/*

 * Copyright (c) 2006, 2011, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * 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,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.security.provider.certpath;

import java.io.InputStream;

import java.io.IOException;

import java.net.HttpURLConnection;

import java.net.URI;

import java.net.URLConnection;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.security.InvalidAlgorithmParameterException;

import java.security.NoSuchAlgorithmException;

import java.security.Provider;

import java.security.cert.CertificateException;

import java.security.cert.CertificateFactory;

import java.security.cert.CertSelector;

import java.security.cert.CertStore;

import java.security.cert.CertStoreException;

import java.security.cert.CertStoreParameters;

import java.security.cert.CertStoreSpi;

import java.security.cert.CRLException;

import java.security.cert.CRLSelector;

import java.security.cert.X509Certificate;

import java.security.cert.X509CertSelector;

import java.security.cert.X509CRL;

import java.security.cert.X509CRLSelector;

import java.util.ArrayList;

import java.util.Collection;

import java.util.Collections;

import java.util.List;

import java.util.Locale;

import sun.security.x509.AccessDescription;

import sun.security.x509.GeneralNameInterface;

import sun.security.x509.URIName;

import sun.security.util.Cache;

import sun.security.util.Debug;

/**

 * A <code>CertStore</code> that retrieves <code>Certificates</code> or

 * <code>CRL</code>s from a URI, for example, as specified in an X.509

 * AuthorityInformationAccess or CRLDistributionPoint extension.

 * <p>

 * For CRLs, this implementation retrieves a single DER encoded CRL per URI.

 * For Certificates, this implementation retrieves a single DER encoded CRL or

 * a collection of Certificates encoded as a PKCS#7 "certs-only" CMS message.

 * <p>

 * This <code>CertStore</code> also implements Certificate/CRL caching.

 * Currently, the cache is shared between all applications in the VM and uses a

 * hardcoded policy. The cache has a maximum size of 185 entries, which are held

 * by SoftReferences. A request will be satisfied from the cache if we last

 * checked for an update within CHECK_INTERVAL (last 30 seconds). Otherwise,

 * we open an URLConnection to download the Certificate(s)/CRL using an

 * If-Modified-Since request (HTTP) if possible. Note that both positive and

 * negative responses are cached, i.e. if we are unable to open the connection

 * or the Certificate(s)/CRL cannot be parsed, we remember this result and

 * additional calls during the CHECK_INTERVAL period do not try to open another

 * connection.

 * <p>

 * The URICertStore is not currently a standard CertStore type. We should

 * consider adding a standard "URI" CertStore type.

 *

 * @author Andreas Sterbenz

 * @author Sean Mullan

 * @since 7.0

 */

class URICertStore extends CertStoreSpi {

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

    // interval between checks for update of cached Certificates/CRLs

    // (30 seconds)

    private final static int CHECK_INTERVAL = 30 * 1000;

    // size of the cache (see Cache class for sizing recommendations)

    private final static int CACHE_SIZE = 185;

    // X.509 certificate factory instance

    private final CertificateFactory factory;

    // cached Collection of X509Certificates (may be empty, never null)

    private Collection<X509Certificate> certs =

        Collections.<X509Certificate>emptySet();

    // cached X509CRL (may be null)

    private X509CRL crl;

    // time we last checked for an update

    private long lastChecked;

    // time server returned as last modified time stamp

    // or 0 if not available

    private long lastModified;

    // the URI of this CertStore

    private URI uri;

    // true if URI is ldap

    private boolean ldap = false;

    private CertStore ldapCertStore;

    private String ldapPath;

    /**

     * Holder class to lazily load LDAPCertStoreHelper if present.

     */

    private static class LDAP {

        private static final String CERT_STORE_HELPER =

            "sun.security.provider.certpath.ldap.LDAPCertStoreHelper";

        private static final CertStoreHelper helper =

            AccessController.doPrivileged(

                new PrivilegedAction<CertStoreHelper>() {

                    public CertStoreHelper run() {

                        try {

                            Class<?> c = Class.forName(CERT_STORE_HELPER, true, null);

                            return (CertStoreHelper)c.newInstance();

                        } catch (ClassNotFoundException cnf) {

                            return null;

                        } catch (InstantiationException e) {

                            throw new AssertionError(e);

                        } catch (IllegalAccessException e) {

                            throw new AssertionError(e);

                        }

                    }});

        static CertStoreHelper helper() {

            return helper;

        }

    }

    /**

     * Creates a URICertStore.

     *

     * @param parameters specifying the URI

     */

    URICertStore(CertStoreParameters params)

        throws InvalidAlgorithmParameterException, NoSuchAlgorithmException {

        super(params);

        if (!(params instanceof URICertStoreParameters)) {

            throw new InvalidAlgorithmParameterException

                ("params must be instanceof URICertStoreParameters");

        }

        this.uri = ((URICertStoreParameters) params).uri;

        // if ldap URI, use an LDAPCertStore to fetch certs and CRLs

        if (uri.getScheme().toLowerCase(Locale.ENGLISH).equals("ldap")) {

            if (LDAP.helper() == null)

                throw new NoSuchAlgorithmException("LDAP not present");

            ldap = true;

            ldapCertStore = LDAP.helper().getCertStore(uri);

            ldapPath = uri.getPath();

            // strip off leading '/'

            if (ldapPath.charAt(0) == '/') {

                ldapPath = ldapPath.substring(1);

            }

        }

        try {

            factory = CertificateFactory.getInstance("X.509");

        } catch (CertificateException e) {

            throw new RuntimeException();

        }

    }

    /**

     * Returns a URI CertStore. This method consults a cache of

     * CertStores (shared per JVM) using the URI as a key.

     */

    private static final Cache certStoreCache =

        Cache.newSoftMemoryCache(CACHE_SIZE);

    static synchronized CertStore getInstance(URICertStoreParameters params)

        throws NoSuchAlgorithmException, InvalidAlgorithmParameterException {

        if (debug != null) {

            debug.println("CertStore URI:" + params.uri);

        }

        CertStore ucs = (CertStore) certStoreCache.get(params);

        if (ucs == null) {

            ucs = new UCS(new URICertStore(params), null, "URI", params);

            certStoreCache.put(params, ucs);

        } else {

            if (debug != null) {

                debug.println("URICertStore.getInstance: cache hit");

            }

        }

        return ucs;

    }

    /**

     * Creates a CertStore from information included in the AccessDescription

     * object of a certificate's Authority Information Access Extension.

     */

    static CertStore getInstance(AccessDescription ad) {

        if (!ad.getAccessMethod().equals((Object)

                AccessDescription.Ad_CAISSUERS_Id)) {

            return null;

        }

        GeneralNameInterface gn = ad.getAccessLocation().getName();

        if (!(gn instanceof URIName)) {

            return null;

        }

        URI uri = ((URIName) gn).getURI();

        try {

            return URICertStore.getInstance

                (new URICertStore.URICertStoreParameters(uri));

        } catch (Exception ex) {

            if (debug != null) {

                debug.println("exception creating CertStore: " + ex);

                ex.printStackTrace();

            }

            return null;

        }

    }

    /**

     * Returns a <code>Collection</code> of <code>X509Certificate</code>s that

     * match the specified selector. If no <code>X509Certificate</code>s

     * match the selector, an empty <code>Collection</code> will be returned.

     *

     * @param selector a <code>CertSelector</code> used to select which

     *  <code>X509Certificate</code>s should be returned. Specify

     *  <code>null</code> to return all <code>X509Certificate</code>s.

     * @return a <code>Collection</code> of <code>X509Certificate</code>s that

     *         match the specified selector

     * @throws CertStoreException if an exception occurs

     */

    @SuppressWarnings("unchecked")

    public synchronized Collection<X509Certificate> engineGetCertificates

        (CertSelector selector) throws CertStoreException {

        // if ldap URI we wrap the CertSelector in an LDAPCertSelector to

        // avoid LDAP DN matching issues (see LDAPCertSelector for more info)

        if (ldap) {

            X509CertSelector xsel = (X509CertSelector) selector;

            try {

                xsel = LDAP.helper().wrap(xsel, xsel.getSubject(), ldapPath);

            } catch (IOException ioe) {

                throw new CertStoreException(ioe);

            }

            // Fetch the certificates via LDAP. LDAPCertStore has its own

            // caching mechanism, see the class description for more info.

            // Safe cast since xsel is an X509 certificate selector.

            return (Collection<X509Certificate>)

                ldapCertStore.getCertificates(xsel);

        }

        // Return the Certificates for this entry. It returns the cached value

        // if it is still current and fetches the Certificates otherwise.

        // For the caching details, see the top of this class.

        long time = System.currentTimeMillis();

        if (time - lastChecked < CHECK_INTERVAL) {

            if (debug != null) {

                debug.println("Returning certificates from cache");

            }

            return getMatchingCerts(certs, selector);

        }

        lastChecked = time;

        InputStream in = null;

        try {

            URLConnection connection = uri.toURL().openConnection();

            if (lastModified != 0) {

                connection.setIfModifiedSince(lastModified);

            }

            in = connection.getInputStream();

            long oldLastModified = lastModified;

            lastModified = connection.getLastModified();

            if (oldLastModified != 0) {

                if (oldLastModified == lastModified) {

                    if (debug != null) {

                        debug.println("Not modified, using cached copy");

                    }

                    return getMatchingCerts(certs, selector);

                } else if (connection instanceof HttpURLConnection) {

                    // some proxy servers omit last modified

                    HttpURLConnection hconn = (HttpURLConnection) connection;

                    if (hconn.getResponseCode()

                                == HttpURLConnection.HTTP_NOT_MODIFIED) {

                        if (debug != null) {

                            debug.println("Not modified, using cached copy");

                        }

                        return getMatchingCerts(certs, selector);

                    }

                }

            }

            if (debug != null) {

                debug.println("Downloading new certificates...");

            }

            // Safe cast since factory is an X.509 certificate factory

            certs = (Collection<X509Certificate>)

                factory.generateCertificates(in);

            return getMatchingCerts(certs, selector);

        } catch (IOException e) {

            if (debug != null) {

                debug.println("Exception fetching certificates:");

                e.printStackTrace();

            }

        } catch (CertificateException e) {

            if (debug != null) {

                debug.println("Exception fetching certificates:");

                e.printStackTrace();

            }

        } finally {

            if (in != null) {

                try {

                    in.close();

                } catch (IOException e) {

                    // ignore

                }

            }

        }

        // exception, forget previous values

        lastModified = 0;

        certs = Collections.<X509Certificate>emptySet();

        return certs;

    }

    /**

     * Iterates over the specified Collection of X509Certificates and

     * returns only those that match the criteria specified in the

     * CertSelector.

     */

    private static Collection<X509Certificate> getMatchingCerts

        (Collection<X509Certificate> certs, CertSelector selector) {

        // if selector not specified, all certs match

        if (selector == null) {

            return certs;

        }

        List<X509Certificate> matchedCerts =

            new ArrayList<X509Certificate>(certs.size());

        for (X509Certificate cert : certs) {

            if (selector.match(cert)) {

                matchedCerts.add(cert);

            }

        }

        return matchedCerts;

    }

    /**

     * Returns a <code>Collection</code> of <code>X509CRL</code>s that

     * match the specified selector. If no <code>X509CRL</code>s

     * match the selector, an empty <code>Collection</code> will be returned.

     *

     * @param selector A <code>CRLSelector</code> used to select which

     *  <code>X509CRL</code>s should be returned. Specify <code>null</code>

     *  to return all <code>X509CRL</code>s.

     * @return A <code>Collection</code> of <code>X509CRL</code>s that

     *         match the specified selector

     * @throws CertStoreException if an exception occurs

     */

    @SuppressWarnings("unchecked")

    public synchronized Collection<X509CRL> engineGetCRLs(CRLSelector selector)

        throws CertStoreException {

        // if ldap URI we wrap the CRLSelector in an LDAPCRLSelector to

        // avoid LDAP DN matching issues (see LDAPCRLSelector for more info)

        if (ldap) {

            X509CRLSelector xsel = (X509CRLSelector) selector;

            try {

                xsel = LDAP.helper().wrap(xsel, null, ldapPath);

            } catch (IOException ioe) {

                throw new CertStoreException(ioe);

            }

            // Fetch the CRLs via LDAP. LDAPCertStore has its own

            // caching mechanism, see the class description for more info.

            // Safe cast since xsel is an X509 certificate selector.

            return (Collection<X509CRL>) ldapCertStore.getCRLs(xsel);

        }

        // Return the CRLs for this entry. It returns the cached value

        // if it is still current and fetches the CRLs otherwise.

        // For the caching details, see the top of this class.

        long time = System.currentTimeMillis();

        if (time - lastChecked < CHECK_INTERVAL) {

            if (debug != null) {

                debug.println("Returning CRL from cache");

            }

            return getMatchingCRLs(crl, selector);

        }

        lastChecked = time;

        InputStream in = null;

        try {

            URLConnection connection = uri.toURL().openConnection();

            if (lastModified != 0) {

                connection.setIfModifiedSince(lastModified);

            }

            in = connection.getInputStream();

            long oldLastModified = lastModified;

            lastModified = connection.getLastModified();

            if (oldLastModified != 0) {

                if (oldLastModified == lastModified) {

                    if (debug != null) {

                        debug.println("Not modified, using cached copy");

                    }

                    return getMatchingCRLs(crl, selector);

                } else if (connection instanceof HttpURLConnection) {

                    // some proxy servers omit last modified

                    HttpURLConnection hconn = (HttpURLConnection) connection;

                    if (hconn.getResponseCode()

                                == HttpURLConnection.HTTP_NOT_MODIFIED) {

                        if (debug != null) {

                            debug.println("Not modified, using cached copy");

                        }

                        return getMatchingCRLs(crl, selector);

                    }

                }

            }

            if (debug != null) {

                debug.println("Downloading new CRL...");

            }

            crl = (X509CRL) factory.generateCRL(in);

            return getMatchingCRLs(crl, selector);

        } catch (IOException e) {

            if (debug != null) {

                debug.println("Exception fetching CRL:");

                e.printStackTrace();

            }

        } catch (CRLException e) {

            if (debug != null) {

                debug.println("Exception fetching CRL:");

                e.printStackTrace();

            }

        } finally {

            if (in != null) {

                try {

                    in.close();

                } catch (IOException e) {

                    // ignore

                }

            }

        }

        // exception, forget previous values

        lastModified = 0;

        crl = null;

        return Collections.<X509CRL>emptyList();

    }

    /**

     * Checks if the specified X509CRL matches the criteria specified in the

     * CRLSelector.

     */

    private static Collection<X509CRL> getMatchingCRLs

        (X509CRL crl, CRLSelector selector) {

        if (selector == null || (crl != null && selector.match(crl))) {

            return Collections.<X509CRL>singletonList(crl);

        } else {

            return Collections.<X509CRL>emptyList();

        }

    }

    /**

     * CertStoreParameters for the URICertStore.

     */

    static class URICertStoreParameters implements CertStoreParameters {

        private final URI uri;

        private volatile int hashCode = 0;

        URICertStoreParameters(URI uri) {

            this.uri = uri;

        }

        public boolean equals(Object obj) {

            if (!(obj instanceof URICertStoreParameters)) {

                return false;

            }

            URICertStoreParameters params = (URICertStoreParameters) obj;

            return uri.equals(params.uri);

        }

        public int hashCode() {

            if (hashCode == 0) {

                int result = 17;

                result = 37*result + uri.hashCode();

                hashCode = result;

            }

            return hashCode;

        }

        public Object clone() {

            try {

                return super.clone();

            } catch (CloneNotSupportedException e) {

                /* Cannot happen */

            }

        }

    }

    /**

     * This class allows the URICertStore to be accessed as a CertStore.

     */

    private static class UCS extends CertStore {

        protected UCS(CertStoreSpi spi, Provider p, String type,

            CertStoreParameters params) {

            super(spi, p, type, params);

        }

    }

}