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From: Kees Cook <keescook@chromium.org>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Alasdair Kergon <agk@redhat.com>,
	Mike Snitzer <snitzer@kernel.org>,
	James Morris <jmorris@namei.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	dm-devel@redhat.com, linux-kernel@vger.kernel.org,
	linux-raid@vger.kernel.org, Song Liu <song@kernel.org>,
	Douglas Anderson <dianders@chromium.org>,
	linux-security-module@vger.kernel.org
Subject: Re: [PATCH v3 1/3] dm: Add verity helpers for LoadPin
Date: Mon, 16 May 2022 20:38:12 -0700	[thread overview]
Message-ID: <202205162035.CABA5B2C6@keescook> (raw)
In-Reply-To: <YoKdSrjVf/tHGoa5@google.com>

On Mon, May 16, 2022 at 11:51:54AM -0700, Matthias Kaehlcke wrote:
> 'targets' are different types of DM mappings like 'linear' or 'verity'. A
> device mapper table contains has one or more targets that define the mapping
> of the blocks of the mapped device.
> 
> Having spelled that out I realize that the above check is wrong. It would
> consider a device like this trusted:
> 
> 0 10000000 linear 8:1
> 10000000 10001000 verity <params>
> 
> In the above case only a small part of the DM device would be backed by verity.
> 
> I think we want a table with a single entry that is a verity target.

Ah-ha! Okay, that's what I was worried about. Yes, a device made up
of only trusted verity targets should be the only trusted device. (So,
technically it could be more than 1 verity target, but each would need
to be trusted. Supporting that arrangement, though, may be overkill --
I would expect a 1:1 mapping as you suggest.

-- 
Kees Cook

WARNING: multiple messages have this Message-ID
From: Kees Cook <keescook@chromium.org>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: linux-security-module@vger.kernel.org,
	Douglas Anderson <dianders@chromium.org>,
	Mike Snitzer <snitzer@kernel.org>,
	linux-kernel@vger.kernel.org, James Morris <jmorris@namei.org>,
	linux-raid@vger.kernel.org, Song Liu <song@kernel.org>,
	dm-devel@redhat.com, Alasdair Kergon <agk@redhat.com>,
	"Serge E . Hallyn" <serge@hallyn.com>
Subject: Re: [dm-devel] [PATCH v3 1/3] dm: Add verity helpers for LoadPin
Date: Mon, 16 May 2022 20:38:12 -0700	[thread overview]
Message-ID: <202205162035.CABA5B2C6@keescook> (raw)
In-Reply-To: <YoKdSrjVf/tHGoa5@google.com>

On Mon, May 16, 2022 at 11:51:54AM -0700, Matthias Kaehlcke wrote:
> 'targets' are different types of DM mappings like 'linear' or 'verity'. A
> device mapper table contains has one or more targets that define the mapping
> of the blocks of the mapped device.
> 
> Having spelled that out I realize that the above check is wrong. It would
> consider a device like this trusted:
> 
> 0 10000000 linear 8:1
> 10000000 10001000 verity <params>
> 
> In the above case only a small part of the DM device would be backed by verity.
> 
> I think we want a table with a single entry that is a verity target.

Ah-ha! Okay, that's what I was worried about. Yes, a device made up
of only trusted verity targets should be the only trusted device. (So,
technically it could be more than 1 verity target, but each would need
to be trusted. Supporting that arrangement, though, may be overkill --
I would expect a 1:1 mapping as you suggest.

-- 
Kees Cook

--
dm-devel mailing list
dm-devel@redhat.com
https://listman.redhat.com/mailman/listinfo/dm-devel


  reply	other threads:[~2022-05-17  3:38 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-04 19:54 [PATCH v3 0/3] LoadPin: Enable loading from trusted dm-verity devices Matthias Kaehlcke
2022-05-04 19:54 ` [dm-devel] " Matthias Kaehlcke
2022-05-04 19:54 ` [PATCH v3 1/3] dm: Add verity helpers for LoadPin Matthias Kaehlcke
2022-05-04 19:54   ` [dm-devel] " Matthias Kaehlcke
2022-05-11 20:54   ` Matthias Kaehlcke
2022-05-11 20:54     ` [dm-devel] " Matthias Kaehlcke
2022-05-12 17:19     ` Mike Snitzer
2022-05-12 17:19       ` [dm-devel] " Mike Snitzer
2022-05-12 18:14       ` Matthias Kaehlcke
2022-05-12 18:14         ` [dm-devel] " Matthias Kaehlcke
2022-05-12 20:44       ` Matthias Kaehlcke
2022-05-12 20:44         ` [dm-devel] " Matthias Kaehlcke
2022-05-13 16:29         ` Mike Snitzer
2022-05-13 16:29           ` [dm-devel] " Mike Snitzer
2022-05-13 16:53           ` Matthias Kaehlcke
2022-05-13 16:53             ` Matthias Kaehlcke
2022-05-13 22:15   ` Kees Cook
2022-05-13 22:15     ` [dm-devel] " Kees Cook
2022-05-16 18:51     ` Matthias Kaehlcke
2022-05-16 18:51       ` [dm-devel] " Matthias Kaehlcke
2022-05-17  3:38       ` Kees Cook [this message]
2022-05-17  3:38         ` Kees Cook
2022-05-04 19:54 ` [PATCH v3 2/3] LoadPin: Enable loading from trusted dm-verity devices Matthias Kaehlcke
2022-05-04 19:54   ` [dm-devel] " Matthias Kaehlcke
2022-05-04 22:26   ` kernel test robot
2022-05-04 22:26     ` [dm-devel] " kernel test robot
2022-05-13 16:32   ` Mike Snitzer
2022-05-13 16:32     ` [dm-devel] " Mike Snitzer
2022-05-13 17:01     ` Matthias Kaehlcke
2022-05-13 17:01       ` [dm-devel] " Matthias Kaehlcke
2022-05-13 18:26     ` Kees Cook
2022-05-13 18:26       ` [dm-devel] " Kees Cook
2022-05-13 22:36   ` Kees Cook
2022-05-13 22:36     ` [dm-devel] " Kees Cook
2022-05-16 18:17     ` Matthias Kaehlcke
2022-05-16 18:17       ` [dm-devel] " Matthias Kaehlcke
2022-05-17  3:44       ` Kees Cook
2022-05-17  3:44         ` [dm-devel] " Kees Cook
2022-05-17 19:28         ` Matthias Kaehlcke
2022-05-17 19:28           ` [dm-devel] " Matthias Kaehlcke
2022-05-04 19:54 ` [PATCH v3 3/3] dm: verity-loadpin: Use CONFIG_SECURITY_LOADPIN_VERITY for conditional compilation Matthias Kaehlcke
2022-05-04 19:54   ` [dm-devel] " Matthias Kaehlcke

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