COMMON WEAKNESS ENUMERATIONDraft

CWE-121

Stack-based Buffer Overflow

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

Soyutlama

Variant

Yapı

Simple

Sömürü İhtimali

High

Problemi anla

Problem nedir?

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

Terminoloji

Alternatif adlar ve kullanım biçimleri

Stack Overflow

"Stack Overflow" is often used to mean the same thing as stack-based buffer overflow, however it is also used on occasion to mean stack exhaustion, usually a result from an excessively recursive function call. Due to the ambiguity of the term, use of stack overflow to describe either circumstance is discouraged.

Stack Buffer Overflow

Kök neden

Problem nasıl ve ne zaman oluşur?

Yaşam döngüsü evresi

Implementation

There are generally several security-critical data on an execution stack that can lead to arbitrary code execution. The most prominent is the stored return address, the memory address at which execution should continue once the current function is finished executing. The attacker can overwrite this value with some memory address to which the attacker also has write access, into which they place arbitrary code to be run with the full privileges of the vulnerable program. Alternately, the attacker can supply the address of an important call, for instance the POSIX system() call, leaving arguments to the call on the stack. This is often called a return into libc exploit, since the attacker generally forces the program to jump at return time into an interesting routine in the C standard library (libc). Other important data commonly on the stack include the stack pointer and frame pointer, two values that indicate offsets for computing memory addresses. Modifying those values can often be leveraged into a "write-what-where" condition.

Risk

Başarılı sömürü neye yol açar?

Modify MemoryDoS: Crash, Exit, or RestartDoS: Resource Consumption (CPU)DoS: Resource Consumption (Memory)

Etkilenen güvenlik alanları: Availability

Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
Modify MemoryExecute Unauthorized Code or CommandsBypass Protection Mechanism

Etkilenen güvenlik alanları: Integrity, Confidentiality, Availability, Access Control

Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy.
Modify MemoryExecute Unauthorized Code or CommandsBypass Protection MechanismOther

Etkilenen güvenlik alanları: Integrity, Confidentiality, Availability, Access Control, Other

When the consequence is arbitrary code execution, this can often be used to subvert any other security service.

Savunma

Nasıl önlenir ve çözülür?

Operation · Build and Compilation

Environment Hardening

Detay
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.

Etkinlik: 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.

Architecture and Design

Mimari ve tasarım yaklaşımı

Detay
Use an abstraction library to abstract away risky APIs. Not a complete solution.

Implementation

Uygulama aşaması savunması

Detay
Implement and perform bounds checking on input.

Implementation

Uygulama aşaması savunması

Detay
Do not use dangerous functions such as gets. Use safer, equivalent functions which check for boundary errors.

Operation · Build and Compilation

Environment Hardening

Detay
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].

Etkinlik: 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].

Doğrulama

Nasıl tespit edilir?

Fuzzing

High
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.

Automated Static Analysis

High
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Automated Dynamic Analysis

Moderate
Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++ [REF-1518].

Crafted inputs are necessary to reach the code containing the error, such as generated by fuzzers. Also, these tools may reduce performance, and they only report the error condition - not the original mistake that led to the error.