LinkedIn has recently open sourced QARK, a static analysis tool meant to discover potential security vulnerabilities existing in Android applications written in Java.
QARK was first introduced at DEFCON 23 earlier this month, then made public on GitHub shortly after. QARK uses PLYJ, a Python tool for parsing Java source code, and Beautiful Soup for parsing the Android manifest file. But QARK can handle binaries also, using multiple decompilers and merging their results: Procyon, JD-Core, CFR, DEX2JAR, and APKTool. The range of issues investigated includes:
- Inadvertently exported components
- Improperly protected exported components
- Intents which are vulnerable to interception or eavesdropping
- Improper x.509 certificate validation
- Creation of world-readable or world-writeable files
- Activities which may leak data
- The use of Sticky Intents
- Insecurely created Pending Intents
- Sending of insecure Broadcast Intents
- Private keys embedded in the source
- Weak or improper cryptography use
- Potentially exploitable WebView configurations
- Exported Preference Activities
- Tapjacking
- Apps which enable backups
- Apps which are debuggable
- Apps supporting outdated API versions, with known vulnerabilities
When pointing to a possible vulnerability, QARK provides some explanation and a link to a web page with more details on the issue. The tool can create a testable APK and ADB commands that can be issued to show how the vulnerabilities found can be exploited.
In the future, they intend to extend QARK to discover Bound Service and Content Provider vulnerabilities, issues not related to Java/Android, parsing ODEX files, improved extensibility, dynamic analysis and others.
While QARK can be integrated in the Android tool chain to automatically detect issues, the authors recommend to continue performing manual reviews of applications because there are categories of vulnerabilities not discoverable during static analysis and there are vulnerabilities not yet covered by the tool.