control 'aws-foundations-cis-4.3' do
  title "Ensure usage of 'root' account is monitored "
  desc "Real-time monitoring of API calls can be achieved by directing CloudTrail Logs to CloudWatch
Logs, or an external Security information and event management (SIEM) environment, and
establishing corresponding metric filters and alarms.

It is recommended that a metric
filter and alarm be established for 'root' login attempts to detect the unauthorized use, or
attempts to use the root account. "
  desc 'rationale', "Monitoring for 'root' account logins will provide visibility into the use of a fully
privileged account and an opportunity to reduce the use of it.

Cloud Watch is an AWS native
service that allows you to observe and monitor resources and applications. CloudTrail Logs
can also be sent to an external Security information and event management (SIEM) environment
for monitoring and alerting. "
  desc 'check', "If you are using CloudTrails and CloudWatch, perform the following to ensure that there is at
least one active multi-region CloudTrail with prescribed metric filters and alarms
configured:

1. Identify the log group name configured for use with active multi-region
CloudTrail:

- List all CloudTrails:

`aws cloudtrail describe-trails`

-
Identify Multi region Cloudtrails: `Trails with \"IsMultiRegionTrail\" set to true`

-
From value associated with CloudWatchLogsLogGroupArn note
`<cloudtrail_log_group_name>`

Example: for CloudWatchLogsLogGroupArn that looks
like `arn:aws:logs:<region>:<aws_account_number>:log-group:NewGroup:*`,
`<cloudtrail_log_group_name>` would be `NewGroup`

- Ensure Identified Multi region
CloudTrail is active

`aws cloudtrail get-trail-status --name <Name of a Multi-region
CloudTrail>`

ensure `IsLogging` is set to `TRUE`

- Ensure identified Multi-region
Cloudtrail captures all Management Events

`aws cloudtrail get-event-selectors
--trail-name <trailname shown in describe-trails>`

Ensure there is at least one Event
Selector for a Trail with `IncludeManagementEvents` set to `true` and `ReadWriteType` set
to `All`

2. Get a list of all associated metric filters for this
`<cloudtrail_log_group_name>`:

```
aws logs describe-metric-filters
--log-group-name \"<cloudtrail_log_group_name>\"
```

3. Ensure the output from the
above command contains the following:

```
\"filterPattern\": \"{ $.userIdentity.type
= \"Root\" && $.userIdentity.invokedBy NOT EXISTS && $.eventType != \"AwsServiceEvent\"
}\"
```

4. Note the `<root_usage_metric>` value associated with the `filterPattern`
found in step 3.

5. Get a list of CloudWatch alarms and filter on the
`<root_usage_metric>` captured in step 4.

```
aws cloudwatch describe-alarms
--query 'MetricAlarms[?MetricName== `<root_usage_metric>`]'
```

6. Note the
`AlarmActions` value - this will provide the SNS topic ARN value.

7. Ensure there is at
least one active subscriber to the SNS topic

```
aws sns list-subscriptions-by-topic
--topic-arn <sns_topic_arn>
```
at least one subscription should have
\"SubscriptionArn\" with valid aws ARN.

```
Example of valid \"SubscriptionArn\": \"arn:aws:sns:<region>:<aws_account_number>:<SnsTopicName>:<SubscriptionID>\"
``` "
  desc 'fix', "If you are using CloudTrails and CloudWatch, perform the following to setup the metric
filter, alarm, SNS topic, and subscription:

1. Create a metric filter based on filter
pattern provided which checks for 'Root' account usage and the
`<cloudtrail_log_group_name>` taken from audit step 1.
```
aws logs
put-metric-filter --log-group-name `<cloudtrail_log_group_name>` --filter-name
`<root_usage_metric>` --metric-transformations metricName= `<root_usage_metric>`
,metricNamespace='CISBenchmark',metricValue=1 --filter-pattern '{
$.userIdentity.type = \"Root\" && $.userIdentity.invokedBy NOT EXISTS && $.eventType !=
\"AwsServiceEvent\" }'
```

**Note**: You can choose your own metricName and
metricNamespace strings. Using the same metricNamespace for all Foundations Benchmark
metrics will group them together.

2. Create an SNS topic that the alarm will
notify
```
aws sns create-topic --name <sns_topic_name>
```

**Note**: you can
execute this command once and then re-use the same topic for all monitoring alarms.

3.
Create an SNS subscription to the topic created in step 2
```
aws sns subscribe
--topic-arn <sns_topic_arn> --protocol <protocol_for_sns> --notification-endpoint
<sns_subscription_endpoints>
```

**Note**: you can execute this command once and
then re-use the SNS subscription for all monitoring alarms.

4. Create an alarm that is
associated with the CloudWatch Logs Metric Filter created in step 1 and an SNS topic created in
step 2
```
aws cloudwatch put-metric-alarm --alarm-name `<root_usage_alarm>`
--metric-name `<root_usage_metric>` --statistic Sum --period 300 --threshold 1
--comparison-operator GreaterThanOrEqualToThreshold --evaluation-periods 1
--namespace 'CISBenchmark' --alarm-actions <sns_topic_arn>
``` "
  desc 'additional_information', "**Configuring log metric filter and alarm on Multi-region (global) CloudTrail**

-
ensures that activities from all regions (used as well as unused) are monitored

- ensures
that activities on all supported global services are monitored

- ensures that all
management events across all regions are monitored "
  impact 0.5
  ref 'https://docs.aws.amazon.com/awscloudtrail/latest/userguide/receive-cloudtrail-log-files-from-multiple-regions.html:https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudwatch-alarms-for-cloudtrail.html:https://docs.aws.amazon.com/sns/latest/dg/SubscribeTopic.html'
  tag nist: ['AU-6', 'AU-6(1)', 'AU-7(1)']
  tag severity: 'medium '
  tag cis_controls: [
    { '8' => ['8.11'] },
  ]

  pattern = '{ $.userIdentity.type = "Root" && $.userIdentity.invokedBy NOT EXISTS && $.eventType != "AwsServiceEvent" }'

  describe aws_cloudwatch_log_metric_filter(pattern: pattern) do
    it { should exist }
  end

  # Find the log_group_name associated with the aws_cloudwatch_log_metric_filter that has the pattern
  log_group_name = aws_cloudwatch_log_metric_filter(pattern: pattern).log_group_name

  # Find cloudtrails associated with with `log_group_name` parsed above
  associated_trails = aws_cloudtrail_trails.names.select { |x| aws_cloudtrail_trail(x).cloud_watch_logs_log_group_arn =~ /log-group:#{log_group_name}:/ }

  # Ensure log_group is associated atleast one cloudtrail
  describe "Cloudtrails associated with log-group: #{log_group_name}" do
    subject { associated_trails }
    it { should_not be_empty }
  end

  # Ensure atleast one of the associated cloudtrail meet the requirements.
  describe.one do
    associated_trails.each do |trail|
      describe aws_cloudtrail_trail(trail) do
        it { should be_multi_region_trail }
        it { should have_event_selector_mgmt_events_rw_type_all }
        it { should be_logging }
      end
    end
  end

  # Parse out `metric_name` and `metric_namespace` for the specified pattern.
  associated_metric_filter = aws_cloudwatch_log_metric_filter(pattern: pattern, log_group_name: log_group_name)
  metric_name = associated_metric_filter.metric_name
  metric_namespace = associated_metric_filter.metric_namespace

  # Ensure aws_cloudwatch_alarm for the specified pattern meets requirements.
  if associated_metric_filter.exists?
    describe aws_cloudwatch_alarm(metric_name: metric_name, metric_namespace: metric_namespace) do
      it { should exist }
      its('alarm_actions') { should_not be_empty }
    end

    aws_cloudwatch_alarm(metric_name: metric_name, metric_namespace: metric_namespace).alarm_actions.each do |sns|
      describe aws_sns_topic(sns) do
        it { should exist }
        its('confirmed_subscription_count') { should cmp >= 1 }
      end
    end
  end
end
