How to list files which has certain tag in S3 bucket?

Question

Here is my code:

import json, boto3
def lambda_handler(event, context):
    client = boto3.client("s3", region_name='us-east-1')
    response = client.list_objects(Bucket='test-bucket')
    return response

Above code is working fine for me. But I want to list all objects in the bucket which has a particular tag on the file(object), let's say

department:finance

I write below policy for it:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": "s3:List*",
            "Resource": "arn:aws:s3:::mynewbucket1122",
            "Condition": {
                "StringEquals": {
                    "s3:ExistingObjectTag/department": "finance"
                }
            }
        }
    ]
}

But I am getting errors, how can I get expected result.

Answer 1

The bucket policy, even if it was correct, does not filter your objects by the tag. You still have to call your list_objects , get the full list of objects, and iteratively , inspect their tags to get only those that you are interested in.

In other words, you have to do the filtering in your code.