From fc6fce3bbf3f2b3ea30e1d154cd9511b1f833e3b Mon Sep 17 00:00:00 2001
From: Emman <emman.sun@cargosmart.com>
Date: Fri, 8 Apr 2022 10:50:11 +0800
Subject: [PATCH] Test Issue 52075 - generic impl panic when scalar has too
 many leading zeroes

---
 sm2/p256_test.go | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/sm2/p256_test.go b/sm2/p256_test.go
index 584c456c..1cde393d 100644
--- a/sm2/p256_test.go
+++ b/sm2/p256_test.go
@@ -277,3 +277,17 @@ func TestP256CombinedMult(t *testing.T) {
 		t.Errorf("1×G + (-1)×G = (%d, %d), should be ∞", x, y)
 	}
 }
+
+func TestIssue52075(t *testing.T) {
+	Gx, Gy := P256().Params().Gx, P256().Params().Gy
+	scalar := make([]byte, 33)
+	scalar[32] = 1
+	x, y := P256().ScalarBaseMult(scalar)
+	if x.Cmp(Gx) != 0 || y.Cmp(Gy) != 0 {
+		t.Errorf("unexpected output (%v,%v)", x, y)
+	}
+	x, y = P256().ScalarMult(Gx, Gy, scalar)
+	if x.Cmp(Gx) != 0 || y.Cmp(Gy) != 0 {
+		t.Errorf("unexpected output (%v,%v)", x, y)
+	}
+}