Refactored Config for Bandit

Problem Description

Bandit’s config file has grown in complexity and size as more testing plugins and options have been added to the project. It has been highlighted by adopters that maintaining a Bandit config file in each projects repository is an undesirable pain point.

Proposed Change

This proposal aims to refactor the Bandit configuration system with the aim of removing the need to include any per project configuration files if no major deviation from preset defaults is required. To accomplish this goal, we first looked at the existing configuration system. The configuration file breaks down into three main areas, and each of these will be dealt with individually. These areas are:

  1. Tunable options, used to tweak miscellaneous bits in the Bandit runtime
  2. Plugin options, used to control the operation of individual test plugin
  3. Profiles, used to select the desired set of test plugins to run or not

Tunable Options

A number of tunable options are provided in the Bandit config. It was originally foreseen that these would be useful in configuring Bandit’s runtime behavior. In all practical scenarios however, these options are redundant and remain at the default setting.

Our proposed strategy is to remove these unnecessary config options and rely on sensible values provided by the Bandit authors.

Plugin Options

This section represents the largest block of configuration data and thus the largest pain point for adopters. It contains a lengthy set of configuration options for all available test plugins, without these options many plugins will malfunction or fail to run at all. The usefulness of many plugins is also directly dependent upon the data provided in this section of the config (e.g. the blacklist plugins) and as such this data should be considered part of the plugins functionality.

Our proposed strategy is to modify the plugin system to provide sensible defaults for all configurable test plugins, directly in the plugin code. This data can then be overridden in an external configuration only when desirable. This removes the need for any configuration data when default functioning is sufficient, and this should be in the majority of cases.

To accomplish this, the test plugin system will be modified to use classes for each plugin instead of the function that is currently used. Each class will provide one or more testing methods, equivalent to the current testing functions, and one method to return a default configuration shared by all testing methods provided by that class. In the default case, this configuration data will be sent back to each test method, or it may be overridden by an external configuration if present.

In addition to removing the need for a configuration file this approach has two advantages. Firstly, it allows external plugins from third parties to provide configuration data along with their plugins without the need to edit a central default config file shipped by the Bandit project. Secondly, it allows for a config generation tool to auto-discover all available plugins and create a default configuration file by simply invoking the config method on each discovered plugin class, or on some desirable subset of these.

Profiles

This section is the primary concern for gate adopters, it is here that they may select the set of plugin tests that they wish to run on their project. It is nearly always configured as part of the initial Bandit setup.

Our proposed strategy is to provide a number of new mechanisms to indicate the desired set of tests to run, deprecating the current situation. Firstly, we allow profiles to be configured in their own individual files that use a much simpler layout than than the current single config file. Secondly, we will permit the specification of test sets directly from the command line interface of Bandit.

The first option will allow manual users of Bandit to easily create and re-use various test profiles that they might need to use frequently.

The second option will permit gate adopters to list their desired test set as part of the Bandit command invocation given within their existing tox.ini file. This has precedent and matches closely to the way PEP8 tests are currently configured.

To further improve upon the current state of affairs, again borrowing from hacking/flake8/pep8, Bandit will support a canonical numbering system for test plugins. These numeric names may be used anywhere that the usual descriptive, but often unwieldy, full test names would be used.

An example canonical scheme may look like the following

B1xx - blacklisted functions B2xx - blacklisted imports B3xx - injections ...

A Note On Blacklists

As implied from the example scheme given above, each blacklisted module and import now will also be assigned a unique identifier. The intention here is to aid in configuration of these lengthy blacklists. So while blacklisted modules and methods will share common logic, individual items will be distinguishable as if they were separate tests when configuring Bandit.

Implementation

See Proposed change, the indicated changes will be made to Bandit to enact the new approach to configuration. Support for the old configuration file will remain, but its use will be marked as deprecated and a message indicating this will be presented to the user when utilizing the text formatted output and an old style configuration.

Assignee(s)

The Bandit core team will lead the development of these changes.

Primary assignee:
tkelsey tmcpeak

Milestones

Target Milestone for completion:
Mitaka 3

Work Items

  • Strip out miscellaneous options from Bandit config
  • Add a separate text formatter that includes terminal output colors, removing the need for these to be configurable.
  • Add support for external profile files.
  • Convert plugins to classes which implement one or more tests and provide a config generation function.
  • Assign canonical numbers to each plugin, including blacklist modules and imports.
  • Add support for test selection via the CLI.
  • Update the config generator to output default configs.
  • Delete the config file bundled with Bandit.

Dependencies

N/A