mirror of https://github.com/cheat/cheat.git
150 lines
3.8 KiB
Go
150 lines
3.8 KiB
Go
// Package ecc implements a generic interface for ECDH, ECDSA, and EdDSA.
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package ecc
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import (
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"crypto/ecdsa"
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"crypto/elliptic"
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"fmt"
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"github.com/ProtonMail/go-crypto/openpgp/errors"
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"io"
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"math/big"
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)
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type genericCurve struct {
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Curve elliptic.Curve
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}
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func NewGenericCurve(c elliptic.Curve) *genericCurve {
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return &genericCurve{
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Curve: c,
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}
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}
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func (c *genericCurve) GetCurveName() string {
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return c.Curve.Params().Name
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}
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func (c *genericCurve) MarshalBytePoint(point []byte) []byte {
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return point
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}
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func (c *genericCurve) UnmarshalBytePoint(point []byte) []byte {
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return point
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}
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func (c *genericCurve) MarshalIntegerPoint(x, y *big.Int) []byte {
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return elliptic.Marshal(c.Curve, x, y)
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}
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func (c *genericCurve) UnmarshalIntegerPoint(point []byte) (x, y *big.Int) {
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return elliptic.Unmarshal(c.Curve, point)
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}
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func (c *genericCurve) MarshalByteSecret(d []byte) []byte {
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return d
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}
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func (c *genericCurve) UnmarshalByteSecret(d []byte) []byte {
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return d
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}
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func (c *genericCurve) MarshalIntegerSecret(d *big.Int) []byte {
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return d.Bytes()
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}
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func (c *genericCurve) UnmarshalIntegerSecret(d []byte) *big.Int {
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return new(big.Int).SetBytes(d)
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}
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func (c *genericCurve) GenerateECDH(rand io.Reader) (point, secret []byte, err error) {
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secret, x, y, err := elliptic.GenerateKey(c.Curve, rand)
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if err != nil {
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return nil, nil, err
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}
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point = elliptic.Marshal(c.Curve, x, y)
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return point, secret, nil
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}
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func (c *genericCurve) GenerateECDSA(rand io.Reader) (x, y, secret *big.Int, err error) {
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priv, err := ecdsa.GenerateKey(c.Curve, rand)
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if err != nil {
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return
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}
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return priv.X, priv.Y, priv.D, nil
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}
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func (c *genericCurve) Encaps(rand io.Reader, point []byte) (ephemeral, sharedSecret []byte, err error) {
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xP, yP := elliptic.Unmarshal(c.Curve, point)
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if xP == nil {
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panic("invalid point")
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}
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d, x, y, err := elliptic.GenerateKey(c.Curve, rand)
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if err != nil {
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return nil, nil, err
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}
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vsG := elliptic.Marshal(c.Curve, x, y)
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zbBig, _ := c.Curve.ScalarMult(xP, yP, d)
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byteLen := (c.Curve.Params().BitSize + 7) >> 3
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zb := make([]byte, byteLen)
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zbBytes := zbBig.Bytes()
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copy(zb[byteLen-len(zbBytes):], zbBytes)
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return vsG, zb, nil
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}
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func (c *genericCurve) Decaps(ephemeral, secret []byte) (sharedSecret []byte, err error) {
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x, y := elliptic.Unmarshal(c.Curve, ephemeral)
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zbBig, _ := c.Curve.ScalarMult(x, y, secret)
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byteLen := (c.Curve.Params().BitSize + 7) >> 3
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zb := make([]byte, byteLen)
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zbBytes := zbBig.Bytes()
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copy(zb[byteLen-len(zbBytes):], zbBytes)
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return zb, nil
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}
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func (c *genericCurve) Sign(rand io.Reader, x, y, d *big.Int, hash []byte) (r, s *big.Int, err error) {
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priv := &ecdsa.PrivateKey{D: d, PublicKey: ecdsa.PublicKey{X: x, Y: y, Curve: c.Curve}}
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return ecdsa.Sign(rand, priv, hash)
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}
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func (c *genericCurve) Verify(x, y *big.Int, hash []byte, r, s *big.Int) bool {
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pub := &ecdsa.PublicKey{X: x, Y: y, Curve: c.Curve}
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return ecdsa.Verify(pub, hash, r, s)
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}
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func (c *genericCurve) validate(xP, yP *big.Int, secret []byte) error {
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// the public point should not be at infinity (0,0)
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zero := new(big.Int)
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if xP.Cmp(zero) == 0 && yP.Cmp(zero) == 0 {
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return errors.KeyInvalidError(fmt.Sprintf("ecc (%s): infinity point", c.Curve.Params().Name))
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}
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// re-derive the public point Q' = (X,Y) = dG
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// to compare to declared Q in public key
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expectedX, expectedY := c.Curve.ScalarBaseMult(secret)
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if xP.Cmp(expectedX) != 0 || yP.Cmp(expectedY) != 0 {
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return errors.KeyInvalidError(fmt.Sprintf("ecc (%s): invalid point", c.Curve.Params().Name))
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}
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return nil
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}
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func (c *genericCurve) ValidateECDSA(xP, yP *big.Int, secret []byte) error {
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return c.validate(xP, yP, secret)
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}
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func (c *genericCurve) ValidateECDH(point []byte, secret []byte) error {
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xP, yP := elliptic.Unmarshal(c.Curve, point)
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if xP == nil {
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return errors.KeyInvalidError(fmt.Sprintf("ecc (%s): invalid point", c.Curve.Params().Name))
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}
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return c.validate(xP, yP, secret)
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}
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