From: Niels Möller <nisse@lysator.liu.se>
Date: Sat, 13 Mar 2021 15:27:50 +0000 (+0100)
Subject: Ensure ecdsa_sign output is canonically reduced.
X-Git-Tag: nettle_3.7.2_release_20210321~5
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=51f643eee00e2caa65c8a2f5857f49acdf3ef1ce;p=thirdparty%2Fnettle.git

Ensure ecdsa_sign output is canonically reduced.

* ecc-ecdsa-sign.c (ecc_ecdsa_sign): Ensure s output is reduced to
canonical range.

(cherry picked from commit c24b36160dc5303f7541dd9da1429c4046f27398)
---

diff --git a/ChangeLog b/ChangeLog
index 63848f53..fb2d7f66 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2021-03-13  Niels Möller  <nisse@lysator.liu.se>
 
+	* ecc-ecdsa-sign.c (ecc_ecdsa_sign): Ensure s output is reduced to
+	canonical range.
+
 	* ecc-ecdsa-verify.c (ecc_ecdsa_verify): Use ecc_mod_mul_canonical
 	to compute the scalars used for ecc multiplication.
 	* testsuite/ecdsa-verify-test.c (test_main): Add test case that
diff --git a/ecc-ecdsa-sign.c b/ecc-ecdsa-sign.c
index f323196e..4adee1d1 100644
--- a/ecc-ecdsa-sign.c
+++ b/ecc-ecdsa-sign.c
@@ -91,9 +91,8 @@ ecc_ecdsa_sign (const struct ecc_curve *ecc,
 
   ecc_mod_mul (&ecc->q, tp, zp, rp, tp);
   ecc_mod_add (&ecc->q, hp, hp, tp);
-  ecc_mod_mul (&ecc->q, tp, hp, kinv, tp);
+  ecc_mod_mul_canonical (&ecc->q, sp, hp, kinv, tp);
 
-  mpn_copyi (sp, tp, ecc->p.size);
 #undef P
 #undef hp
 #undef kinv