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yaklang/explotación-de-cadena-de-formato

Manual de explotación de cadenas de formato. Úsalo cuando las funciones de la familia printf reciban cadenas de formato controladas por el usuario, permitiendo lecturas arbitrarias de la pila (%p/%s), escrituras arbitrarias en memoria (%n/%hn/%hhn), sobrescrituras de GOT/hook, y fugas de canary/libc/PIE.

¿Qué es explotación-de-cadena-de-formato?

Este playbook detalla la explotación de vulnerabilidades de cadena de formato en aplicaciones C/C++, comunes cuando funciones como printf, sprintf o fprintf usan cadenas de formato proporcionadas por el atacante. La habilidad cubre técnicas esenciales: lectura arbitraria de la pila con %p y %s para filtrar direcciones y datos; escritura arbitraria de memoria mediante %n, %hn y %hhn para modificar GOT, ganchos o variables de control; y fugas de información como canary, direcciones de libc y PIE. Es compatible con herramientas como yaklang, GDB y pwntools, y se aplica en plataformas Linux/x86-64. El flujo típico incluye identificar la vulnerabilidad, calcular offsets de pila, explotar escrituras para redirigir ejecución y, finalmente, obtener una shell o ejecutar código arbitrario. Su enfoque metódico y ejemplos prácticos lo convierten en un recurso valioso para desarrolladores de seguridad y entusiastas de la explotación binaria.

Compatible con~Claude Code~Codex CLI~Cursor
npx skills add https://github.com/yaklang/hack-skills/tree/main/skills/format-string-exploitation

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Documentación

yaklang/exploitación-de-cadena-de-formato

Manual de explotación de cadenas de formato. Úsalo cuando las funciones de la familia printf reciban cadenas de formato controladas por el usuario, permitiendo lecturas arbitrarias de la pila (%p/%s), escrituras arbitrarias en memoria (%n/%hn/%hhn), sobrescrituras de GOT/hook, y fugas de canary/libc/PIE.

Técnicas principales

  • Lectura arbitraria de pila: Usa %p o %s para filtrar direcciones de retorno, canary o direcciones base de libc/PIE.
  • Escritura arbitraria de memoria: Emplea %n, %hn o %hhn para modificar valores en GOT o variables objetivo.
  • Fugas de información: Combina lecturas para obtener canary, dirección de libc y PIE base.
  • Sobrescritura de GOT: Redirige la ejecución reemplazando entradas de la tabla GOT.

Componentes del ecosistema

HerramientaPropósito
yaklangLenguaje de scripting para automatizar la explotación
GDBDepuración y análisis dinámico
pwntoolsBiblioteca Python para construcción de exploits
checksecVerificación de protecciones (NX, PIE, RELRO)

Flujo de trabajo típico

  1. Identificar la vulnerabilidad: Busca funciones printf sin cadena de formato fija (ej. printf(user_input)).
  2. Calcular offsets de pila: Usa %p repetido para encontrar la posición de tu entrada en la pila.
  3. Filtrar información: Extrae canary, dirección de libc y PIE base.
  4. Preparar escritura: Calcula direcciones objetivo (ej. puts@GOT) y valores a escribir.
  5. Ejecutar escritura: Usa %hn/%hhn para modificar memoria de forma controlada.
  6. Obtener shell: Redirige ejecución a system("/bin/sh") o similar.

Ejemplo básico con yaklang

// Ejemplo de exploit de cadena de formato
vuln = openProcess("./vuln")

// Enviar payload para filtrar dirección
payload = "%7$p.%8$p.%9$p"
vuln.sendLine(payload)
resp = vuln.recvLine()
println("Respuesta: " + resp)

Referencias

Individual skills in this repo

This repo contains 20 individual skills — each has its own dedicated page.

yaklang/401-403-bypass-techniques

401/403 bypass playbook. Use when encountering access-denied responses on admin panels, API endpoints, or restricted paths. Covers path manipulation, HTTP method tampering, header injection, protocol downgrade, and automated bypass tools.

yaklang/active-directory-acl-abuse

Active Directory ACL abuse playbook. Use when exploiting misconfigured AD permissions including GenericAll, WriteDACL, DCSync rights, shadow credentials, LAPS reading, GPO abuse, and BloodHound-guided attack paths.

yaklang/active-directory-certificate-services

AD Certificate Services attack playbook. Use when targeting misconfigured AD CS for privilege escalation via ESC1-ESC13 template abuse, NTLM relay to enrollment, CA officer abuse, and certificate-based persistence.

yaklang/active-directory-kerberos-attacks

Kerberos attack playbook for Active Directory. Use when targeting AD authentication via AS-REP roasting, Kerberoasting, golden/silver/diamond tickets, delegation abuse, or pass-the-ticket attacks.

yaklang/ai-ml-security

AI/ML security playbook. Use when assessing model supply chain attacks (pickle RCE, poisoned weights), adversarial examples, model poisoning, model stealing, data privacy attacks (membership inference, model inversion), and autonomous agent security risks.

yaklang/android-pentesting-tricks

Android pentesting playbook. Use when testing Android applications for SSL pinning bypass, exported component abuse, WebView vulnerabilities, intent redirection, root detection bypass, tapjacking, and backup extraction during authorized mobile security assessments.

yaklang/anti-debugging-techniques

Anti-debugging detection and bypass playbook. Use when reversing protected binaries that detect debuggers via ptrace, PEB flags, timing checks, or signal/exception handlers on Linux and Windows.

yaklang/api-auth-and-jwt-abuse

API authentication and JWT abuse playbook. Use when testing bearer tokens, API keys, claim trust, header spoofing, rate limits, and API auth boundary weaknesses.

yaklang/api-authorization-and-bola

API authorization and BOLA testing playbook. Use when APIs expose object identifiers, nested resources, hidden writable fields, or weak function-level authorization.

yaklang/api-recon-and-docs

API reconnaissance and documentation review playbook. Use when discovering endpoints, schemas, versions, OpenAPI specs, hidden docs, and surface area for API testing.

yaklang/api-sec

Entry P1 category router for API security. Use when choosing between API recon, authorization, token abuse, and hidden-parameter workflows before any deeper API topic skill.

yaklang/arbitrary-write-to-rce

Arbitrary write to RCE playbook. Use when you have an arbitrary write primitive (from heap exploitation, format string, or OOB write) and need to convert it into code execution by targeting GOT, hooks, _IO_FILE vtable, exit_funcs, TLS_dtor_list, modprobe_path, .fini_array, or C++ vtables.

yaklang/authbypass-authentication-flaws

Authentication bypass testing playbook. Use when assessing login flows, password reset logic, account recovery, MFA bypass, token predictability, brute-force resistance, and session boundary flaws.

yaklang/auth-sec

Entry P1 category router for authentication and authorization. Use when testing login flows, sessions, object authorization, JWT, OAuth, CORS, CSRF, and enterprise SSO weaknesses before any deeper auth topic skill.

yaklang/binary-protection-bypass

Binary protection bypass playbook. Use when identifying and bypassing ASLR, PIE, NX/DEP, stack canary, RELRO, FORTIFY_SOURCE, CET, and MTE protections in ELF binaries to enable exploitation.

yaklang/browser-exploitation-v8

Browser and V8 exploitation playbook. Use when exploiting JavaScript engine vulnerabilities including JIT type confusion, incorrect bounds elimination, and V8 sandbox bypass to achieve renderer RCE and sandbox escape in Chrome/Chromium.

yaklang/business-logic-vuln

Entry P1 category router for business logic testing. Use when workflow abuse, race conditions, pricing flaws, or multi-step state attacks matter more than parser-level input injection.

yaklang/business-logic-vulnerabilities

Business logic vulnerability playbook. Use when reasoning about workflows, race conditions, price manipulation, coupon abuse, state machines, and multi-step authorization gaps.

yaklang/classical-cipher-analysis

Classical cipher analysis playbook. Use when encountering substitution ciphers, Vigenere, transposition, XOR, or encoded text in CTF challenges that requires frequency analysis, Kasiski examination, or known-plaintext cryptanalysis.

yaklang/clickjacking

Clickjacking playbook. Use when testing whether target pages can be framed, whether X-Frame-Options or CSP frame-ancestors are properly configured, and whether UI redress attacks can trigger sensitive actions.

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