Privileged Service Binding / Binder Interface Exposure

← Improper Platform Usage

privileged_service_binding_exposure   HARD

Description

An exported/bindable Service exposes a privileged Binder interface (AIDL/Messenger) that any app can bindService() to and call without a caller-identity / permission check, so an untrusted client invokes privileged operations or reads state established by another client. The binding model - not just ‘service exported’ - is the boundary (Android service IPC MASTG-KNOW-0133 class).

How it works

An exported, bindable Service exposes a privileged Binder interface (AIDL or Messenger) that any app can bindService() to and invoke with no caller-identity or permission check. An untrusted client reads a protected secret, elevates its role, and can observe state another client established; the binding model is the boundary (Android service IPC MASTG-KNOW-0133). This is an offline, deterministic simulation. The secure path verifies the caller against a signature-level allowlist before returning a usable binder, refusing the untrusted client.

How to exercise it. DVMA is the harness - open this module from the home index and tap the demo action. The screen ships the malicious input and simulates the attacker (e.g. the companion app, crafted intent, or scanned payload) in-process, and the evidence panel prints the proof. The Tools (optional) and Attack inputs below are only needed to reproduce the exploit end-to-end on a real device.

Exploit steps

1. Set up. Build DVMA with a flavor that enables the Improper Platform Usage category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an Android emulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: adb, drozer, jadx, frida.
2. Locate the target. From the home index, open Privileged Service Binding / Binder Interface Exposure (privileged_service_binding_exposure). The How it works section above describes this module’s specific weakness; the screen states the intended-secure behavior and exposes the vulnerable action.
3. Exploit. From a co-resident/attacker context (adb shell am start/drozer, or a crafted deep link / QR), send the untrusted input to the exported component or WebView and confirm the app performs the unsafe action (navigation, JS execution, file/URI access) with no validation.
4. Observe the evidence. Trigger the vulnerable action and read the evidence panel - it prints the concrete proof (leaked value, accepted replay, executed payload, or unauthorized result).
5. Contrast with the secure path. Run the module’s secure/hardened action (where provided) and confirm the same attack is rejected - this is what a correct implementation should do.
6. Map it back. Cross-reference the MASTG v2 test(s) MASTG-TEST-0365 for the canonical procedure and remediation.

Tools (optional)

• adb
• drozer
• jadx
• frida

Attack inputs

Payloads/artifacts you author for the on-device attack. The demo already ships and simulates these in-process (e.g. the malicious companion app / crafted intent is emulated inside the screen), so you only need to craft them to reproduce the exploit on a real device:

• malicious companion app

Real-world references

Concrete public disclosures that match this vulnerability class:

• OWASP MASTG-KNOW-0133: Android Services (binding as an IPC entry point)