COMMON WEAKNESS ENUMERATIONDraft

CWE-479

Signal Handler Use of a Non-reentrant Function

The product defines a signal handler that calls a non-reentrant function.

Soyutlama

Variant

Yapı

Simple

Sömürü İhtimali

Low

Problemi anla

Problem nedir?

The product defines a signal handler that calls a non-reentrant function.

Genişletilmiş açıklama

Non-reentrant functions are functions that cannot safely be called, interrupted, and then recalled before the first call has finished without resulting in memory corruption. This can lead to an unexpected system state and unpredictable results with a variety of potential consequences depending on context, including denial of service and code execution. Many functions are not reentrant, but some of them can result in the corruption of memory if they are used in a signal handler. The function call syslog() is an example of this. In order to perform its functionality, it allocates a small amount of memory as "scratch space." If syslog() is suspended by a signal call and the signal handler calls syslog(), the memory used by both of these functions enters an undefined, and possibly, exploitable state. Implementations of malloc() and free() manage metadata in global structures in order to track which memory is allocated versus which memory is available, but they are non-reentrant. Simultaneous calls to these functions can cause corruption of the metadata.

Kök neden

Problem nasıl ve ne zaman oluşur?

Yaşam döngüsü evresi

Implementation

Risk

Başarılı sömürü neye yol açar?

Execute Unauthorized Code or Commands

Etkilenen güvenlik alanları: Integrity, Confidentiality, Availability

It may be possible to execute arbitrary code through the use of a write-what-where condition.
Modify MemoryModify Application Data

Etkilenen güvenlik alanları: Integrity

Signal race conditions often result in data corruption.

Savunma

Nasıl önlenir ve çözülür?

Requirements

Güvenlik gereksinimi

Detay
Require languages or libraries that provide reentrant functionality, or otherwise make it easier to avoid this weakness.

Architecture and Design

Mimari ve tasarım yaklaşımı

Detay
Design signal handlers to only set flags rather than perform complex functionality.

Implementation

Uygulama aşaması savunması

Detay
Ensure that non-reentrant functions are not found in signal handlers.

Implementation

Uygulama aşaması savunması

Detay
Use sanity checks to reduce the timing window for exploitation of race conditions. This is only a partial solution, since many attacks might fail, but other attacks still might work within the narrower window, even accidentally.

Etkinlik: Defense in Depth

Doğrulama

Nasıl tespit edilir?

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.)