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CloudTrail not integrated with CloudWatch

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Metadata

Id: terraform-aws-cloudtrail-not-integrated-with-cloudwatch

Provider: AWS

Platform: Terraform

Severity: Low

Category: Observability

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Description

Integrating AWS CloudTrail with CloudWatch Logs is essential for real-time monitoring and alerting on account activity. If the cloud_watch_logs_group_arn and cloud_watch_logs_role_arn attributes are not set in the aws_cloudtrail resource, as in the following insecure configuration, CloudTrail events will only be stored in S3 with no efficient mechanism for real-time detection or automated response to suspicious activities:

resource "aws_cloudtrail" "example" {
  name = "tf-trail-foobar"
  s3_bucket_name = aws_s3_bucket.foo.id
  // cloud_watch_logs_group_arn and cloud_watch_logs_role_arn not set
}

Without CloudWatch integration, critical security or operational issues could go unnoticed, increasing the risk of unauthorized behavior persisting undetected in your AWS environment.

A secure Terraform configuration should explicitly connect CloudTrail to CloudWatch Logs. For example:

resource "aws_cloudtrail" "example" {
  name                          = "tf-trail-secure"
  s3_bucket_name                = aws_s3_bucket.foo.id
  cloud_watch_logs_group_arn    = aws_cloudwatch_log_group.cloudtrail_logs.arn
  cloud_watch_logs_role_arn     = aws_iam_role.cloudtrail_cloudwatch_role.arn
}

Compliant Code Examples

resource "aws_cloudwatch_log_group" "cloudtrail_log_group" {
  name = "aws-foundations-benchmark-1-4-0-terraform-3-4-remediated"
}


resource "aws_iam_role" "cloud_watch_logs_role" {
  name = "aws-foundations-benchmark-1-4-0-terraform-3-4-remediated"

  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "",
      "Effect": "Allow",
      "Principal": {
        "Service": "cloudtrail.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}
EOF
}

resource "aws_iam_role_policy" "cloud_watch_policy" {
  name = "CloudWatch-policy"
  role = aws_iam_role.cloud_watch_logs_role.id

  policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "logs:CreateLogStream"
      ],
      "Resource": [
        "${aws_cloudwatch_log_group.cloudtrail_log_group.arn}:*"
      ]
    },
    {
      "Effect": "Allow",
      "Action": [
        "logs:PutLogEvents"
      ],
      "Resource": [
        "${aws_cloudwatch_log_group.cloudtrail_log_group.arn}:*"
      ]
    }
  ]
}
EOF
}


data "aws_caller_identity" "current" {}

resource "aws_cloudtrail" "negative1" {
  name                          = "tf-trail-foobar"
  s3_bucket_name                = aws_s3_bucket.foo.id
  s3_key_prefix                 = "prefix"
  include_global_service_events = false
  cloud_watch_logs_group_arn    = "${aws_cloudwatch_log_group.cloudtrail_log_group.arn}:*"
  cloud_watch_logs_role_arn     = aws_iam_role.cloud_watch_logs_role.arn
}

resource "aws_s3_bucket" "negative2" {
  bucket        = "tf-test-trail"
  force_destroy = true

  policy = <<POLICY
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AWSCloudTrailAclCheck",
            "Effect": "Allow",
            "Principal": {
              "Service": "cloudtrail.amazonaws.com"
            },
            "Action": "s3:GetBucketAcl",
            "Resource": "arn:aws:s3:::tf-test-trail"
        },
        {
            "Sid": "AWSCloudTrailWrite",
            "Effect": "Allow",
            "Principal": {
              "Service": "cloudtrail.amazonaws.com"
            },
            "Action": "s3:PutObject",
            "Resource": "arn:aws:s3:::tf-test-trail/prefix/AWSLogs/${data.aws_caller_identity.current.account_id}/*",
            "Condition": {
                "StringEquals": {
                    "s3:x-amz-acl": "bucket-owner-full-control"
                }
            }
        }
    ]
}
POLICY
}

Non-Compliant Code Examples

resource "aws_cloudtrail" "positive1" {
  name                          = "tf-trail-foobar"
  s3_bucket_name                = aws_s3_bucket.foo.id
  s3_key_prefix                 = "prefix"
  include_global_service_events = false
}

data "aws_caller_identity" "current" {}

resource "aws_s3_bucket" "positive4" {
  bucket        = "tf-test-trail"
  force_destroy = true

  policy = <<POLICY
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AWSCloudTrailAclCheck",
            "Effect": "Allow",
            "Principal": {
              "Service": "cloudtrail.amazonaws.com"
            },
            "Action": "s3:GetBucketAcl",
            "Resource": "arn:aws:s3:::tf-test-trail"
        },
        {
            "Sid": "AWSCloudTrailWrite",
            "Effect": "Allow",
            "Principal": {
              "Service": "cloudtrail.amazonaws.com"
            },
            "Action": "s3:PutObject",
            "Resource": "arn:aws:s3:::tf-test-trail/prefix/AWSLogs/${data.aws_caller_identity.current.account_id}/*",
            "Condition": {
                "StringEquals": {
                    "s3:x-amz-acl": "bucket-owner-full-control"
                }
            }
        }
    ]
}
POLICY
}