Permissions on keyfile for sftp

The question is tagged with "AWS Transfer for SFTP" so i assume your question is about an AWS Transfer SFTP service that you have setup.

The keyfile doesn't grant privileges, it just authenticates the user to allow access. When the user was setup in AWS Transfer it will have had an IAM role assigned to it, and that role will have a policy (or policies) attached to it that grant levels of access to the user.

So if you only have read-only privileges when you login to AWS Transfer then it sounds like the user you are logging in with needs to have the policies associated with their role uplifted (or assign to the user a role whose policies allow more access).

More information https://docs.aws.amazon.com/transfer/latest/userguide/users-policies.html