From af5e48260d099ebcd138e04e18ac9a28a1880e3f Mon Sep 17 00:00:00 2001 From: ostorlab Date: Fri, 17 Nov 2023 15:46:19 +0100 Subject: [PATCH] Update KB --- .../_MEDIUM/IMPLICIT_PENDINGINTENT/context.md | 84 ------------------- .../IMPLICIT_PENDINGINTENT/recommendation.md | 6 +- 2 files changed, 5 insertions(+), 85 deletions(-) delete mode 100644 MOBILE_CLIENT/ANDROID/_MEDIUM/IMPLICIT_PENDINGINTENT/context.md diff --git a/MOBILE_CLIENT/ANDROID/_MEDIUM/IMPLICIT_PENDINGINTENT/context.md b/MOBILE_CLIENT/ANDROID/_MEDIUM/IMPLICIT_PENDINGINTENT/context.md deleted file mode 100644 index e57f4679..00000000 --- a/MOBILE_CLIENT/ANDROID/_MEDIUM/IMPLICIT_PENDINGINTENT/context.md +++ /dev/null @@ -1,84 +0,0 @@ -`PendingIntent` in Android is indeed a powerful class, and with great power comes the need for careful consideration. Here are the main concerns you should be aware of when using `PendingIntent`: - -1. **Security Risks**: The primary concern with `PendingIntent` is security. Since it allows an application to pass a future Intent to another application, it can potentially be misused if not handled properly. If the `PendingIntent` is not properly specified, other apps or malicious actors might intercept or access it, leading to potential security breaches. - -2. **Immutable vs. Mutable**: In recent Android versions, there's a distinction between immutable and mutable `PendingIntent`s. Immutable instances can't be modified after creation, which is safer in terms of security. However, mutable `PendingIntent`s are required in some cases but must be used cautiously. - -3. **Intent Data Leakage**: Be careful about the data you put in the Intent that is wrapped by the `PendingIntent`. Sensitive information should not be exposed unless necessary and should be protected appropriately. - -4. **Resource Usage and Leaks**: `PendingIntent`s use system resources. If they are not managed properly (e.g., not cancelled when no longer needed), they can lead to resource leaks and impact the performance of your app and the device. - -5. **BroadcastReceiver Vulnerabilities**: If your `PendingIntent` is used with a `BroadcastReceiver`, ensure that the receiver is secured. For instance, specifying an explicit broadcast intent, using permissions, and validating the data received in the `BroadcastReceiver`. - -6. **Unintended Behaviour**: Since a `PendingIntent` keeps a reference to the context of its creation, it might lead to unexpected behavior if the underlying application's state changes. For example, if the context in which the `PendingIntent` was created is destroyed, this might cause issues when the `PendingIntent` is executed. - -7. **Updates and Compatibility**: Android's security model and best practices evolve with each version. What might be a secure implementation in one version might become a vulnerability in another. It's important to keep your application updated with the latest Android practices. - -To mitigate these risks, follow best practices such as: - -- Use explicit intents when creating `PendingIntent`. -- Mark `PendingIntent`s as immutable whenever possible. -- Be cautious with the data you include in the intents. -- Cancel `PendingIntent`s when they are no longer needed. -- Keep your app updated with the latest Android security practices. - -By being aware of these concerns and adhering to best practices, you can effectively use `PendingIntent` without compromising the security and performance of your application. - -Canceling a `PendingIntent` in Android is a straightforward process. It's important to cancel a `PendingIntent` when it is no longer needed to prevent resource leaks and potential unintended behavior. Here's how you can do it: - -1. **Retrieve the Same PendingIntent**: To cancel a `PendingIntent`, you must create a PendingIntent that matches the one you want to cancel. This is because the PendingIntent itself is identified by its equivalence to another PendingIntent, not by a specific ID or reference. This means you need to recreate the PendingIntent with the same context, intent, and flags as the one you are trying to cancel. - -2. **Call cancel() Method**: Once you have a PendingIntent that matches the one you want to cancel, you can call the `cancel()` method on it. This effectively cancels the pending operation. - -Here's a simple example in code: - -```java -// Assume this is the Intent and the requestCode used to create the original PendingIntent -Intent intent = new Intent(context, YourServiceOrReceiver.class); -int requestCode = 123; // the request code you used to create the PendingIntent - -// Create a PendingIntent that matches the one you want to cancel -PendingIntent pendingIntent = PendingIntent.getService(context, requestCode, intent, PendingIntent.FLAG_NO_CREATE); - -// Check if it exists -if (pendingIntent != null) { - pendingIntent.cancel(); -} -``` - -In this example, `PendingIntent.getService` is used, but you should use the appropriate method (like `getService`, `getBroadcast`, or `getActivity`) depending on what kind of `PendingIntent` you are dealing with. - -Remember: - -- The context, intent, request code, and flags should match exactly the ones used when the PendingIntent was created. -- If you are using mutable PendingIntents (i.e., not setting `PendingIntent.FLAG_IMMUTABLE`), you might need to consider that they can be altered after being created. -- The `FLAG_NO_CREATE` flag is used in the retrieval method (`getService`, `getBroadcast`, `getActivity`) to ensure that the system returns `null` if the described PendingIntent does not currently exist. This way, you're not accidentally creating a new PendingIntent when attempting to cancel one. - -By following these steps, you can effectively cancel a `PendingIntent` and ensure that it no longer triggers any action in your Android application. - -Making a `PendingIntent` immutable in Android is a crucial step for enhancing the security of your application. An immutable `PendingIntent` cannot be altered after it's created. This is especially important when passing intents between different components or applications, as it prevents potential malicious modifications. Here's how you can create an immutable `PendingIntent`: - -1. **Use the `FLAG_IMMUTABLE` Flag**: When creating a `PendingIntent`, you can specify its mutability by using the `FLAG_IMMUTABLE` flag. This flag is available from API level 23 (Android 6.0, Marshmallow) onwards. If you're targeting a version lower than API level 23, `PendingIntent` is immutable by default, and you don't need to specify this flag. - -2. **Creating the PendingIntent**: When creating the `PendingIntent`, use the `FLAG_IMMUTABLE` flag along with any other flags you might need. Here’s an example of how to create an immutable `PendingIntent` for a broadcast: - - ```java - Intent intent = new Intent(context, YourBroadcastReceiver.class); - // Other intent setup code... - - // Use FLAG_IMMUTABLE to make the PendingIntent immutable - PendingIntent pendingIntent = PendingIntent.getBroadcast(context, requestCode, intent, PendingIntent.FLAG_IMMUTABLE); - ``` - -3. **Targeting Different Android Versions**: If your app targets a version of Android older than 6.0 (API level 23) but also needs to run on newer versions, you can conditionally add this flag to maintain compatibility. Here's an example: - - ```java - int flags = (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) ? PendingIntent.FLAG_IMMUTABLE : 0; - PendingIntent pendingIntent = PendingIntent.getBroadcast(context, requestCode, intent, flags); - ``` - -4. **Considerations for Mutable PendingIntents**: If you need a `PendingIntent` that can be modified after creation (mutable PendingIntent), you can use the `FLAG_UPDATE_CURRENT` flag. However, be mindful of the security implications and use mutable `PendingIntents` only when necessary. - -5. **Reviewing Existing Code**: If you have existing code that creates `PendingIntent`s, it's a good practice to review it and ensure that you're using the `FLAG_IMMUTABLE` flag where appropriate for better security. - -By following these guidelines, you can create immutable `PendingIntent`s in your Android applications, enhancing their security and integrity. diff --git a/MOBILE_CLIENT/ANDROID/_MEDIUM/IMPLICIT_PENDINGINTENT/recommendation.md b/MOBILE_CLIENT/ANDROID/_MEDIUM/IMPLICIT_PENDINGINTENT/recommendation.md index 9ea24b93..17810e0c 100644 --- a/MOBILE_CLIENT/ANDROID/_MEDIUM/IMPLICIT_PENDINGINTENT/recommendation.md +++ b/MOBILE_CLIENT/ANDROID/_MEDIUM/IMPLICIT_PENDINGINTENT/recommendation.md @@ -1,8 +1,12 @@ Developers can address the vulnerability by applying any (or even better, all) of the following: -- Ensuring that the action, package, and component fields of the base Intent are set; +- Ensuring that the action, package, and component fields of the base Intent are set (explicit Intent); - Ensuring that the PendingIntent is only delivered to trusted components; - Using `FLAG_IMMUTABLE` (added in SDK 23) to create `PendingIntents`. This prevents apps that receive the `PendingIntent` from filling in unpopulated properties. In case the app also runs on devices running SDK 22 or older, we recommend developers to apply the previous options while strengthening the PendingIntent creation with the pattern: +- Being cautious with the data included in the intents. +- Canceling `PendingIntent`s when they are no longer needed. +- Keeping your app updated with the latest Android security practices. + === "Java" ```java