crypto: ecc - Handle exceptional points in Shamir multiplication

Shamir multiplication mishandles equal points, opposite points and the
point at infinity. This rejects valid ECDSA signatures and can accept
invalid digest/signature tuples when the public key is G or -G. The
kernel incorrectly rejects 16 valid signatures from Wycheproof.

Handle doubling, cancellation and the point at infinity in precomputation
and accumulation. Add regression tests for P-256 ECDSA and 256/512-bit
EC-RDSA. The valid vectors are Wycheproof P1363 secp256r1/SHA-256 cases
60 and 210 converted to X9.62, two constructed ECDSA signatures for
Q = +/-G with k = 2, and six constructed EC-RDSA signatures for Q = G,
-G and -2G. Also add two invalid P-256 digest/signature tuples for
Q = +/-G that must return -EKEYREJECTED.

Fixes: 0d7a78643f69 ("crypto: ecrdsa - add EC-RDSA (GOST 34.10) algorithm")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
Reviewed-by: Ignat Korchagin <ignat@linux.win>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

0 files changed, 0 insertions, 0 deletions