linux-kernel - [PATCH v3 0/8] ima: support fs-verity digests and signatures

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Message-Id: <20220126000658.138345-1-zohar@linux.ibm.com>
Date:   Tue, 25 Jan 2022 19:06:50 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Stefan Berger <stefanb@...ux.ibm.com>,
        linux-fscrypt@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/8] ima: support fs-verity digests and signatures

Support for including fs-verity file digests and signatures in the IMA
measurement list as well as verifying the fs-verity file digest based
signatures, all based on IMA policy rules, was discussed from the
beginning, prior to fs-verity being upstreamed[1,2].

Support including fs-verity file digests in the 'd-ng' template field
based on a new policy rule option named 'digest_type=hash|verity'.
Also support verifying fs-verity file digest based signatures based on
policy.

A new template field named 'd-type' as well as a new template named
'ima-ngv2' are defined to differentiate betweeen file hashes and fs-verity
file digests, when file signatures are not included in the IMA measurement
list.

To disambiguate the type of file signature, define IMA_VERITY_SIG xattr
type and a new signature format version, which is a hash of the new
ima_file_id structure.

[1] https://events19.linuxfoundation.org/wp-content/uploads/2017/11/fs-verify_Mike-Halcrow_Eric-Biggers.pdf
[2] Documentation/filesystems/fsverity.rst

Changelog v3:
- Addressed Eric Bigger's comments: included Ack, incremented the
  signature format version, the crypto issues are generic and will be
  addressed by him separately.
- Addressed Vitaly Chikunov's comments: hard coded maximum digest size
  rather than using a flexible array, removed unnecessary assignment, and
  fixed comment to match variable name.
- Defined new "ima_max_digest_size" struct to avoid wrapping the
  "ima_digest_data" struct inside a function local structure or
  having to dynamically allocate it with enough memory for the specific
  hash algo size.

Changelog v2:
- Addressed Eric Bigger's comments: sign the hash of fsverity's digest
  and the digest's metadata, use match_string, use preferred function
  name fsverity_get_digest(), support including unsigned fs-verity's
  digests in the IMA measurement list.
- Remove signatures requirement for including fs-verity's file digests in
  the 'd-ng' field of the measurement list.

Changelog v1:
- Updated both fsverity and IMA documentation.
- Addressed both Eric Bigger's and Lakshmi's comments.

Mimi Zohar (8):
  ima: rename IMA_ACTION_FLAGS to IMA_NONACTION_FLAGS
  ima: define ima_max_digest_data struct without a flexible array
    variable
  fs-verity: define a function to return the integrity protected file
    digest
  ima: define a new template field 'd-type' and a new template
    'ima-ngv2'
  ima: include fsverity's file digests in the IMA measurement list
  ima: define signature version 3
  ima: support fs-verity file digest based version 3 signatures
  fsverity: update the documentation

 Documentation/ABI/testing/ima_policy      | 17 +++++
 Documentation/filesystems/fsverity.rst    | 22 +++---
 Documentation/security/IMA-templates.rst  | 10 ++-
 fs/verity/Kconfig                         |  1 +
 fs/verity/fsverity_private.h              |  7 --
 fs/verity/measure.c                       | 39 +++++++++++
 include/linux/fsverity.h                  | 18 +++++
 security/integrity/digsig.c               |  3 +-
 security/integrity/ima/ima.h              |  2 +-
 security/integrity/ima/ima_api.c          | 29 +++++++-
 security/integrity/ima/ima_appraise.c     | 83 ++++++++++++++++++++++-
 security/integrity/ima/ima_crypto.c       |  2 +-
 security/integrity/ima/ima_init.c         |  9 +--
 security/integrity/ima/ima_main.c         |  2 +-
 security/integrity/ima/ima_policy.c       | 40 ++++++++++-
 security/integrity/ima/ima_template.c     |  3 +
 security/integrity/ima/ima_template_lib.c | 26 ++++++-
 security/integrity/ima/ima_template_lib.h |  2 +
 security/integrity/integrity.h            | 53 +++++++++++++--
 19 files changed, 329 insertions(+), 39 deletions(-)

-- 
2.27.0