// parseECDSA parses an ECDSA key according to RFC 5656, section 3.1.
func parseECDSA(in []byte) (out PublicKey, rest []byte, err error) {
var identifier []byte
var ok bool
if identifier, in, ok = parseString(in); !ok {
return nil, nil, errShortRead
}
key := new(ecdsa.PublicKey)
switch string(identifier) {
case "nistp256":
key.Curve = elliptic.P256()
case "nistp384":
key.Curve = elliptic.P384()
case "nistp521":
key.Curve = elliptic.P521()
default:
return nil, nil, errors.New("ssh: unsupported curve")
}
var keyBytes []byte
if keyBytes, in, ok = parseString(in); !ok {
return nil, nil, errShortRead
}
key.X, key.Y = elliptic.Unmarshal(key.Curve, keyBytes)
if key.X == nil || key.Y == nil {
return nil, nil, errors.New("ssh: invalid curve point")
}
return (*ecdsaPublicKey)(key), in, nil
}
// parseECDSA parses an ECDSA key according to RFC 5656, section 3.1.
func parseECDSA(in []byte) (out *ecdsa.PublicKey, rest []byte, ok bool) {
var identifier []byte
if identifier, in, ok = parseString(in); !ok {
return
}
key := new(ecdsa.PublicKey)
switch string(identifier) {
case "nistp256":
key.Curve = elliptic.P256()
case "nistp384":
key.Curve = elliptic.P384()
case "nistp521":
key.Curve = elliptic.P521()
default:
ok = false
return
}
var keyBytes []byte
if keyBytes, in, ok = parseString(in); !ok {
return
}
key.X, key.Y = elliptic.Unmarshal(key.Curve, keyBytes)
if key.X == nil || key.Y == nil {
ok = false
return
}
return key, in, ok
}
// 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
}
// parseECDSA parses an ECDSA key according to RFC 5656, section 3.1.
func parseECDSA(in []byte) (out PublicKey, rest []byte, err error) {
var w struct {
Curve string
KeyBytes []byte
Rest []byte `ssh:"rest"`
}
if err := Unmarshal(in, &w); err != nil {
return nil, nil, err
}
key := new(ecdsa.PublicKey)
switch w.Curve {
case "nistp256":
key.Curve = elliptic.P256()
case "nistp384":
key.Curve = elliptic.P384()
case "nistp521":
key.Curve = elliptic.P521()
default:
return nil, nil, errors.New("ssh: unsupported curve")
}
key.X, key.Y = elliptic.Unmarshal(key.Curve, w.KeyBytes)
if key.X == nil || key.Y == nil {
return nil, nil, errors.New("ssh: invalid curve point")
}
return (*ecdsaPublicKey)(key), w.Rest, nil
}
// 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 NewEcdsaPublicKey(pk *ecdsa.PublicKey) *EcdsaPublicKey {
pubkey := &EcdsaPublicKey{
Curve: jwa.EllipticCurveAlgorithm(pk.Params().Name),
}
pubkey.X.SetBytes(pk.X.Bytes())
pubkey.Y.SetBytes(pk.Y.Bytes())
return pubkey
}
// NewEcdsaPublicKey creates a new JWK from a EC-DSA public key
func NewEcdsaPublicKey(pk *ecdsa.PublicKey) *EcdsaPublicKey {
pubkey := &EcdsaPublicKey{
EssentialHeader: &EssentialHeader{KeyType: jwa.EC},
Curve: jwa.EllipticCurveAlgorithm(pk.Params().Name),
}
n := pk.Params().BitSize / 8
pubkey.X.SetBytes(i2osp(pk.X, n))
pubkey.Y.SetBytes(i2osp(pk.Y, n))
return pubkey
}
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
}
func (sv *x509ECDSASignatureVerifierImpl) verifyImpl(vk *ecdsa.PublicKey, signature, message []byte) (bool, error) {
ecdsaSignature := new(ECDSASignature)
_, err := asn1.Unmarshal(signature, ecdsaSignature)
if err != nil {
return false, err
}
h, err := computeHash(message, vk.Params().BitSize)
if err != nil {
return false, err
}
return ecdsa.Verify(vk, h, ecdsaSignature.R, ecdsaSignature.S), nil
}
// 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
}
func verify(signerKeyFile, userKeyFile, sigFile string) bool {
rawSigner, err := ioutil.ReadFile(signerKeyFile)
if err != nil {
fmt.Printf("Failed to read signature key: %v\n", err)
return false
}
var signer ecdsa.PublicKey
signer.X, signer.Y = elliptic.Unmarshal(elliptic.P521(), rawSigner)
if signer.X == nil {
fmt.Println("Invalid signature key.")
return false
}
signer.Curve = elliptic.P521()
rawUser, err := ioutil.ReadFile(userKeyFile)
if err != nil {
fmt.Printf("Failed to read user key: %v\n", err)
return false
}
x, _ := elliptic.Unmarshal(elliptic.P521(), rawUser)
if x == nil {
fmt.Println("Invalid user key.")
return false
}
rawSig, err := ioutil.ReadFile(sigFile)
if err != nil {
fmt.Printf("Failed to load signature: %v\n", err)
return false
}
var sig ECDSASignature
_, err = asn1.Unmarshal(rawSig, &sig)
if err != nil {
fmt.Printf("Failed to parse signature: %v\n", err)
return false
}
h := sha512.Sum384(rawUser)
return ecdsa.Verify(&signer, h[:], sig.R, sig.S)
}
// marshalPubECDSA serializes an ECDSA public key according to RFC 5656, section 3.1.
func marshalPubECDSA(key *ecdsa.PublicKey) []byte {
var identifier []byte
switch key.Params().BitSize {
case 256:
identifier = []byte("nistp256")
case 384:
identifier = []byte("nistp384")
case 521:
identifier = []byte("nistp521")
default:
panic("ssh: unsupported ecdsa key size")
}
keyBytes := elliptic.Marshal(key.Curve, key.X, key.Y)
length := stringLength(len(identifier))
length += stringLength(len(keyBytes))
ret := make([]byte, length)
r := marshalString(ret, identifier)
r = marshalString(r, keyBytes)
return ret
}
// Multiply a large integer and a point. The resulting point
// is represented as an ECDSA public key.
func ScalarMult(k *big.Int, B *ecdsa.PublicKey) *ecdsa.PublicKey {
key := new(ecdsa.PublicKey)
key.Curve = Secp256k1()
key.X, key.Y = Secp256k1().ScalarMult(B.X, B.Y, k.Bytes())
return key
}
// GoodKeyECDSA determines if an ECDSA pubkey meets our requirements
func (policy *KeyPolicy) goodKeyECDSA(key ecdsa.PublicKey) (err error) {
// Check the curve.
//
// The validity of the curve is an assumption for all following tests.
err = policy.goodCurve(key.Curve)
if err != nil {
return err
}
// Key validation routine adapted from NIST SP800-56A § 5.6.2.3.2.
// <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-56Ar2.pdf>
//
// Assuming a prime field since a) we are only allowing such curves and b)
// crypto/elliptic only supports prime curves. Where this assumption
// simplifies the code below, it is explicitly stated and explained. If ever
// adapting this code to support non-prime curves, refer to NIST SP800-56A §
// 5.6.2.3.2 and adapt this code appropriately.
params := key.Params()
// SP800-56A § 5.6.2.3.2 Step 1.
// Partial check of the public key for an invalid range in the EC group:
// Verify that key is not the point at infinity O.
// This code assumes that the point at infinity is (0,0), which is the
// case for all supported curves.
if isPointAtInfinityNISTP(key.X, key.Y) {
return core.MalformedRequestError("Key x, y must not be the point at infinity")
}
// SP800-56A § 5.6.2.3.2 Step 2.
// "Verify that x_Q and y_Q are integers in the interval [0,p-1] in the
// case that q is an odd prime p, or that x_Q and y_Q are bit strings
// of length m bits in the case that q = 2**m."
//
// Prove prime field: ASSUMED.
// Prove q != 2: ASSUMED. (Curve parameter. No supported curve has q == 2.)
// Prime field && q != 2 => q is an odd prime p
// Therefore "verify that x, y are in [0, p-1]" satisfies step 2.
//
// Therefore verify that both x and y of the public key point have the unique
// correct representation of an element in the underlying field by verifying
// that x and y are integers in [0, p-1].
if key.X.Sign() < 0 || key.Y.Sign() < 0 {
return core.MalformedRequestError("Key x, y must not be negative")
}
if key.X.Cmp(params.P) >= 0 || key.Y.Cmp(params.P) >= 0 {
return core.MalformedRequestError("Key x, y must not exceed P-1")
}
// SP800-56A § 5.6.2.3.2 Step 3.
// "If q is an odd prime p, verify that (y_Q)**2 === (x_Q)***3 + a*x_Q + b (mod p).
// If q = 2**m, verify that (y_Q)**2 + (x_Q)*(y_Q) == (x_Q)**3 + a*(x_Q)*2 + b in
// the finite field of size 2**m.
// (Ensures that the public key is on the correct elliptic curve.)"
//
// q is an odd prime p: proven/assumed above.
// a = -3 for all supported curves.
//
// Therefore step 3 is satisfied simply by showing that
// y**2 === x**3 - 3*x + B (mod P).
//
// This proves that the public key is on the correct elliptic curve.
// But in practice, this test is provided by crypto/elliptic, so use that.
if !key.Curve.IsOnCurve(key.X, key.Y) {
return core.MalformedRequestError("Key point is not on the curve")
}
// SP800-56A § 5.6.2.3.2 Step 4.
// "Verify that n*Q == O.
// (Ensures that the public key has the correct order. Along with check 1,
// ensures that the public key is in the correct range in the correct EC
// subgroup, that is, it is in the correct EC subgroup and is not the
// identity element.)"
//
// Ensure that public key has the correct order:
// verify that n*Q = O.
//
// n*Q = O iff n*Q is the point at infinity (see step 1).
ox, oy := key.Curve.ScalarMult(key.X, key.Y, params.N.Bytes())
if !isPointAtInfinityNISTP(ox, oy) {
return core.MalformedRequestError("Public key does not have correct order")
}
// End of SP800-56A § 5.6.2.3.2 Public Key Validation Routine.
// Key is valid.
return nil
}
// Adds two points to create a third. Points are represented as
// ECDSA public keys.
func Add(a, b *ecdsa.PublicKey) *ecdsa.PublicKey {
key := new(ecdsa.PublicKey)
key.Curve = Secp256k1()
key.X, key.Y = Secp256k1().Add(a.X, a.Y, b.X, b.Y)
return key
}
// 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
}
// Multiplies the base G by a large integer. The resulting
// point is represented as an ECDSA public key since that's
// typically how they're used.
func ScalarBaseMult(k *big.Int) *ecdsa.PublicKey {
key := new(ecdsa.PublicKey)
key.Curve = Secp256k1()
key.X, key.Y = Secp256k1().ScalarBaseMult(k.Bytes())
return key
}