COMMON ATTACK PATTERN ENUMERATION AND CLASSIFICATIONMITRE canlı kaydı

CAPEC-135

Format String Injection

An adversary includes formatting characters in a string input field on the target application. Most applications assume that users will provide static text and may respond unpredictably to the presence of formatting character. For example, in certain functions of the C programming languages such as printf, the formatting character %s will print the contents of a memory location expecting this location to identify a string and the formatting character %n prints the number of DWORD written in the memory. An adversary can use this to read or write to memory locations or files, or simply to manipulate the value of the resulting text in unexpected ways. Reading or writing memory may result in program crashes and writing memory could result in the execution of arbitrary code if the adversary can write to the program stack.

Soyutlama

Standard

Tipik ciddiyet

High

Saldırı ihtimali

High

Saldırıyı anla

Bu saldırı kalıbı nedir?

An adversary includes formatting characters in a string input field on the target application. Most applications assume that users will provide static text and may respond unpredictably to the presence of formatting character. For example, in certain functions of the C programming languages such as printf, the formatting character %s will print the contents of a memory location expecting this location to identify a string and the formatting character %n prints the number of DWORD written in the memory. An adversary can use this to read or write to memory locations or files, or simply to manipulate the value of the resulting text in unexpected ways. Reading or writing memory may result in program crashes and writing memory could result in the execution of arbitrary code if the adversary can write to the program stack.

Uygulama akışı

Saldırı adım adım nasıl ilerler?

1

Explore

Survey application

The adversary takes an inventory of the entry points of the application.

Kullanılan teknikler

  • Spider web sites for all available links
  • List parameters, external variables, configuration files variables, etc. that are possibly used by the application.
2

Experiment

Determine user-controllable input susceptible to format string injection

Determine the user-controllable input susceptible to format string injection. For each user-controllable input that the adversary suspects is vulnerable to format string injection, attempt to inject formatting characters such as %n, %s, etc.. The goal is to manipulate the string creation using these formatting characters.

Kullanılan teknikler

  • Inject probe payload which contains formatting characters (%s, %d, %n, etc.) through input parameters.
3

Exploit

Try to exploit the Format String Injection vulnerability

After determining that a given input is vulnerable to format string injection, hypothesize what the underlying usage looks like and the associated constraints.

Kullanılan teknikler

  • Insert various formatting characters to read or write the memory, e.g. overwrite return address, etc.

Gereksinimler

Saldırının gerçekleşmesi için ne gerekir?

Ön koşullar

  • The target application must accept a strings as user input, fail to sanitize string formatting characters in the user input, and process this string using functions that interpret string formatting characters.

Gerekli beceri

  • High: In order to discover format string vulnerabilities it takes only low skill, however, converting this discovery into a working exploit requires advanced knowledge on the part of the adversary.

Gerekli kaynak

  • None: No specialized resources are required to execute this type of attack.

Etki

Başarılı saldırı neye yol açar?

Modify Data

Etkilenen alanlar: Integrity

Read Data

Etkilenen alanlar: Confidentiality

Gain Privileges

Etkilenen alanlar: Access Control

Execute Unauthorized Commands

Etkilenen alanlar: Integrity

Bypass Protection Mechanism

Etkilenen alanlar: Access Control

Savunma

Nasıl önlenir ve etkisi azaltılır?

1
Limit the usage of formatting string functions.
2
Strong input validation - All user-controllable input must be validated and filtered for illegal formatting characters.

Gerçek dünya

MITRE örnek olayları

Örnek olay 1Detay
Untrusted search path vulnerability in the add_filename_to_string function in intl/gettext/loadmsgcat.c for Elinks 0.11.1 allows local users to cause Elinks to use an untrusted gettext message catalog (.po file) in a "../po" directory, which can be leveraged to conduct format string attacks. See also: CVE-2007-2027
CAPEC-135: Format String Injection — DayBreach Saldırı Sözlüğü · DayBreach