s3.listObjectsV2 AccessDenied - node.js

Question

Hi I try to list all files in a "folder" of a S3 bucket. So I try:
const params = {
Bucket: s3bucketname,
Prefix: foldername + "/"
};
const data = await s3.listObjectsV2(params).promise()
console.log(data)
which give me an AccessDenied error.
Files itself are stored like this
const params = {
Bucket: s3bucketname,
Key: foldername + "/" + filename,
ContentType: 'image/jpeg',
ACL: 'public-read',
Body: data
};
await s3.upload(params, tags).promise();
and public available. which works fine. Also using
const params = {
Bucket: s3bucketname,
Key: folderfilename
};
await s3.headObject(params).promise()
works fine.
yml file looks like this
S3BucketampstoryscreenshotsPolicy:
Type: AWS::S3::BucketPolicy
Properties:
Bucket:
Ref: S3Bucketampstoryscreenshots
PolicyDocument:
Statement:
-
Action:
- "s3:Get*"
Effect: "Allow"
I tested multiple small variations but cant find the problem here?

Answer 1

The ListBucket statement was needed. Important here to have Ref once with /* and once without /* Not having it set like that causes
Action does not apply to any resource(s) in statement (Service: Amazon
S3; Status Code: 400; Error Code: MalformedPolicy;
This works in my case:
PolicyDocument:
Statement:
-
Action:
- "s3:GetObject"
Effect: "Allow"
Resource:
Fn::Join:
- ""
-
- "arn:aws:s3:::"
-
Ref: "S3Bucketampstoryscreenshots"
- "/*"
Principal: "*"
-
Action:
- "s3:ListBucket"
Effect: "Allow"
Resource:
Fn::Join:
- ""
-
- "arn:aws:s3:::"
-
Ref: "S3Bucketampstoryscreenshots"
Principal: "*"
Thanks to jarmod for the hint