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/*
 * Copyright 2016 Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.keycloak.jose.jwk;

import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.spec.ECParameterSpec;
import java.security.spec.ECPoint;
import java.security.spec.ECPublicKeySpec;
import java.security.spec.RSAPublicKeySpec;

import org.keycloak.common.crypto.CryptoIntegration;
import org.keycloak.common.util.Base64Url;
import org.keycloak.crypto.KeyType;

/**
 * @author Stian Thorgersen
 */
public abstract class AbstractJWKParser {

    protected JWK jwk;

    public JWK getJwk() {
        return jwk;
    }

    public PublicKey toPublicKey() {
        String keyType = jwk.getKeyType();
        if (keyType.equals(KeyType.RSA)) {
            return createRSAPublicKey();
        } else if (keyType.equals(KeyType.EC)) {
            return createECPublicKey();

        } else {
            throw new RuntimeException("Unsupported keyType " + keyType);
        }
    }

    protected PublicKey createECPublicKey() {
        /* Check if jwk.getOtherClaims return an empty map */
        if (jwk.getOtherClaims().size() == 0) {
            throw new RuntimeException("JWK Otherclaims map is empty.");
        }

        /* Try retrieving the necessary fields */
        String crv = (String) jwk.getOtherClaims().get(ECPublicJWK.CRV);
        String xStr = (String) jwk.getOtherClaims().get(ECPublicJWK.X);
        String yStr = (String) jwk.getOtherClaims().get(ECPublicJWK.Y);

        /* Check if the retrieving of necessary fields success */
        if (crv == null || xStr == null || yStr == null) {
            throw new RuntimeException("Fail to retrieve ECPublicJWK.CRV, ECPublicJWK.X or ECPublicJWK.Y field.");
        }

        BigInteger x = new BigInteger(1, Base64Url.decode(xStr));
        BigInteger y = new BigInteger(1, Base64Url.decode(yStr));

        String name;
        switch (crv) {
            case "P-256" :
                name = "secp256r1";
                break;
            case "P-384" :
                name = "secp384r1";
                break;
            case "P-521" :
                name = "secp521r1";
                break;
            default :
                throw new RuntimeException("Unsupported curve");
        }

        try {
            
            ECPoint point = new ECPoint(x, y);
            ECParameterSpec params = CryptoIntegration.getProvider().createECParams(name);
            ECPublicKeySpec pubKeySpec = new ECPublicKeySpec(point, params);

            KeyFactory kf = CryptoIntegration.getProvider().getKeyFactory("ECDSA");
            return kf.generatePublic(pubKeySpec);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    protected PublicKey createRSAPublicKey() {
        BigInteger modulus = new BigInteger(1, Base64Url.decode(jwk.getOtherClaims().get(RSAPublicJWK.MODULUS).toString()));
        BigInteger publicExponent = new BigInteger(1, Base64Url.decode(jwk.getOtherClaims().get(RSAPublicJWK.PUBLIC_EXPONENT).toString()));

        try {
            KeyFactory kf = KeyFactory.getInstance("RSA");
            return kf.generatePublic(new RSAPublicKeySpec(modulus, publicExponent));
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public boolean isKeyTypeSupported(String keyType) {
        return (RSAPublicJWK.RSA.equals(keyType) || ECPublicJWK.EC.equals(keyType));
    }

}