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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright {yyyy} {name of copyright owner} 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # cwe-monitor-secgrp 2 | This CloudWatch Events rule Lambda function is used to look at invocations of the authorize_security_group_ingress() and revoke_security_group_ingress() API calls. When such as call is made, the function examines the contents of the applicable security group to determine if it matches a pre-configured policy. The policy is hardcoded into the Lambda function using an IpPermisions structure which is in the same format as the IpPermissions structure used by the describe_security_groups() API call. If the security group permissions do not match the pre-configured policy, the function sends log messages to CloudWatch logs saying what permissions need to be added or revoked in order to bring the group ingress rules into compliance. 3 | 4 | In order to select the appropriate API call and security group for the CloudWatch events rule, you should use a JSON event selector. An example of such a selector appears below. Substitute "sg-abc12345" with the id of the specific security group you wish to inspect. 5 | 6 | ``` 7 | { 8 | "detail-type": [ 9 | "AWS API Call via CloudTrail" 10 | ], 11 | "detail": { 12 | "eventSource": [ 13 | "ec2.amazonaws.com" 14 | ], 15 | "eventName": [ 16 | "AuthorizeSecurityGroupIngress", 17 | "RevokeSecurityGroupIngress" 18 | ], 19 | "requestParameters": { 20 | "groupId": [ 21 | "sg-abc12345" 22 | ] 23 | } 24 | } 25 | } 26 | ``` 27 | -------------------------------------------------------------------------------- /amzcwevents_lambda_security_group.py: -------------------------------------------------------------------------------- 1 | # Copyright [2016]-[2016] Amazon.com, Inc. or its affiliates. All Rights Reserved. 2 | # 3 | # Licensed under the Apache License, Version 2.0 (the "License"). 4 | # You may not use this file except in compliance with the License. 5 | # A copy of the License is located at 6 | # 7 | # http://aws.amazon.com/apache2.0/ 8 | # 9 | # or in the "license" file accompanying this file. 10 | # This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 11 | # either express or implied. See the License for the specific language governing permissions 12 | # and limitations under the License. 13 | # 14 | # Description: Checks that all security groups block access to the specified ports. 15 | # 16 | # awscwevents_lambda_security_group.py 17 | # 18 | # Author: jeffscottlevine 19 | # Date: 2016-09-05 20 | # 21 | # This file contains an AWS Lambda handler which responds to AWS API calls that modify the ingress 22 | # permissions of security groups to see if the permissions now differ from the required permissions 23 | # as specificed in the REQUIRED_PERMISSIONS variable below. 24 | # 25 | # Note: The permissions are not remediated within this function because doing so could possibly 26 | # trigger a recursion issue with this Lambda function triggering itself. 27 | # 28 | # 2017-01-13 - Added "Ipv6Ranges" to REQUIRED_PERMISSIONS to accommodate IPv6 within Amazon VPC. 29 | 30 | import boto3 31 | import botocore 32 | import json 33 | 34 | 35 | APPLICABLE_APIS = ["AuthorizeSecurityGroupIngress", "RevokeSecurityGroupIngress"] 36 | 37 | # Specify the required ingress permissions using the same key layout as that provided in the 38 | # describe_security_group API response and authorize_security_group_ingress/egress API calls. 39 | 40 | REQUIRED_PERMISSIONS = [ 41 | { 42 | "IpProtocol" : "tcp", 43 | "FromPort" : 80, 44 | "ToPort" : 80, 45 | "UserIdGroupPairs" : [], 46 | "IpRanges" : [{"CidrIp" : "0.0.0.0/0", "Description": ""}], 47 | "PrefixListIds" : [], 48 | "Ipv6Ranges": [] 49 | }, 50 | { 51 | "IpProtocol" : "tcp", 52 | "FromPort" : 443, 53 | "ToPort" : 443, 54 | "UserIdGroupPairs" : [], 55 | "IpRanges" : [{"CidrIp" : "0.0.0.0/0", "Description": ""}], 56 | "PrefixListIds" : [], 57 | "Ipv6Ranges": [] 58 | }] 59 | 60 | 61 | # evaluate_compliance 62 | # 63 | # This is the main compliance evaluation function. 64 | 65 | def evaluate_compliance(event): 66 | event_name = event["detail"]["eventName"] 67 | if event_name not in APPLICABLE_APIS: 68 | print("This rule does not apply for the event ", event_name, ".") 69 | return 70 | 71 | group_id = event["detail"]["requestParameters"]["groupId"] 72 | print("group id: ", group_id) 73 | 74 | client = boto3.client("ec2"); 75 | 76 | try: 77 | response = client.describe_security_groups(GroupIds=[group_id]) 78 | except botocore.exceptions.ClientError as e: 79 | print("describe_security_groups failure on group ", group_id, " .") 80 | return 81 | 82 | print("security group definition: ", json.dumps(response, indent=2)) 83 | 84 | ip_permissions = response["SecurityGroups"][0]["IpPermissions"] 85 | authorize_permissions = [perm for perm in REQUIRED_PERMISSIONS if perm not in ip_permissions] 86 | revoke_permissions = [perm for perm in ip_permissions if perm not in REQUIRED_PERMISSIONS] 87 | 88 | if authorize_permissions or revoke_permissions: 89 | if authorize_permissions: 90 | for perm in authorize_permissions: 91 | print("This permission must be authorized: ", json.dumps(perm, separators=(',',':'))) 92 | if revoke_permissions: 93 | for perm in revoke_permissions: 94 | print("This permission must be revoked: ", json.dumps(perm, separators=(',',':'))) 95 | else: 96 | print("All permissions are correct.") 97 | 98 | # lambda_handler 99 | # 100 | # This is the main handle for the Lambda function. AWS Lambda passes the function an event and a context. 101 | 102 | def lambda_handler(event, context): 103 | print("event: ", json.dumps(event)) 104 | 105 | evaluation = evaluate_compliance(event) --------------------------------------------------------------------------------