Improper Authorization in Handler for Custom URL Scheme

Opis

The product uses a handler for a custom URL scheme, but it does not properly restrict which actors can invoke the handler using the scheme.

Mobile platforms and other architectures allow the use of custom URL schemes to facilitate communication between applications. In the case of iOS, this is the only method to do inter-application communication. The implementation is at the developer's discretion which may open security flaws in the application. An example could be potentially dangerous functionality such as modifying files through a custom URL scheme.

Skutki

• Access Control, Other

  Gain Privileges or Assume Identity; Varies by Context; Bypass Protection Mechanism

  An attacker can access any functionality that is inadvertently accessible to the source.

Zapobieganie

• Architecture and Design

  Utilize a user prompt pop-up to authorize potentially harmful actions such as those modifying data or dealing with sensitive information.

  When designing functionality of actions in the URL scheme, consider whether the action should be accessible to all mobile applications, or if an allowlist of applications to interface with is appropriate.

Przykłady podatności

• CVE-2013-5725 URL scheme has action replace which requires no user prompt and allows remote attackers to perform undesired actions.
• CVE-2013-5726 URL scheme has action follow and favorite which allows remote attackers to force user to perform undesired actions.

Słabość nadrzędna

• CWE-862 Missing Authorization
• CWE-940 Improper Verification of Source of a Communication Channel

Kiedy powstaje

• Implementation — REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Dotyczy

Mobile

Źródła

1. Scheming for Privacy and Security — Guillaume Ross, 2013