is non-trivial (16 bytes/EA) for storing
12 bytes worth of data, so it is probably just better to keep extending
the original capability fields as was in the proposal.

> > What we definitely do NOT want to happen is an application that needs
> > priviledged access (e.g. e2fsck, mount) to stop running because the
> > new capabilities _would_ have been granted by the new kernel and are
> > not by the old kernel and STRICTXATTR is used.
> > 
> > To me it would seem that having extra capabilities on an old kernel
> > is relatively harmless if the old kernel doesn't know what they are.
> > It's like having a key to a door that you don't know where it is.
> 
> If we ditch the STRICTXATTR option do the semantics seem sane to you?

Seems reasonable.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/