core/vm, crypto/bn256: switch over to cloudflare library (#16203)

* core/vm, crypto/bn256: switch over to cloudflare library

* crypto/bn256: unmarshal constraint + start pure go impl

* crypto/bn256: combo cloudflare and google lib

* travis: drop 386 test job

core/vm/contracts.go

@@ -251,41 +251,22 @@ func (c *bigModExp) Run(input []byte) ([]byte, error) {
 	return common.LeftPadBytes(base.Exp(base, exp, mod).Bytes(), int(modLen)), nil
 }
 
-var (
-	// errNotOnCurve is returned if a point being unmarshalled as a bn256 elliptic
-	// curve point is not on the curve.
-	errNotOnCurve = errors.New("point not on elliptic curve")
-
-	// errInvalidCurvePoint is returned if a point being unmarshalled as a bn256
-	// elliptic curve point is invalid.
-	errInvalidCurvePoint = errors.New("invalid elliptic curve point")
-)
-
 // newCurvePoint unmarshals a binary blob into a bn256 elliptic curve point,
 // returning it, or an error if the point is invalid.
 func newCurvePoint(blob []byte) (*bn256.G1, error) {
-	p, onCurve := new(bn256.G1).Unmarshal(blob)
-	if !onCurve {
-		return nil, errNotOnCurve
-	}
-	gx, gy, _, _ := p.CurvePoints()
-	if gx.Cmp(bn256.P) >= 0 || gy.Cmp(bn256.P) >= 0 {
-		return nil, errInvalidCurvePoint
+	p := new(bn256.G1)
+	if _, err := p.Unmarshal(blob); err != nil {
+		return nil, err
 	}
 	return p, nil
 }
 
 // newTwistPoint unmarshals a binary blob into a bn256 elliptic curve point,
 // returning it, or an error if the point is invalid.
 func newTwistPoint(blob []byte) (*bn256.G2, error) {
-	p, onCurve := new(bn256.G2).Unmarshal(blob)
-	if !onCurve {
-		return nil, errNotOnCurve
-	}
-	x2, y2, _, _ := p.CurvePoints()
-	if x2.Real().Cmp(bn256.P) >= 0 || x2.Imag().Cmp(bn256.P) >= 0 ||
-		y2.Real().Cmp(bn256.P) >= 0 || y2.Imag().Cmp(bn256.P) >= 0 {
-		return nil, errInvalidCurvePoint
+	p := new(bn256.G2)
+	if _, err := p.Unmarshal(blob); err != nil {
+		return nil, err
 	}
 	return p, nil
 }

crypto/bn256/bn256_amd64.go

@@ -0,0 +1,63 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// +build amd64,!appengine,!gccgo
+
+// Package bn256 implements the Optimal Ate pairing over a 256-bit Barreto-Naehrig curve.
+package bn256
+
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/crypto/bn256/cloudflare"
+)
+
+// G1 is an abstract cyclic group. The zero value is suitable for use as the
+// output of an operation, but cannot be used as an input.
+type G1 struct {
+	bn256.G1
+}
+
+// Add sets e to a+b and then returns e.
+func (e *G1) Add(a, b *G1) *G1 {
+	e.G1.Add(&a.G1, &b.G1)
+	return e
+}
+
+// ScalarMult sets e to a*k and then returns e.
+func (e *G1) ScalarMult(a *G1, k *big.Int) *G1 {
+	e.G1.ScalarMult(&a.G1, k)
+	return e
+}
+
+// G2 is an abstract cyclic group. The zero value is suitable for use as the
+// output of an operation, but cannot be used as an input.
+type G2 struct {
+	bn256.G2
+}
+
+// PairingCheck calculates the Optimal Ate pairing for a set of points.
+func PairingCheck(a []*G1, b []*G2) bool {
+	as := make([]*bn256.G1, len(a))
+	for i, p := range a {
+		as[i] = &p.G1
+	}
+	bs := make([]*bn256.G2, len(b))
+	for i, p := range b {
+		bs[i] = &p.G2
+	}
+	return bn256.PairingCheck(as, bs)
+}

crypto/bn256/bn256_other.go

@@ -0,0 +1,63 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// +build !amd64 appengine gccgo
+
+// Package bn256 implements the Optimal Ate pairing over a 256-bit Barreto-Naehrig curve.
+package bn256
+
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/crypto/bn256/google"
+)
+
+// G1 is an abstract cyclic group. The zero value is suitable for use as the
+// output of an operation, but cannot be used as an input.
+type G1 struct {
+	bn256.G1
+}
+
+// Add sets e to a+b and then returns e.
+func (e *G1) Add(a, b *G1) *G1 {
+	e.G1.Add(&a.G1, &b.G1)
+	return e
+}
+
+// ScalarMult sets e to a*k and then returns e.
+func (e *G1) ScalarMult(a *G1, k *big.Int) *G1 {
+	e.G1.ScalarMult(&a.G1, k)
+	return e
+}
+
+// G2 is an abstract cyclic group. The zero value is suitable for use as the
+// output of an operation, but cannot be used as an input.
+type G2 struct {
+	bn256.G2
+}
+
+// PairingCheck calculates the Optimal Ate pairing for a set of points.
+func PairingCheck(a []*G1, b []*G2) bool {
+	as := make([]*bn256.G1, len(a))
+	for i, p := range a {
+		as[i] = &p.G1
+	}
+	bs := make([]*bn256.G2, len(b))
+	for i, p := range b {
+		bs[i] = &p.G2
+	}
+	return bn256.PairingCheck(as, bs)
+}