"""
Copyright 2020 Skyscanner Ltd
Licensed under the Apache License, Version 2.0 (the "License"); you may not use
this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed
under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
CONDITIONS OF ANY KIND, either express or implied. See the License for the
specific language governing permissions and limitations under the License.
"""
import boto3
from lambdaguard.utils.iterator import iterate
from lambdaguard.utils.paginator import paginate
LAMBDA_WRITE_PERMISSIONS = [x.lower() for x in [
'*',
'lambda:*',
'lambda:Create*',
'lambda:Delete*',
'lambda:Invoke*',
'lambda:Publish*',
'lambda:Put*',
'lambda:Tag*',
'lambda:Untag*',
'lambda:Update*',
'lambda:CreateAlias',
'lambda:CreateFunction',
'lambda:DeleteAlias',
'lambda:DeleteEventSourceMapping',
'lambda:DeleteFunction',
'lambda:DeleteFunctionConcurrency',
'lambda:DeleteLayerVersion',
'lambda:InvokeAsync',
'lambda:InvokeFunction',
'lambda:PublishLayerVersion',
'lambda:PublishVersion',
'lambda:PutFunctionConcurrency',
'lambda:TagResource',
'lambda:UntagResource',
'lambda:UpdateAlias',
'lambda:UpdateEventSourceMapping',
'lambda:UpdateFunctionCode',
'lambda:UpdateFunctionConfiguration'
]]
def is_write_action(action):
return action.lower() in LAMBDA_WRITE_PERMISSIONS
class LambdaWrite:
"""
This is a class for tracking attached IAM policies
that have Lambda Write permissions
"""
def __init__(self, args):
self.args = args
self.writes = {}
self.get_writes()
def get_writes(self):
for policy_arn, policy in self.get_attached_local_policies():
for lambda_arn, actions in self.parse(policy):
if lambda_arn not in self.writes:
self.writes[lambda_arn] = {}
if policy_arn not in self.writes[lambda_arn]:
self.writes[lambda_arn][policy_arn] = {}
self.writes[lambda_arn][policy_arn] = actions
def get_attached_local_policies(self):
client = boto3.Session(
profile_name=self.args.profile,
aws_access_key_id=self.args.keys[0],
aws_secret_access_key=self.args.keys[1],
region_name=self.args.region
).client('iam')
pages = paginate(
client,
'list_policies',
Scope='Local',
OnlyAttached=True
)
for page in pages:
for policy in page['Policies']:
version = client.get_policy_version(
PolicyArn=policy['Arn'],
VersionId=policy['DefaultVersionId']
)['PolicyVersion']
yield policy['Arn'], version
def parse(self, policy):
if 'Document' not in policy:
return StopIteration
if 'Statement' not in policy['Document']:
return StopIteration
if not isinstance(policy['Document']['Statement'], list):
statements = [policy['Document']['Statement']]
else:
statements = policy['Document']['Statement']
for statement in statements:
if 'Effect' not in statement:
continue # Unknown
if statement['Effect'] != 'Allow':
continue # Not allowed
if 'Action' not in statement:
continue # No permissions
# Identify all write Actions
write_actions = []
for action in iterate(statement['Action']):
if not is_write_action(action):
continue
write_actions.append(action)
if not write_actions:
return StopIteration
# Return all write Actions per Resource
for arn in iterate(statement['Resource']):
yield arn, write_actions
def get_for_lambda(self, arn):
for w_arn, w_actions in self.writes.items():
if w_arn == '*':
yield w_actions
elif w_arn == arn:
yield w_actions
