/*
 * nimbus-jose-jwt
 *
 * Copyright 2012-2016, Connect2id Ltd.
 *
 * 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 com.nimbusds.jose.crypto;


import java.security.InvalidKeyException;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.SignatureException;

import static com.nimbusds.jose.jwk.gen.RSAKeyGenerator.MIN_KEY_SIZE_BITS;

import com.nimbusds.jose.JOSEException;
import com.nimbusds.jose.JWSHeader;
import com.nimbusds.jose.JWSSigner;
import com.nimbusds.jose.crypto.impl.RSAKeyUtils;
import com.nimbusds.jose.crypto.impl.RSASSA;
import com.nimbusds.jose.crypto.impl.RSASSAProvider;
import com.nimbusds.jose.jwk.RSAKey;
import com.nimbusds.jose.util.Base64URL;
import net.jcip.annotations.ThreadSafe;



/**
 * RSA Signature-Scheme-with-Appendix (RSASSA) signer of 
 * {@link com.nimbusds.jose.JWSObject JWS objects}. Expects a private RSA key.
 *
 * <p>See RFC 7518, sections
 * <a href="https://tools.ietf.org/html/rfc7518#section-3.3">3.3</a> and
 * <a href="https://tools.ietf.org/html/rfc7518#section-3.5">3.5</a> for more
 * information.
 *
 * <p>This class is thread-safe.
 *
 * <p>Supports the following algorithms:
 *
 * <ul>
 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#RS256}
 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#RS384}
 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#RS512}
 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#PS256}
 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#PS384}
 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#PS512}
 * </ul>
 * 
 * @author Vladimir Dzhuvinov
 * @author Omer Levi Hevroni
 * @version 2018-10-11
 */
@ThreadSafe
public class RSASSASigner extends RSASSAProvider implements JWSSigner {


        /**
         * The private RSA key. Represented by generic private key interface to
         * support key stores that prevent exposure of the private key
         * parameters via the {@link java.security.interfaces.RSAPrivateKey}
         * API.
         *
         * See https://bitbucket.org/connect2id/nimbus-jose-jwt/issues/169
         */
        private final PrivateKey privateKey;


        /**
         * Creates a new RSA Signature-Scheme-with-Appendix (RSASSA) signer.
         * This constructor can also accept a private RSA key located in a
         * PKCS#11 store that doesn't expose the private key parameters (such
         * as a smart card or HSM).
         *
         * @param privateKey The private RSA key. Its algorithm must be "RSA"
         *                   and its length at least 2048 bits. Note that the
         *                   length of an RSA key in a PKCS#11 store cannot be
         *                   checked. Must not be {@code null}.
         */
        public RSASSASigner(final PrivateKey privateKey) {

                this(privateKey, false);
        }


        /**
         * Creates a new RSA Signature-Scheme-with-Appendix (RSASSA) signer.
         * This constructor can also accept a private RSA key located in a
         * PKCS#11 store that doesn't expose the private key parameters (such
         * as a smart card or HSM).
         *
         * @param privateKey   The private RSA key. Its algorithm must be
         *                     "RSA" and its length at least 2048 bits. Note
         *                     that the length of an RSA key in a PKCS#11 store
         *                     cannot be checked. Must not be {@code null}.
         * @param allowWeakKey {@code true} to allow an RSA key shorter than
         *                     2048 bits.
         */
        public RSASSASigner(final PrivateKey privateKey, final boolean allowWeakKey) {

                if (! "RSA".equalsIgnoreCase(privateKey.getAlgorithm())) {
                        throw new IllegalArgumentException("The private key algorithm must be RSA");
                }
                
                if (! allowWeakKey) {
                        
                        int keyBitLength = RSAKeyUtils.keyBitLength(privateKey);
                        
                        if (keyBitLength > 0 && keyBitLength < MIN_KEY_SIZE_BITS) {
                                throw new IllegalArgumentException("The RSA key size must be at least " + MIN_KEY_SIZE_BITS + " bits");
                        }
                }

                this.privateKey = privateKey;
        }


        /**
         * Creates a new RSA Signature-Scheme-with-Appendix (RSASSA) signer.
         *
         * @param rsaJWK The RSA JSON Web Key (JWK). Must contain or reference
         *               a private part. Its length must be at least 2048 bits.
         *               Note that the length of an RSA key in a PKCS#11 store
         *               cannot be checked. Must not be {@code null}.
         *
         * @throws JOSEException If the RSA JWK doesn't contain a private part
         *                       or its extraction failed.
         */
        public RSASSASigner(final RSAKey rsaJWK)
                throws JOSEException {

                this(rsaJWK, false);
        }


        /**
         * Creates a new RSA Signature-Scheme-with-Appendix (RSASSA) signer.
         *
         * @param rsaJWK       The RSA JSON Web Key (JWK). Must contain or
         *                     reference a private part. Its length must be at
         *                     least 2048 bits. Note that the length of an RSA
         *                     key in a PKCS#11 store cannot be checked. Must
         *                     not be {@code null}.
         * @param allowWeakKey {@code true} to allow an RSA key shorter than
         *                     2048 bits.
         *
         * @throws JOSEException If the RSA JWK doesn't contain a private part
         *                       or its extraction failed.
         */
        public RSASSASigner(final RSAKey rsaJWK, final boolean allowWeakKey)
                throws JOSEException {

                this(RSAKeyUtils.toRSAPrivateKey(rsaJWK), allowWeakKey);
        }


        /**
         * Gets the private RSA key.
         *
         * @return The private RSA key. Casting to
         *         {@link java.security.interfaces.RSAPrivateKey} may not be
         *         possible if the key is located in a PKCS#11 store that
         *         doesn't expose the private key parameters.
         */
        public PrivateKey getPrivateKey() {

                return privateKey;
        }


        @Override
        public Base64URL sign(final JWSHeader header, final byte[] signingInput)
                throws JOSEException {

                Signature signer = RSASSA.getSignerAndVerifier(header.getAlgorithm(), getJCAContext().getProvider());

                try {
                        signer.initSign(privateKey);
                        signer.update(signingInput);
                        return Base64URL.encode(signer.sign());

                } catch (InvalidKeyException e) {
                        throw new JOSEException("Invalid private RSA key: " + e.getMessage(), e);

                } catch (SignatureException e) {
                        throw new JOSEException("RSA signature exception: " + e.getMessage(), e);
                }
        }
}