app_debug.py

#
# Copyright 2015 Hewlett-Packard Development Company, L.P.
#
# SPDX-License-Identifier: Apache-2.0
r"""
======================================================
B201: Test for use of flask app with debug set to true
======================================================

Running Flask applications in debug mode results in the Werkzeug debugger
being enabled. This includes a feature that allows arbitrary code execution.
Documentation for both Flask [1]_ and Werkzeug [2]_ strongly suggests that
debug mode should never be enabled on production systems.

Operating a production server with debug mode enabled was the probable cause
of the Patreon breach in 2015 [3]_.

:Example:

.. code-block:: none

    >> Issue: A Flask app appears to be run with debug=True, which exposes
    the Werkzeug debugger and allows the execution of arbitrary code.
       Severity: High   Confidence: High
       CWE: CWE-94 (https://cwe.mitre.org/data/definitions/94.html)
       Location: examples/flask_debug.py:10
    9 #bad
    10    app.run(debug=True)
    11

.. seealso::

 .. [1] https://flask.palletsprojects.com/en/1.1.x/quickstart/#debug-mode
 .. [2] https://werkzeug.palletsprojects.com/en/1.0.x/debug/
 .. [3] https://labs.detectify.com/2015/10/02/how-patreon-got-hacked-publicly-exposed-werkzeug-debugger/
 .. https://cwe.mitre.org/data/definitions/94.html

.. versionadded:: 0.15.0

.. versionchanged:: 1.7.3
    CWE information added

"""  # noqa: E501
import bandit
from bandit.core import issue
from bandit.core import test_properties as test


@test.test_id("B201")
@test.checks("Call")
def flask_debug_true(context):
    if context.is_module_imported_like("flask"):
        if context.call_function_name_qual.endswith(".run"):
            if context.check_call_arg_value("debug", "True"):
                return bandit.Issue(
                    severity=bandit.HIGH,
                    confidence=bandit.MEDIUM,
                    cwe=issue.Cwe.CODE_INJECTION,
                    text="A Flask app appears to be run with debug=True, "
                    "which exposes the Werkzeug debugger and allows "
                    "the execution of arbitrary code.",
                    lineno=context.get_lineno_for_call_arg("debug"),
                )