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Attack Tree Analysis for facebookarchive/kvocontroller

Objective: Gain Unauthorized Access/Control via KVOController

Attack Tree Visualization

Goal: Gain Unauthorized Access/Control via KVOController ├── 1. Manipulate Observed Objects/Properties │ ├── 1.1 Trigger Unexpected KVO Notifications │ │ └── 1.1.1 Exploit Weak Object Lifetime Management (Use-After-Free) [HIGH RISK] [CRITICAL] │ │ └── 1.1.1.1 Deallocate observed object, then trigger notification via dangling pointer. │ └── 1.2 Observe Properties Without Authorization │ └── 1.2.1 Exploit Incorrect Access Control on Observed Objects [HIGH RISK] │ └── 1.2.1.1 If the application doesn't properly restrict access to objects being observed, gain access to sensitive data through KVO. └── 2. Exploit KVOController Implementation Vulnerabilities (Less Likely, but Important) [CRITICAL] ├── 2.1 Memory Corruption in KVOController Itself │ └── 2.1.1 Identify and exploit buffer overflows, use-after-free, or other memory safety issues within the kvocontroller library code. ├── 2.2 Logic Errors in KVOController Itself │ └── 2.2.1 Find flaws in how kvocontroller manages observers, notifications, or object lifetimes, leading to unexpected behavior. └── 2.3 Thread Safety Issues └── 2.3.1 If KVOController is not thread-safe, exploit race conditions by accessing it from multiple threads simultaneously.

Attack Tree Path: 1.1.1 Exploit Weak Object Lifetime Management (Use-After-Free)

  • Description: This attack exploits the common Objective-C issue of use-after-free, made more dangerous by KVO. If an object is being observed via KVO and is deallocated without the observer being unregistered, the KVOController (or underlying KVO mechanism) will still hold a dangling pointer to the deallocated object. When a notification is triggered for that (now invalid) object, the application will attempt to access the deallocated memory, leading to a crash, undefined behavior, or potentially, remote code execution (RCE).

  • Attack Steps:

    1. Identify an object that is being observed via KVOController.
    2. Find a way to trigger the deallocation of that object without the corresponding observer being unregistered. This might involve exploiting other vulnerabilities in the application, manipulating user input, or triggering specific application logic.
    3. After the object is deallocated, trigger a change to a property that would normally cause a KVO notification to be sent. This could be done directly if the attacker has some control over the observed object's properties, or indirectly through other application interactions.
    4. The KVO mechanism will attempt to access the deallocated memory, leading to the exploit.

  • Likelihood: High (Common Objective-C error, especially with KVO)

  • Impact: High to Very High (Crash, DoS, potential RCE)

  • Effort: Low to Medium (Depends on application complexity)

  • Skill Level: Intermediate

  • Detection Difficulty: Medium (Crashes are obvious, but root cause analysis can be challenging)

  • Mitigations:

    • Strong Ownership: Ensure observed objects have strong references to prevent premature deallocation.
    • Unregister Observers: Always unregister observers in the dealloc method of the observing object. Use FBKVOController's automatic unregistration features.
    • Code Review: Thoroughly review code for proper object lifetime management and observer handling.
    • Static Analysis: Use static analysis tools to detect potential use-after-free issues.

Attack Tree Path: 1.2.1 Exploit Incorrect Access Control on Observed Objects

  • Description: This attack leverages weak or missing access controls on objects that are being observed. If the application doesn't properly restrict which objects can observe other objects, an attacker might be able to register an observer on an object they shouldn't have access to, thereby gaining access to sensitive data through KVO notifications.

  • Attack Steps:

    1. Identify objects that contain sensitive data and are being observed via KVO.
    2. Determine if there are any access control checks in place to prevent unauthorized objects from registering as observers.
    3. If access controls are weak or missing, register an observer on the target object using KVOController.
    4. Monitor KVO notifications to receive updates about the sensitive data.

  • Likelihood: Medium (Depends on application's access control implementation)

  • Impact: High (Data breach of sensitive information)

  • Effort: Low to Medium

  • Skill Level: Intermediate

  • Detection Difficulty: Medium to Hard (Requires understanding of application's data model and access controls)

  • Mitigations:

    • Principle of Least Privilege: Ensure only authorized objects can observe sensitive properties.
    • Access Control Mechanisms: Use private properties, access control lists, or other appropriate mechanisms.
    • Code Review: Carefully review code to ensure KVO doesn't bypass intended access restrictions.

Attack Tree Path: 2. Exploit KVOController Implementation Vulnerabilities (Category)

  • Description: This category encompasses vulnerabilities within the kvocontroller library itself. Since the library is archived, any such vulnerabilities will remain unpatched, making this a critical, albeit less likely, area of concern.

  • Sub-Categories:

    • 2.1 Memory Corruption: Buffer overflows, use-after-free, or other memory safety issues within the library's code.
      • Likelihood: Low
      • Impact: Very High (RCE)
      • Effort: Very High
      • Skill Level: Expert
      • Detection Difficulty: Very Hard
    • 2.2 Logic Errors: Flaws in how the library manages observers, notifications, or object lifetimes.
      • Likelihood: Very Low
      • Impact: Variable
      • Effort: Very High
      • Skill Level: Expert
      • Detection Difficulty: Very Hard
    • 2.3 Thread Safety Issues: Race conditions due to improper thread synchronization within the library.
      • Likelihood: Low to Medium
      • Impact: Medium to High
      • Effort: Medium to High
      • Skill Level: Advanced
      • Detection Difficulty: Hard

  • Mitigations (for the entire category):

    • Replacement (Recommended): Replace kvocontroller with a modern, actively maintained KVO solution (e.g., Swift Combine). This is the best mitigation.
    • Code Audit (Difficult): A thorough code audit of the library is needed to identify specific vulnerabilities.
    • Fuzzing: Fuzzing the library could help identify potential crashes.