CloudTrail log files S3 bucket is publicly accessible

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Metadata

Id: terraform-aws-cloudtrail-log-files-s3-bucket-is-publicly-accessible

Provider: AWS

Platform: Terraform

Severity: High

Category: Observability

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Provider Reference

Description

This check identifies when CloudTrail logs are stored in an S3 bucket that is publicly accessible, creating a significant security risk. CloudTrail logs contain sensitive information about API calls and activities in your AWS environment that could be exposed to unauthorized parties if stored in a public bucket. To remediate this issue, ensure your S3 bucket has its ACL set to private instead of public-read, as shown in the example below:

resource "aws_s3_bucket" "b" {
  bucket = "my-tf-test-bucket"
  acl    = "private"  // Correct setting instead of "public-read"
}

Compliant Code Examples

provider "aws" {
  region = "us-east-1"
}

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.0"
    }
  }
}

data "aws_caller_identity" "current2" {}

resource "aws_cloudtrail" "foobar2" {
  name                          = "tf-trail-foobar"
  s3_bucket_name                = aws_s3_bucket.b2.id
  s3_key_prefix                 = "prefix"
  include_global_service_events = false
}

resource "aws_s3_bucket" "b2" {
  bucket = "my-tf-test-bucket"
  acl    = "private"

  tags = {
    Name        = "My bucket"
    Environment = "Dev"
  }
}

terraform {
  required_providers {
    aws = {
      source = "hashicorp/aws"
      version = "4.2.0"
    }
  }
}

provider "aws" {
  # Configuration options
}

resource "aws_cloudtrail" "foobar4" {
  name                          = "tf-trail-foobar"
  s3_bucket_name                = aws_s3_bucket.bbb.id
  s3_key_prefix                 = "prefix"
  include_global_service_events = false
}

resource "aws_s3_bucket" "bb" {
  bucket = "my-tf-test-bucket"
}

resource "aws_s3_bucket_acl" "example_bucket_acl2" {
  bucket = aws_s3_bucket.bbb.id
  acl    = "private"
}

# This module has a public ACL but is NOT referenced by any aws_cloudtrail
# resource anywhere in this test run, so it must stay silent under
# all_cloudtrail_linked_modules' linkage check - this rule only reports
# CloudTrail's own log bucket, not every public-ACL module unconditionally.
variable "aws_access_key" {}
variable "aws_secret_key" {}
variable "private_key_path" {}
variable "key_name" {}
variable "region" {
  default = "us-west-2"
}
provider "aws" {
  access_key = var.aws_access_key
  secret_key = var.aws_secret_key
  region     = var.region
}

module "standalone_s3_bucket" {
  source  = "terraform-aws-modules/s3-bucket/aws"
  version = "3.7.0"

  versioning = {
    enabled = true
  }

  bucket = "my_bucket"
  acl    = "public-read"
}

Non-Compliant Code Examples

provider "aws" {
  region = "us-east-1"
}

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.0"
    }
  }
}

data "aws_caller_identity" "current" {}

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

resource "aws_s3_bucket" "b" {
  bucket = "my-tf-test-bucket"
  acl    = "public-read"

  tags = {
    Name        = "My bucket"
    Environment = "Dev"
  }
}

terraform {
  required_providers {
    aws = {
      source = "hashicorp/aws"
      version = "4.2.0"
    }
  }
}

provider "aws" {
  # Configuration options
}


module "s3_bucket" {
  source  = "terraform-aws-modules/s3-bucket/aws"
  version = "3.7.0"

  versioning = {
    enabled = true
  }

  bucket = "my_bucket"
  acl    = "public-read"
}

resource "aws_cloudtrail" "module_trail" {
  name                          = "tf-trail-module"
  s3_bucket_name                = module.s3_bucket.s3_bucket_id
  s3_key_prefix                 = "prefix"
  include_global_service_events = false
}

resource "aws_cloudtrail" "foobar2" {
  name                          = "tf-trail-foobar"
  s3_bucket_name                = aws_s3_bucket.bb.id
  s3_key_prefix                 = "prefix"
  include_global_service_events = false
}

resource "aws_s3_bucket" "bb" {
  bucket = "my-tf-test-bucket"
}

resource "aws_s3_bucket_acl" "example_bucket_acl" {
  bucket = aws_s3_bucket.bb.id
  acl    = "public-read"
}

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "4.2.0"
    }
  }
}

provider "aws" {
  # Configuration options
}

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

resource "aws_s3_bucket" "logs" {
  bucket = "cloudtrail-logs-bucket"
}

resource "aws_s3_bucket_acl" "logs_acl" {
  bucket = aws_s3_bucket.logs.id
  acl    = "public-read"
}