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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package sun.security.ssl;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Locale;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.ConcurrentHashMap;
import javax.net.ssl.SSLSession;
import javax.net.ssl.SSLSessionContext;

import sun.security.util.Cache;
import sun.security.util.KeyUtil;

/**
 * {@systemProperty jdk.tls.server.enableSessionTicketExtension} determines if the
 * server will provide stateless session tickets, if the client supports it,
 * as described in RFC 5077 and RFC 8446.  a stateless session ticket
 * contains the encrypted server's state which saves server resources.
 *
 * {@systemProperty jdk.tls.client.enableSessionTicketExtension} determines if the
 * client will send an extension in the ClientHello in the pre-TLS 1.3.
 * This extension allows the client to accept the server's session state for
 * Server Side stateless resumption (RFC 5077).  Setting the property to
 * "false" turns this off, by default it is true.  For TLS 1.3, the system
 * property is not needed as this support is part of the spec.
 *
 * {@systemProperty jdk.tls.server.sessionTicketTimeout} determines how long
 * a session in the server cache or the stateless resumption tickets are
 * available for use.  The value set by the property can be modified by
 * {@code SSLSessionContext.setSessionTimeout()} during runtime.
 *
 */

final class SSLSessionContextImpl implements SSLSessionContext {
    private static final int DEFAULT_MAX_CACHE_SIZE = 20480;
    private static final int DEFAULT_MAX_QUEUE_SIZE = 10;
    // Default lifetime of a session. 24 hours
    static final int DEFAULT_SESSION_TIMEOUT = 86400;

    private final Cache<SessionId, SSLSessionImpl> sessionCache;
                                        // session cache, session id as key
    private final Cache<String, SSLSessionImpl> sessionHostPortCache;
                                        // session cache, "host:port" as key
    private int cacheLimit;             // the max cache size
    private int timeout;                // timeout in seconds

    // The current session ticket encryption key ID (only used in server context)
    private int currentKeyID;
    // Session ticket encryption keys and IDs map (only used in server context)
    private final Map<Integer, SessionTicketExtension.StatelessKey> keyHashMap;

    // Default setting for stateless session resumption support (RFC 5077)
    private boolean statelessSession = true;

    // package private
    SSLSessionContextImpl(boolean server) {
        timeout = DEFAULT_SESSION_TIMEOUT;
        cacheLimit = getDefaults(server);    // default cache size

        // use soft reference
        if (server) {
            sessionCache = Cache.newSoftMemoryCache(cacheLimit, timeout);
            sessionHostPortCache = Cache.newSoftMemoryCache(cacheLimit, timeout);
            keyHashMap = new ConcurrentHashMap<>();
            // Should be "randomly generated" according to RFC 5077,
            // but doesn't necessarily have to be a true random number.
            currentKeyID = new Random(System.nanoTime()).nextInt();
        } else {
            sessionCache = Cache.newSoftMemoryCache(cacheLimit, timeout);
            sessionHostPortCache = Cache.newSoftMemoryQueue(cacheLimit, timeout,
                DEFAULT_MAX_QUEUE_SIZE);
            keyHashMap = Map.of();
        }
    }

    // Stateless sessions when available, but there is a cache
    boolean statelessEnabled() {
        return statelessSession;
    }

    /**
     * Returns the <code>SSLSession</code> bound to the specified session id.
     */
    @Override
    public SSLSession getSession(byte[] sessionId) {
        if (sessionId == null) {
            throw new NullPointerException("session id cannot be null");
        }

        SSLSessionImpl sess = sessionCache.get(new SessionId(sessionId));
        if (!isTimedout(sess)) {
            return sess;
        }

        return null;
    }

    /**
     * Returns an enumeration of the active SSL sessions.
     */
    @Override
    public Enumeration<byte[]> getIds() {
        SessionCacheVisitor scVisitor = new SessionCacheVisitor();
        sessionCache.accept(scVisitor);

        return scVisitor.getSessionIds();
    }

    /**
     * Sets the timeout limit for cached <code>SSLSession</code> objects
     *
     * Note that after reset the timeout, the cached session before
     * should be timed within the shorter one of the old timeout and the
     * new timeout.
     */
    @Override
    public void setSessionTimeout(int seconds)
                 throws IllegalArgumentException {
        if (seconds < 0) {
            throw new IllegalArgumentException();
        }

        if (timeout != seconds) {
            sessionCache.setTimeout(seconds);
            sessionHostPortCache.setTimeout(seconds);
            timeout = seconds;
        }
    }

    /**
     * Gets the timeout limit for cached <code>SSLSession</code> objects
     */
    @Override
    public int getSessionTimeout() {
        return timeout;
    }

    /**
     * Sets the size of the cache used for storing
     * <code>SSLSession</code> objects.
     */
    @Override
    public void setSessionCacheSize(int size)
                 throws IllegalArgumentException {
        if (size < 0)
            throw new IllegalArgumentException();

        if (cacheLimit != size) {
            sessionCache.setCapacity(size);
            sessionHostPortCache.setCapacity(size);
            cacheLimit = size;
        }
    }

    /**
     * Gets the size of the cache used for storing
     * <code>SSLSession</code> objects.
     */
    @Override
    public int getSessionCacheSize() {
        return cacheLimit;
    }

    private void cleanupStatelessKeys() {
        Iterator<Map.Entry<Integer, SessionTicketExtension.StatelessKey>> it =
            keyHashMap.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry<Integer, SessionTicketExtension.StatelessKey> entry = it.next();
            SessionTicketExtension.StatelessKey k = entry.getValue();
            if (k.isInvalid(this)) {
                it.remove();
                KeyUtil.destroySecretKeys(k.key);
            }
        }
    }

    // Package-private, used only from SessionTicketExtension.KeyState::getCurrentKey.
    SessionTicketExtension.StatelessKey getKey(HandshakeContext hc) {
        SessionTicketExtension.StatelessKey ssk = keyHashMap.get(currentKeyID);
        if (ssk != null && !ssk.isExpired()) {
            return ssk;
        }
        synchronized (this) {
            // If the current key is no longer expired, it was already
            // updated by a concurrent request, and we can return.
            ssk = keyHashMap.get(currentKeyID);
            if (ssk != null && !ssk.isExpired()) {
                return ssk;
            }
            int newID = currentKeyID + 1;
            ssk = new SessionTicketExtension.StatelessKey(hc, newID);
            keyHashMap.put(Integer.valueOf(newID), ssk);
            currentKeyID = newID;
        }
        // Check for and delete invalid keys every time we create a new stateless key.
        cleanupStatelessKeys();
        return ssk;
    }

    // Package-private, used only from SessionTicketExtension.KeyState::getKey.
    SessionTicketExtension.StatelessKey getKey(int id) {
        return keyHashMap.get(id);
    }

    // package-private method, used ONLY by ServerHandshaker
    SSLSessionImpl get(byte[] id) {
        return (SSLSessionImpl)getSession(id);
    }

    // package-private method, find and remove session from cache
    // return found session
    SSLSessionImpl pull(byte[] id) {
        if (id != null) {
            return sessionCache.pull(new SessionId(id));
        }
        return null;
    }

    // package-private method, used ONLY by ClientHandshaker
    SSLSessionImpl get(String hostname, int port) {
        /*
         * If no session caching info is available, we won't
         * get one, so exit before doing a lookup.
         */
        if (hostname == null && port == -1) {
            return null;
        }

        SSLSessionImpl sess = sessionHostPortCache.get(getKey(hostname, port));
        if (!isTimedout(sess)) {
            return sess;
        }

        return null;
    }

    private static String getKey(String hostname, int port) {
        return (hostname + ":" + port).toLowerCase(Locale.ENGLISH);
    }

    // cache a SSLSession
    //
    // In SunJSSE implementation, a session is created while getting a
    // client hello or a server hello message, and cached while the
    // handshaking finished.
    // Here we time the session from the time it cached instead of the
    // time it created, which is a little longer than the expected. So
    // please do check isTimedout() while getting entry from the cache.
    void put(SSLSessionImpl s) {
        put(s, false);
    }

    /**
     * Put an entry in the cache
     * @param s SSLSessionImpl entry to be stored
     * @param canQueue True if multiple entries may exist under one
     *                 session entry.
     */
    void put(SSLSessionImpl s, boolean canQueue) {
        sessionCache.put(s.getSessionId(), s);

        // If no hostname/port info is available, don't add this one.
        if ((s.getPeerHost() != null) && (s.getPeerPort() != -1)) {
            sessionHostPortCache.put(
                getKey(s.getPeerHost(), s.getPeerPort()), s, canQueue);
        }

        s.setContext(this);
    }

    // package-private method, remove a cached SSLSession
    void remove(SessionId key) {
        remove(key, false);
    }
    void remove(SessionId key, boolean isClient) {
        SSLSessionImpl s = sessionCache.get(key);
        if (s != null) {
            sessionCache.remove(key);
            // A client keeps the cache entry for queued NST resumption.
            if (!isClient) {
                sessionHostPortCache.remove(
                    getKey(s.getPeerHost(), s.getPeerPort()));
            }
        }
    }

    private int getDefaults(boolean server) {
        try {
            String st;

            // Property for Session Cache state
            if (server) {
                st = System.getProperty(
                        "jdk.tls.server.enableSessionTicketExtension", "true");
            } else {
                st = System.getProperty(
                        "jdk.tls.client.enableSessionTicketExtension", "true");
            }

            if (st.compareToIgnoreCase("false") == 0) {
                statelessSession = false;
            }

            // Property for Session Ticket Timeout.  The value can be changed
            // by SSLSessionContext.setSessionTimeout(int)
            String s = System.getProperty(
                    "jdk.tls.server.sessionTicketTimeout");
            if (s != null) {
                try {
                    int t = Integer.parseInt(s);
                    if (t < 0 ||
                            t > NewSessionTicket.MAX_TICKET_LIFETIME) {
                        timeout = DEFAULT_SESSION_TIMEOUT;
                        if (SSLLogger.isOn && SSLLogger.isOn("ssl")) {
                            SSLLogger.warning("Invalid timeout given " +
                                    "jdk.tls.server.sessionTicketTimeout: " + t +
                                    ".  Set to default value " + timeout);
                        }
                    } else {
                        timeout = t;
                    }
                } catch (NumberFormatException e) {
                    setSessionTimeout(DEFAULT_SESSION_TIMEOUT);
                    if (SSLLogger.isOn && SSLLogger.isOn("ssl")) {
                        SSLLogger.warning("Invalid timeout for " +
                                "jdk.tls.server.sessionTicketTimeout: " + s +
                                ".  Set to default value " + timeout);

                    }
                }
            }

            int defaultCacheLimit = Integer.getInteger(
                    "javax.net.ssl.sessionCacheSize", DEFAULT_MAX_CACHE_SIZE);

            if (defaultCacheLimit >= 0) {
                return defaultCacheLimit;
            } else if (SSLLogger.isOn && SSLLogger.isOn("ssl")) {
                SSLLogger.warning(
                    "invalid System Property javax.net.ssl.sessionCacheSize, " +
                    "use the default session cache size (" +
                    DEFAULT_MAX_CACHE_SIZE + ") instead");
            }
        } catch (Exception e) {
            // unlikely, log it for safe
            if (SSLLogger.isOn && SSLLogger.isOn("ssl")) {
                SSLLogger.warning(
                    "the System Property javax.net.ssl.sessionCacheSize is " +
                    "not available, use the default value (" +
                    DEFAULT_MAX_CACHE_SIZE + ") instead");
            }
        }

        return DEFAULT_MAX_CACHE_SIZE;
    }

    private boolean isTimedout(SSLSession sess) {
        if (timeout == 0) {
            return false;
        }

        if ((sess != null) && ((sess.getCreationTime() + timeout * 1000L)
                                        <= (System.currentTimeMillis()))) {
            sess.invalidate();
            return true;
        }

        return false;
    }

    private final class SessionCacheVisitor
            implements Cache.CacheVisitor<SessionId, SSLSessionImpl> {
        ArrayList<byte[]> ids = null;

        // public void visit(java.util.Map<K,V> map) {}
        @Override
        public void visit(java.util.Map<SessionId, SSLSessionImpl> map) {
            ids = new ArrayList<>(map.size());

            for (SessionId key : map.keySet()) {
                SSLSessionImpl value = map.get(key);
                if (!isTimedout(value)) {
                    ids.add(key.getId());
                }
            }
        }

        Enumeration<byte[]> getSessionIds() {
            return  ids != null ? Collections.enumeration(ids) :
                                  Collections.emptyEnumeration();
        }
    }
}