// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package org.chromium.base;
import android.app.Activity;
import android.app.Application;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.ContextWrapper;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.os.Build;
import android.os.Handler;
import android.os.Process;
import android.preference.PreferenceManager;
import androidx.annotation.Nullable;
import org.jni_zero.JNINamespace;
import org.chromium.build.BuildConfig;
/** This class provides Android application context related utility methods. */
@JNINamespace("base::android")
public class ContextUtils {
private static final String TAG = "ContextUtils";
private static Context sApplicationContext;
/**
* Flag for {@link Context#registerReceiver}: The receiver can receive broadcasts from other
* Apps. Has the same behavior as marking a statically registered receiver with "exported=true".
*
* TODO(mthiesse): Move to ApiHelperForT when we build against T SDK.
*/
public static final int RECEIVER_EXPORTED = 0x2;
public static final int RECEIVER_NOT_EXPORTED = 0x4;
/** Initialization-on-demand holder. This exists for thread-safe lazy initialization. */
private static class Holder {
// Not final for tests.
private static SharedPreferences sSharedPreferences = fetchAppSharedPreferences();
}
/**
* Get the Android application context.
*
* Under normal circumstances there is only one application context in a process, so it's safe
* to treat this as a global. In WebView it's possible for more than one app using WebView to be
* running in a single process, but this mechanism is rarely used and this is not the only
* problem in that scenario, so we don't currently forbid using it as a global.
*
* Do not downcast the context returned by this method to Application (or any subclass). It may
* not be an Application object; it may be wrapped in a ContextWrapper. The only assumption you
* may make is that it is a Context whose lifetime is the same as the lifetime of the process.
*/
public static Context getApplicationContext() {
return sApplicationContext;
}
/**
* Initializes the java application context.
*
* This should be called exactly once early on during startup, before native is loaded and
* before any other clients make use of the application context through this class.
*
* @param appContext The application context.
*/
public static void initApplicationContext(Context appContext) {
// Conceding that occasionally in tests, native is loaded before the browser process is
// started, in which case the browser process re-sets the application context.
assert sApplicationContext == null
|| sApplicationContext == appContext
|| ((ContextWrapper) sApplicationContext).getBaseContext() == appContext;
initJavaSideApplicationContext(appContext);
}
/**
* Only called by the static holder class and tests.
*
* @return The application-wide shared preferences.
*/
@SuppressWarnings("DefaultSharedPreferencesCheck")
private static SharedPreferences fetchAppSharedPreferences() {
// This may need to create the prefs directory if we've never used shared prefs before, so
// allow disk writes. This is rare but can happen if code used early in startup reads prefs.
try (StrictModeContext ignored = StrictModeContext.allowDiskWrites()) {
return PreferenceManager.getDefaultSharedPreferences(sApplicationContext);
}
}
/**
* This is used to ensure that we always use the application context to fetch the default shared
* preferences. This avoids needless I/O for android N and above. It also makes it clear that
* the app-wide shared preference is desired, rather than the potentially context-specific one.
*
* @return application-wide shared preferences.
*/
public static SharedPreferences getAppSharedPreferences() {
return Holder.sSharedPreferences;
}
/**
* Occasionally tests cannot ensure the application context doesn't change between tests (junit)
* and sometimes specific tests has its own special needs, initApplicationContext should be used
* as much as possible, but this method can be used to override it.
*
* @param appContext The new application context.
*/
public static void initApplicationContextForTests(Context appContext) {
Context prevValue = sApplicationContext;
initJavaSideApplicationContext(appContext);
// initApplicationContext() lets <clinit> create sSharedPreferences, but that does not work
// when setting it multiple times.
SharedPreferences prevPrefs = Holder.sSharedPreferences;
Holder.sSharedPreferences = fetchAppSharedPreferences();
ResettersForTesting.register(
() -> {
sApplicationContext = prevValue;
Holder.sSharedPreferences = prevPrefs;
});
}
private static void initJavaSideApplicationContext(Context appContext) {
assert appContext != null;
// Guard against anyone trying to downcast.
if (BuildConfig.ENABLE_ASSERTS && appContext instanceof Application) {
appContext = new ContextWrapper(appContext);
}
sApplicationContext = appContext;
}
/**
* @return Whether the process is isolated.
*/
@SuppressWarnings("NewApi")
public static boolean isIsolatedProcess() {
// Was not made visible until Android P, but the method has always been there.
return Process.isIsolated();
}
/**
* @return if current process is SdkSandbox process.
*/
public static boolean isSdkSandboxProcess() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
return Process.isSdkSandbox();
} else {
return false;
}
}
/**
* @return The name of the current process. E.g. "org.chromium.chrome:privileged_process0".
*/
public static String getProcessName() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
return Application.getProcessName();
}
try {
Class<?> activityThreadClazz = Class.forName("android.app.ActivityThread");
return (String) activityThreadClazz.getMethod("currentProcessName").invoke(null);
} catch (Exception e) {
// If fallback logic is ever needed, refer to:
// https://chromium-review.googlesource.com/c/chromium/src/+/905563/1
throw JavaUtils.throwUnchecked(e);
}
}
/**
* @return Whether the current process is 64-bit.
*/
public static boolean isProcess64Bit() {
return Process.is64Bit();
}
/**
* Extract the {@link Activity} if the given {@link Context} either is or wraps one.
*
* @param context The context to check.
* @return Extracted activity if it exists, otherwise null.
*/
public static @Nullable Activity activityFromContext(@Nullable Context context) {
// Only retrieves the base context if the supplied context is a ContextWrapper but not an
// Activity, because Activity is a subclass of ContextWrapper.
while (context instanceof ContextWrapper) {
if (context instanceof Activity) return (Activity) context;
context = ((ContextWrapper) context).getBaseContext();
}
return null;
}
/**
* Register a broadcast receiver that may only accept protected broadcasts.
*
* You should (only) use this method when:
* <p><ul>
* <li>You need to receive protected broadcasts.
* </ul><p>
* This method does not presently verify that the provided IntentFilter covers only protected
* broadcasts, so you should make sure that the broadcasts you register for are in fact
* protected broadcasts. The Android platform's <a
* href="https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/res/AndroidManifest.xml">
* AndroidManifest.xml</a> contains a list of broadcasts which should be common to all devices.
* You should be careful about using broadcasts which appear to be protected, but are not listed
* in the platform's manifest, as they may not be protected on all devices. Different versions
* or builds of Android may have different sets of protected broadcasts, so add appropriate
* guards if needed.
* <p>
* You can unregister receivers using the normal {@link Context#unregisterReceiver} method.
*/
public static Intent registerProtectedBroadcastReceiver(
Context context, BroadcastReceiver receiver, IntentFilter filter) {
return registerBroadcastReceiver(
context, receiver, filter, /* permission= */ null, /* scheduler= */ null, 0);
}
public static Intent registerProtectedBroadcastReceiver(
Context context, BroadcastReceiver receiver, IntentFilter filter, Handler scheduler) {
return registerBroadcastReceiver(
context, receiver, filter, /* permission= */ null, scheduler, 0);
}
/**
* Register a broadcast receiver that may accept broadcasts from any UID.
*
* You should (only) use exported receivers when:
* <p><ul>
* <li>You need to receive unprotected broadcasts from other applications.
* <li>Using unprotected sticky broadcasts - either from this application or another.
* </ul><p>
* Broadcasts received by exported receivers are untrustworthy and must be treated with caution.
* <p>
* You can unregister receivers using the normal {@link Context#unregisterReceiver} method.
*/
public static Intent registerExportedBroadcastReceiver(
Context context, BroadcastReceiver receiver, IntentFilter filter, String permission) {
return registerBroadcastReceiver(
context, receiver, filter, permission, /* scheduler= */ null, RECEIVER_EXPORTED);
}
/**
* Register a broadcast receiver that may only accept broadcasts coming from the root, system,
* or this app's own UIDs.
*
* You should generally prefer using this over the exported counterpart,
* {@link #registerExportedBroadcastReceiver(Context, BroadcastReceiver, IntentFilter, String)},
* unless you meet a specific requirement specified in that method's documentation.
* <p>
* Even though most protected broadcasts come from the system UID, and could thus be received by
* a non-exported receiver, you should instead use registerProtectedBroadcastReceiver for all
* protected broadcasts.
* <p>
* You should (only) use non-exported receivers when:
* <p><ul>
* <li>You want to send and receive (non-sticky) broadcasts solely within the same application.
* <li>You want to receive the result of a PendingIntent that you have provided to some other
* application or service.
* </ul><p>
* Note that older versions of Android do not enforce non-exported receivers, so you should
* still not trust received Intents without some additional authentication mechanism. Note that
* you generally cannot use Android permissions for this because embedded WebViews will only
* inherit the permissions of the embedding application. Consider using
* {@link org.chromium.base.IntentUtils#addTrustedIntentExtras} and
* {@link org.chromium.base.IntentUtils#isTrustedIntentFromSelf} to verify the Intent's sender.
* <p>
* Usually, when working with non-exported receivers, you should also make sure that any related
* Intents that you send are not broadcast to other apps. This can be done using
* {@link Intent#setPackage} with {@link Context#getPackageName}, and must be done before
* calling {@link org.chromium.base.IntentUtils#addTrustedIntentExtras}.
* <p>
* You can unregister receivers using the normal {@link Context#unregisterReceiver} method.
*/
public static Intent registerNonExportedBroadcastReceiver(
Context context, BroadcastReceiver receiver, IntentFilter filter) {
return registerBroadcastReceiver(
context,
receiver,
filter,
/* permission= */ null,
/* scheduler= */ null,
RECEIVER_NOT_EXPORTED);
}
public static Intent registerNonExportedBroadcastReceiver(
Context context, BroadcastReceiver receiver, IntentFilter filter, Handler scheduler) {
return registerBroadcastReceiver(
context,
receiver,
filter,
/* permission= */ null,
scheduler,
RECEIVER_NOT_EXPORTED);
}
private static Intent registerBroadcastReceiver(
Context context,
BroadcastReceiver receiver,
IntentFilter filter,
String permission,
Handler scheduler,
int flags) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
return context.registerReceiver(receiver, filter, permission, scheduler, flags);
} else {
return context.registerReceiver(receiver, filter, permission, scheduler);
}
}
}
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