Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@xxxxxxxxxxxxx> Tested-by: Marcelo Henrique Cerri <marcelo.cerri@xxxxxxxxxxxxx> On Mon, Jul 20, 2020 at 07:05:45PM +0200, Stephan Müller wrote: > 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 v2: > > - add reference to GnuMP providing the basis for patch 2 and updating > the copyright note in patch 2 > > 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 | 78 ++++++++++++++++++++++++++++++++++++++++++++ > 6 files changed, 172 insertions(+), 4 deletions(-) > create mode 100644 lib/mpi/mpi-sub-ui.c > > -- > 2.26.2 > > > > -- Regards, Marcelo
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