Improper Export of Android Application Components

Incomplete Variant
Structure: Simple
Description

The Android application exports a component for use by other applications, but does not properly restrict which applications can launch the component or access the data it contains.

Extended Description

The attacks and consequences of improperly exporting a component may depend on the exported component: - If access to an exported Activity is not restricted, any application will be able to launch the activity. This may allow a malicious application to gain access to sensitive information, modify the internal state of the application, or trick a user into interacting with the victim application while believing they are still interacting with the malicious application. - If access to an exported Service is not restricted, any application may start and bind to the Service. Depending on the exposed functionality, this may allow a malicious application to perform unauthorized actions, gain access to sensitive information, or corrupt the internal state of the application. - If access to a Content Provider is not restricted to only the expected applications, then malicious applications might be able to access the sensitive data. Note that in Android before 4.2, the Content Provider is automatically exported unless it has been explicitly declared as NOT exported.

Common Consequences 3
Scope: AvailabilityIntegrity

Impact: Unexpected StateDoS: Crash, Exit, or RestartDoS: InstabilityVaries by Context

Other applications, possibly untrusted, can launch the Activity.

Scope: AvailabilityIntegrity

Impact: Unexpected StateGain Privileges or Assume IdentityDoS: Crash, Exit, or RestartDoS: InstabilityVaries by Context

Other applications, possibly untrusted, can bind to the Service.

Scope: ConfidentialityIntegrity

Impact: Read Application DataModify Application Data

Other applications, possibly untrusted, can read or modify the data that is offered by the Content Provider.

Detection Methods 1
Automated Static AnalysisHigh
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Potential Mitigations 4
Phase: Build and Compilation

Strategy: Attack Surface Reduction

If they do not need to be shared by other applications, explicitly mark components with android:exported="false" in the application manifest.
Phase: Build and Compilation

Strategy: Attack Surface Reduction

If you only intend to use exported components between related apps under your control, use android:protectionLevel="signature" in the xml manifest to restrict access to applications signed by you.
Phase: Build and CompilationArchitecture and Design

Strategy: Attack Surface Reduction

Limit Content Provider permissions (read/write) as appropriate.
Phase: Build and CompilationArchitecture and Design

Strategy: Separation of Privilege

Limit Content Provider permissions (read/write) as appropriate.
Demonstrative Examples 2
This application is exporting an activity and a service in its manifest.xml:

Code Example:

Bad
XML
xml

...* ```

xml

...* ```

xml
Because these components have intent filters but have not explicitly set 'android:exported=false' elsewhere in the manifest, they are automatically exported so that any other application can launch them. This may lead to unintended behavior or exploits.
This application has created a content provider to enable custom search suggestions within the application:

Code Example:

Bad
XML
xml
Because this content provider is only intended to be used within the application, it does not need to be exported. However, in Android before 4.2, it is automatically exported thus potentially allowing malicious applications to access sensitive information.
References 1
Security Tips
Android Open Source Project
16-07-2013
ID: REF-923
Applicable Platforms
Languages:
Not Language-Specific : Undetermined
Technologies:
Mobile : Undetermined
Modes of Introduction
Architecture and Design
Related Weaknesses