1 files changed, 139 insertions, 0 deletions
diff --git a/src/crypto/elliptic/p224.go b/src/crypto/elliptic/p224.go
new file mode 100644
index 0000000..8a431c4
--- /dev/null
+++ b/src/crypto/elliptic/p224.go
@@ -0,0 +1,139 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package elliptic
+
+import (
+	"crypto/elliptic/internal/nistec"
+	"crypto/rand"
+	"math/big"
+)
+
+// p224Curve is a Curve implementation based on nistec.P224Point.
+//
+// It's a wrapper that exposes the big.Int-based Curve interface and encodes the
+// legacy idiosyncrasies it requires, such as invalid and infinity point
+// handling.
+//
+// To interact with the nistec package, points are encoded into and decoded from
+// properly formatted byte slices. All big.Int use is limited to this package.
+// Encoding and decoding is 1/1000th of the runtime of a scalar multiplication,
+// so the overhead is acceptable.
+type p224Curve struct {
+	params *CurveParams
+}
+
+var p224 p224Curve
+var _ Curve = p224
+
+func initP224() {
+	p224.params = &CurveParams{
+		Name:    "P-224",
+		BitSize: 224,
+		// FIPS 186-4, section D.1.2.2
+		P:  bigFromDecimal("26959946667150639794667015087019630673557916260026308143510066298881"),
+		N:  bigFromDecimal("26959946667150639794667015087019625940457807714424391721682722368061"),
+		B:  bigFromHex("b4050a850c04b3abf54132565044b0b7d7bfd8ba270b39432355ffb4"),
+		Gx: bigFromHex("b70e0cbd6bb4bf7f321390b94a03c1d356c21122343280d6115c1d21"),
+		Gy: bigFromHex("bd376388b5f723fb4c22dfe6cd4375a05a07476444d5819985007e34"),
+	}
+}
+
+func (curve p224Curve) Params() *CurveParams {
+	return curve.params
+}
+
+func (curve p224Curve) IsOnCurve(x, y *big.Int) bool {
+	// IsOnCurve is documented to reject (0, 0), the conventional point at
+	// infinity, which however is accepted by p224PointFromAffine.
+	if x.Sign() == 0 && y.Sign() == 0 {
+		return false
+	}
+	_, ok := p224PointFromAffine(x, y)
+	return ok
+}
+
+func p224PointFromAffine(x, y *big.Int) (p *nistec.P224Point, ok bool) {
+	// (0, 0) is by convention the point at infinity, which can't be represented
+	// in affine coordinates. Marshal incorrectly encodes it as an uncompressed
+	// point, which SetBytes would correctly reject. See Issue 37294.
+	if x.Sign() == 0 && y.Sign() == 0 {
+		return nistec.NewP224Point(), true
+	}
+	if x.Sign() < 0 || y.Sign() < 0 {
+		return nil, false
+	}
+	if x.BitLen() > 224 || y.BitLen() > 224 {
+		return nil, false
+	}
+	p, err := nistec.NewP224Point().SetBytes(Marshal(P224(), x, y))
+	if err != nil {
+		return nil, false
+	}
+	return p, true
+}
+
+func p224PointToAffine(p *nistec.P224Point) (x, y *big.Int) {
+	out := p.Bytes()
+	if len(out) == 1 && out[0] == 0 {
+		// This is the correct encoding of the point at infinity, which
+		// Unmarshal does not support. See Issue 37294.
+		return new(big.Int), new(big.Int)
+	}
+	x, y = Unmarshal(P224(), out)
+	if x == nil {
+		panic("crypto/elliptic: internal error: Unmarshal rejected a valid point encoding")
+	}
+	return x, y
+}
+
+// p224RandomPoint returns a random point on the curve. It's used when Add,
+// Double, or ScalarMult are fed a point not on the curve, which is undefined
+// behavior. Originally, we used to do the math on it anyway (which allows
+// invalid curve attacks) and relied on the caller and Unmarshal to avoid this
+// happening in the first place. Now, we just can't construct a nistec.P224Point
+// for an invalid pair of coordinates, because that API is safer. If we panic,
+// we risk introducing a DoS. If we return nil, we risk a panic. If we return
+// the input, ecdsa.Verify might fail open. The safest course seems to be to
+// return a valid, random point, which hopefully won't help the attacker.
+func p224RandomPoint() (x, y *big.Int) {
+	_, x, y, err := GenerateKey(P224(), rand.Reader)
+	if err != nil {
+		panic("crypto/elliptic: failed to generate random point")
+	}
+	return x, y
+}
+
+func (p224Curve) Add(x1, y1, x2, y2 *big.Int) (*big.Int, *big.Int) {
+	p1, ok := p224PointFromAffine(x1, y1)
+	if !ok {
+		return p224RandomPoint()
+	}
+	p2, ok := p224PointFromAffine(x2, y2)
+	if !ok {
+		return p224RandomPoint()
+	}
+	return p224PointToAffine(p1.Add(p1, p2))
+}
+
+func (p224Curve) Double(x1, y1 *big.Int) (*big.Int, *big.Int) {
+	p, ok := p224PointFromAffine(x1, y1)
+	if !ok {
+		return p224RandomPoint()
+	}
+	return p224PointToAffine(p.Double(p))
+}
+
+func (p224Curve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, *big.Int) {
+	p, ok := p224PointFromAffine(Bx, By)
+	if !ok {
+		return p224RandomPoint()
+	}
+	return p224PointToAffine(p.ScalarMult(p, scalar))
+}
+
+func (p224Curve) ScalarBaseMult(scalar []byte) (*big.Int, *big.Int) {
+	p := nistec.NewP224Generator()
+	return p224PointToAffine(p.ScalarMult(p, scalar))
+}