How to set access permissions of google cloud storage bucket folder

Question

How do I set access permissions for entire folder in storage bucket? Example; I have 2 folders (containing many subfolders/objects) in single bucket (let's call them folder 'A' and 'B') and 4 members in project team. All 4 members can have read/edit access for folder A but only 2 of the members are allowed to have access to folder 'B'. Is there a simple way to set these permissions for each folder? There are hundreds/thousands of files within each folder and it would be very time consuming to set permissions for each individual file. Thanks for any help.

Answer 1

It's very poorly documented, but search for "folder" in the gsutil acl ch manpage:

Grant the user with the specified canonical ID READ access to all objects in example-bucket that begin with folder/:

gsutil acl ch -r \
  -u 84fac329bceSAMPLE777d5d22b8SAMPLE785ac2SAMPLE2dfcf7c4adf34da46:R \
  gs://example-bucket/folder/

Answer 2

It looks like this has become possible through IAM Conditions.

You need to set a IAM Condition like: resource.name.startsWith('projects/_/buckets/[BUCKET_NAME]/objects/[OBJECT_PREFIX]')

There are some limitations here, such as no longer being able to use the gsutil acl ch commands referenced in other answers.