/*
 * oauth2-oidc-sdk
 *
 * Copyright 2012-2016, Connect2id Ltd and contributors.
 *
 * 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.openid.connect.sdk.validators;


import java.util.Date;
import java.util.List;
import java.util.Objects;

import net.jcip.annotations.ThreadSafe;

import com.nimbusds.jose.proc.SecurityContext;
import com.nimbusds.jwt.JWTClaimsSet;
import com.nimbusds.jwt.proc.BadJWTException;
import com.nimbusds.jwt.proc.ClockSkewAware;
import com.nimbusds.jwt.proc.JWTClaimsSetVerifier;
import com.nimbusds.jwt.util.DateUtils;
import com.nimbusds.oauth2.sdk.id.ClientID;
import com.nimbusds.oauth2.sdk.id.Issuer;
import com.nimbusds.oauth2.sdk.util.CollectionUtils;
import com.nimbusds.openid.connect.sdk.Nonce;


/**
 * ID token claims verifier.
 *
 * <p>Related specifications:
 *
 * <ul>
 *     <li>OpenID Connect Core 1.0, section 3.1.3.7 for code flow.
 *     <li>OpenID Connect Core 1.0, section 3.2.2.11 for implicit flow.
 *     <li>OpenID Connect Core 1.0, sections 3.3.2.12 and 3.3.3.7 for hybrid
 *         flow.
 * </ul>
 */
@ThreadSafe
public class IDTokenClaimsVerifier implements JWTClaimsSetVerifier, ClockSkewAware {


        /**
         * The expected ID token issuer.
         */
        private final Issuer expectedIssuer;


        /**
         * The requesting client.
         */
        private final ClientID expectedClientID;


        /**
         * The expected nonce, {@code null} if not required or specified.
         */
        private final Nonce expectedNonce;


        /**
         * The maximum acceptable clock skew, in seconds.
         */
        private int maxClockSkew;


        /**
         * Creates a new ID token claims verifier.
         *
         * @param issuer       The expected ID token issuer. Must not be
         *                     {@code null}.
         * @param clientID     The client ID. Must not be {@code null}.
         * @param nonce        The nonce, required in the implicit flow or for
         *                     ID tokens returned by the authorisation endpoint
         *                     int the hybrid flow. {@code null} if not
         *                     required or specified.
         * @param maxClockSkew The maximum acceptable clock skew (absolute
         *                     value), in seconds. Must be zero (no clock skew)
         *                     or positive integer.
         */
        public IDTokenClaimsVerifier(final Issuer issuer,
                                     final ClientID clientID,
                                     final Nonce nonce,
                                     final int maxClockSkew) {

                this.expectedIssuer = Objects.requireNonNull(issuer);
                this.expectedClientID = Objects.requireNonNull(clientID);
                this.expectedNonce = nonce;
                setMaxClockSkew(maxClockSkew);
        }


        /**
         * Returns the expected ID token issuer.
         *
         * @return The ID token issuer.
         */
        public Issuer getExpectedIssuer() {

                return expectedIssuer;
        }


        /**
         * Returns the client ID for verifying the ID token audience.
         *
         * @return The client ID.
         */
        public ClientID getClientID() {

                return expectedClientID;
        }


        /**
         * Returns the expected nonce.
         *
         * @return The nonce, {@code null} if not required or specified.
         */
        public Nonce getExpectedNonce() {

                return expectedNonce;
        }


        @Override
        public int getMaxClockSkew() {

                return maxClockSkew;
        }


        @Override
        public void setMaxClockSkew(final int maxClockSkew) {
                if (maxClockSkew < 0) {
                        throw new IllegalArgumentException("The max clock skew must be zero or positive");
                }
                this.maxClockSkew = maxClockSkew;
        }


        @Override
        public void verify(final JWTClaimsSet claimsSet, final SecurityContext ctx)
                throws BadJWTException {

                // See http://openid.net/specs/openid-connect-core-1_0.html#IDTokenValidation

                final String tokenIssuer = claimsSet.getIssuer();

                if (tokenIssuer == null) {
                        throw BadJWTExceptions.MISSING_ISS_CLAIM_EXCEPTION;
                }

                if (! expectedIssuer.getValue().equals(tokenIssuer)) {
                        throw new BadJWTException("Unexpected JWT issuer: " + tokenIssuer);
                }

                if (claimsSet.getSubject() == null) {
                        throw BadJWTExceptions.MISSING_SUB_CLAIM_EXCEPTION;
                }

                final List<String> tokenAudience = claimsSet.getAudience();

                if (CollectionUtils.isEmpty(tokenAudience)) {
                        throw BadJWTExceptions.MISSING_AUD_CLAIM_EXCEPTION;
                }

                if (! tokenAudience.contains(expectedClientID.getValue())) {
                        throw new BadJWTException("Unexpected JWT audience: " + tokenAudience);
                }

                try {
                        // The optional "azp" claim is only checked for being
                        // a string, extension-specific "azp" checks should be
                        // subclassed or performed elsewhere.
                        claimsSet.getStringClaim("azp");
                } catch (java.text.ParseException e) {
                        throw new BadJWTException("Invalid JWT authorized party (azp) claim: " + e.getMessage());
                }

                final Date exp = claimsSet.getExpirationTime();

                if (exp == null) {
                        throw BadJWTExceptions.MISSING_EXP_CLAIM_EXCEPTION;
                }

                final Date iat = claimsSet.getIssueTime();

                if (iat == null) {
                        throw BadJWTExceptions.MISSING_IAT_CLAIM_EXCEPTION;
                }


                final Date nowRef = new Date();

                // Expiration must be after current time, given acceptable clock skew
                if (! DateUtils.isAfter(exp, nowRef, maxClockSkew)) {
                        throw BadJWTExceptions.EXPIRED_EXCEPTION;
                }

                // Issue time must be before current time, given acceptable clock skew, or equal to current time
                if (! (iat.equals(nowRef) || DateUtils.isBefore(iat, nowRef, maxClockSkew))) {
                        throw BadJWTExceptions.IAT_CLAIM_AHEAD_EXCEPTION;
                }


                if (expectedNonce != null) {

                        final String tokenNonce;

                        try {
                                tokenNonce = claimsSet.getStringClaim("nonce");
                        } catch (java.text.ParseException e) {
                                throw new BadJWTException("Invalid JWT nonce (nonce) claim: " + e.getMessage());
                        }

                        if (tokenNonce == null) {
                                throw BadJWTExceptions.MISSING_NONCE_CLAIM_EXCEPTION;
                        }

                        if (! expectedNonce.getValue().equals(tokenNonce)) {
                                throw new BadJWTException("Unexpected JWT nonce (nonce) claim: " + tokenNonce);
                        }
                }
        }
}