320
Fuzzing
Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs
- either randomly or algorithmically - and dynamically invoking the code with those inputs.
Even with random inputs, it is often capable of generating unexpected results such as crashes,
memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases
that clearly indicate bugs, which helps developers to diagnose the issues.
Effectiveness = High
Potential Mitigations
Pre-design: Use a language or compiler that performs automatic bounds checking.
Phase: Architecture and Design
Use an abstraction library to abstract away risky APIs. Not a complete solution.
Phase: Operation
Phase: Build and Compilation
Strategy = Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or
compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat
FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms
including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary
Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
Effectiveness = Defense in Depth
This is not necessarily a complete solution, since these mechanisms only detect certain types of
overflows. In addition, the result is still a denial of service, since the typical response is to exit the
application.
Phase: Operation
Phase: Build and Compilation
Strategy = Environment Hardening
Run or compile the software using features or extensions that randomly arrange the positions
of a program's executable and libraries in memory. Because this makes the addresses
unpredictable, it can prevent an attacker from reliably jumping to exploitable code. Examples
include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-
Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their
default memory addresses conflict with other modules, in a process known as "rebasing" (for
Windows) and "prelinking" (for Linux) [REF-1332] using randomly generated addresses. ASLR
for libraries cannot be used in conjunction with prelink since it would require relocating the
libraries at run-time, defeating the whole purpose of prelinking. For more information on these
techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
Effectiveness = Defense in Depth
These techniques do not provide a complete solution. For instance, exploits frequently use a bug
that discloses memory addresses in order to maximize reliability of code execution [REF-1337]. It
has also been shown that a side-channel attack can bypass ASLR [REF-1333]
Phase: Implementation
Implement and perform bounds checking on input.
Phase: Implementation
Strategy = Libraries or Frameworks
CWE Version 4.14
CWE-122: Heap-based Buffer Overflow
CWE-122: Heap-based Buffer Overflow