#!/usr/bin/env bash

# Prowler - the handy cloud security tool (copyright 2019) by Toni de la Fuente
#
# 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.
#
# Remediation:
#
#   https://d1.awsstatic.com/whitepapers/compliance/AWS_CIS_Foundations_Benchmark.pdf
#
#   aws logs put-metric-filter \
#     --region us-east-1 \
#     --log-group-name CloudTrail/CloudWatchLogGroup \
#     --filter-name S3BucketConfigChanges \
#     --filter-pattern '{ ($.eventSource = s3.amazonaws.com) && (($.eventName = PutBucketAcl) || ($.eventName = PutBucketPolicy) || ($.eventName = PutBucketCors) || ($.eventName = PutBucketLifecycle) || ($.eventName = PutBucketReplication) || ($.eventName = DeleteBucketPolicy) || ($.eventName = DeleteBucketCors) || ($.eventName = DeleteBucketLifecycle) || ($.eventName = DeleteBucketReplication)) }' \
#     --metric-transformations metricName=S3BucketEventCount,metricNamespace=CloudTrailMetrics,metricValue=1
#
#   aws cloudwatch put-metric-alarm \
#     --region us-east-1 \
#     --alarm-name S3BucketConfigChangesAlarm \
#     --alarm-description "Triggered by AWS S3 Bucket config changes." \
#     --metric-name S3BucketEventCount \
#     --namespace CloudTrailMetrics \
#     --statistic Sum \
#     --comparison-operator GreaterThanOrEqualToThreshold \
#     --evaluation-periods 1 \
#     --period 300 \
#     --threshold 1 \
#     --actions-enabled \
#     --alarm-actions arn:aws:sns:us-east-1:123456789012:CloudWatchAlarmTopic

CHECK_ID_check38="3.8"
CHECK_TITLE_check38="[check38] Ensure a log metric filter and alarm exist for S3 bucket policy changes"
CHECK_SCORED_check38="SCORED"
CHECK_CIS_LEVEL_check38="LEVEL1"
CHECK_SEVERITY_check38="Medium"
CHECK_ASFF_TYPE_check38="Software and Configuration Checks/Industry and Regulatory Standards/CIS AWS Foundations Benchmark"
CHECK_ASFF_RESOURCE_TYPE_check38="AwsCloudTrailTrail"
CHECK_ALTERNATE_check308="check38"
CHECK_SERVICENAME_check38="s3"
CHECK_RISK_check38='Monitoring unauthorized API calls will help reveal application errors and may reduce time to detect malicious activity.'
CHECK_REMEDIATION_check38='It is recommended that a metric filter and alarm be established for unauthorized requests.'
CHECK_DOC_check38='https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudwatch-alarms-for-cloudtrail.html'
CHECK_CAF_EPIC_check38='Logging and Monitoring'

check38(){
  check3x '\$\.eventSource\s*=\s*s3.amazonaws.com.+\$\.eventName\s*=\s*PutBucketAcl.+\$\.eventName\s*=\s*PutBucketPolicy.+\$\.eventName\s*=\s*PutBucketCors.+\$\.eventName\s*=\s*PutBucketLifecycle.+\$\.eventName\s*=\s*PutBucketReplication.+\$\.eventName\s*=\s*DeleteBucketPolicy.+\$\.eventName\s*=\s*DeleteBucketCors.+\$\.eventName\s*=\s*DeleteBucketLifecycle.+\$\.eventName\s*=\s*DeleteBucketReplication'
}