Passkey Credential Exfiltration

← Insecure Authentication / Authorization

passkey_credential_exfiltration   MEDIUM

Description

Passkey/credential material is cached in app-private storage without hardware-backed protection, allowing extraction.

How it works

Passkey private-key material must stay in hardware-backed storage (Keystore StrongBox / Secure Enclave) and be non-exportable. Here the app caches the private key in cleartext SharedPreferences, so it can be pulled off-device with adb or objection and the passkey cloned. Scope: the FIDO2 signature is assumed valid (signature verification is out of scope); the flaw demonstrated is in the relying-party authorization logic on top of it.

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 Insecure Authentication / Authorization category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an emulator/simulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: objection, frida, r2frida · Android: adb, run-as, SharedPreferences/XML inspection · iOS: objection, keychain-dumper, ifuse.
2. Locate the target. From the home index, open Passkey Credential Exfiltration (passkey_credential_exfiltration). 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 authentication/authorization path, capture the token / assertion / decision, then replay or tamper with it (mitmproxy, a WebAuthn test harness, or by editing the value) and confirm the server-side check accepts the manipulated request.
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-0287, MASTG-TEST-0301, MASTG-TEST-0302 for the canonical procedure and remediation.

Tools (optional)

• objection
• frida
• r2frida

Android

• adb
• run-as
• SharedPreferences/XML inspection

iOS

• objection
• keychain-dumper
• ifuse