From: nicolas@belouin.fr
Subject: Re: [RFC PATCH 1/2] security, capabilities: create CAP_TRUSTED
Date: Sat, 21 Oct 2017 21:09:32 +0200
Message-ID: <201710211909.v9LJ9Zg8033866__37124.3884125308$1508613169$gmane$org@smtp6.infomaniak.ch>
References: <20171021134558.21195-1-nicolas@belouin.fr> <20171021160302.GA2842@mail.hallyn.com>
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Cc: Jan Kara <jack@suse.com>, "Theodore Ts'o" <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <yuchao0@huawei.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Dave Kleikamp <shaggy@kernel.org>,
        Mark Fasheh <mfasheh@versity.com>,
        Joel Becker <jlbec@evilplan.org>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Phillip Lougher <phillip@squashfs.org.uk>,
        Richard Weinberger <richard@nod.at>,
        Artem Bityutskiy <dedekind1@gmail.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Serge Hallyn <serge@hallyn.com>,
        Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Eric Paris <eparis@parisplace.org>,
        James.Morris@smtp6.infomaniak.ch
To: "Serge E. Hallyn" <serge@hallyn.com>
In-Reply-To: <20171021160302.GA2842@mail.hallyn.com>
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From: Nicolas Belouin <nicolas@belouin.fr>
Message-ID: <99179B10-4EAE-4FAB-9D14-B885156261B3@belouin.fr>


On October 21, 2017 6:03:02 PM GMT+02:00, "Serge E. Hallyn" <serge@hallyn.com> wrote:
>Quoting Nicolas Belouin (nicolas@belouin.fr):
>> with CAP_SYS_ADMIN being bloated, the usefulness of using it to
>> flag a process to be entrusted for e.g reading and writing trusted
>> xattr is near zero.
>> CAP_TRUSTED aims to provide userland with a way to mark a process as
>> entrusted to do specific (not specially admin-centered) actions. It
>> would for example allow a process to red/write the trusted xattrs.
>
>You say "for example".  Are you intending to add more uses?  If so,
>what
>are they?  If not, how about renaming it CAP_TRUSTED_XATTR?
>

I don't see any other use for now, but I don't want it to be too narrow and non usable in a similar context in the future. So I believe the underlying purpose of marking a process as "trusted" (even if for now it only means rw permission on trusted xattr) is more meaningful.

>What all does allowing writes to trusted xattrs give you?  There are
>the overlayfs whiteouts, what else?

Nicolas