Overview

A custom keyboard is an app extension that replaces the system keyboard across all apps on the device (see MASTG-KNOW-0141). By default it runs without "Full Access", which keeps it from making network requests or reaching shared containers. A keyboard requests "Full Access" with the RequestsOpenAccess key in its Info.plist, and once the user grants it the keyboard can check the hasFullAccess property and then send what the user types off the device.

Because a custom keyboard receives the characters the user types in other apps, a keyboard that requests Full Access and transmits input is in a position to exfiltrate sensitive data such as passwords, messages, or payment details. Apple requires Full Access to be justified and limited to features that genuinely need it (for example, network-based predictions the user opted into).

This test checks whether a custom keyboard extension bundled with the app requests Full Access, and whether it uses that access to transmit typed data off the device or to reach shared storage. The analysis targets the keyboard extension binary (the .appex under PlugIns/) and its Info.plist.

Steps

  1. Use MASTG-TECH-0058 to extract the app package, including the keyboard extension in the PlugIns/*.appex bundle.
  2. Inspect the keyboard extension's Info.plist for the RequestsOpenAccess key under NSExtension > NSExtensionAttributes.
  3. Use MASTG-TECH-0066 to look for the relevant APIs in the keyboard extension binary, in particular hasFullAccess and networking APIs such as URLSession.

Observation

The output should indicate:

Evaluation

The test case fails if the keyboard extension requests Full Access (RequestsOpenAccess is true) and uses it to send typed data off the device or to write it to a shared container, without a feature that justifies the access.

Further Validation Required:

Inspect the keyboard extension implementation using MASTG-TECH-0076 to determine:

Свързани задачи

Връзки
is related to MASTG-BEST-0069 Keep Sensitive Input on the System Keyboard (iOS)