Companion Device Pairing / Capability Confusion

← Privileged System-Provider Activation

companion_device_pairing_confusion   MEDIUM

Description

An app pairs with a nearby companion device (watch / peripheral / car / IoT) via CompanionDeviceManager and then treats ‘paired’ as ‘authorized for every capability’ - a spoofed or lower-trust device is granted actions it should not have, or the paired-device identity is confused. Pairing establishes a relationship, not per-capability authorization (Android CompanionDeviceManager trusted-device boundary class).

How it works

Pairing with a companion device (watch / peripheral / car / IoT) via CompanionDeviceManager only establishes proximity and identity; it is not a grant for every privileged action. Here the app equates “paired” with “authorized for every capability”, so a spoofed, low-trust advertiser that completed pairing is granted a high-privilege capability (unlock the door) it should never hold (Android CompanionDeviceManager trusted-device boundary class). The secure path binds each capability to the device’s verified trust level, so a spoofed or low-trust device is denied high-privilege capabilities. The “real state” panel lists this app’s actual CompanionDeviceManager associations (getAssociations); to fully arm the capability, create an association via CompanionDeviceManager.associate() and pick a device in the system dialog.

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 Privileged System-Provider Activation 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.
2. Locate the target. From the home index, open Companion Device Pairing / Capability Confusion (companion_device_pairing_confusion). 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. Drive the provider-activation / enablement workflow (accessibility, notification-listener, VPN, IME, phone-account, MediaProjection, credential-provider) and confirm the granted capability is invoked on an untrusted caller’s behalf - the enablement flow is the boundary.
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.

Tools (optional)

• adb
• drozer
• jadx

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:

• spoofed companion device
• malicious companion app

Real-world references

Concrete public disclosures that match this vulnerability class:

• Android: CompanionDeviceManager (user-confirmed pairing establishes a relationship)