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FindInMap.py
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FindInMap.py
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"""
Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
SPDX-License-Identifier: MIT-0
"""
from cfnlint.rules import CloudFormationLintRule, RuleMatch
class FindInMap(CloudFormationLintRule):
"""Check if FindInMap values are correct"""
id = "E1011"
shortdesc = "FindInMap validation of configuration"
description = "Making sure the function is a list of appropriate config"
source_url = "https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-findinmap.html"
tags = ["functions", "findinmap"]
supported_functions = ["Fn::FindInMap", "Ref"]
enhanced_supported_functions = [
"Fn::FindInMap",
"Ref",
"Fn::Select",
"Fn::Split",
"Fn::Join",
"Fn::Sub",
"Fn::If",
"Fn::Length",
"Fn::ToJsonString",
"Fn::Sub",
]
default_value_key = "DefaultValue"
def check_dict(self, obj, tree):
"""
Check that obj is a dict with Ref as the only key
Mappings only support Ref inside them
"""
matches = []
if isinstance(obj, dict):
if len(obj) == 1:
for key_name, _ in obj.items():
if key_name not in self.supported_functions:
message = "FindInMap only supports [{0}] functions at {1}"
matches.append(
RuleMatch(
tree[:] + [key_name],
message.format(
", ".join(map(str, self.supported_functions)),
"/".join(map(str, tree)),
),
)
)
else:
message = (
"FindInMap only supports an object of 1 of [{0}] functions at {1}"
)
matches.append(
RuleMatch(
tree[:],
message.format(
", ".join(map(str, self.supported_functions)),
"/".join(map(str, tree)),
),
)
)
return matches
def map_name(self, map_name, mappings, tree):
"""Check the map name"""
matches = []
if isinstance(map_name, (str, dict)):
if isinstance(map_name, dict):
matches.extend(self.check_dict(map_name, tree[:] + [0]))
else:
if map_name not in mappings:
message = "Map Name {0} does not exist for {0}"
matches.append(
RuleMatch(
tree[:] + [0],
message.format(map_name, "/".join(map(str, tree))),
)
)
else:
message = "Map Name should be a {0}, or string at {1}"
matches.append(
RuleMatch(
tree[:] + [0],
message.format(
", ".join(map(str, self.supported_functions)),
"/".join(map(str, tree)),
),
)
)
return matches
def match_key(self, key, tree, key_name, key_index):
"""Check the validity of a key"""
matches = []
if isinstance(key, (str, int)):
return matches
if isinstance(key, dict):
matches.extend(self.check_dict(key, tree[:] + [key_index]))
else:
message = "FindInMap {0} should be a {1}, string, or int at {2}"
matches.append(
RuleMatch(
tree[:] + [key_index],
message.format(
key_name,
", ".join(map(str, self.supported_functions)),
"/".join(map(str, tree)),
),
)
)
return matches
def validate_intrinsic_function(self, obj, tree):
matches = []
if not isinstance(obj, dict):
return matches
error_message = (
"FindInMap only supports an object of 1 of [{0}] functions at {1}"
)
if len(obj) != 1:
matches.append(
RuleMatch(
tree[:],
error_message.format(
"/".join(map(str, self.enhanced_supported_functions)),
"/".join(map(str, tree)),
),
)
)
return matches
function_name = next(iter(obj))
if function_name not in self.enhanced_supported_functions:
matches.append(
RuleMatch(
tree[:],
error_message.format(
"/".join(map(str, self.enhanced_supported_functions)),
"/".join(map(str, tree)),
),
)
)
return matches
def validate_enhanced_map_name(self, map_name, mappings, tree):
matches = []
if isinstance(map_name, str):
if map_name not in mappings:
error_message = "Map Name {0} does not exist for {1}"
matches.append(
RuleMatch(
tree[:] + [0],
error_message.format(map_name, "/".join(map(str, tree))),
)
)
elif isinstance(map_name, dict):
return self.validate_intrinsic_function(map_name, tree)
else:
error_message = "Map Name should be an intrinsic function that resolves to a string, or a string at {0}"
matches.append(
RuleMatch(tree[:] + [0], error_message.format("/".join(map(str, tree))))
)
return matches
def validate_enhanced_key(self, key, tree, key_name, key_index):
matches = []
if isinstance(key, (str, int)):
return matches
if isinstance(key, dict):
return self.validate_intrinsic_function(key, tree)
error_message = "FindInMap {0} should be a string, int or an intrinsic function resolves to a string or int at {1}"
matches.append(
RuleMatch(
tree[:] + [key_index],
error_message.format(key_name, "/".join(map(str, tree))),
)
)
return matches
def validate_default_value_shape(self, default_value, tree):
matches = []
error_message = "Fn::FindInMap default value must be an object whose key is 'DefaultValue' at {0}"
if (not isinstance(default_value, dict)) or (len(default_value) != 1):
matches.append(
RuleMatch(tree[:], error_message.format("/".join(map(str, tree))))
)
return matches
key = next(iter(default_value))
if key != self.default_value_key:
matches.append(
RuleMatch(tree[:], error_message.format("/".join(map(str, tree))))
)
return matches
def validate_enhanced_default_value(self, default_value_dict, tree):
matches = []
matches.extend(self.validate_default_value_shape(default_value_dict, tree))
if not isinstance(default_value_dict, dict):
return matches
if self.default_value_key not in default_value_dict:
return matches
default_value = default_value_dict[self.default_value_key]
if isinstance(default_value, (int, float, str)):
return matches
if isinstance(default_value, dict):
matches.extend(self.validate_intrinsic_function(default_value, tree))
if isinstance(default_value, list):
for value in default_value:
if isinstance(value, dict):
matches.extend(self.validate_intrinsic_function(value, tree))
elif isinstance(value, (int, float, str)):
continue
else:
error_message = "Elements in Fn::FindInMap default value must be a string, number or an intrinsic function resolves to string at {0}"
matches.append(
RuleMatch(
tree[:], error_message.format("/".join(map(str, tree)))
)
)
return matches
def validate_enhanced_find_in_map(self, find_in_map, cfn):
mappings = cfn.get_mappings()
tree = find_in_map[:-1]
map_obj = find_in_map[-1]
matches = []
if not isinstance(map_obj, list):
error_message = "FindInMap is a list with 3 or 4 values for {0}"
matches.append(
RuleMatch(tree[:], error_message.format("/".join(map(str, tree))))
)
return matches
if len(map_obj) in (3, 4):
map_name = map_obj[0]
first_key = map_obj[1]
second_key = map_obj[2]
matches.extend(self.validate_enhanced_map_name(map_name, mappings, tree))
matches.extend(self.validate_enhanced_key(first_key, tree, "first key", 1))
matches.extend(
self.validate_enhanced_key(second_key, tree, "second key", 2)
)
if len(map_obj) == 4:
default_value = map_obj[3]
matches.extend(
self.validate_enhanced_default_value(default_value, tree)
)
else:
error_message = "FindInMap is a list with 3 or 4 values for {0}"
matches.append(
RuleMatch(tree[:] + [1], error_message.format("/".join(map(str, tree))))
)
return matches
def _match_with_language_extensions(self, cfn):
matches = []
find_in_maps = cfn.search_deep_keys("Fn::FindInMap")
for in_map in find_in_maps:
matches.extend(
self.validate_enhanced_find_in_map(find_in_map=in_map, cfn=cfn)
)
return matches
def _match(self, cfn):
matches = []
findinmaps = cfn.search_deep_keys("Fn::FindInMap")
mappings = cfn.get_mappings()
for findinmap in findinmaps:
tree = findinmap[:-1]
map_obj = findinmap[-1]
if not isinstance(map_obj, list):
message = "FindInMap is a list with 3 values for {0}"
matches.append(RuleMatch(tree[:], message.format("/".join(tree))))
continue
if len(map_obj) == 3:
map_name = map_obj[0]
first_key = map_obj[1]
second_key = map_obj[2]
matches.extend(self.map_name(map_name, mappings, tree))
matches.extend(self.match_key(first_key, tree, "first key", 1))
matches.extend(self.match_key(second_key, tree, "second key", 2))
else:
message = "FindInMap is a list with 3 values for {0}"
matches.append(
RuleMatch(tree[:] + [1], message.format("/".join(map(str, tree))))
)
return matches
def match(self, cfn):
if cfn.has_language_extensions_transform():
return self._match_with_language_extensions(cfn=cfn)
return self._match(cfn=cfn)