OpenBao lacks user confirmation for OIDC direct callback mode

Impact

OpenBao does not prompt for user confirmation when logging in via JWT/OIDC and a role with callback_mode set to direct.

This allows an attacker to start an authentication request and perform "remote phishing" by having the victim visit the URL and automatically log-in to the session of the attacker. Despite being based on the authorization code flow, the direct mode calls back directly to the API and allows an attacker to poll for an OpenBao token until it is issued.

Patches

Version 2.5.2 includes an additional confirmation screen for direct type logins that requires manual user interaction in order to finish the authentication.

Workarounds

This issue can be worked around either by removing any roles with callback_mode=direct or enforcing confirmation for every session on the token issuer side for the Client ID used by OpenBao.