IntentWithGesturesHandler.java

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package org.chromium.chrome.browser.externalnav;

import android.annotation.SuppressLint;
import android.content.Intent;
import android.os.AsyncTask;

import org.chromium.base.Log;
import org.chromium.base.SecureRandomInitializer;
import org.chromium.chrome.browser.IntentHandler;
import org.chromium.chrome.browser.util.IntentUtils;

import java.io.IOException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.concurrent.ExecutionException;

/**
 * This class hold a token for the most recent launched external intent that has
 * user gesture. If the external intent resolves to chrome itself, the user
 * gesture will be applied to the new url request. Since there could be at most
 * one intent chooser at a time, this class only stores the most recent intent
 * that has user gesture. A previously launched intent with user gesture will
 * have its token invalidated if a new one comes.
 */
public class IntentWithGesturesHandler {
    /**
     * Extra to record whether the intent is launched by user gesture.
     */
    public static final String EXTRA_USER_GESTURE_TOKEN =
            "org.chromium.chrome.browser.user_gesture_token";

    private static final String TAG = "IntentGestureHandler";

    private static final Object INSTANCE_LOCK = new Object();
    private static IntentWithGesturesHandler sIntentWithGesturesHandler;
    private SecureRandom mSecureRandom;
    private AsyncTask<Void, Void, SecureRandom> mSecureRandomInitializer;
    private byte[] mIntentToken;
    private String mUri;

    /**
     * Get the singleton instance of this object.
     */
    public static IntentWithGesturesHandler getInstance() {
        synchronized (INSTANCE_LOCK) {
            if (sIntentWithGesturesHandler == null) {
                sIntentWithGesturesHandler = new IntentWithGesturesHandler();
            }
        }
        return sIntentWithGesturesHandler;
    }

    private IntentWithGesturesHandler() {
        mSecureRandomInitializer = new AsyncTask<Void, Void, SecureRandom>() {
            // SecureRandomInitializer addresses the bug in SecureRandom that "TrulyRandom"
            // warns about, so this lint warning can safely be suppressed.
            @SuppressLint("TrulyRandom")
            @Override
            protected SecureRandom doInBackground(Void... params) {
                SecureRandom secureRandom = null;
                try {
                    secureRandom = new SecureRandom();
                    SecureRandomInitializer.initialize(secureRandom);
                } catch (IOException ioe) {
                    Log.e(TAG, "Cannot initialize SecureRandom", ioe);
                }
                return secureRandom;
            }
        }.execute();
    }

    /**
     * Generate a new token for the intent that has user gesture. This will
     * invalidate the token on the previously launched intent with user gesture.
     *
     * @param intent Intent with user gesture.
     */
    public void onNewIntentWithGesture(Intent intent) {
        if (mSecureRandomInitializer != null) {
            try {
                mSecureRandom = mSecureRandomInitializer.get();
            } catch (InterruptedException | ExecutionException e) {
                Log.e(TAG, "Error fetching SecureRandom", e);
            }
            mSecureRandomInitializer = null;
        }
        if (mSecureRandom == null) return;
        mIntentToken = new byte[32];
        mSecureRandom.nextBytes(mIntentToken);
        intent.putExtra(EXTRA_USER_GESTURE_TOKEN, mIntentToken);
        mUri = IntentHandler.getUrlFromIntent(intent);
    }

    /**
     * Get the user gesture from the intent and clear the stored token.
     *
     * @param intent Intent that is used to launch chrome.
     * @return true if the intent has user gesture, or false otherwise.
     */
    public boolean getUserGestureAndClear(Intent intent) {
        if (mIntentToken == null || mUri == null) return false;
        byte[] bytes = IntentUtils.safeGetByteArrayExtra(intent, EXTRA_USER_GESTURE_TOKEN);
        boolean ret = (bytes != null) && Arrays.equals(bytes, mIntentToken)
                && mUri.equals(IntentHandler.getUrlFromIntent(intent));
        clear();
        return ret;
    }

    /**
     * Clear the gesture token.
     */
    public void clear() {
        mIntentToken = null;
        mUri = null;
    }
}