Move EC curve utility functions

impl/src/main/java/io/jsonwebtoken/impl/security/AbstractEcJwkFactory.java

@@ -15,54 +15,26 @@
  */
 package io.jsonwebtoken.impl.security;
 
-import io.jsonwebtoken.impl.lang.CheckedFunction;
 import io.jsonwebtoken.impl.lang.Converters;
 import io.jsonwebtoken.impl.lang.Field;
 import io.jsonwebtoken.io.Encoders;
-import io.jsonwebtoken.security.Curve;
 import io.jsonwebtoken.security.Jwk;
 import io.jsonwebtoken.security.UnsupportedKeyException;
 
 import java.math.BigInteger;
 import java.security.Key;
-import java.security.KeyFactory;
 import java.security.interfaces.ECKey;
-import java.security.interfaces.ECPrivateKey;
-import java.security.interfaces.ECPublicKey;
-import java.security.spec.ECFieldFp;
-import java.security.spec.ECParameterSpec;
-import java.security.spec.ECPoint;
-import java.security.spec.ECPublicKeySpec;
-import java.security.spec.EllipticCurve;
-import java.security.spec.InvalidKeySpecException;
 import java.util.Set;
 
 abstract class AbstractEcJwkFactory<K extends Key & ECKey, J extends Jwk<K>> extends AbstractFamilyJwkFactory<K, J> {
 
-    private static final BigInteger TWO = BigInteger.valueOf(2);
-    private static final BigInteger THREE = BigInteger.valueOf(3);
-    private static final String UNSUPPORTED_CURVE_MSG = "The specified ECKey curve does not match a JWA standard curve id.";
-
-    protected static ECParameterSpec getCurveByJwaId(String jwaCurveId) {
-        ECParameterSpec spec = null;
-        Curve curve = Curves.findById(jwaCurveId);
-        if (curve instanceof ECCurve) {
-            ECCurve ecCurve = (ECCurve) curve;
-            spec = ecCurve.toParameterSpec();
-        }
-        if (spec == null) {
-            String msg = "Unrecognized JWA curve id '" + jwaCurveId + "'";
+    protected static ECCurve getCurveByJwaId(String jwaCurveId) {
+        ECCurve curve = ECCurve.findById(jwaCurveId);
+        if (curve == null) {
+            String msg = "Unrecognized JWA EC curve id '" + jwaCurveId + "'";
             throw new UnsupportedKeyException(msg);
         }
-        return spec;
-    }
-
-    protected static String getJwaIdByCurve(EllipticCurve curve) {
-        ECCurve c = Curves.findBy(curve);
-        if (c == null) {
-            throw new UnsupportedKeyException(UNSUPPORTED_CURVE_MSG);
-        }
-        return c.getId();
+        return curve;
     }
 
     /**
@@ -85,146 +57,7 @@ static String toOctetString(int fieldSize, BigInteger coordinate) {
         return Encoders.BASE64URL.encode(bytes);
     }
 
-    /**
-     * Returns {@code true} if a given elliptic {@code curve} contains the specified {@code point}, {@code false}
-     * otherwise.  Assumes elliptic curves over finite fields adhering to the reduced (a.k.a short or narrow)
-     * Weierstrass form:
-     * <p>
-     * <code>y<sup>2</sup> = x<sup>3</sup> + ax + b</code>
-     * </p>
-     *
-     * @param curve the Elliptic Curve to check
-     * @param point a point that may or may not be defined on the specified elliptic curve
-     * @return {@code true} if a given elliptic curve contains the specified {@code point}, {@code false} otherwise.
-     */
-    @SuppressWarnings("BooleanMethodIsAlwaysInverted")
-    static boolean contains(EllipticCurve curve, ECPoint point) {
-
-        if (ECPoint.POINT_INFINITY.equals(point)) {
-            return false;
-        }
-
-        final BigInteger a = curve.getA();
-        final BigInteger b = curve.getB();
-        final BigInteger x = point.getAffineX();
-        final BigInteger y = point.getAffineY();
-
-        // The reduced Weierstrass form y^2 = x^3 + ax + b reflects an elliptic curve E over any field K (e.g. all real
-        // numbers or all complex numbers, etc). For computational simplicity, cryptographic (e.g. NIST) elliptic curves
-        // restrict K to be a field of integers modulo a prime number 'p'.  As such, we apply modulo p (the field prime)
-        // to the equation to account for the restricted field.  For a nice overview of the math behind EC curves and
-        // their application in cryptography, see
-        // https://web.northeastern.edu/dummit/docs/cryptography_5_elliptic_curves_in_cryptography.pdf
-
-        final BigInteger p = ((ECFieldFp) curve.getField()).getP();
-
-        // Verify the point coordinates are in field range:
-        if (x.compareTo(BigInteger.ZERO) < 0 || x.compareTo(p) >= 0 ||
-            y.compareTo(BigInteger.ZERO) < 0 || y.compareTo(p) >= 0) {
-            return false;
-        }
-
-        // Finally, assert Weierstrass form equality:
-        final BigInteger lhs = y.modPow(TWO, p); //mod p to account for field prime
-        final BigInteger rhs = x.modPow(THREE, p).add(a.multiply(x)).add(b).mod(p); //mod p to account for field prime
-        return lhs.equals(rhs);
-    }
-
-    /**
-     * Multiply a point {@code p} by scalar {@code s} on the curve identified by {@code spec}.
-     *
-     * @param p    the Elliptic Curve point to multiply
-     * @param s    the scalar value to multiply
-     * @param spec the domain parameters that identify the Elliptic Curve containing point {@code p}.
-     */
-    private static ECPoint multiply(ECPoint p, BigInteger s, ECParameterSpec spec) {
-        if (ECPoint.POINT_INFINITY.equals(p)) {
-            return p;
-        }
-
-        EllipticCurve curve = spec.getCurve();
-        BigInteger n = spec.getOrder();
-        BigInteger k = s.mod(n);
-
-        ECPoint r0 = ECPoint.POINT_INFINITY;
-        ECPoint r1 = p;
-
-        // Montgomery Ladder implementation to mitigate side-channel attacks (i.e. an 'add' operation and a 'double'
-        // operation is calculated for every loop iteration, regardless if the 'add'' is needed or not)
-        // See: https://en.wikipedia.org/wiki/Elliptic_curve_point_multiplication#Montgomery_ladder
-        while (k.compareTo(BigInteger.ZERO) > 0) {
-            ECPoint temp = add(r0, r1, curve);
-            r0 = k.testBit(0) ? temp : r0;
-            r1 = doublePoint(r1, curve);
-            k = k.shiftRight(1);
-        }
-
-        return r0;
-    }
-
-    private static ECPoint add(ECPoint P, ECPoint Q, EllipticCurve curve) {
-
-        if (ECPoint.POINT_INFINITY.equals(P)) {
-            return Q;
-        } else if (ECPoint.POINT_INFINITY.equals(Q)) {
-            return P;
-        } else if (P.equals(Q)) {
-            return doublePoint(P, curve);
-        }
-
-        final BigInteger Px = P.getAffineX();
-        final BigInteger Py = P.getAffineY();
-        final BigInteger Qx = Q.getAffineX();
-        final BigInteger Qy = Q.getAffineY();
-        final BigInteger prime = ((ECFieldFp) curve.getField()).getP();
-        final BigInteger slope = Qy.subtract(Py).multiply(Qx.subtract(Px).modInverse(prime)).mod(prime);
-        final BigInteger Rx = slope.pow(2).subtract(Px).subtract(Qx).mod(prime);
-        final BigInteger Ry = slope.multiply(Px.subtract(Rx)).subtract(Py).mod(prime);
-
-        return new ECPoint(Rx, Ry);
-    }
-
-    private static ECPoint doublePoint(ECPoint P, EllipticCurve curve) {
-
-        if (ECPoint.POINT_INFINITY.equals(P)) {
-            return P;
-        }
-
-        final BigInteger Px = P.getAffineX();
-        final BigInteger Py = P.getAffineY();
-        final BigInteger p = ((ECFieldFp) curve.getField()).getP();
-        final BigInteger a = curve.getA();
-        final BigInteger s = THREE.multiply(Px.pow(2)).add(a).mod(p).multiply(TWO.multiply(Py).modInverse(p)).mod(p);
-        final BigInteger x = s.pow(2).subtract(TWO.multiply(Px)).mod(p);
-        final BigInteger y = s.multiply(Px.subtract(x)).subtract(Py).mod(p);
-
-        return new ECPoint(x, y);
-    }
-
     AbstractEcJwkFactory(Class<K> keyType, Set<Field<?>> fields) {
         super(DefaultEcPublicJwk.TYPE_VALUE, keyType, fields);
     }
-
-    // visible for testing
-    protected ECPublicKey derivePublic(KeyFactory keyFactory, ECPublicKeySpec spec) throws InvalidKeySpecException {
-        return (ECPublicKey) keyFactory.generatePublic(spec);
-    }
-
-    protected ECPublicKey derivePublic(final JwkContext<ECPrivateKey> ctx) {
-        final ECPrivateKey key = ctx.getKey();
-        final ECParameterSpec params = key.getParams();
-        final ECPoint w = multiply(params.getGenerator(), key.getS(), params);
-        final ECPublicKeySpec spec = new ECPublicKeySpec(w, params);
-        return generateKey(ctx, ECPublicKey.class, new CheckedFunction<KeyFactory, ECPublicKey>() {
-            @Override
-            public ECPublicKey apply(KeyFactory kf) {
-                try {
-                    return derivePublic(kf, spec);
-                } catch (Exception e) {
-                    String msg = "Unable to derive ECPublicKey from ECPrivateKey: " + e.getMessage();
-                    throw new UnsupportedKeyException(msg, e);
-                }
-            }
-        });
-    }
 }