S3 Bucket Public ACL Overridden By Public Access Block

• Query id: bf878b1a-7418-4de3-b13c-3a86cf894920
• Query name: S3 Bucket Public ACL Overridden By Public Access Block
• Platform: Terraform
• Severity: High
• Category: Access Control
• URL: Github

Description

S3 bucket public access is overridden by S3 bucket Public Access Block when the following attributes are set to true - 'block_public_acls', 'block_public_policy', 'ignore_public_acls', and 'restrict_public_buckets'
Documentation

Code samples

Code samples with security vulnerabilities

Positive test num. 1 - tf file

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

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

resource "aws_s3_bucket" "public-bucket" {
  bucket = "bucket-with-public-acl-3"
  acl = "public-read-write"
}

resource "aws_s3_bucket_public_access_block" "block_public_bucket_3" {
  bucket = aws_s3_bucket.public-bucket.id
  block_public_acls = true
  block_public_policy = true
  ignore_public_acls = true
  restrict_public_buckets = true
}

Positive test num. 2 - tf file

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

  version = "3.7.0"

  bucket = "my-s3-bucket"
  acl    = "public-read-write"

  versioning = {
    enabled = true
  }

  block_public_acls = true
  block_public_policy = true
  ignore_public_acls = true
  restrict_public_buckets = true

}

Positive test num. 3 - tf file

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

provider "aws" {
  # Configuration options
}

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

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

resource "aws_s3_bucket_public_access_block" "block_public_bucket_3" {
  bucket = aws_s3_bucket.bu.id
  block_public_acls = true
  block_public_policy = true
  ignore_public_acls = true
  restrict_public_buckets = true
}

Code samples without security vulnerabilities

Negative test num. 1 - tf file

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

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 3.0"
    }
  }
}
resource "aws_s3_bucket" "public-bucket2" {
  bucket = "bucket-with-public-acl-32"
  acl = "public-read-write"
}

resource "aws_s3_bucket_public_access_block" "block_public_bucket_32" {
  bucket = aws_s3_bucket.public-bucket2.id
  block_public_acls = false
  block_public_policy = true
  ignore_public_acls = false
  restrict_public_buckets = true
}

Negative test num. 2 - tf file

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

  version = "3.7.0"

  bucket = "my-s3-bucket"
  acl    = "public-read-write"

  versioning = {
    enabled = true
  }

  block_public_acls = false
  block_public_policy = true
  ignore_public_acls = false
  restrict_public_buckets = true

}

Negative test num. 3 - tf file

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

provider "aws" {
  # Configuration options
}

resource "aws_s3_bucket" "bu2" {
  bucket = "my-tf-test-bucket"
}

resource "aws_s3_bucket_acl" "example_bucket_acl2" {
  bucket = aws_s3_bucket.bu2.id
  acl = "public-read-write"
}

resource "aws_s3_bucket_public_access_block" "block_public_bucket_322" {
  bucket = aws_s3_bucket.bu2.id
  block_public_acls = false
  block_public_policy = true
  ignore_public_acls = false
  restrict_public_buckets = true
}