App Extension Activation != Input Authorization

← Privileged System-Provider Activation

extension_activation_input_confusion   MEDIUM

Description

An iOS app extension (Share / Action / File Provider / etc.) trusts the item it is handed simply because the system activated it - activation rules decide WHEN the extension is offered, not WHETHER the received NSItemProvider file/URL/text is safe. A crafted payload from any host app then drives a privileged extension operation. Extension activation != input authorization (Apple app-extension input-trust class, OWASP MASTG-TECH-0170).

How it works

An iOS app extension (Share / Action / File Provider) is handed an NSItemProvider item when the system activates it. Activation rules decide when the extension is offered, not whether the file, URL, or text it received is safe. Here a crafted file:// URL using ../ traversal (or a javascript: URL) drives a privileged import/open because the extension mistakes “we were activated” for “the input is authorized”. On device the vulnerable import writes the payload outside its import root on the real filesystem. The secure path validates type and content (canonicalize path, allowlist schemes, reject traversal) before acting, refusing the crafted payload.

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 iOS simulator / a device you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: frida, objection, idb, Hopper.
2. Locate the target. From the home index, open App Extension Activation != Input Authorization (extension_activation_input_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.
6. Map it back. Cross-reference the MASTG v2 test(s) MASTG-TEST-0072 for the canonical procedure and remediation.

Tools (optional)

• frida
• objection
• idb
• Hopper

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:

• crafted NSItemProvider payload

Real-world references

Concrete public disclosures that match this vulnerability class:

• OWASP MASTG-TECH-0170: enumerating app extensions (activation vs input trust)