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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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package sun.security.validator;

import java.security.cert.X509Certificate;
import java.time.LocalDate;
import java.time.Month;
import java.time.ZoneOffset;
import java.util.Date;
import java.util.Map;
import java.util.Set;

import sun.security.util.Debug;
import sun.security.x509.X509CertImpl;

/**
 * This class checks if Chunghwa issued TLS Server certificates should be
 * restricted.
 */
final class ChunghwaTLSPolicy {

    private static final Debug debug = Debug.getInstance("certpath");

    // SHA-256 certificate fingerprint of distrusted root for TLS
    // cacerts alias: chunghwaepkirootca
    // DN: OU=ePKI Root Certification Authority,
    //     O="Chunghwa Telecom Co., Ltd.", C=TW
    private static final String FINGERPRINT =
            "C0A6F4DC63A24BFDCF54EF2A6A082A0A72DE35803E2FF5FF527AE5D87206DFD5";

    // Any TLS Server certificate that is anchored by the Chunghwa
    // root above and is issued after this date will be distrusted.
    private static final LocalDate MARCH_17_2026 =
        LocalDate.of(2026, Month.MARCH, 17);

    /**
     * This method assumes the eeCert is a TLS Server Cert and chains back to
     * the anchor.
     *
     * @param chain the end-entity's certificate chain. The end entity cert
     *              is at index 0, the trust anchor at index n-1.
     * @throws ValidatorException if the certificate is distrusted
     */
    static void checkDistrust(X509Certificate[] chain)
                              throws ValidatorException {
        X509Certificate anchor = chain[chain.length-1];
        String fp = fingerprint(anchor);
        if (fp == null) {
            throw new ValidatorException("Cannot generate fingerprint for "
                + "trust anchor of TLS server certificate");
        }
        if (FINGERPRINT.equalsIgnoreCase(fp)) {
            Date notBefore = chain[0].getNotBefore();
            LocalDate ldNotBefore = LocalDate.ofInstant(notBefore.toInstant(),
                                                        ZoneOffset.UTC);
            // reject if certificate is issued after March 17, 2026
            checkNotBefore(ldNotBefore, MARCH_17_2026, anchor);
        }
    }

    private static String fingerprint(X509Certificate cert) {
        return X509CertImpl.getFingerprint("SHA-256", cert, debug);
    }

    // Check whether the certificate's notBeforeDate is after the
    // distrust date for the anchor (root CA). Throw ValidatorException
    // if it is after the distrust date.
    private static void checkNotBefore(LocalDate notBeforeDate,
            LocalDate distrustDate, X509Certificate anchor)
            throws ValidatorException {
        if (notBeforeDate.isAfter(distrustDate)) {
            throw new ValidatorException
                ("TLS Server certificate issued after " + distrustDate +
                 " and anchored by a distrusted legacy Chunghwa root CA: "
                 + anchor.getSubjectX500Principal(),
                 ValidatorException.T_UNTRUSTED_CERT, anchor);
        }
    }

    private ChunghwaTLSPolicy() {}
}