This policy would allow read permissions for all secrets at path secret/bar, as well as list permissions
for the secret/bar/ path. The list permission is required to be able to see the names of the secrets
under a given path1. The wildcard () character matches any number of characters within a single path
segment, while the slash (/) character matches the end of the path2. Therefore, the policy would
grant read access to any secret that starts with secret/bar/, such as secret/bar/foo or secret/bar/baz,
but not to secret/bar itself. To grant list access to secret/bar, the policy needs to specify the exact
path with a slash at the end. This policy follows the principle of least privilege, which means that it
only grants the minimum permissions necessary for the users to perform their tasks3.
The other options are not correct because they either grant too much or too little permissions.
Option A would grant both read and list permissions to all secrets under secret/bar, which is more
than what is required. Option B would grant list permissions to all secrets under secret/bar, but only
read permissions to secret/bar itself, which is not what is required. Option D would use an invalid
character (+) in the policy, which would cause an error.
Reference:
Policy Syntax | Vault | HashiCorp Developer
Policy Syntax | Vault | HashiCorp Developer
Policies | Vault | HashiCorp Developer