Persistent URI-Grant Capability Abuse

← Improper Platform Usage

persistable_uri_grant_abuse   HARD

Description

An exported component receives an attacker-controlled content:// URI carrying FLAG_GRANT_PERSISTABLE_URI_PERMISSION and calls takePersistableUriPermission(), converting a one-shot, ephemeral grant into a LONG-LIVED capability the attacker’s provider can later swap behind - so a transient read becomes durable, revocation-resistant access. Distinct from ordinary URI-grant abuse: the bug is the PERSISTENCE. The secure path never persists grants for untrusted URIs and re-validates the provider on each use (Android persistable-grant class).

How it works

An exported component receives an attacker-controlled content:// URI carrying FLAG_GRANT_PERSISTABLE_URI_PERMISSION and calls takePersistableUriPermission(), converting a one-shot, intent-scoped grant into a long-lived capability that survives revocation. Because the URI is backed by the attacker’s own provider, the attacker can later swap the bytes it serves for the same URI, so a transient read becomes durable, mutable access. The distinguishing bug is the persistence. This is an offline, deterministic simulation. The secure path never persists grants for untrusted authorities and re-validates the provider on each use.

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 Persistent URI-Grant Capability Abuse (persistable_uri_grant_abuse). 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-0357 for the canonical procedure and remediation.

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:

• attacker-controlled content:// URI

Real-world references

Concrete public disclosures that match this vulnerability class:

• Android: takePersistableUriPermission and persistable URI grants