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bandit 1.4.0

Security oriented static analyser for python code.

Bandit

A security linter from OpenStack Security

Overview

Bandit is a tool designed to find common security issues in Python code. To do this Bandit processes each file, builds an AST from it, and runs appropriate plugins against the AST nodes. Once Bandit has finished scanning all the files it generates a report.

Installation

Bandit is distributed on PyPI. The best way to install it is with pip:

Create a virtual environment (optional):

virtualenv bandit-env

Install Bandit:

pip install bandit
# Or if you're working with a Python 3.5 project
pip3.5 install bandit

Run Bandit:

bandit -r path/to/your/code

Bandit can also be installed from source. To do so, download the source tarball from PyPI, then install it:

python setup.py install

Usage

Example usage across a code tree:

bandit -r ~/openstack-repo/keystone

Example usage across the examples/ directory, showing three lines of context and only reporting on the high-severity issues:

bandit examples/*.py -n 3 -lll

Bandit can be run with profiles. To run Bandit against the examples directory using only the plugins listed in the ShellInjection profile:

bandit examples/*.py -p ShellInjection

Bandit also supports passing lines of code to scan using standard input. To run Bandit with standard input:

cat examples/imports.py | bandit -

Usage:

$ bandit -h
usage: bandit [-h] [-r] [-a {file,vuln}] [-n CONTEXT_LINES] [-c CONFIG_FILE]
              [-p PROFILE] [-t TESTS] [-s SKIPS] [-l] [-i]
              [-f {csv,html,json,screen,txt,xml}] [-o [OUTPUT_FILE]] [-v] [-d]
              [--ignore-nosec] [-x EXCLUDED_PATHS] [-b BASELINE]
              [--ini INI_PATH] [--version]
              targets [targets ...]

Bandit - a Python source code security analyzer

positional arguments:
  targets               source file(s) or directory(s) to be tested

optional arguments:
  -h, --help            show this help message and exit
  -r, --recursive       find and process files in subdirectories
  -a {file,vuln}, --aggregate {file,vuln}
                        aggregate output by vulnerability (default) or by
                        filename
  -n CONTEXT_LINES, --number CONTEXT_LINES
                        maximum number of code lines to output for each issue
  -c CONFIG_FILE, --configfile CONFIG_FILE
                        optional config file to use for selecting plugins and
                        overriding defaults
  -p PROFILE, --profile PROFILE
                        profile to use (defaults to executing all tests)
  -t TESTS, --tests TESTS
                        comma-separated list of test IDs to run
  -s SKIPS, --skip SKIPS
                        comma-separated list of test IDs to skip
  -l, --level           report only issues of a given severity level or higher
                        (-l for LOW, -ll for MEDIUM, -lll for HIGH)
  -i, --confidence      report only issues of a given confidence level or
                        higher (-i for LOW, -ii for MEDIUM, -iii for HIGH)
  -f {csv,html,json,screen,txt,xml}, --format {csv,html,json,screen,txt,xml}
                        specify output format
  -o [OUTPUT_FILE], --output [OUTPUT_FILE]
                        write report to filename
  -v, --verbose         output extra information like excluded and included
                        files
  -d, --debug           turn on debug mode
  --ignore-nosec        do not skip lines with # nosec comments
  -x EXCLUDED_PATHS, --exclude EXCLUDED_PATHS
                        comma-separated list of paths to exclude from scan
                        (note that these are in addition to the excluded paths
                        provided in the config file)
  -b BASELINE, --baseline BASELINE
                        path of a baseline report to compare against (only
                        JSON-formatted files are accepted)
  --ini INI_PATH        path to a .bandit file that supplies command line
                        arguments
  --version             show program's version number and exit

The following tests were discovered and loaded:
  B101  assert_used
  B102  exec_used
  B103  set_bad_file_permissions
  B104  hardcoded_bind_all_interfaces
  B105  hardcoded_password_string
  B106  hardcoded_password_funcarg
  B107  hardcoded_password_default
  B108  hardcoded_tmp_directory
  B109  password_config_option_not_marked_secret
  B110  try_except_pass
  B111  execute_with_run_as_root_equals_true
  B112  try_except_continue
  B201  flask_debug_true
  B301  pickle
  B302  marshal
  B303  md5
  B304  ciphers
  B305  cipher_modes
  B306  mktemp_q
  B307  eval
  B308  mark_safe
  B309  httpsconnection
  B310  urllib_urlopen
  B311  random
  B312  telnetlib
  B313  xml_bad_cElementTree
  B314  xml_bad_ElementTree
  B315  xml_bad_expatreader
  B316  xml_bad_expatbuilder
  B317  xml_bad_sax
  B318  xml_bad_minidom
  B319  xml_bad_pulldom
  B320  xml_bad_etree
  B321  ftplib
  B322  input
  B401  import_telnetlib
  B402  import_ftplib
  B403  import_pickle
  B404  import_subprocess
  B405  import_xml_etree
  B406  import_xml_sax
  B407  import_xml_expat
  B408  import_xml_minidom
  B409  import_xml_pulldom
  B410  import_lxml
  B411  import_xmlrpclib
  B412  import_httpoxy
  B501  request_with_no_cert_validation
  B502  ssl_with_bad_version
  B503  ssl_with_bad_defaults
  B504  ssl_with_no_version
  B505  weak_cryptographic_key
  B506  yaml_load
  B601  paramiko_calls
  B602  subprocess_popen_with_shell_equals_true
  B603  subprocess_without_shell_equals_true
  B604  any_other_function_with_shell_equals_true
  B605  start_process_with_a_shell
  B606  start_process_with_no_shell
  B607  start_process_with_partial_path
  B608  hardcoded_sql_expressions
  B609  linux_commands_wildcard_injection
  B701  jinja2_autoescape_false
  B702  use_of_mako_templates

Configuration

An optional config file may be supplied and may include:
  • lists of tests which should or shouldn’t be run
  • exclude_dirs - sections of the path, that if matched, will be excluded from scanning
  • overridden plugin settings - may provide different settings for some plugins

Per Project Command Line Args

Projects may include a .bandit file that specifies command line arguments that should be supplied for that project. The currently supported arguments are:

  • exclude: comma separated list of excluded paths
  • skips: comma separated list of tests to skip
  • tests: comma separated list of tests to run

To use this, put a .bandit file in your project’s directory. For example:

[bandit]
exclude: /test
[bandit]
tests: B101,B102,B301

Exclusions

In the event that a line of code triggers a Bandit issue, but that the line has been reviewed and the issue is a false positive or acceptable for some other reason, the line can be marked with a # nosec and any results associated with it will not be reported.

For example, although this line may cause Bandit to report a potential security issue, it will not be reported:

self.process = subprocess.Popen('/bin/echo', shell=True)  # nosec

Vulnerability Tests

Vulnerability tests or “plugins” are defined in files in the plugins directory.

Tests are written in Python and are autodiscovered from the plugins directory. Each test can examine one or more type of Python statements. Tests are marked with the types of Python statements they examine (for example: function call, string, import, etc).

Tests are executed by the BanditNodeVisitor object as it visits each node in the AST.

Test results are maintained in the BanditResultStore and aggregated for output at the completion of a test run.

Writing Tests

To write a test:
  • Identify a vulnerability to build a test for, and create a new file in examples/ that contains one or more cases of that vulnerability.
  • Consider the vulnerability you’re testing for, mark the function with one or more of the appropriate decorators: - @checks(‘Call’) - @checks(‘Import’, ‘ImportFrom’) - @checks(‘Str’)
  • Create a new Python source file to contain your test, you can reference existing tests for examples.
  • The function that you create should take a parameter “context” which is an instance of the context class you can query for information about the current element being examined. You can also get the raw AST node for more advanced use cases. Please see the context.py file for more.
  • Extend your Bandit configuration file as needed to support your new test.
  • Execute Bandit against the test file you defined in examples/ and ensure that it detects the vulnerability. Consider variations on how this vulnerability might present itself and extend the example file and the test function accordingly.

Extending Bandit

Bandit allows users to write and register extensions for checks and formatters. Bandit will load plugins from two entry-points:

  • bandit.formatters
  • bandit.plugins

Formatters need to accept 4 things:

  • result_store: An instance of bandit.core.BanditResultStore
  • file_list: The list of files which were inspected in the scope
  • scores: The scores awarded to each file in the scope
  • excluded_files: The list of files that were excluded from the scope

Plugins tend to take advantage of the bandit.checks decorator which allows the author to register a check for a particular type of AST node. For example

@bandit.checks('Call')
def prohibit_unsafe_deserialization(context):
    if 'unsafe_load' in context.call_function_name_qual:
        return bandit.Issue(
            severity=bandit.HIGH,
            confidence=bandit.HIGH,
            text="Unsafe deserialization detected."
        )

To register your plugin, you have two options:

  1. If you’re using setuptools directly, add something like the following to your setup call:

    # If you have an imaginary bson formatter in the bandit_bson module
    # and a function called `formatter`.
    entry_points={'bandit.formatters': ['bson = bandit_bson:formatter']}
    # Or a check for using mako templates in bandit_mako that
    entry_points={'bandit.plugins': ['mako = bandit_mako']}
    
  2. If you’re using pbr, add something like the following to your setup.cfg file:

    [entry_points]
    bandit.formatters =
        bson = bandit_bson:formatter
    bandit.plugins =
        mako = bandit_mako
    

Contributing

Contributions to Bandit are always welcome! We can be found on #openstack-security on Freenode IRC.

The best way to get started with Bandit is to grab the source:

git clone https://git.openstack.org/openstack/bandit.git

You can test any changes with tox:

pip install tox
tox -e pep8
tox -e py27
tox -e py35
tox -e docs
tox -e cover

Reporting Bugs

Bugs should be reported on Launchpad. To file a bug against Bandit, visit: https://bugs.launchpad.net/bandit/+filebug

Under Which Version of Python Should I Install Bandit?

The answer to this question depends on the project(s) you will be running Bandit against. If your project is only compatible with Python 2.7, you should install Bandit to run under Python 2.7. If your project is only compatible with Python 3.5, then use 3.5 respectively. If your project supports both, you could run Bandit with both versions but you don’t have to.

Bandit uses the ast module from Python’s standard library in order to analyze your Python code. The ast module is only able to parse Python code that is valid in the version of the interpreter from which it is imported. In other words, if you try to use Python 2.7’s ast module to parse code written for 3.5 that uses, for example, yield from with asyncio, then you’ll have syntax errors that will prevent Bandit from working properly. Alternatively, if you are relying on 2.7’s octal notation of 0777 then you’ll have a syntax error if you run Bandit on 3.x.

References

Bandit wiki: https://wiki.openstack.org/wiki/Security/Projects/Bandit

Python AST module documentation: https://docs.python.org/2/library/ast.html

Green Tree Snakes - the missing Python AST docs: http://greentreesnakes.readthedocs.org/en/latest/

Documentation of the various types of AST nodes that Bandit currently covers or could be extended to cover: http://greentreesnakes.readthedocs.org/en/latest/nodes.html

 
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