Unauthenticated DCR previously accepted any redirect_uri; combined with the
auto-approving /consent handler an attacker could register a client pointing at
their domain, phish a logged-in user, and silently receive an auth code for the
victim's identity. Reject non-allowlisted redirect_uri hosts at registration
(default: claude.ai, claude.com, and the BETTER_AUTH_URL/portal host).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
MCP clients send resource=<mcp url>; Better Auth rejected it because the default
allowed audience is only baseURL. List the MCP resource so the token exchange
succeeds and the access token becomes a JWT with aud=resource.
Claude forces the consent screen with prompt=consent; the consent endpoint's
signed-query round-trip is brittle. Simpler: drop prompt=consent from the initial
unsigned authorize so skipConsent applies and no consent page is shown. Also pass
raw query bytes to the login/consent handlers.
Google login worked; the flow died on the unimplemented consent page. Auto-accept
via auth.api.oauth2Consent with the signed oauth_query + session, then 302 to the
client callback with the code.
Claude's OAuth window doesn't run page JS, so the button never fired. Initiate
Google sign-in server-side via auth.api.signInSocial and 302 straight to Google;
after Google, callbackURL returns to /oauth2/authorize and the flow resumes. Pure
redirect chain, no client JS.
Better Auth redirects to the login page with the original signed authorize params;
hand them back to /oauth2/authorize as the post-sign-in callback so a code is
issued (was defaulting to '/', producing a blank page).
Current OAuth 2.1 provider plugin (versioned with core, 1.6.23). Bundles JWT
(access tokens verifiable at /jwks), DCR via /oauth2/register incl. unauthenticated
registration (MCP clients register before they have creds), skipConsent since
sign-in is the authorization for a personal connector.
- Explicitly track latest core (1.6.23); the @better-auth/cli lags at 1.4.21 and
pulled a second core copy — replaced with a getMigrations() script on the same
version (src/migrate.ts).
- CI build job matches the proven pattern (no setup-buildx; plain build/push).
DCR-capable (RFC 7591) OAuth authorization server so Claude's MCP connector
self-registers — the thing Authentik can't do until 2026.8.0. Users sign in with
Google/Apple; oidcProvider + jwt issue asymmetric JWTs (JWKS) the MCP server
verifies. Shares the existing CNPG Postgres (own `betterauth` schema).
Scaffold: auth config, minimal Node server + login page, Dockerfile, CI.
Chris Farhood