AWSTemplateFormatVersion: 2010-09-09
Description: Create the automation code for the IAM Credential Report Blog Post

Metadata:
  AWS::CloudFormation::Interface:
    ParameterGroups:
      - Label:
          default: Role Attributes
        Parameters:
          - pIAMCredReportDeliveryBucketArn
          - pOrganizationId
          - pLogsRetentionInDays
          - pScheduleExpression
          - pOrgPrimaryLambdaRoleName
          - pIAMCredReportKeyArn
          - pTagKey1
          - pTagValue1

    ParameterLabels:
      pIAMCredReportDeliveryBucketArn:
        default: Arn of the IAM Credential S3 Bucket
      pOrganizationId:
        default: Organization ID
      pLogsRetentionInDays:
        default: Log retention
      pOrgPrimaryLambdaRoleName:
        default: Organization Primary Lambda Role Name
      pScheduleExpression:
        default: EventBridge Scheduler
      pIAMCredReportKeyArn:
        default: IAM Credential Report Delivery KMS Key Arn
      pTagKey1:
        default: Credential Report Role Tag Key
      pTagValue1:
        default: Credential Report Role Tag Key Value

Parameters:
  pIAMCredReportDeliveryBucketArn:
    Type: String
    Description: The Arn of the IAM Credential Report S3 Bucket
  pOrganizationId:
    Type: String
    Description: AWS Organization ID
    MinLength: 12
    MaxLength: 12
    AllowedPattern: '^o-[a-z0-9]{10,32}$'
    ConstraintDescription: >
      The Organization Id must be a 12 character string starting with o- and followed by 10 lower case
      alphanumeric characters
  pLogsRetentionInDays:
    Description: Specifies the number of days you want to retain log events in the CloudWatch log group
    Type: Number
    Default: 90
    AllowedValues: [1, 3, 5, 7, 14, 30, 60, 90, 120, 150, 180, 365, 400, 545, 731, 1827, 3653]
  pScheduleExpression:
    Type: String
    Description: EventBridge Schedule Expression to Trigger Lambda Function
    Default: rate(7 days)
  pOrgPrimaryLambdaRoleName:
    Type: String
    Description: Organization Primary Account Lambda Role Name
  pIAMCredReportKeyArn:
    Type: String
    Description: IAM Credential Report Delivery KMS Key Arn
  pTagKey1:
    Type: String
    Description: Tag key
    Default: managed-by
  pTagValue1:
    Type: String
    Description: Tag key value
    Default: credential-cfn


Resources:
  rIAMRoleForLambdaFunction:
    Type: AWS::IAM::Role
    Metadata:
      cfn_nag:
        rules_to_suppress:
          - id: W11
            reason: IAM role should not allow * resource on its permissions policy
          - id: F3
            reason: IAM role should not allow * resource on its permissions policy
    Properties:
      RoleName: !Ref pOrgPrimaryLambdaRoleName
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          -
            Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
            Action:
              - sts:AssumeRole
      Path: /
      Policies:
        -
          PolicyName: iam-credential-report-lambda-policy
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              -
                Effect: Allow
                Action:
                  - logs:CreateLogGroup
                  - logs:CreateLogStream
                  - logs:PutLogEvents
                  - logs:GetLogEvents
                  - logs:StartQuery
                  - logs:PutMetricFilter
                Resource: '*'
              -
                Effect: Allow
                Action:
                  - cloudwatch:DescribeAlarms
                  - cloudwatch:GetMetricData
                  - cloudwatch:GetMetricStatistics
                  - cloudwatch:ListMetrics
                  - cloudwatch:PutMetricAlarm
                  - cloudwatch:PutMetricData
                  - cloudwatch:PutDashboard
                  - cloudwatch:GetDashboard
                  - cloudwatch:EnableAlarmActions
                Resource: '*'
              -
                Effect: Allow
                Action:
                  - sts:AssumeRole
                Resource: 'arn:aws:iam::*:role/iam-credential-report'
                Condition:
                 StringEquals:
                    "aws:PrincipalOrgID": !Sub ${pOrganizationId}
              -
                Effect: Allow
                Action:
                  - organizations:ListAccounts
                Resource: '*'
              -
                Effect: Allow
                Action:
                  - s3:PutObject
                  - s3:PutObjectAcl
                Resource: !Sub ${pIAMCredReportDeliveryBucketArn}/*
              -
                Effect: Allow
                Action:
                  - kms:GenerateDataKey
                  - kms:GenerateDataKeyWithoutPlaintext
                Resource: !Ref pIAMCredReportKeyArn
      Tags:
        - Key: !Ref pTagKey1
          Value: !Ref pTagValue1

  rIAMCredentialReportLambdaFunction:
    Type: "AWS::Lambda::Function"
    Properties:
      FunctionName: IAMCredentialReportLambda
      Handler: "index.lambda_handler"
      Environment:
        Variables:
          BUCKET_ARN: !Ref pIAMCredReportDeliveryBucketArn
      Role: !GetAtt rIAMRoleForLambdaFunction.Arn
      Code:
        ZipFile: |
            # coding=utf-8
            ## Import boto3 and start clients
            import os
            import boto3
            import time
            from botocore.exceptions import ClientError
            from datetime import date

            ## Define Organization and STS Clients
            orgClient = boto3.client('organizations')
            stsClient = boto3.client('sts')

            ## Define current date
            today = str(date.today())

            ## Read environment Variables from Lambda Function
            BUCKET_ARN = os.environ['BUCKET_ARN']

            ## Setup bucket for storing reports
            s3 = boto3.resource('s3')
            bucketName = BUCKET_ARN.split(":", -1)[-1]
            bucketConnection = s3.Bucket(bucketName)

            listedAccounts = orgClient.list_accounts()


            failedAccounts = []


            def assumeRole(accountId):
                try:
                    assumedRoleObject=stsClient.assume_role(
                    RoleArn=f"arn:aws:iam::{accountId}:role/iam-credential-report",
                    RoleSessionName="IAMCredentialReport")
                    credentials=assumedRoleObject['Credentials']

                    iamClient=boto3.client('iam',
                    aws_access_key_id=credentials['AccessKeyId'],
                    aws_secret_access_key=credentials['SecretAccessKey'],
                    aws_session_token=credentials['SessionToken'])

                    # Generate Credential Report
                    reportcomplete = False
                    while not reportcomplete:
                      gencredentialreport = iamClient.generate_credential_report()
                      print('IAM credential report successfully generated for account Id: ' + accountId)
                      reportcomplete = gencredentialreport['State'] == 'COMPLETE'
                      time.sleep (1)
                    
                    # Obtain credential report and send to S3 
                    if gencredentialreport['State'] == 'COMPLETE':
                        credentialReport = iamClient.get_credential_report()
                        decodedCredentialReport = credentialReport['Content'].decode("utf-8")
                        ## Save credential Report into CSV file
                        reportFileName = f"credentialReport_{accountId}.csv"
                        with open("/tmp/"+reportFileName, "w") as file:
                            file.write(decodedCredentialReport)
                        s3.Object(bucketName, today+"/"+reportFileName).put(Body=open("/tmp/"+reportFileName, 'rb'),ACL='bucket-owner-full-control')
                        return reportFileName


                except ClientError as error:
                    failedAccounts.append(accountId)
                    print(error)
                    pass

            def lambda_handler(event, context):
                for account in listedAccounts['Accounts']:
                    if account['Status'] != 'SUSPENDED':
                        assumeRole(account['Id'])
                return("Completed! Failed Accounts: ", failedAccounts)

      Runtime: "python3.7"
      Timeout: 35

  rLambdaLogGroup:
    Type: 'AWS::Logs::LogGroup'
    Properties:
      LogGroupName: !Sub /aws/lambda/${rIAMCredentialReportLambdaFunction}
      RetentionInDays: !Ref pLogsRetentionInDays

  rScheduledRule:
    Type: AWS::Events::Rule
    Properties:
      Description: IAM Credential Report Enabler
      Name: iam-credential-report-enabler
      ScheduleExpression: !Ref pScheduleExpression
      State: "ENABLED"
      Targets:
        -
          Arn: !GetAtt rIAMCredentialReportLambdaFunction.Arn
          Id: "DailyChecks"

  rIAMCredentialReportLambdaFunctionInvokePermissions:
    DependsOn:
      - rIAMCredentialReportLambdaFunction
    Type: "AWS::Lambda::Permission"
    Properties:
      FunctionName: !Ref rIAMCredentialReportLambdaFunction
      Action: "lambda:InvokeFunction"
      Principal: "events.amazonaws.com"

Outputs:
  oIAMCredentialReportLambdaFunction:
    Value: !GetAtt rIAMCredentialReportLambdaFunction.Arn
  oIAMLambdaExecutionIAMRoleArn:
    Value: !GetAtt rIAMRoleForLambdaFunction.Arn