From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Subject: Re: [RFC PATCH v3 07/18] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl Date: Mon, 18 Mar 2019 16:08:31 -0700 Message-ID: <20190318230830.GA40545@gmail.com> References: <20190220065249.32099-1-ebiggers@kernel.org> <20190221054938.GA12467@sol.localdomain> <2024630.T9XyBPH5Ub@blindfold> <20190221184203.GB140206@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1h61N2-0004bo-Bm for linux-f2fs-devel@lists.sourceforge.net; Mon, 18 Mar 2019 23:08:40 +0000 Received: from mail.kernel.org ([198.145.29.99]) by sfi-mx-1.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) id 1h61N1-006uQe-0B for linux-f2fs-devel@lists.sourceforge.net; Mon, 18 Mar 2019 23:08:40 +0000 Content-Disposition: inline In-Reply-To: <20190221184203.GB140206@gmail.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Richard Weinberger Cc: linux-ext4@vger.kernel.org, "open list:ABI/API" , linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, keyrings@vger.kernel.org, linux-mtd@lists.infradead.org, linux-crypto@vger.kernel.org, linux-fsdevel , Satya Tangirala , Paul Crowley Hi Richard, On Thu, Feb 21, 2019 at 10:42:03AM -0800, Eric Biggers wrote: > On Thu, Feb 21, 2019 at 10:33:12AM +0100, Richard Weinberger wrote: > > Eric, > > > > Am Donnerstag, 21. Februar 2019, 06:49:39 CET schrieb Eric Biggers: > > > Hi Richard, > > > > > > On Thu, Feb 21, 2019 at 12:52:38AM +0100, Richard Weinberger wrote: > > > > On Wed, Feb 20, 2019 at 7:55 AM Eric Biggers wrote: > > > > > +#define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE \ > > > > > + (CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id)) > > > > > + > > > > > +#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_DESCRIPTOR_SIZE + 1) > > > > > + > > > > > +static void format_fs_keyring_description( > > > > > + char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE], > > > > > + const struct super_block *sb) > > > > > +{ > > > > > + sprintf(description, "fscrypt-%s", sb->s_id); > > > > > +} > > > > > > > > I fear ->s_id is not the right thing. > > > > For filesystems such as ext4 ->s_id is the name of the backing block device, > > > > so it is per filesysem instance unique. > > > > But this is not guaranteed. For UBIFS ->s_id is just "ubifs", always. > > > > So the names will clash. > > > > > > > > > > What name do you suggest using for UBIFS filesystems? The keyring name could be > > > set by the filesystem via a fscrypt_operations callback if needed. > > > > IMHO the BDI name should be used. I tried using sb->s_bdi->name, but it's still "ubifs" for all UBIFS filesystems. Perhaps there's a way you can make ->s_id for UBIFS unique? There are already existing places that log ->s_id, so perhaps you should do it anyway regardless of this patchset? > > > > > Note that the keyring name isn't particularly important, since the ioctls will > > > work regardless. But we might as well choose something logical, since the > > > keyring name will still show up in /proc/keys. > > > > I'm not done with reviewing your patches, but will it be possible to use keyctl? > > For the a unique name is helpful. :) > > > > Not for adding keys, removing keys, or getting a key's status -- those are what > the ioctls are for. > > See e.g. the discussion in patch 7 ("fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY > ioctl") for why the keyrings syscalls are a poor fit for fscrypt. > Anyway, perhaps I should reconsider whether fscrypt should even use the keyrings subsystem at all, even just "internally", as its quirks still leak out a bit. I'd prefer a nice clean API without any quirks like having to name the keyrings and assign SELinux labels to the keys just to make the keyrings subsystem happy. - Eric