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-rw-r--r--crypto/openssl/crypto/ecdsa/ecs_ossl.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/crypto/openssl/crypto/ecdsa/ecs_ossl.c b/crypto/openssl/crypto/ecdsa/ecs_ossl.c
index 551cf5068fa2..1bbf328de54f 100644
--- a/crypto/openssl/crypto/ecdsa/ecs_ossl.c
+++ b/crypto/openssl/crypto/ecdsa/ecs_ossl.c
@@ -144,6 +144,14 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
}
while (BN_is_zero(k));
+ /* We do not want timing information to leak the length of k,
+ * so we compute G*k using an equivalent scalar of fixed
+ * bit-length. */
+
+ if (!BN_add(k, k, order)) goto err;
+ if (BN_num_bits(k) <= BN_num_bits(order))
+ if (!BN_add(k, k, order)) goto err;
+
/* compute r the x-coordinate of generator * k */
if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx))
{