// publicKeyCurve returns the Curve public key from the DNSKEY record.
func (k *RR_DNSKEY) publicKeyCurve() *ecdsa.PublicKey {
keybuf, err := packBase64([]byte(k.PublicKey))
if err != nil {
return nil
}
pubkey := new(ecdsa.PublicKey)
switch k.Algorithm {
case ECDSAP256SHA256:
pubkey.Curve = elliptic.P256()
if len(keybuf) != 64 {
// wrongly encoded key
return nil
}
case ECDSAP384SHA384:
pubkey.Curve = elliptic.P384()
if len(keybuf) != 96 {
// Wrongly encoded key
return nil
}
}
pubkey.X = big.NewInt(0)
pubkey.X.SetBytes(keybuf[:len(keybuf)/2])
pubkey.Y = big.NewInt(0)
pubkey.Y.SetBytes(keybuf[len(keybuf)/2:])
return pubkey
}
// toECDSA takes the internal ECPublicKey and returns an equivalent
// an ecdsa.PublicKey
func (pk *ECPublicKey) toECDSA() *ecdsa.PublicKey {
ecdsaPub := new(ecdsa.PublicKey)
ecdsaPub.Curve = pk.Curve
ecdsaPub.X = pk.X
ecdsaPub.Y = pk.Y
return ecdsaPub
}
func UnmarshalPublicCertificate(data []byte) PublicCertificate {
x, y := elliptic.Unmarshal(curve, data)
cert := new(ecdsa.PublicKey)
cert.Curve = curve
cert.X = x
cert.Y = y
return cert
}
// Extract the Curve public key from the Key record
func (k *RR_DNSKEY) pubKeyCurve() *ecdsa.PublicKey {
keybuf, err := packBase64([]byte(k.PublicKey))
if err != nil {
return nil
}
var c *elliptic.Curve
switch k.Algorithm {
case ECDSAP256SHA256:
c = elliptic.P256()
case ECDSAP384SHA384:
c = elliptic.P384()
}
x, y := c.Unmarshal(keybuf)
pubkey := new(ecdsa.PublicKey)
pubkey.X = x
pubkey.Y = y
pubkey.Curve = c
return pubkey
}
// ParsePubKey parses a public key for a koblitz curve from a bytestring into a
// ecdsa.Publickey, verifying that it is valid. It supports compressed,
// uncompressed and hybrid signature formats.
func ParsePubKey(pubKeyStr []byte, curve *KoblitzCurve) (key *ecdsa.PublicKey, err error) {
pubkey := ecdsa.PublicKey{}
pubkey.Curve = curve
format := pubKeyStr[0]
ybit := (format & 0x1) == 0x1
format &= ^byte(0x1)
switch len(pubKeyStr) {
case 65: // normal public key
if format != pubkeyUncompressed && format != pubkeyHybrid {
return nil, fmt.Errorf("invalid magic in pubkey str: "+
"%d", pubKeyStr[0])
}
pubkey.X = new(big.Int).SetBytes(pubKeyStr[1:33])
pubkey.Y = new(big.Int).SetBytes(pubKeyStr[33:])
// hybrid keys have extra information, make use of it.
if format == pubkeyHybrid && ybit != isOdd(pubkey.Y) {
return nil, fmt.Errorf("ybit doesn't match oddness")
}
case 33: // compressed public key
// format is 0x2 | solution, <X coordinate>
// solution determines which solution of the curve we use.
/// y^2 = x^3 + Curve.B
if format != pubkeyCompressed {
return nil, fmt.Errorf("invalid magic in compressed "+
"pubkey string: %d", pubKeyStr[0])
}
pubkey.X = new(big.Int).SetBytes(pubKeyStr[1:33])
// Y = +-sqrt(x^3 + B)
x3 := new(big.Int).Mul(pubkey.X, pubkey.X)
x3.Mul(x3, pubkey.X)
x3.Add(x3, pubkey.Curve.Params().B)
// now calculate sqrt mod p of x2 + B
// This code used to do a full sqrt based on tonelli/shanks,
// but this was replaced by the algorithms referenced in
// https://bitcointalk.org/index.php?topic=162805.msg1712294#msg1712294
y := new(big.Int).Exp(x3, curve.QPlus1Div4(), pubkey.Curve.Params().P)
if ybit != isOdd(y) {
y.Sub(pubkey.Curve.Params().P, y)
}
if ybit != isOdd(y) {
return nil, fmt.Errorf("ybit doesn't match oddness")
}
pubkey.Y = y
default: // wrong!
return nil, fmt.Errorf("invalid pub key length %d",
len(pubKeyStr))
}
if pubkey.X.Cmp(pubkey.Curve.Params().P) >= 0 {
return nil, fmt.Errorf("pubkey X parameter is >= to P")
}
if pubkey.Y.Cmp(pubkey.Curve.Params().P) >= 0 {
return nil, fmt.Errorf("pubkey Y parameter is >= to P")
}
if !pubkey.Curve.IsOnCurve(pubkey.X, pubkey.Y) {
return nil, fmt.Errorf("pubkey isn't on secp265k1 curve")
}
return &pubkey, nil
}