73 lines
1.3 KiB
Go
73 lines
1.3 KiB
Go
package jwk
|
|
|
|
import (
|
|
"crypto/ecdsa"
|
|
"crypto/elliptic"
|
|
"encoding/base64"
|
|
"encoding/json"
|
|
"errors"
|
|
"fmt"
|
|
"math/big"
|
|
)
|
|
|
|
// Represents an ECDSA public key according to RFC 7518.
|
|
type ECDSAPublicKeyHeader struct {
|
|
Curve string `json:"crv"`
|
|
X string `json:"x"`
|
|
Y string `json:"y"`
|
|
}
|
|
|
|
var (
|
|
ErrInvalidCurvePoint = errors.New("Invalid curve point")
|
|
)
|
|
|
|
// Rejects on invalid curve points with a branch
|
|
func ParseECDSAPublicKey(data []byte) (*ecdsa.PublicKey, error) {
|
|
var header ECDSAPublicKeyHeader
|
|
|
|
err := json.Unmarshal(data, &header)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
rawX, err := base64.RawURLEncoding.DecodeString(header.X)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
rawY, err := base64.RawURLEncoding.DecodeString(header.Y)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
x := new(big.Int).SetBytes(rawX)
|
|
y := new(big.Int).SetBytes(rawY)
|
|
|
|
var curve elliptic.Curve
|
|
|
|
switch header.Curve {
|
|
case "P-256":
|
|
curve = elliptic.P256()
|
|
case "P-384":
|
|
curve = elliptic.P384()
|
|
case "P-521":
|
|
curve = elliptic.P521()
|
|
default:
|
|
return nil, fmt.Errorf("Invalid curve type %s", header.Curve)
|
|
}
|
|
|
|
// Invalid curve attacks don't exactly apply here?
|
|
if !curve.IsOnCurve(x, y) {
|
|
return nil, ErrInvalidCurvePoint
|
|
}
|
|
|
|
key := &ecdsa.PublicKey{
|
|
Curve: curve,
|
|
X: x,
|
|
Y: y,
|
|
}
|
|
|
|
return key, nil
|
|
|
|
}
|