Skip to content

S3 Access Block should Ignore Public Acl

Default Severity: high

Explanation

S3 buckets should ignore public ACLs on buckets and any objects they contain. By ignoring rather than blocking, PUT calls with public ACLs will still be applied but the ACL will be ignored.

Possible Impact

PUT calls with public ACLs specified can make objects public

Suggested Resolution

Enable ignoring the application of public ACLs in PUT calls

Insecure Example

The following example will fail the aws-s3-ignore-public-acls check. 

resource "aws_s3_bucket" "example" {
    bucket = "bucket"
}


 resource "aws_s3_bucket_public_access_block" "bad_example" {
    bucket = aws_s3_bucket.example.id
 }

 resource "aws_s3_bucket_public_access_block" "bad_example" {
    bucket = aws_s3_bucket.example.id

    ignore_public_acls = false
 }

Secure Example

The following example will pass the aws-s3-ignore-public-acls check. 

resource "aws_s3_bucket" "example" {
    bucket = "bucket"
}

 resource "aws_s3_bucket_public_access_block" "good_example" {
    bucket = aws_s3_bucket.example.id

    ignore_public_acls = true
 }