From: Sergey Matveev <stargrave@stargrave.org>
Date: Wed, 14 Dec 2016 08:48:24 +0000 (+0300)
Subject: Fix private key value's assertion: it can not be equal to zero, not to the one
X-Git-Tag: 3.0~40
X-Git-Url: http://www.git.cypherpunks.ru/?p=gogost.git;a=commitdiff_plain;h=b7c8ff70c07784ae7d8d854f02c628e88c32a8a2

Fix private key value's assertion: it can not be equal to zero, not to the one
---

diff --git a/src/cypherpunks.ru/gogost/gost3410/2001_test.go b/src/cypherpunks.ru/gogost/gost3410/2001_test.go
index 3c13122..a21c195 100644
--- a/src/cypherpunks.ru/gogost/gost3410/2001_test.go
+++ b/src/cypherpunks.ru/gogost/gost3410/2001_test.go
@@ -161,3 +161,24 @@ func BenchmarkVerify2001(b *testing.B) {
 		pub.VerifyDigest(digest, sign)
 	}
 }
+
+func TestPrvEqualsTo1(t *testing.T) {
+	c, _ := NewCurveFromParams(CurveParamsGostR34102001Test)
+	prv, err := NewPrivateKey(c, Mode2001, []byte{0x01})
+	if err != nil {
+		t.FailNow()
+	}
+	pub, err := prv.PublicKey()
+	if err != nil {
+		t.FailNow()
+	}
+	digest := []byte{0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}
+	sign, err := prv.SignDigest(digest, rand.Reader)
+	if err != nil {
+		t.FailNow()
+	}
+	valid, err := pub.VerifyDigest(digest, sign)
+	if err != nil || !valid {
+		t.FailNow()
+	}
+}
diff --git a/src/cypherpunks.ru/gogost/gost3410/curve.go b/src/cypherpunks.ru/gogost/gost3410/curve.go
index 70f5a66..fb00375 100644
--- a/src/cypherpunks.ru/gogost/gost3410/curve.go
+++ b/src/cypherpunks.ru/gogost/gost3410/curve.go
@@ -116,14 +116,14 @@ func (c *Curve) add(p1x, p1y, p2x, p2y *big.Int) {
 }
 
 func (c *Curve) Exp(degree, xS, yS *big.Int) (*big.Int, *big.Int, error) {
+	if degree.Cmp(zero) == 0 {
+		return nil, nil, errors.New("Bad degree value")
+	}
 	dg := big.NewInt(0).Sub(degree, bigInt1)
 	tx := big.NewInt(0).Set(xS)
 	ty := big.NewInt(0).Set(yS)
 	cx := big.NewInt(0).Set(xS)
 	cy := big.NewInt(0).Set(yS)
-	if dg.Cmp(zero) == 0 {
-		return nil, nil, errors.New("Bad degree value")
-	}
 	for dg.Cmp(zero) != 0 {
 		if dg.Bit(0) == 1 {
 			c.add(tx, ty, cx, cy)