Do not hardcode temporary file or directory names

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Metadata

ID: python-security/hardcoded-tmp-file

Language: Python

Severity: Info

Category: Best Practices

CWE: 377

Description

Do not hardcode the names of temporary files or directories. This may constitute a security vulnerability because an attacker might use that name to create a link to a file they want to overwrite or read.

Instead of hardcoding values, use the tempfile Python module to create unpredictable names.

Learn More

Non-Compliant Code Examples

with open("/tmp/acme.pub", "rb") as key_file:
    public_key = serialization.load_pem_public_key(
        key_file.read(),
        backend=default_backend()
    )

def foobar():
    api_key_file = Path('/tmp/supersecret.txt')

keyfile = '/tmp/vulpy.apikey.{}.{}'.format(username, key)
keyfile = f"/tmp/vulpy.apikey.{username}.{key}"
def authenticate(request):
    if 'X-APIKEY' not in request.headers:
        return None

    key = request.headers['X-APIKEY']

    for f in Path('/tmp/').glob('vulpy.apikey.*.' + key):
        return f.name.split('.')[2]

    return None

Compliant Code Examples

secure_temp = tempfile.mkstemp(prefix="pre_",suffix="_suf")
print(secure_temp)

temp = tempfile.NamedTemporaryFile()
print(temp)
print(temp.name)