CAPEC-8 Buffer Overflow in an API Call

This attack targets libraries or shared code modules which are vulnerable to buffer overflow attacks. An adversary who has knowledge of known vulnerable libraries or shared code can easily target software that makes use of these libraries. All clients that make use of the code library thus become vulnerable by association. This has a very broad effect on security across a system, usually affecting more than one software process.

1. [Explore] [Identify target application] The adversary, with knowledge of vulnerable libraries or shared code modules, identifies a target application or program that makes use of these. 2. [Experiment] [Find injection vector] The adversary attempts to use the API, and if they can they send a large amount of data to see if the buffer overflow attack really does work. 3. [Experiment] [Craft overflow content] The adversary crafts the content to be injected based on their knowledge of the vulnerability and their desired outcome. If the intent is to simply cause the software to crash, the content need only consist of an excessive quantity of random data. If the intent is to leverage the overflow for execution of arbitrary code, the adversary will craft a set of content that not only overflows the targeted buffer but does so in such a way that the overwritten return address is replaced with one of the adversaries' choosing which points to code injected by the adversary. 4. [Exploit] [Overflow the buffer] Using the API as the injection vector, the adversary injects the crafted overflow content into the buffer.

• The target host exposes an API to the user. • One or more API functions exposed by the target host has a buffer overflow vulnerability.

• [Low] An adversary can simply overflow a buffer by inserting a long string into an adversary-modifiable injection vector. The result can be a DoS. • [High] Exploiting a buffer overflow to inject malicious code into the stack of a software system or even the heap can require a higher skill level.

• Availability: Unreliable Execution • Confidentiality, Integrity, Availability: Execute Unauthorized Commands • Confidentiality: Read Data • Integrity: Modify Data

• Use a language or compiler that performs automatic bounds checking. • Use secure functions not vulnerable to buffer overflow. • If you have to use dangerous functions, make sure that you do boundary checking. • Compiler-based canary mechanisms such as StackGuard, ProPolice and the Microsoft Visual Studio /GS flag. Unless this provides automatic bounds checking, it is not a complete solution. • Use OS-level preventative functionality. Not a complete solution.