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From 54211caa2e0e5163aefef390daf88a971367a702 Mon Sep 17 00:00:00 2001
From: Glenn Strauss <gstrauss@gluelogic.com>
Date: Tue, 4 Oct 2022 17:09:24 -0400
Subject: [PATCH 6/7] dpp_pkex: EC point mul w/ value < prime
crypto_ec_point_mul() with mbedtls requires point
be multiplied by a multiplicand with value < prime
Signed-off-by: Glenn Strauss <gstrauss@gluelogic.com>
---
src/common/dpp_crypto.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/src/common/dpp_crypto.c
+++ b/src/common/dpp_crypto.c
@@ -1588,7 +1588,9 @@ dpp_pkex_derive_Qr(const struct dpp_curv
Pr = crypto_ec_key_get_public_key(Pr_key);
Qr = crypto_ec_point_init(ec);
hash_bn = crypto_bignum_init_set(hash, curve->hash_len);
- if (!Pr || !Qr || !hash_bn || crypto_ec_point_mul(ec, Pr, hash_bn, Qr))
+ if (!Pr || !Qr || !hash_bn ||
+ crypto_bignum_mod(hash_bn, crypto_ec_get_prime(ec), hash_bn) ||
+ crypto_ec_point_mul(ec, Pr, hash_bn, Qr))
goto fail;
if (crypto_ec_point_is_at_infinity(ec, Qr)) {
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