(#) Unsafe Protected `BroadcastReceiver` !!! WARNING: Unsafe Protected `BroadcastReceiver` This is a warning. Id : `UnsafeProtectedBroadcastReceiver` Summary : Unsafe Protected `BroadcastReceiver` Severity : Warning Category : Security Platform : Android Vendor : Android Open Source Project Feedback : https://issuetracker.google.com/issues/new?component=192708 Since : 1.5.0 (November 2015) Affects : Kotlin and Java files and manifest files Editing : This check runs on the fly in the IDE editor See : https://goo.gle/UnsafeProtectedBroadcastReceiver Implementation : [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/UnsafeBroadcastReceiverDetector.java) Tests : [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/UnsafeBroadcastReceiverDetectorTest.java) `BroadcastReceiver`s that declare an intent-filter for a protected-broadcast action string must check that the received intent's action string matches the expected value, otherwise it is possible for malicious actors to spoof intents. (##) Example Here is an example of lint warnings produced by this check: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text src/test/pkg/TestReceiver.java:10:Warning: This broadcast receiver declares an intent-filter for a protected broadcast action string, which can only be sent by the system, not third-party applications. However, the receiver's onReceive method does not appear to call getAction to ensure that the received Intent's action string matches the expected value, potentially making it possible for another actor to send a spoofed intent with no action string or a different action string and cause undesired behavior. [UnsafeProtectedBroadcastReceiver] public void onReceive(Context context, Intent intent) { --------- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here are the relevant source files: `AndroidManifest.xml`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="test.pkg" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="14" /> <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <receiver android:label="@string/app_name" android:name=".TestReceiver" > <intent-filter> <action android:name="android.intent.action.BOOT_COMPLETED"/> </intent-filter> </receiver> </application> </manifest> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ `src/test/pkg/TestReceiver.java`: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers package test.pkg; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; public class TestReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { } // Anonymous classes should NOT be counted as a must-register private static BroadcastReceiver sample() { return new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { } }; } } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can also visit the [source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/UnsafeBroadcastReceiverDetectorTest.java) for the unit tests for this check to see additional scenarios. The above example was automatically extracted from the first unit test found for this lint check, `UnsafeBroadcastReceiverDetector.testBroken`. To report a problem with this extracted sample, visit https://issuetracker.google.com/issues/new?component=192708. (##) Suppressing You can suppress false positives using one of the following mechanisms: * Adding the suppression attribute `tools:ignore="UnsafeProtectedBroadcastReceiver"` on the problematic XML element (or one of its enclosing elements). You may also need to add the following namespace declaration on the root element in the XML file if it's not already there: `xmlns:tools="http://schemas.android.com/tools"`. ```xml <?xml version="1.0" encoding="UTF-8"?> <manifest xmlns:tools="http://schemas.android.com/tools"> ... <receiver tools:ignore="UnsafeProtectedBroadcastReceiver" .../> ... </manifest> ``` * Using a suppression annotation like this on the enclosing element: ```kt // Kotlin @Suppress("UnsafeProtectedBroadcastReceiver") fun method() { problematicStatement() } ``` or ```java // Java @SuppressWarnings("UnsafeProtectedBroadcastReceiver") void method() { problematicStatement(); } ``` * Using a suppression comment like this on the line above: ```kt //noinspection UnsafeProtectedBroadcastReceiver problematicStatement() ``` * Using a special `lint.xml` file in the source tree which turns off the check in that folder and any sub folder. A simple file might look like this: ```xml <?xml version="1.0" encoding="UTF-8"?> <lint> <issue id="UnsafeProtectedBroadcastReceiver" severity="ignore" /> </lint> ``` Instead of `ignore` you can also change the severity here, for example from `error` to `warning`. You can find additional documentation on how to filter issues by path, regular expression and so on [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html). * In Gradle projects, using the DSL syntax to configure lint. For example, you can use something like ```gradle lintOptions { disable 'UnsafeProtectedBroadcastReceiver' } ``` In Android projects this should be nested inside an `android { }` block. * For manual invocations of `lint`, using the `--ignore` flag: ``` $ lint --ignore UnsafeProtectedBroadcastReceiver ...` ``` * Last, but not least, using baselines, as discussed [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).