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Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
SPDX-License-Identifier: MIT-0
"""
import regex as re
from cfnlint._typing import RuleMatches
from cfnlint.rules import CloudFormationLintRule, RuleMatch
from cfnlint.template import Template
class HardCodedArnProperties(CloudFormationLintRule):
"""
Checks Resources if ARNs use correctly placed Pseudo Parameters
instead of hardcoded Partition, Region, and Account Number
"""
id = "I3042"
shortdesc = "ARNs should use correctly placed Pseudo Parameters"
description = (
"Checks Resources if ARNs use correctly placed Pseudo Parameters instead of"
" hardcoded Partition, Region, and Account Number"
)
source_url = ""
tags = ["resources"]
# using \r\n inside ${ } because there can be spaces in the sub parameter naming
# using \s for matching outside of Sub parameters as no space will work
regex = re.compile(
r"arn:(\$\{[^:\r\n]*::[^:\r\n]*}|[^:\s]*):[^:\s]+:(\$\{[^:\r\n]*::[^:\r\n]*}|[^:\s]*):(\$\{[^:\r\n]*::[^:\r\n]*}|[^:\s]*)"
)
def __init__(self):
"""Init"""
super().__init__()
self.config_definition = {
"partition": {
"default": True,
"type": "boolean",
},
"region": {
"default": False,
"type": "boolean",
},
"accountId": {
"default": False,
"type": "boolean",
},
}
self.configure()
def _match_values(self, cfnelem, path):
"""Recursively search for values matching the searchRegex"""
values = []
if isinstance(cfnelem, dict):
for key in cfnelem:
pathprop = path[:]
pathprop.append(key)
values.extend(self._match_values(cfnelem[key], pathprop))
elif isinstance(cfnelem, list):
for index, item in enumerate(cfnelem):
pathprop = path[:]
pathprop.append(index)
values.extend(self._match_values(item, pathprop))
else:
# Leaf node
if isinstance(cfnelem, str): # and re.match(searchRegex, cfnelem):
for variable in re.findall(self.regex, cfnelem):
if "Fn::Sub" in path:
values.append(path + [variable])
return values
def match_values(self, cfn):
"""
Search for values in all parts of the templates that match the searchRegex
"""
results = []
results.extend(self._match_values(cfn.template.get("Resources", {}), []))
# Globals are removed during a transform. They need to be checked manually
results.extend(self._match_values(cfn.template.get("Globals", {}), []))
return results
def match(self, cfn: Template) -> RuleMatches:
matches: RuleMatches = []
transforms = cfn.transform_pre["Transform"]
transforms = transforms if isinstance(transforms, list) else [transforms]
if "AWS::Serverless-2016-10-31" in cfn.transform_pre["Transform"]:
return matches
# Get a list of paths to every leaf node string containing at least one ${parameter}
parameter_string_paths = self.match_values(cfn)
# We want to search all of the paths to check if each one contains an 'Fn::Sub'
for parameter_string_path in parameter_string_paths:
path = ["Resources"] + parameter_string_path[:-1]
candidate = parameter_string_path[-1]
# ruff: noqa: E501
# !Sub arn:${AWS::Partition}:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
# is valid even with aws as the account #. This handles empty string
if self.config["partition"] and not re.match(
r"^\$\{\w+}|\$\{AWS::Partition}|$", candidate[0]
):
# or not re.match(r'^(\$\{\w+}|\$\{AWS::Region}|)$',candidate[1])
# or not re.match(r'^\$\{\w+}|\$\{AWS::AccountId}|aws|$', candidate[2]):
message = (
"ARN in Resource {0} contains hardcoded Partition in ARN or"
" incorrectly placed Pseudo Parameters"
)
matches.append(RuleMatch(path, message.format(path[1])))
if self.config["region"] and not re.match(
r"^(\$\{\w+}|\$\{AWS::Region}|)$", candidate[1]
):
# or or not re.match(r'^\$\{\w+}|\$\{AWS::AccountId}|aws|$', candidate[2]):
message = (
"ARN in Resource {0} contains hardcoded Region in ARN or"
" incorrectly placed Pseudo Parameters"
)
matches.append(RuleMatch(path, message.format(path[1])))
# Lambda is added for authorizer's Uniform Resource Identifier (URI)
# https://github.com/aws-cloudformation/cfn-lint/issues/3716
if self.config["accountId"] and not re.match(
r"^\$\{\w+}|\$\{AWS::AccountId}|aws|lambda|$", candidate[2]
):
if candidate[2] not in ["cloudfront"]:
message = (
"ARN in Resource {0} contains hardcoded AccountId in ARN or"
" incorrectly placed Pseudo Parameters"
)
matches.append(RuleMatch(path, message.format(path[1])))
return matches
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