remove uneccessary error from random scalar generator

Author: jwasinger

tests/fuzzers/bls12381/bls12381_fuzz.go

@@ -36,10 +36,7 @@ import (
 
 func fuzzG1SubgroupChecks(data []byte) int {
 	input := bytes.NewReader(data)
-	cpG1, blG1, err := getG1Points(input)
-	if err != nil {
-		return 0
-	}
+	cpG1, blG1 := getG1Points(input)
 	inSubGroupGnark := cpG1.IsInSubGroup()
 	inSubGroupBLST := blG1.InG1()
 	if inSubGroupGnark != inSubGroupBLST {
@@ -50,10 +47,7 @@ func fuzzG1SubgroupChecks(data []byte) int {
 
 func fuzzG2SubgroupChecks(data []byte) int {
 	input := bytes.NewReader(data)
-	gpG2, blG2, err := getG2Points(input)
-	if err != nil {
-		return 0
-	}
+	gpG2, blG2 := getG2Points(input)
 	inSubGroupGnark := gpG2.IsInSubGroup()
 	inSubGroupBLST := blG2.InG2()
 	if inSubGroupGnark != inSubGroupBLST {
@@ -66,16 +60,10 @@ func fuzzCrossPairing(data []byte) int {
 	input := bytes.NewReader(data)
 
 	// get random G1 points
-	cpG1, blG1, err := getG1Points(input)
-	if err != nil {
-		return 0
-	}
+	cpG1, blG1 := getG1Points(input)
 
 	// get random G2 points
-	cpG2, blG2, err := getG2Points(input)
-	if err != nil {
-		return 0
-	}
+	cpG2, blG2 := getG2Points(input)
 
 	// compute pairing using gnark
 	cResult, err := bls12381.Pair([]bls12381.G1Affine{*cpG1}, []bls12381.G2Affine{*cpG2})
@@ -122,16 +110,10 @@ func fuzzCrossG1Add(data []byte) int {
 	input := bytes.NewReader(data)
 
 	// get random G1 points
-	cp1, bl1, err := getG1Points(input)
-	if err != nil {
-		return 0
-	}
+	cp1, bl1 := getG1Points(input)
 
 	// get random G1 points
-	cp2, bl2, err := getG1Points(input)
-	if err != nil {
-		return 0
-	}
+	cp2, bl2 := getG1Points(input)
 
 	// compute cp = cp1 + cp2
 	_cp1 := new(bls12381.G1Jac).FromAffine(cp1)
@@ -150,16 +132,10 @@ func fuzzCrossG2Add(data []byte) int {
 	input := bytes.NewReader(data)
 
 	// get random G2 points
-	gp1, bl1, err := getG2Points(input)
-	if err != nil {
-		return 0
-	}
+	gp1, bl1 := getG2Points(input)
 
 	// get random G2 points
-	gp2, bl2, err := getG2Points(input)
-	if err != nil {
-		return 0
-	}
+	gp2, bl2 := getG2Points(input)
 
 	// compute cp = cp1 + cp2
 	_gp1 := new(bls12381.G2Jac).FromAffine(gp1)
@@ -183,15 +159,10 @@ func fuzzCrossG1MultiExp(data []byte) int {
 	// n random scalars (max 17)
 	for i := 0; i < 17; i++ {
 		// note that geth/crypto/bls12381 works only with scalars <= 32bytes
-		s, err := randomScalar(input, fr.Modulus())
-		if err != nil {
-			break
-		}
+		s := randomScalar(input, fr.Modulus())
 		// get a random G1 point as basis
-		cp1, _, err := getG1Points(input)
-		if err != nil {
-			break
-		}
+		cp1, _ := getG1Points(input)
+
 		var gnarkScalar = &fr.Element{}
 		gnarkScalar = gnarkScalar.SetBigInt(s)
 		gnarkScalars = append(gnarkScalars, *gnarkScalar)
@@ -210,12 +181,9 @@ func fuzzCrossG1MultiExp(data []byte) int {
 	return 1
 }
 
-func getG1Points(input io.Reader) (*bls12381.G1Affine, *blst.P1Affine, error) {
+func getG1Points(input io.Reader) (*bls12381.G1Affine, *blst.P1Affine) {
 	// sample a random scalar
-	s, err := randomScalar(input, fp.Modulus())
-	if err != nil {
-		return nil, nil, err
-	}
+	s := randomScalar(input, fp.Modulus())
 
 	// compute a random point
 	cp := new(bls12381.G1Affine)
@@ -230,15 +198,12 @@ func getG1Points(input io.Reader) (*bls12381.G1Affine, *blst.P1Affine, error) {
 		panic("bytes(blst.G1) != bytes(geth.G1)")
 	}
 
-	return cp, p1, nil
+	return cp, p1
 }
 
-func getG2Points(input io.Reader) (*bls12381.G2Affine, *blst.P2Affine, error) {
+func getG2Points(input io.Reader) (*bls12381.G2Affine, *blst.P2Affine) {
 	// sample a random scalar
-	s, err := randomScalar(input, fp.Modulus())
-	if err != nil {
-		return nil, nil, err
-	}
+	s := randomScalar(input, fp.Modulus())
 
 	// compute a random point
 	gp := new(bls12381.G2Affine)
@@ -254,16 +219,12 @@ func getG2Points(input io.Reader) (*bls12381.G2Affine, *blst.P2Affine, error) {
 		panic("bytes(blst.G2) != bytes(bls12381.G2)")
 	}
 
-	return gp, p2, nil
+	return gp, p2
 }
 
-func randomScalar(r io.Reader, max *big.Int) (k *big.Int, err error) {
-	for {
-		k, err = rand.Int(r, max)
-		if err != nil || k.Sign() > 0 {
-			return
-		}
-	}
+func randomScalar(r io.Reader, max *big.Int) *big.Int {
+	k, _ := rand.Int(r, max)
+	return k
 }
 
 // multiExpG1 is a naive implementation of G1 multi-exponentiation