+MASTG-BEST-0068 Secure Data Sharing Between App Extensions and Containing Apps (iOS)

MASTG-BEST-0068 Secure Data Sharing Between App Extensions and Containing Apps (iOS)

Platform: iOS
Knowledge: MASTG-KNOW-0082

When an app and its extensions share data through an App Group, the shared container is readable and writable by every member of the group, with no per-item access control between members (see MASTG-KNOW-0082). Choose the sharing channel based on the sensitivity of the data, and protect what you store.

Prefer a Shared Keychain for Secrets

Store credentials, tokens, and keys that both the app and an extension need in a shared Keychain Access Group (the keychain-access-groups entitlement), not in shared UserDefaults or a shared file container. The Keychain provides dedicated, access-controlled key storage with its own accessibility class. Set an appropriate accessibility attribute such as kSecAttrAccessibleWhenUnlockedThisDeviceOnly.

Protect Sensitive Files in the Shared Container

When sensitive data must live in the shared file container, apply Data Protection so its contents are encrypted while the device is locked. Write files with the NSFileProtectionComplete class:

try data.write(to: sharedContainerURL, options: .completeFileProtection)

This applies to all shared storage, in the same way it applies to the app's private storage (see MASTG-TEST-0299).

Minimize What You Share

Limit the shared container to the data each extension actually needs. Avoid placing whole datasets or secrets there when an extension only needs a subset, and grant each extension only the App Group identifiers required for its functionality.

1. Преглед

Наименование	Стандарт

1.1 Препратки

1.2 Идентифицирани изисквания

1.3 Свързани регулации

2. Идентифицирани изисквания

Изисквания
Източник	Изискване

3. Свързани регулации

Регулации
Източник	Регулация

Свързани задачи

Връзки
Тип връзка	Задача
is related to	MASTG-TEST-0388 References to Sensitive Data Stored Unprotected in Shared App Group Containers (iOS)

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- OWASP Application Security Verification Standard (ASVS) 5.0.0, Mai 2025, aus OWASP/ASVS: © 2008-2025 The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in Abschnitte aufgeteilt und in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
- OWASP Mobile Application Security Verification Standard (MASVS) v2.1.0, Januar 2024, aus OWASP/masvs: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
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