Cubbyhole authentication uses Vault primitives to provide a secured authentication workflow. Cubbyhole authentication uses tokens as primary login method. An ephemeral token is used to obtain a second, login VaultToken from Vault’s Cubbyhole secret backend. The login token is usually longer-lived and used to interact with Vault. The login token can be retrieved either from a wrapped response or from the data section.
Fixes gh-3
Support top level auth mount response and nested (within `data`) mount responses. Add build matrix to TravisCI. Adopt tests to earlier Vault responses.
Fixes gh-2
