src/com/android/phone/common/mail/store/ImapConnection.java

/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * 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.android.phone.common.mail.store;

import android.provider.VoicemailContract.Status;
import android.text.TextUtils;

import com.android.phone.common.mail.AuthenticationFailedException;
import com.android.phone.common.mail.CertificateValidationException;
import com.android.phone.common.mail.MailTransport;
import com.android.phone.common.mail.MessagingException;
import com.android.phone.common.mail.store.imap.ImapConstants;
import com.android.phone.common.mail.store.imap.ImapResponse;
import com.android.phone.common.mail.store.imap.ImapResponseParser;
import com.android.phone.common.mail.store.imap.ImapUtility;
import com.android.phone.common.mail.utils.LogUtils;
import com.android.phone.common.mail.store.ImapStore.ImapException;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

import javax.net.ssl.SSLException;

/**
 * A cacheable class that stores the details for a single IMAP connection.
 */
public class ImapConnection {
    private final String TAG = "ImapConnection";

    private String mLoginPhrase;
    private ImapStore mImapStore;
    private MailTransport mTransport;
    private ImapResponseParser mParser;

    static final String IMAP_REDACTED_LOG = "[IMAP command redacted]";

    /**
     * Next tag to use.  All connections associated to the same ImapStore instance share the same
     * counter to make tests simpler.
     * (Some of the tests involve multiple connections but only have a single counter to track the
     * tag.)
     */
    private final AtomicInteger mNextCommandTag = new AtomicInteger(0);

    ImapConnection(ImapStore store) {
        setStore(store);
    }

    void setStore(ImapStore store) {
        // TODO: maybe we should throw an exception if the connection is not closed here,
        // if it's not currently closed, then we won't reopen it, so if the credentials have
        // changed, the connection will not be reestablished.
        mImapStore = store;
        mLoginPhrase = null;
    }

    /**
     * Generates and returns the phrase to be used for authentication. This will be a LOGIN with
     * username and password.
     *
     * @return the login command string to sent to the IMAP server
     */
    String getLoginPhrase() {
        if (mLoginPhrase == null) {
            if (mImapStore.getUsername() != null && mImapStore.getPassword() != null) {
                // build the LOGIN string once (instead of over-and-over again.)
                // apply the quoting here around the built-up password
                mLoginPhrase = ImapConstants.LOGIN + " " + mImapStore.getUsername() + " "
                        + ImapUtility.imapQuoted(mImapStore.getPassword());
            }
        }
        return mLoginPhrase;
    }

    void open() throws IOException, MessagingException {
        if (mTransport != null && mTransport.isOpen()) {
            return;
        }

        try {
            // copy configuration into a clean transport, if necessary
            if (mTransport == null) {
                mTransport = mImapStore.cloneTransport();
            }

            mTransport.open();

            createParser();

            // LOGIN
            doLogin();
        } catch (SSLException e) {
            LogUtils.d(TAG, "SSLException ", e);
            mImapStore.getImapHelper().setDataChannelState(Status.DATA_CHANNEL_STATE_SERVER_ERROR);
            throw new CertificateValidationException(e.getMessage(), e);
        } catch (IOException ioe) {
            LogUtils.d(TAG, "IOException", ioe);
            mImapStore.getImapHelper()
                    .setDataChannelState(Status.DATA_CHANNEL_STATE_COMMUNICATION_ERROR);
            throw ioe;
        } finally {
            destroyResponses();
        }
    }

    /**
     * Closes the connection and releases all resources. This connection can not be used again
     * until {@link #setStore(ImapStore)} is called.
     */
    void close() {
        if (mTransport != null) {
            mTransport.close();
            mTransport = null;
        }
        destroyResponses();
        mParser = null;
        mImapStore = null;
    }

    /**
     * Logs into the IMAP server
     */
    private void doLogin() throws IOException, MessagingException, AuthenticationFailedException {
        try {
            executeSimpleCommand(getLoginPhrase(), true);
        } catch (ImapException ie) {
            LogUtils.d(TAG, "ImapException", ie);
            final String status = ie.getStatus();
            final String code = ie.getResponseCode();
            final String alertText = ie.getAlertText();

            // if the response code indicates expired or bad credentials, throw a special exception
            if (ImapConstants.AUTHENTICATIONFAILED.equals(code) ||
                    ImapConstants.EXPIRED.equals(code) ||
                    (ImapConstants.NO.equals(status) && TextUtils.isEmpty(code))) {
                mImapStore.getImapHelper()
                        .setDataChannelState(Status.DATA_CHANNEL_STATE_BAD_CONFIGURATION);
                throw new AuthenticationFailedException(alertText, ie);
            }

            throw new MessagingException(alertText, ie);
        }
    }

    /**
     * Create an {@link ImapResponseParser} from {@code mTransport.getInputStream()} and
     * set it to {@link #mParser}.
     *
     * If we already have an {@link ImapResponseParser}, we
     * {@link #destroyResponses()} and throw it away.
     */
    private void createParser() {
        destroyResponses();
        mParser = new ImapResponseParser(mTransport.getInputStream());
    }


    void destroyResponses() {
        if (mParser != null) {
            mParser.destroyResponses();
        }
    }

    ImapResponse readResponse() throws IOException, MessagingException {
        return mParser.readResponse();
    }

    List<ImapResponse> executeSimpleCommand(String command)
            throws IOException, MessagingException{
        return executeSimpleCommand(command, false);
    }

    /**
     * Send a single command to the server.  The command will be preceded by an IMAP command
     * tag and followed by \r\n (caller need not supply them).
     * Execute a simple command at the server, a simple command being one that is sent in a single
     * line of text
     *
     * @param command the command to send to the server
     * @param sensitive whether the command should be redacted in logs (used for login)
     * @return a list of ImapResponses
     * @throws IOException
     * @throws MessagingException
     */
    List<ImapResponse> executeSimpleCommand(String command, boolean sensitive)
            throws IOException, MessagingException {
        // TODO: It may be nice to catch IOExceptions and close the connection here.
        // Currently, we expect callers to do that, but if they fail to we'll be in a broken state.
        sendCommand(command, sensitive);
        return getCommandResponses();
    }

    String sendCommand(String command, boolean sensitive) throws IOException, MessagingException {
        open();

        if (mTransport == null) {
            throw new IOException("Null transport");
        }
        String tag = Integer.toString(mNextCommandTag.incrementAndGet());
        String commandToSend = tag + " " + command;
        mTransport.writeLine(commandToSend, (sensitive ? IMAP_REDACTED_LOG : command));

        return tag;
    }

    /**
     * Read and return all of the responses from the most recent command sent to the server
     *
     * @return a list of ImapResponses
     * @throws IOException
     * @throws MessagingException
     */
    List<ImapResponse> getCommandResponses() throws IOException, MessagingException {
        final List<ImapResponse> responses = new ArrayList<ImapResponse>();
        ImapResponse response;
        do {
            response = mParser.readResponse();
            responses.add(response);
        } while (!response.isTagged());

        if (!response.isOk()) {
            final String toString = response.toString();
            final String status = response.getStatusOrEmpty().getString();
            final String alert = response.getAlertTextOrEmpty().getString();
            final String responseCode = response.getResponseCodeOrEmpty().getString();
            destroyResponses();
            mImapStore.getImapHelper().setDataChannelState(Status.DATA_CHANNEL_STATE_SERVER_ERROR);
            // if the response code indicates an error occurred within the server, indicate that
            if (ImapConstants.UNAVAILABLE.equals(responseCode)) {

                throw new MessagingException(MessagingException.SERVER_ERROR, alert);
            }
            throw new ImapException(toString, status, alert, responseCode);
        }
        return responses;
    }
}