// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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.cloud.consoleproxy;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Date;
import java.util.Objects;

import org.apache.cloudstack.consoleproxy.ConsoleAccessManager;
import org.apache.cloudstack.framework.config.dao.ConfigurationDao;
import org.apache.cloudstack.framework.security.keys.KeysManager;
import org.apache.cloudstack.framework.security.keystore.KeystoreManager;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.lang3.StringUtils;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;

import com.cloud.agent.AgentManager;
import com.cloud.agent.api.AgentControlAnswer;
import com.cloud.agent.api.Answer;
import com.cloud.agent.api.ConsoleAccessAuthenticationAnswer;
import com.cloud.agent.api.ConsoleAccessAuthenticationCommand;
import com.cloud.agent.api.ConsoleProxyLoadReportCommand;
import com.cloud.agent.api.GetVncPortAnswer;
import com.cloud.agent.api.GetVncPortCommand;
import com.cloud.agent.api.StartupCommand;
import com.cloud.agent.api.StartupProxyCommand;
import com.cloud.agent.api.proxy.StartConsoleProxyAgentHttpHandlerCommand;
import com.cloud.exception.AgentUnavailableException;
import com.cloud.exception.OperationTimedoutException;
import com.cloud.host.Host;
import com.cloud.host.HostVO;
import com.cloud.host.Status;
import com.cloud.host.dao.HostDao;
import com.cloud.hypervisor.Hypervisor;
import com.cloud.servlet.ConsoleProxyPasswordBasedEncryptor;
import com.cloud.servlet.ConsoleProxyServlet;
import com.cloud.utils.Ternary;
import com.cloud.vm.VirtualMachine;
import com.cloud.vm.dao.VMInstanceDao;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/**
 * Utility class to manage interactions with agent-based console access
 * Extracted from ConsoleProxyManagerImpl so that other console proxy managers
 * can reuse
 */
public abstract class AgentHookBase implements AgentHook {
    protected Logger logger = LogManager.getLogger(getClass());

    VMInstanceDao _instanceDao;
    HostDao _hostDao;
    ConfigurationDao _configDao;
    AgentManager _agentMgr;
    KeystoreManager _ksMgr;
    KeysManager _keysMgr;
    ConsoleAccessManager consoleAccessManager;

    protected AgentHookBase(VMInstanceDao instanceDao, HostDao hostDao, ConfigurationDao cfgDao, KeystoreManager ksMgr,
                         AgentManager agentMgr, KeysManager keysMgr, ConsoleAccessManager consoleAccessMgr) {
        _instanceDao = instanceDao;
        _hostDao = hostDao;
        _agentMgr = agentMgr;
        _configDao = cfgDao;
        _ksMgr = ksMgr;
        _keysMgr = keysMgr;
        consoleAccessManager = consoleAccessMgr;
    }

    @Override
    public AgentControlAnswer onConsoleAccessAuthentication(ConsoleAccessAuthenticationCommand cmd) {
        Long vmId = null;

        String ticketInUrl = cmd.getTicket();
        String sessionUuid = cmd.getSessionUuid();
        String clientAddress = cmd.getClientAddress();

        if (ticketInUrl == null) {
            logger.error("Access ticket could not be found, you could be running an old version of console proxy. vmId: " + cmd.getVmId());
            return new ConsoleAccessAuthenticationAnswer(cmd, false);
        }

        if (logger.isDebugEnabled()) {
            logger.debug("Console authentication. Ticket in url for " + cmd.getHost() + ":" + cmd.getPort() + "-" + cmd.getVmId() + " is " + ticketInUrl);
        }

        if (!cmd.isReauthenticating()) {
            String ticket = consoleAccessManager.genAccessTicket(cmd.getHost(), cmd.getPort(), cmd.getSid(), cmd.getVmId(), sessionUuid);
            if (logger.isDebugEnabled()) {
                logger.debug("Console authentication. Ticket in 1 minute boundary for " + cmd.getHost() + ":" + cmd.getPort() + "-" + cmd.getVmId() + " is " + ticket);
            }

            if (!consoleAccessManager.isSessionAllowed(sessionUuid)) {
                logger.error(String.format("Session [%s] has been already used or does not exist.", sessionUuid));
                return new ConsoleAccessAuthenticationAnswer(cmd, false);
            }

            logger.debug(String.format("Acquiring session [%s] as it was just used.", sessionUuid));
            consoleAccessManager.acquireSession(sessionUuid, clientAddress);

            if (!ticket.equals(ticketInUrl)) {
                Date now = new Date();
                // considering of minute round-up
                String minuteEarlyTicket = consoleAccessManager.genAccessTicket(cmd.getHost(), cmd.getPort(), cmd.getSid(), cmd.getVmId(), new Date(now.getTime() - 60 * 1000), sessionUuid);

                if (logger.isDebugEnabled()) {
                    logger.debug("Console authentication. Ticket in 2-minute boundary for " + cmd.getHost() + ":" + cmd.getPort() + "-" + cmd.getVmId() + " is " +
                        minuteEarlyTicket);
                }

                if (!minuteEarlyTicket.equals(ticketInUrl)) {
                    logger.error("Access ticket expired or has been modified. vmId: " + cmd.getVmId() + "ticket in URL: " + ticketInUrl +
                        ", tickets to check against: " + ticket + "," + minuteEarlyTicket);
                    return new ConsoleAccessAuthenticationAnswer(cmd, false);
                }
            }
        }

        if (cmd.getVmId() != null && cmd.getVmId().isEmpty()) {
            if (logger.isDebugEnabled()) {
                logger.debug("Invalid vm id sent from proxy(happens when proxy session has terminated)");
            }
            return new ConsoleAccessAuthenticationAnswer(cmd, false);
        }

        VirtualMachine vm = _instanceDao.findByUuid(cmd.getVmId());
        if (vm == null) {
            vm = _instanceDao.findById(Long.parseLong(cmd.getVmId()));
        }
        if (vm == null) {
            logger.error("Invalid vm id " + cmd.getVmId() + " sent from console access authentication");
            return new ConsoleAccessAuthenticationAnswer(cmd, false);
        }

        if (vm.getHostId() == null) {
            logger.warn("VM " + vmId + " lost host info, failed authentication request");
            return new ConsoleAccessAuthenticationAnswer(cmd, false);
        }

        HostVO host = _hostDao.findById(vm.getHostId());
        if (host == null) {
            logger.warn("VM " + vmId + "'s host does not exist, fail authentication request");
            return new ConsoleAccessAuthenticationAnswer(cmd, false);
        }

        String sid = cmd.getSid();
        if (sid == null || !sid.equals(vm.getVncPassword())) {
            if (Hypervisor.HypervisorType.External.equals(vm.getHypervisorType())) {
                logger.debug("{} is on External hypervisor, skip checking sid", vm.getHypervisorType());
            } else {
                logger.warn("sid {} in url does not match stored sid.", sid);
                return new ConsoleAccessAuthenticationAnswer(cmd, false);
            }
        }

        if (cmd.isReauthenticating()) {
            ConsoleAccessAuthenticationAnswer authenticationAnswer = new ConsoleAccessAuthenticationAnswer(cmd, true);
            authenticationAnswer.setReauthenticating(true);

            logger.info("Re-authentication request, ask host " + vm.getHostId() + " for new console info");
            GetVncPortAnswer answer = (GetVncPortAnswer)_agentMgr.easySend(vm.getHostId(), new GetVncPortCommand(vm.getId(), vm.getInstanceName()));

            if (answer != null && answer.getResult()) {
                Ternary<String, String, String> parsedHostInfo = ConsoleProxyServlet.parseHostInfo(answer.getAddress());

                if (parsedHostInfo.second() != null && parsedHostInfo.third() != null) {

                    logger.info("Re-authentication result. vm: " + vm.getId() + ", tunnel url: " + parsedHostInfo.second() + ", tunnel session: " +
                        parsedHostInfo.third());

                    authenticationAnswer.setTunnelUrl(parsedHostInfo.second());
                    authenticationAnswer.setTunnelSession(parsedHostInfo.third());
                } else {
                    logger.info("Re-authentication result. vm: " + vm.getId() + ", host address: " + parsedHostInfo.first() + ", port: " + answer.getPort());

                    authenticationAnswer.setHost(parsedHostInfo.first());
                    authenticationAnswer.setPort(answer.getPort());
                }
            } else {
                logger.warn("Re-authentication request failed");

                authenticationAnswer.setSuccess(false);
            }

            return authenticationAnswer;
        }

        return new ConsoleAccessAuthenticationAnswer(cmd, true);
    }

    @Override
    public void startAgentHttpHandlerInVM(StartupProxyCommand startupCmd) {
        StartConsoleProxyAgentHttpHandlerCommand cmd = null;

        try {
            SecureRandom random = SecureRandom.getInstance("SHA1PRNG");

            byte[] randomBytes = new byte[16];
            random.nextBytes(randomBytes);
            String storePassword = Base64.encodeBase64String(randomBytes);

            byte[] ksBits = null;

            HostVO consoleProxyHost = findConsoleProxyHost(startupCmd);

            if (Objects.isNull(consoleProxyHost)) {
                throw new IllegalStateException("Console proxy host is null");
            }

            Long datacenterId = consoleProxyHost.getDataCenterId();
            String consoleProxyUrlDomain = ConsoleProxyManager.ConsoleProxyUrlDomain.valueIn(datacenterId);
            Boolean consoleProxySslEnabled = ConsoleProxyManager.ConsoleProxySslEnabled.valueIn(datacenterId);
            if (!StringUtils.isEmpty(consoleProxyUrlDomain) && Boolean.TRUE.equals(consoleProxySslEnabled)) {
                ksBits = _ksMgr.getKeystoreBits(ConsoleProxyManager.CERTIFICATE_NAME, ConsoleProxyManager.CERTIFICATE_NAME, storePassword);
                //ks manager raises exception if ksBits are null, hence no need to explicltly handle the condition
            } else {
                logger.debug("SSL is disabled for console proxy. To enable SSL, please configure consoleproxy.sslEnabled and consoleproxy.url.domain global settings.");
            }

            cmd = new StartConsoleProxyAgentHttpHandlerCommand(ksBits, storePassword);
            cmd.setEncryptorPassword(getEncryptorPassword());
            cmd.setIsSourceIpCheckEnabled(Boolean.parseBoolean(_configDao.getValue(ConsoleProxyManager.NoVncConsoleSourceIpCheckEnabled.key())));

            if (consoleProxyHost != null) {
                Answer answer = _agentMgr.send(consoleProxyHost.getId(), cmd);
                if (answer == null || !answer.getResult()) {
                    logger.error("Console proxy agent reported that it failed to execute http handling startup command");
                } else {
                    logger.info("Successfully sent out command to start HTTP handling in console proxy agent");
                }
            }
        }catch (NoSuchAlgorithmException e) {
            logger.error("Unexpected exception in SecureRandom Algorithm selection ", e);
        } catch (AgentUnavailableException e) {
            logger.error("Unable to send http handling startup command to the console proxy resource for proxy:" + startupCmd.getProxyVmId(), e);
        } catch (OperationTimedoutException e) {
            logger.error("Unable to send http handling startup command(time out) to the console proxy resource for proxy:" + startupCmd.getProxyVmId(), e);
        } catch (OutOfMemoryError e) {
            logger.error("Unrecoverable OutOfMemory Error, exit and let it be re-launched");
            System.exit(1);
        } catch (Exception e) {
            logger.error(
                "Unexpected exception when sending http handling startup command(time out) to the console proxy resource for proxy:" + startupCmd.getProxyVmId(), e);
        }
    }

    private String getEncryptorPassword() {
        String key;
        String iv;
        ConsoleProxyPasswordBasedEncryptor.KeyIVPair keyIvPair = null;

        // if we failed after reset, something is definitely wrong
        for (int i = 0; i < 2; i++) {
            key = _keysMgr.getEncryptionKey();
            iv = _keysMgr.getEncryptionIV();

            keyIvPair = new ConsoleProxyPasswordBasedEncryptor.KeyIVPair(key, iv);

            if (keyIvPair.getIvBytes() == null || keyIvPair.getIvBytes().length != 16 || keyIvPair.getKeyBytes() == null || keyIvPair.getKeyBytes().length != 16) {

                logger.warn("Console access AES KeyIV sanity check failed, reset and regenerate");
                _keysMgr.resetEncryptionKeyIV();
            } else {
                break;
            }
        }

        Gson gson = new GsonBuilder().create();
        return gson.toJson(keyIvPair);
    }

    protected abstract HostVO findConsoleProxyHost(StartupProxyCommand cmd);

    @Override
    public void onLoadReport(ConsoleProxyLoadReportCommand cmd) {
        // no-op since we do not auto-scale
    }

    @Override
    public void onAgentConnect(Host host, StartupCommand cmd) {
        // no-op
    }

    @Override
    public void onAgentDisconnect(long agentId, Status state) {
        // no-op since we do not autoscale
    }
}