linux-kernel - Re: [RFC PATCH v13 17/20] ipe: enable support for fs-verity as a trust provider

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]

Message-ID: <a6061c25-1f7d-4954-b5d3-5d21c6d6df82@linux.microsoft.com>
Date: Thu, 29 Feb 2024 11:59:39 -0800
From: Fan Wu <wufan@...ux.microsoft.com>
To: Eric Biggers <ebiggers@...nel.org>
Cc: corbet@....net, zohar@...ux.ibm.com, jmorris@...ei.org, serge@...lyn.com,
 tytso@....edu, axboe@...nel.dk, agk@...hat.com, snitzer@...nel.org,
 eparis@...hat.com, paul@...l-moore.com, linux-doc@...r.kernel.org,
 linux-integrity@...r.kernel.org, linux-security-module@...r.kernel.org,
 linux-fscrypt@...r.kernel.org, linux-block@...r.kernel.org,
 dm-devel@...ts.linux.dev, audit@...r.kernel.org,
 linux-kernel@...r.kernel.org, Deven Bowers <deven.desai@...ux.microsoft.com>
Subject: Re: [RFC PATCH v13 17/20] ipe: enable support for fs-verity as a
 trust provider



On 2/29/2024 11:42 AM, Eric Biggers wrote:
> On Thu, Feb 29, 2024 at 10:59:21AM -0800, Fan Wu wrote:
>>>
>>> So IPE is interested in whether a file has an fsverity builtin signature, but it
>>> doesn't care what the signature is or whether it has been checked.  What is the
>>> point?
>>>
>>> - Eric
>>
>> It does make sure the signature is checked. This hook call can only be
>> triggered after fsverity_verify_signature() succeed. Therefore, for files
>> that are marked with the security blob inode_sec->fs_verity_sign as true,
>> they must successfully pass the fsverity_verify_signature() check.
>>
>> Regarding the other question, the current version does not support defining
>> policies to trust files based on the inner content of their signatures
>> because the current patch set is already too large.
>>
>> We plan to introduce new policy grammars to enable the policy to define
>> which certificate of the signature can be trusted after this version is
>> accepted.
> 
> Ah, I see, you're relying on the fact that fsverity_verify_signature() verifies
> the signature (if present) even if fs.verity.require_signatures hasn't been set.
> That does happen to be its behavior, but this isn't clearly documented since
> there previously wasn't really a use case for the builtin signatures without
> setting fs.verity.require_signatures.  Can you please make sure this behavior is
> documented properly in Documentation/filesystems/fsverity.rst and in function
> comments?  Otherwise I worry that it could get changed and break your code.
> 
> - Eric

Thanks for the suggestion. I will add this info in the next version.
-Fan