AllowedPattern.py

"""
Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
SPDX-License-Identifier: MIT-0
"""
import re
import six
from cfnlint.rules import CloudFormationLintRule
from cfnlint.rules import RuleMatch

from cfnlint.helpers import RESOURCE_SPECS


class AllowedPattern(CloudFormationLintRule):
    """Check if properties have a valid value"""
    id = 'E3031'
    shortdesc = 'Check if property values adhere to a specific pattern'
    description = 'Check if properties have a valid value in case of a pattern (Regular Expression)'
    source_url = 'https://github.com/awslabs/cfn-python-lint/blob/master/docs/cfn-resource-specification.md#allowedpattern'
    tags = ['resources', 'property', 'allowed pattern', 'regex']

    def initialize(self, cfn):
        """Initialize the rule"""
        for resource_type_spec in RESOURCE_SPECS.get(cfn.regions[0]).get('ResourceTypes'):
            self.resource_property_types.append(resource_type_spec)
        for property_type_spec in RESOURCE_SPECS.get(cfn.regions[0]).get('PropertyTypes'):
            self.resource_sub_property_types.append(property_type_spec)

    def check_value(self, value, path, property_name, **kwargs):
        """Check Value"""
        matches = []

        # Get the Allowed Pattern Regex
        value_pattern_regex = kwargs.get('value_specs', {}).get('AllowedPatternRegex', {})
        # Get the "Human Readable" version for the error message. Optional, if not specified,
        # the RegEx itself is used.
        value_pattern = kwargs.get('value_specs', {}).get('AllowedPattern', value_pattern_regex)

        if isinstance(value, (int, float)):
            value = str(value)

        if isinstance(value, six.string_types):
            if value_pattern_regex:
                regex = re.compile(value_pattern_regex)

                # Ignore values with dynamic references. Simple check to prevent false-positives
                # See: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/dynamic-references.html
                if '{{resolve:' not in value:
                    if not regex.match(value):
                        full_path = ('/'.join(str(x) for x in path))

                        message = '{} contains invalid characters (Pattern: {}) at {}'
                        matches.append(RuleMatch(path, message.format(
                            property_name, value_pattern, full_path)))

        return matches

    def check(self, cfn, properties, value_specs, property_specs, path):
        """Check itself"""
        matches = list()
        for p_value, p_path in properties.items_safe(path[:]):
            for prop in p_value:
                if prop in value_specs:
                    value = value_specs.get(prop).get('Value', {})
                    if value:
                        value_type = value.get('ValueType', '')
                        property_type = property_specs.get('Properties').get(prop).get('Type')
                        matches.extend(
                            cfn.check_value(
                                p_value, prop, p_path,
                                check_value=self.check_value,
                                value_specs=RESOURCE_SPECS.get(cfn.regions[0]).get(
                                    'ValueTypes').get(value_type, {}),
                                cfn=cfn, property_type=property_type, property_name=prop
                            )
                        )
        return matches

    def match_resource_sub_properties(self, properties, property_type, path, cfn):
        """Match for sub properties"""
        matches = list()

        specs = RESOURCE_SPECS.get(cfn.regions[0]).get(
            'PropertyTypes').get(property_type, {}).get('Properties', {})
        property_specs = RESOURCE_SPECS.get(cfn.regions[0]).get('PropertyTypes').get(property_type)
        matches.extend(self.check(cfn, properties, specs, property_specs, path))

        return matches

    def match_resource_properties(self, properties, resource_type, path, cfn):
        """Check CloudFormation Properties"""
        matches = list()

        specs = RESOURCE_SPECS.get(cfn.regions[0]).get(
            'ResourceTypes').get(resource_type, {}).get('Properties', {})
        resource_specs = RESOURCE_SPECS.get(cfn.regions[0]).get('ResourceTypes').get(resource_type)
        matches.extend(self.check(cfn, properties, specs, resource_specs, path))

        return matches