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Lightweight, extensible schema and data validation tool for Cloudformation Templates.

Project description

Features

cfn_nagger provides type checking and other base functionality out of the box and is designed to be non-blocking and easily extensible, allowing for custom validation. It has no dependencies and is thoroughly tested under Python 2.7, Python 3.3, Python 3.4, Python 3.5, Python 3.6.

Funding

cfn_nagger is a open source, collaboratively funded project. If you run a business and are using cfn_nagger in a revenue-generating product, it would make business sense to sponsor its development: it ensures the project that your product relies on stays healthy and actively maintained. Individual users are also welcome to make a recurring pledge or a one time donation if cfn-nagger has helped you in your work or personal projects.

Every single sign-up makes a significant impact towards making cfn_nagger possible.

Want Custom Rules and Support For Your Application

Submit an issue on my github page if you would like additional custom rules and I will try and get them added as soon as possible.

I you would like other functionality, just submit an issue and I will see what I can do to get it added.

Installation

cfn_nagger is on PyPI so all you need is:

$ pip install cfn-nagger

Testing

Just run:

$ python setup.py test

Or you can use tox to run the tests under all supported Python versions. Make sure the required python versions are installed and run:

$ pip install tox  # first time only
$ tox

Listing Rules

$ cfn-nagger dump_rules
##################################
########## WARNINGS ##############
##################################
{'id': 'F4', 'type': 'VIOLATION::WARNING', 'message': 'IAM policy should not allow * action'}
{'id': 'W1', 'type': 'VIOLATION::WARNING', 'message': 'Specifying credentials in the template itself is probably not the safest thing'}
...

Example

Getting help

$ cfn-nagger validate --help
Usage: cfn-nagger validate [OPTIONS]

  primary function for validating a template :param template_path: :param
  template_file: :param debug: :param rules_directory: :param profile_path:
  :param allow_suppression: :param print_suppression: :param
  parameter_values_path: :param isolate_custom_rule_exceptions: :param
  version: :return:

Options:
  -s, --suppress-errors           Whether to suppress misc errors to get hash only
  -t, --template-path TEXT        base directory to search for templates
  -f, --template-file TEXT        single_template_file
  --debug                         Turn on debugging
  -r, --rules-directory TEXT      Extra rule directory
  -o, --profile-path TEXT         Path to a profile file
  --allow-suppression / --no-allow-suppression
                                  Allow using Metadata to suppress violations
  -p, --print-suppression         Emit suppressions to stderr
  -m, --parameter-values-path TEXT
                                  Path to a JSON file to pull Parameter values
                                  from
  -i, --isolate-custom-rule-exceptions
                                  Isolate custom rule exceptions - just emit
                                  the exception without stack trace and keep
                                  chugging
  -v, --version                   Print version and exit
  --help                          Show this message and exit.

Validate a file

$cfn-nagger validate -f cloudfront_distribution_without_logging.json

Evaluating: cloudfront_distribution_without_logging.json
[
    {
        'failure_count': '0',
        'filename': 'cloudfront_distribution_without_logging.json',
        'file_results': [
            {
                'id': 'W10',
                'type': 'VIOLATION::WARNING',
                'message': 'CloudFront Distribution should enable access logging',
                'logical_resource_ids': [
                    'rDistribution2'
                ]
            }
        ]
    }
]

Validate all files in a path

$cfn-nagger validate -f /projects
...

Programmatically call cfn-nagger to analyze a file

from cfn_nagger.ValidateUtility import ValidateUtility

config_dict = {}
config_dict['template_file'] = '/tmp/template.json'
validator = ValidateUtility(config_dict)
real_result =  validator.validate()
print(real_result)

[
    {
        'failure_count': '0',
        'filename': '/tmp/template.json',
        'file_results': [
            {
                'id': 'W1',
                'type': 'VIOLATION::WARNING',
                'message': 'Specifying credentials in the template itself is probably not the safest thing',
                'logical_resource_ids': [
                    'EC2I4LBA1'
                ]
            }
        ]
    }
]

I you get some errors and warnings in your out put, you can pass-in the flag to suppress all errors

from cfn_nagger.ValidateUtility import ValidateUtility

config_dict = {}
config_dict['suppress_errors'] = True
config_dict['template_file'] = '/tmp/template.json'
validator = ValidateUtility(config_dict)
real_result =  validator.validate()
print(real_result)

[
    {
        'failure_count': '0',
        'filename': '/tmp/template.json',
        'file_results': [
            {
                'id': 'W1',
                'type': 'VIOLATION::WARNING',
                'message': 'Specifying credentials in the template itself is probably not the safest thing',
                'logical_resource_ids': [
                    'EC2I4LBA1'
                ]
            }
        ]
    }
]

Writing your own rules

  • Utilize the format for existing rules in the /cfn_nagger/custom_rules directory
  • Places the files in a new directory
  • The __init__, rule_text, rule_type and rule_id methods should be amount the same, just change of the rule, the text for a failure, and the type to either ‘VIOLATION::FAILING_VIOLATION’ or VIOLATION::WARNNING’
  • Set the id to ‘W’ for warnings, and ‘F’ for failure. Pick a number not utilized elsewhere…
  • NOTE: Currently working on functionality for controlling and listing rules
  • For the audit_impl function - portion with will test the resource objects, you will need to review the object model for the resource to see what objects are available, and then review the parser for the resource. Also, look at other similar rules for the resource, and model after them. The basic concept of the function is to identify resources which apply, iterate over the selected resources, and identify specific aspects to evaluate in the rule
  • pass in the –rules-directory /directory in the command line, and the extra rules directory will get added to the existing rules
def audit_impl(self):

  violating_rules = []

  # This defines which type of resource we are going to test
  resources = self.cfn_model.resources_by_type('AWS::SQS::QueuePolicy')

  if len(resources)>0:
    for resource in resources:
        if hasattr(resource, 'policy_document'):
          if resource.policy_document:
            if resource.policy_document.wildcard_allowed_actions():
              violating_rules.append(resource.logical_resource_id)

  return violating_rules

Unit Testing

Run unit tests

(python3) => pytest
================================================ test session starts =================================================
collected 22 items

test/test_cloudfront_distribution.py .                                                                         [  4%]
test/test_ec2_instance.py .                                                                                    [  9%]
test/test_ec2_volume.py ..                                                                                     [ 18%]
test/test_elasticloadbalancing_loadbalancer.py .                                                               [ 22%]
test/test_iam_user.py .                                                                                        [ 27%]
test/test_lambda_permission.py .                                                                               [ 31%]
test/test_rds_instance.py ...                                                                                  [ 45%]
test/test_s3_bucket.py .                                                                                       [ 50%]
test/test_s3_bucket_policy.py .                                                                                [ 54%]
test/test_security_group.py ........                                                                           [ 90%]
test/test_sns_policy.py .                                                                                      [ 95%]
test/test_sqs_policy.py .                                                                                      [100%]

Source

I am just getting started on this, so any suggestions would be welcome. <https://github.com/rubelw/cfn-nagger>

Project details


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This version
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0.2.26

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