blog-rust-postgres/extras/auth-clerk

Auth via Clerk

Replaces the local email+password auth with Clerk hosted auth. The app stops issuing tokens itself and instead verifies Clerk session JWTs (RS256) against your instance's JWKS, checking the issuer.

Setup

1. Create an application in the Clerk dashboard and note your instance's Frontend API URL (e.g. https://your-instance.clerk.accounts.dev) — that is the token issuer.

2. Add the HTTP client to Cargo.toml:

   reqwest = { version = "0.13", features = ["json"] }
   

3. Copy clerk.rs to src/clerk.rs and delete src/auth.rs — Clerk hosts sign-up and sign-in. In src/main.rs, replace mod auth; with mod clerk;, then remove the /auth/register and /auth/login routes, the unused post import, and the jwt_secret state field along with its AUTH_SECRET line.

4. In src/posts.rs:

   • import the new extractor: use crate::clerk::AuthUser;
   • Clerk user ids are strings (user_...), not UUIDs: change author_id: Uuid in Post to author_id: String, the user_id: Uuid parameter of find_own_post to user_id: String, and .bind(author_id) in create to .bind(&author_id).

5. In schema.sql, make the column match and drop the foreign key (CREATE TABLE IF NOT EXISTS won't alter an existing table, so start from an empty database):

   author_id TEXT NOT NULL
   

6. Set the environment variable:

   CLERK_ISSUER=https://your-instance.clerk.accounts.dev
   

What to delete

• The users table in schema.sql — Clerk is the user store now. Keep it only if you mirror users locally (e.g. via Clerk webhooks), without password_hash.

Notes

• Clients send the Clerk session token as Authorization: Bearer <token> (await session.getToken() in Clerk's frontend SDKs).
• The JWKS is fetched on first use and cached. A token signed with an unknown key id triggers a refetch (at most once a minute), so key rotations need no restart.
• Clerk also puts the requesting origin in the azp claim; if browsers from other sites could hold your users' tokens, add an azp: String field to Claims and compare it with your frontend's origin.