From: Eric Biggers <ebiggers@kernel.org>
To: Fan Wu <wufan@linux.microsoft.com>
Cc: corbet@lwn.net, zohar@linux.ibm.com, jmorris@namei.org,
serge@hallyn.com, tytso@mit.edu, axboe@kernel.dk, agk@redhat.com,
snitzer@kernel.org, eparis@redhat.com, paul@paul-moore.com,
linux-doc@vger.kernel.org, linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org, fsverity@lists.linux.dev,
linux-block@vger.kernel.org, dm-devel@lists.linux.dev,
audit@vger.kernel.org, linux-kernel@vger.kernel.org,
Deven Bowers <deven.desai@linux.microsoft.com>
Subject: Re: [PATCH v16 16/20] fsverity: consume fsverity built-in signatures via LSM hook
Date: Tue, 2 Apr 2024 22:02:51 -0700 [thread overview]
Message-ID: <20240403050251.GJ2576@sol.localdomain> (raw)
In-Reply-To: <1711657047-10526-17-git-send-email-wufan@linux.microsoft.com>
On Thu, Mar 28, 2024 at 01:17:23PM -0700, Fan Wu wrote:
> fsverity: consume fsverity built-in signatures via LSM hook
Nothing is being "consumed" in this patch. I think you might mean something
like "expose verified fsverity built-in signatures to LSMs".
> It enables a policy enforcement layer within LSMs for fsverity, offering
> granular control over the usage of authenticity claims. For instance, a policy
> could be established to permit the execution of all files with built-in
> fsverity signatures while restricting kernel module loading to specified
> hashes.
No, this patch does not enable "restricting kernel module loading to specified
hashes." That can be done without this patch.
> The introduction of a security_inode_setintegrity() hook call within
> fsverity's workflow ensures that the verified built-in signature of a file
> is stored in the inode's LSM blobs.
No, it doesn't. As I said on v15, this is not what IPE actually uses it for.
Also, even if IPE did cache the built-in signature in i_security, the mere fact
that it's cached would say nothing about what it's actually used for.
> diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
> index 13e4b18e5dbb..e13cf10211c8 100644
> --- a/Documentation/filesystems/fsverity.rst
> +++ b/Documentation/filesystems/fsverity.rst
> @@ -86,6 +86,19 @@ authenticating fs-verity file hashes include:
> signature in their "security.ima" extended attribute, as controlled
> by the IMA policy. For more information, see the IMA documentation.
>
> +- Integrity Policy Enforcement (IPE). IPE supports enforcing access
> + control decisions based on immutable security properties of files,
> + including those protected by fs-verity's built-in signatures.
> + "IPE policy" specifically allows for the authorization of fs-verity
> + files using properties such as ``fsverity_digest`` for identifying
> + files by their verity digest, and ``fsverity_signature`` to validate
> + files signed with fs-verity's built-in signature mechanism.
Maybe leave out the "such as" above, since fsverity_digest and
fsverity_signature are all the IPE properties related to fs-verity.
> + This integration enhances security by ensuring the integrity and
> + authenticity of files on a per-file basis, leveraging fs-verity's
> + robust protection capabilities in conjunction with IPE's policy-driven
> + access control.
This reads a bit like a marketing blurb and feels a bit out of place, especially
when it comes right after the paragraph about IMA which didn't include a similar
sentence even though the exact same sentence would apply to IMA too. Maybe just
leave this sentence out.
> @@ -457,7 +470,10 @@ Enabling this option adds the following:
> On success, the ioctl persists the signature alongside the Merkle
> tree. Then, any time the file is opened, the kernel verifies the
> file's actual digest against this signature, using the certificates
> - in the ".fs-verity" keyring.
> + in the ".fs-verity" keyring. This verification happens as long as the
> + file's signature exists, regardless of the state of the sysctl variable
> + "fs.verity.require_signatures" described in the next item. The IPE LSM
> + relies on this behavior to save verified signatures into LSM blobs.
No, IPE doesn't do that.
- Eric
next prev parent reply other threads:[~2024-04-03 5:02 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-28 20:17 [PATCH v16 00/20] Integrity Policy Enforcement LSM (IPE) Fan Wu
2024-03-28 20:17 ` [PATCH v16 01/20] security: add ipe lsm Fan Wu
2024-03-28 20:45 ` Jarkko Sakkinen
2024-03-28 22:11 ` Randy Dunlap
2024-03-30 11:11 ` Jarkko Sakkinen
2024-03-28 20:17 ` [PATCH v16 02/20] ipe: add policy parser Fan Wu
2024-03-28 20:46 ` Jarkko Sakkinen
2024-03-28 20:47 ` Jarkko Sakkinen
2024-03-28 20:17 ` [PATCH v16 03/20] ipe: add evaluation loop Fan Wu
2024-03-28 20:49 ` Jarkko Sakkinen
2024-03-28 20:17 ` [PATCH v16 04/20] ipe: add LSM hooks on execution and kernel read Fan Wu
2024-03-28 20:17 ` [PATCH v16 05/20] initramfs|security: Add a security hook to do_populate_rootfs() Fan Wu
2024-03-28 20:17 ` [PATCH v16 06/20] ipe: introduce 'boot_verified' as a trust provider Fan Wu
2024-03-28 20:17 ` [PATCH v16 07/20] security: add new securityfs delete function Fan Wu
2024-03-28 20:17 ` [PATCH v16 08/20] ipe: add userspace interface Fan Wu
2024-03-28 20:17 ` [PATCH v16 09/20] uapi|audit|ipe: add ipe auditing support Fan Wu
2024-03-28 20:17 ` [PATCH v16 10/20] ipe: add permissive toggle Fan Wu
2024-03-28 20:17 ` [PATCH v16 11/20] block|security: add LSM blob to block_device Fan Wu
2024-03-30 11:26 ` kernel test robot
2024-04-02 1:26 ` Paul Moore
2024-03-28 20:17 ` [PATCH v16 12/20] dm: add finalize hook to target_type Fan Wu
2024-03-28 20:17 ` [PATCH v16 13/20] dm verity: consume root hash digest and signature data via LSM hook Fan Wu
2024-04-02 1:26 ` Paul Moore
2024-03-28 20:17 ` [PATCH v16 14/20] ipe: add support for dm-verity as a trust provider Fan Wu
2024-04-02 1:26 ` Paul Moore
2024-03-28 20:17 ` [PATCH v16 15/20] security: add security_inode_setintegrity() hook Fan Wu
2024-04-02 1:26 ` Paul Moore
2024-03-28 20:17 ` [PATCH v16 16/20] fsverity: consume fsverity built-in signatures via LSM hook Fan Wu
2024-04-03 5:02 ` Eric Biggers [this message]
2024-03-28 20:17 ` [PATCH v16 17/20] ipe: enable support for fs-verity as a trust provider Fan Wu
2024-04-03 5:10 ` Eric Biggers
2024-03-28 20:17 ` [PATCH v16 18/20] scripts: add boot policy generation program Fan Wu
2024-03-28 20:17 ` [PATCH v16 19/20] ipe: kunit test for parser Fan Wu
2024-03-28 20:17 ` [PATCH v16 20/20] documentation: add ipe documentation Fan Wu
2024-03-28 20:36 ` [PATCH v16 00/20] Integrity Policy Enforcement LSM (IPE) Jarkko Sakkinen
2024-03-28 20:38 ` Jarkko Sakkinen
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