A session that is already signed in is not enough authority for every action. Step-up authentication limits what a stolen session or an unattended unlocked phone can do, but only if the server checks the proof.
- Ask for additional authentication before high-impact actions, and decide which actions qualify in the threat model.
- Have the device sign a one-time server challenge with an authentication-bound key, and verify the signature on the server.
- Bind the approval to the transaction it authorizes, such as the amount and payee.
MASTG tests in the local projects
Neither local project runs a MASTG test for MASVS-AUTH-3. The guides below explain the platform mechanisms, and the control’s page on mas.owasp.org links the MASTG tests and weaknesses OWASP maps to it.
Guides on this site
Harden an iOS app's storage, network and entry points
Store secrets in the Keychain with the narrowest accessibility class, set file protection explicitly, keep App Transport Security on, prefer universal links, constrain WKWebView bridges, keep step-up keys in the Secure Enclave, verify App Attest on the server and ship an accurate privacy manifest, mapped to OWASP MASVS 2.1.
Harden an Android app's storage, network and entry points
Encrypt local secrets with Android Keystore keys now that Jetpack Security is deprecated, set transport policy in Network Security Configuration, close exported components and mutable PendingIntents, confine WebViews, verify App Links and judge Play Integrity verdicts on the server, mapped to OWASP MASVS 2.1.
Worked threat model: a mobile banking app
A complete worked threat model for a mobile banking-style app: the data-flow diagram and its elements, STRIDE threats on the client, the transport and the backend, and the mitigations mapped to OWASP MASVS v2 controls and current Android and iOS platform APIs.
Practice
- Keep an iOS app's storage, links and web bridge in bounds · Local project
- Repair an Android app's links, components, network policy and storage · Local project
References
List data from the publisher. A guide is listed as the main subject when the weakness or risk is what the guide is about, and as covering it when a dedicated section or worked example addresses it.
Control statements are quoted from OWASP MASVS v2.1.0, licensed CC BY-SA 4.0; the rest is this site's summary. MASTG tests are those the iOS and Android projects here run, with their titles from mas.owasp.org. License.