@logi-auth/server

Server-side "Sign in with logi" for Node backends — confidential OAuth 2.0 Authorization Code exchange + id_token (RS256) verification. Zero runtime dependencies (uses the Node global WebCrypto). Works in Next.js route handlers / server actions, Express, Fastify, or any Node server.

This is the confidential / backend counterpart to the public-client SDKs (@logi-auth/browser, iOS, Android, Flutter). If your RP has a backend, verify on the server with this library — do not rely on a client-side check.

Why it matters: a backend that skips the id_token aud check can be tricked into accepting a token minted for a different client (cross-client account takeover). exchangeCodeAndVerify() always verifies signature + iss + aud + exp + nonce before returning sub.

Supported versions

Requirement	Version
Node.js	>= 20 (global fetch + crypto.subtle; on Node 18 pass your own fetch)
Next.js	>= 13.4 (App Router — route handlers / server actions); Pages API routes also fine
Express / Fastify	any current version
TypeScript	>= 5.0 (types shipped; JS consumers fine too)

Install

npm i @logi-auth/server

Next.js (App Router) example

// app/api/auth/logi/route.ts  (start the flow)
import { LogiAuthServer } from "@logi-auth/server";
import { cookies } from "next/headers";
import { randomBytes } from "node:crypto";

const logi = new LogiAuthServer({
  clientId: process.env.LOGI_CLIENT_ID!,
  clientSecret: process.env.LOGI_CLIENT_SECRET!, // confidential client
  redirectUri: "https://app.example.com/api/auth/logi/callback",
});

export async function GET() {
  const state = randomBytes(16).toString("hex");
  const nonce = randomBytes(16).toString("hex");
  const jar = await cookies();
  jar.set("logi_state", state, { httpOnly: true, secure: true, sameSite: "lax" });
  jar.set("logi_nonce", nonce, { httpOnly: true, secure: true, sameSite: "lax" });
  return Response.redirect(logi.authorizationUrl({ state, nonce }));
}

// app/api/auth/logi/callback/route.ts  (finish + verify)
export async function GET(req: Request) {
  const url = new URL(req.url);
  const jar = await cookies();
  if (url.searchParams.get("state") !== jar.get("logi_state")?.value) {
    return new Response("state mismatch", { status: 400 });
  }
  const session = await logi.exchangeCodeAndVerify({
    code: url.searchParams.get("code")!,
    nonce: jar.get("logi_nonce")!.value,
  });
  // session.sub is the verified pairwise subject — key your user record on it.
  // ...set your own session cookie here...
  return Response.redirect("https://app.example.com/");
}

Public client (PKCE, no secret)

Omit clientSecret and pass a codeChallenge / codeVerifier:

const logi = new LogiAuthServer({ clientId, redirectUri }); // no secret
const url = logi.authorizationUrl({ state, nonce, codeChallenge });
const session = await logi.exchangeCodeAndVerify({ code, nonce, codeVerifier });

License

MIT