• Platform: Android
• Weakness: MASWE-0034
• Weakness in the numbering of the MASWE beta: MASWE-0069
• Profiles: L1 (basic security), L2 (advanced security)
• Type: dynamic, hooks, manual
• APIs: WebView, WebSettings, getSettings, setAllowFileAccess, setAllowFileAccessFromFileURLs, setAllowUniversalAccessFromFileURLs
• Knowledge: MASTG-KNOW-0018
• Best practices: MASTG-BEST-0010, MASTG-BEST-0011, MASTG-BEST-0012

Overview

This test is the dynamic counterpart to MASTG-TEST-0252.

In this case you can follow one of these approaches:

• enumerate instances of WebView in the app and list their configuration values
• or explicitly hook the setters of the WebView settings, including:
• setJavaScriptEnabled
• setAllowFileAccess
• setAllowFileAccessFromFileURLs
• setAllowUniversalAccessFromFileURLs

Steps

1. Use MASTG-TECH-0005 to install the app.
2. Use MASTG-TECH-0043 to hook the relevant API calls.
3. Exercise the app extensively to trigger as many flows as possible and enter sensitive data wherever you can.

Observation

The output should contain a list of WebView setting calls, including the argument values and backtraces of each call.

Evaluation

The test case fails if all of the following applies (based on the [API behavior across different Android versions](../../../Document/0x05h-Testing-Platform-Interaction.md#webview-local-file-access-settings)):

• setJavaScriptEnabled is explicitly set to true.
• setAllowFileAccess is explicitly set to true (or not used at all when minSdkVersion < 30, inheriting the default value, true).
• Either setAllowFileAccessFromFileURLs or setAllowUniversalAccessFromFileURLs is explicitly set to true (or not used at all when minSdkVersion < 16, inheriting the default value, true).

Further Validation Required:

Using the backtraces from the hook output, inspect the code locations using MASTG-TECH-0023:

• Determine whether the settings are explicitly used and configured to the identified values.
• Determine which WebView instance receives the configuration and whether it handles sensitive information or functionality.
• Determine whether that WebView loads local file:// content, for example via loadUrl("file://...") or loadDataWithBaseURL with a file:// base URL.

For the identified WebViews, determine whether attacker-controlled JavaScript could execute in the local file context, for example through HTML injection, JavaScript injection, or other untrusted content. Also determine whether the attacker could exfiltrate local files or other sensitive data accessible via file:// URLs.

Note

AllowFileAccess being true does not represent a security vulnerability by itself, but it can be used in combination with other vulnerabilities to escalate the impact of an attack.

Linked Issues

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