Default-Role / Role-Holder Confusion

← Improper Platform Usage

default_role_holder_confusion   MEDIUM

Description

The app resolves a system role (default browser / dialer / SMS / wallet / credential provider / NFC handler) with resolveActivity() / an implicit intent and TRUSTS whichever app the OS returns, then hands it a sensitive URI / credential / IPC - without verifying the current RoleManager role holder or the target’s signature. A co-resident app that registers the matching intent-filter becomes the ‘default’ and receives the secret. The secure path checks the actual role holder (RoleManager) / pins the package + signature before delegating (Android dynamic-role class).

How it works

The app resolves a system role (default browser, dialer, SMS, wallet, credential provider, or NFC) with resolveActivity() or an implicit intent and trusts whichever app the OS returns, handing it a sensitive URI or credential, without checking the authoritative RoleManager role holder or pinning the target package and signature. A co-resident app that registers the matching intent-filter with a higher priority becomes the resolved default and receives the secret. On Android, DVMA broadcasts the secret to the resolved default holder and the companion attacker receives it. The secure path consults RoleManager for the real holder and pins package and signature, refusing an unexpected holder.

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.
2. Locate the target. From the home index, open Default-Role / Role-Holder Confusion (default_role_holder_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. 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.

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:

• malicious app claiming the role intent-filter

Real-world references

Concrete public disclosures that match this vulnerability class:

• Android RoleManager: verifying the current role holder before delegating