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From:   Stephan =?ISO-8859-1?Q?M=FCller?= <smueller@chronox.de>
To:     herbert@gondor.apana.org.au
Cc:     linux-crypto@vger.kernel.org,
        Marcelo Cerri <marcelo.cerri@canonical.com>,
        Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
        ard.biesheuvel@linaro.org, nhorman@redhat.com, simo@redhat.com
Subject: [PATCH v2 0/5] DH: SP800-56A rev 3 compliant validation checks
Date:   Sun, 12 Jul 2020 18:38:49 +0200
Message-ID: <5722559.lOV4Wx5bFT@positron.chronox.de>
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Hi,

This patch set adds the required checks to make all aspects of
(EC)DH compliant with SP800-56A rev 3 assuming that all keys
are ephemeral. The use of static keys adds yet additional
validations which are hard to achieve in the kernel.

SP800-56A rev 3 mandates various checks:

- validation of remote public key defined in section 5.6.2.2.2
  is already implemented in:

  * ECC: crypto_ecdh_shared_secret with the call of
    ecc_is_pubkey_valid_partial

  * FFC: dh_compute_val when the req->src is read and validated with
    dh_is_pubkey_valid

- validation of generated shared secret: The patch set adds the
  shared secret validation as defined by SP800-56A rev 3. For
  ECDH this only implies that the validation of the shared secret
  is moved before the shared secret is returned to the caller.

  For DH, the validation is required to be performed against the prime
  of the domain parameter set.

  This patch adds the MPI library file mpi_sub_ui that is required
  to calculate P - 1 for the DH check. It would be possible, though
  to simply set the LSB of the prime to 0 to obtain P - 1 (since
  P is odd per definition) which implies that mpi_sub_ui would not
  be needed. However, this would require a copy operation from
  the existing prime MPI value into a temporary MPI where the
  modification can be performed. Such copy operation is not available.
  Therefore, the solution with the addition of mpi_sub_ui was chosen.

  NOTE: The function mpi_sub_ui is also added with the patch set
  "[PATCH v5 2/8] lib/mpi: Extend the MPI library" currently sent
  to the linux-crypto mailing list.

- validation of the generated local public key: Patches 4 and 5 of
  this patch set adds the required checks.

Changes to v1:

- fix reference to Gnu MP as outlined by Ard Biesheuvel
- addition of patches 4 and 5

Marcelo Henrique Cerri (1):
  lib/mpi: Add mpi_sub_ui()

Stephan Mueller (4):
  crypto: ECDH - check validity of Z before export
  crypto: DH - check validity of Z before export
  crypto: DH SP800-56A rev 3 local public key validation
  crypto: ECDH SP800-56A rev 3 local public key validation

 crypto/dh.c          | 38 ++++++++++++++++++++++++++++
 crypto/ecc.c         | 42 ++++++++++++++++++++++++++++---
 crypto/ecc.h         | 14 +++++++++++
 include/linux/mpi.h  |  3 +++
 lib/mpi/Makefile     |  1 +
 lib/mpi/mpi-sub-ui.c | 60 ++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 154 insertions(+), 4 deletions(-)
 create mode 100644 lib/mpi/mpi-sub-ui.c

-- 
2.26.2