Audit required: External control of file name or path PTC-W6004
External variable 'filename' used in file path
35 data (dict): Json string to be saved
36 filename (str): Path to file
37 """
38 with open(filename, "w") as f: 39 json.dump(data, f)
40
41External variable 'filename' used in file path
48 Returns:
49 dict: Json string
50 """
51 with open(filename, "r") as f: 52 data = json.load(f)
53 return data
54
Description
Python's open() function can take in a relative or absolute path and read its file contents.
If a user is provided direct access to the path that is opened, it can have serious security risks.
Bad practice
def read_file(path):
with open(os.path.join('some/path', path)) as f:
f.read()
# Someone can exploit `read_file` and see your secrets this way:
read_file('../../../secrets.txt')
Recommended
Either use a static path:
def read_file(path):
with open('some/path/to/file.txt') as f:
f.read()
Or, do some kind of validation to make sure you're not allowing arbitrary file access:
def read_file(filename):
if filename not in ('x.txt', 'y.txt'):
return 'Invalid filename'
with open(os.path.join('some/path', path)) as f:
f.read()
References
- OWASP Top 10 2021 Category A01 - Broken Access Control
- OWASP Top 10 2021 Category A04 - Insecure Design
- CWE-73 External Control of File Name or Path