Provide auditing on CodePipeline approval gate

CFN-CodePipelineApprovalAudit.yaml

# CodePipeline does not record gate approval outside of CloudTrail.  Includes Lambda to write to S3.  Not fully self contained, missing parameters, conditions.

Resources:
  PipelineApprovalTrackingBucket:
    Type: AWS::S3::Bucket
    Condition: ShouldCreateAudit
    Properties: 
      AccessControl: Private
      BucketName: 
        !Sub 
        - '${LocalFindInMapAccountName}-${ProjectName}-pipeline-approval-tracking'
        - { LocalFindInMapAccountName: !FindInMap [ Environments, !Ref Environment, accountName ] }
      VersioningConfiguration:
        Status: Enabled
      Tags: 
      - Key: repository
        Value: !Ref repo
      - Key: environment 
        Value: !Ref Environment
  LambdaNotificationTopic:
    Type: 'AWS::SNS::Topic'
    Condition: ShouldCreateAudit
    Properties:
      TopicName: !Sub '${CodeBuildTerraformAction}-pipeline-approval-gate-tracking-topic'
      Subscription: !If
        - SnsEmailAddressExists
        -
          - Endpoint: !Ref SnsTopicEmailAddress
            Protocol: email
        - !Ref AWS::NoValue
      Tags: 
      - Key: repository
        Value: !Ref repo
      - Key: environment 
        Value: !Ref Environment
  LambdaNotificationTopicPolicy:
    Type: 'AWS::SNS::TopicPolicy'
    Condition: ShouldCreateAudit
    Properties:
      Topics:
      - !Ref LambdaNotificationTopic
      PolicyDocument:
        Version: 2012-10-17
        Id: __default_policy_ID
        Statement:
          Sid: AWSLambda
          Effect: Allow
          Principal:
            Service: 
            - lambda.amazonaws.com
            - events.amazonaws.com
          Action: sns:Publish
          Resource: !Ref LambdaNotificationTopic
  CloudWatchApproval:
    Type: AWS::Events::Rule
    Condition: ShouldCreateAudit
    Properties: 
      Description: Event Rule that tracks whenever someone approves/rejects an approval gate in a pipeline
      EventPattern:
        source:
        - aws.codepipeline
        detail-type:
        - AWS API Call via CloudTrail
        detail:
          requestParameters:
            pipelineName:
              !If
              - ShouldCreateDestroy
              - - !Ref PipelineDestroy
                - !Ref PipelineDeploy
              - - !Ref PipelineDeploy
          eventName:
          - PutApprovalResult
      Name: !Sub '${CodeBuildTerraformAction}-pipeline-approval-event'
      State: ENABLED
      Targets:
        - 
          Arn: 
            Fn::GetAtt: 
              - "ApprovalGateEventTrackingLambda"
              - "Arn"
          Id: "TargetFunctionV1"
  PermissionForEventsToInvokeLambda: 
    Type: AWS::Lambda::Permission
    Condition: ShouldCreateAudit
    Properties: 
      FunctionName: 
        !Ref ApprovalGateEventTrackingLambda
      Action: "lambda:InvokeFunction"
      Principal: "events.amazonaws.com"
      SourceArn: 
        !GetAtt CloudWatchApproval.Arn
  ApprovalGateEventTrackingLambda:
    Type: "AWS::Lambda::Function"
    Condition: ShouldCreateAudit
    Properties: 
      Code:
        ZipFile: |
          import json
          import boto3
          import os
          import time
          import datetime
          from datetime import datetime
          from dateutil import tz
          sns = boto3.client('sns')
          s3 = boto3.client('s3')
          bucket = os.environ['BUCKETNAME']
          sns_topic_arn = os.environ['SNSTOPICARN']
          # Method for sending SNS notification messages
          def send_sns_message(sns_topic_arn, sns_message, message_subject):
            sns.publish(
              TargetArn=sns_topic_arn,
              Message=sns_message,
              Subject=message_subject
            )
          # Method for tagging S3 objects with tag set
          def tag_s3_object(bucket, key, tag_set):
            s3.put_object_tagging(
              Bucket=bucket,
              Key=key,
              Tagging={
                  'TagSet': tag_set
              }
            )
          # Lambda handler
          def lambda_handler(event, context):
            body = event["detail"]
            # Record CloudTrail event body information to Lambda Function's CloudWatch log group
            print(body)
            iam_user_arn = body["userIdentity"]["arn"]
            pipeline_name = body["requestParameters"]["pipelineName"]
            approval_gate = body["requestParameters"]["stageName"]
            approval_status = body["requestParameters"]["result"]["status"]
            approval_summary = body["requestParameters"]["result"]["summary"]
            approval_date = body["responseElements"]["approvedAt"]
            account_id = body["userIdentity"]["accountId"]
            region = body["awsRegion"]
            # Change approval date time from UTC to EST
            date_str = approval_date
            from_zone = tz.gettz('UTC')
            to_zone = tz.gettz('US/Eastern')
            utc = datetime.strptime(date_str, '%b %d, %Y %I:%M:%S %p')
            utc = utc.replace(tzinfo=from_zone)
            est_time = utc.astimezone(to_zone)
            est_time_approval_date = datetime.strftime(est_time, '%b %d, %Y %I:%M:%S %p')
            year = est_time.strftime("%Y")
            month = est_time.strftime("%m")
            day = est_time.strftime("%d")
            time_of_day = est_time.strftime("%I:%M:%S %p").replace(" ", "-")
            # Create SNS message body
            sns_message = (f"Approval Gate {approval_gate} \
          for Pipeline {pipeline_name} \
          was {approval_status} \
          by {iam_user_arn} \
          on {est_time_approval_date} \
          inside the {region} region \
          in AWS Account {account_id}. \
          Approval Gate Response Summary: \
          {approval_summary}")
            message_subject = 'Pipeline Approval Gate Information'
            # Send SNS message containing information about the approval gate action
            send_sns_message(sns_topic_arn, sns_message, message_subject)
            
            # Open up temp file and write the CloudTrail JSON event body information to JSON file.
            # This JSON file will be the S3 object that gets uploaded and stored in S3.
            with open(f"/tmp/{approval_gate}__{est_time_approval_date}.txt".replace(" ", "-").replace(",", ""), 'w') as outfile:  
              json.dump(body, outfile)
            file = (f"/tmp/{approval_gate}__{est_time_approval_date}.txt").replace(" ", "-").replace(",", "")
            object_key = (f"PipelineApprovalGateActions/{pipeline_name}/{year}/{month}/{day}/{approval_gate}-{approval_status.upper()}-{time_of_day}.txt")
            s3.upload_file(file, bucket, object_key)
            # Sleep for 5 seconds to allow object upload to complete. 
            time.sleep(5)
            # Create S3 object tag set
            s3_tag_set = []
            s3_tag_set.append({"Key": "Pipeline Name",  "Value": pipeline_name})
            s3_tag_set.append({"Key": "Approval Gate",  "Value": approval_gate})
            s3_tag_set.append({"Key": "Approval Gate Status",  "Value": approval_status})
            s3_tag_set.append({"Key": "IAM Approver",  "Value": iam_user_arn})
            # Tag newly upload S3 object
            tag_s3_object(bucket, object_key, s3_tag_set)
      FunctionName: !Sub '${CodeBuildTerraformAction}-pipeline-approval-gate-tracking'
      Handler: index.lambda_handler
      Environment:
        Variables: 
          SNSTOPICARN: !Ref LambdaNotificationTopic
          BUCKETNAME: !Ref PipelineApprovalTrackingBucket
      MemorySize: 128
      Role: !GetAtt AuditTrackingEventLambdaRole.Arn
      Runtime: python3.6
      Timeout: 10
      Tags: 
      - Key: repository
        Value: !Ref GHCBRepo
      - Key: environment 
        Value: !Ref Environment
      - Key: project_name
        Value: !Ref ProjectName
      - Key: documentation
        Value: See Repository readme.md
      - Key: technical_owner
        Value: _cloudanddevops@webcentralgroup.com.au
      - Key: iac
        Value: CloudFormation
      - Key: pipeline
        Value: none
  AuditTrackingEventLambdaRole:
    Type: AWS::IAM::Role
    Condition: ShouldCreateAudit
    Properties:
      AssumeRolePolicyDocument:
        Statement:
        - Sid: ''
          Effect: Allow
          Principal:
            Service:
            - lambda.amazonaws.com
          Action: sts:AssumeRole
      Path: "/"
      Tags: 
      - Key: repository
        Value: !Ref GHCBRepo
      - Key: environment 
        Value: !Ref Environment
      - Key: project_name
        Value: !Ref ProjectName
      - Key: documentation
        Value: See Repository readme.md
      - Key: technical_owner
        Value: _cloudanddevops@webcentralgroup.com.au
      - Key: iac
        Value: CloudFormation
      - Key: pipeline
        Value: none
      Policies:
      - PolicyName:
          !Sub '${CodeBuildTerraformAction}-pipeline-approval-gate-tracking'
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Effect: Allow
            Action: 
            - 'sns:Publish'
            Resource: 
            - !Ref LambdaNotificationTopic
          - Effect: Allow
            Action:
            - s3:PutObject
            - s3:PutObjectTagging
            Resource:
            - !Sub arn:aws:s3:::${PipelineApprovalTrackingBucket}
            - !Sub arn:aws:s3:::${PipelineApprovalTrackingBucket}/*
          - Effect: Allow
            Action:
            - logs:CreateLogGroup
            - logs:CreateLogStream
            - logs:PutLogEvents
            Resource:
            - !Sub arn:aws:logs:${AWS::Region}:${AWS::AccountId}:*
          - Effect: Allow
            Action: 
            - 'cloudtrail:LookupEvents'
            - 'cloudtrail:DescribeTrails'
            Resource: 
            - '*'
          - Effect: Allow
            Action: 
            - 'cloudtrail:GetTrailStatus'
            Resource: 
            - !Sub 'arn:aws:cloudtrail:${AWS::Region}:${AWS::AccountId}:trail/*'