How to create a S3 bucket policy for the multiple existing manually created (not through terraform) s3 buckets using terraform - terraform-provider-aws

Question

How to create a S3 bucket policy for the multiple existing manually created (not through terraform) s3 buckets using terraform
For Example : I have A,B,C buckets created manually and now I wanted to add a s3 buket policy for all 3 S3 buckets , How can I achieve this through Terraform? Can we use some loop sort of thing here Please advise

Answer 1

Do you want the same policy applied to each bucket? That doesn't really work because the policies need to include the bucket name in the resource section. It's a weird limitation of S3 bucket policies that I've never quite understood, you can't use a wildcard (*) for the bucket name.
Anyways, you could do something like this, where you dynamically set the bucket name in the policy.
I'm just typing this from memory so please excuse any syntax errors.
locals {
// The names of the buckets you want to apply policies to
buckets = [
"mybucket",
"anotherbucket",
]
}
// Create a unique policy for each bucket, using
// the bucket name in the policy.
data "aws_iam_policy_document" "bucket_policies" {
for_each = toset(local.buckets)
statement {
actions = [
"s3:PutObject"
]
resources = [
"arn:aws:s3:::${each.key}/*"
]
principals {
type = "AWS"
identifiers = [
var.my_user_arn
]
}
}
}
// Apply each policy to its respective bucket
resource "aws_s3_bucket_policy" "policies" {
for_each = toset(local.buckets)
bucket = each.key
policy = data.aws_iam_policy_document.bucket_policies[each.key].json
}