netris-nestri/apps/api/app/middleware/auth.ts

import { createClient } from '@nestri/auth/client';
import { AccessToken } from '@nestri/core/access-token/index';
import { Actor } from '@nestri/core/actor';
import { subjects } from '@nestri/core/auth/subjects';
import { Env } from '@nestri/core/env';
import { ErrorCodes, VisibleError } from '@nestri/core/error';
import { Machine } from '@nestri/core/machine/index';
import { Member } from '@nestri/core/team/member';
import type { MiddlewareHandler } from 'hono';

/**
 * Reaches the issuer, over a binding where the platform offers one.
 *
 * A binding routes by binding rather than by hostname, which saves a trip out
 * to the internet and back for a call this middleware makes on nearly every
 * request. The host in the URL is then arbitrary — but `new Request` still
 * demands an absolute URL, and stripping down to a bare path threw
 * `Invalid URL` before the token was even looked at.
 *
 * Where there is no such binding the issuer is an ordinary HTTP origin at
 * `AUTH_ISSUER_URL` and plain `fetch` is the whole of it. Nothing else here
 * changes, because the URL being fetched is the same one either way.
 */
function issuerFetch(env: Record<string, unknown>, issuer: string) {
	const binding = env?.AUTH as { fetch: typeof fetch } | undefined;
	if (typeof binding?.fetch === 'function') {
		return (input: RequestInfo | URL, init?: RequestInit) => {
			const url = asUrl(input);
			return binding.fetch(new Request(url, init));
		};
	}

	// The same split the binding makes, spelled out: `AUTH_INTERNAL_URL` is
	// the route and `issuer` stays the name. The client builds its URLs from
	// the name, so the swap happens here, on the way out, and every claim
	// checked afterwards is still checked against the name.
	const internal = Env.get().AUTH_INTERNAL_URL?.replace(/\/+$/, '');
	if (!internal || internal === issuer) {
		return (input: RequestInfo | URL, init?: RequestInit) => fetch(asUrl(input), init);
	}
	return (input: RequestInfo | URL, init?: RequestInit) => {
		const url = asUrl(input);
		return fetch(url.startsWith(issuer) ? internal + url.slice(issuer.length) : url, init);
	};
}

function asUrl(input: RequestInfo | URL): string {
	return typeof input === 'string' ? input : input instanceof URL ? input.href : input.url;
}

/**
 * The issuer must be its **public** URL.
 *
 * `verify` checks a token's `iss` claim against the issuer the client was
 * built with, and the issuer derives what it advertises from the URL it was
 * reached on. Tokens are minted through the public URL, so they carry it. A
 * placeholder like `https://auth.internal` addresses a binding perfectly well
 * — the hostname is ignored there — and then disagrees with every real token.
 * Discovery through the binding does not help: it answers with the placeholder
 * too, because that is the host it was asked on.
 *
 * The failure is silent by nature. A rejected claim is reported as `err`,
 * which is indistinguishable from an expired or forged token, so the whole
 * bearer path returns 401 and looks like ordinary auth working correctly.
 * Hence the explicit throw rather than a fallback: a misconfiguration here
 * takes down every user session, and it should say so.
 */
function getClient(env: Record<string, unknown>) {
	const configured = Env.get().AUTH_ISSUER_URL;
	if (!configured) {
		throw new Error(
			'AUTH_ISSUER_URL is not configured; every bearer token would be rejected as unsigned'
		);
	}
	// The trailing slash matters twice, and both failures are quiet. It is
	// appended to build the discovery URL, where `…:1337//.well-known/…` is a
	// 404; and it is compared literally against the `iss` claim, which carries
	// no trailing slash. A worker URL from the platform arrives with one.
	const issuer = configured.replace(/\/+$/, '');
	return createClient({
		issuer,
		clientID: 'api',
		fetch: issuerFetch(env, issuer)
	});
}

export const auth: MiddlewareHandler = async (c, next) => {
	// A registered nessh host proves it is itself, rather than asserting an id
	// nobody checks. Wrong credentials fall through to public rather than
	// erroring, so probing tells an attacker nothing about which ids exist.
	const machineId = c.req.header('x-nestri-machine-id');
	const machineSecret = c.req.header('x-nestri-machine-secret');
	if (machineId && machineSecret) {
		const machine = await Machine.authenticate({ id: machineId, secret: machineSecret });
		if (machine) {
			await Machine.touchLastSeen({ id: machine.id });
			return Actor.with(
				{
					type: 'machine',
					properties: {
						machineID: machine.id,
						ownerUserID: machine.ownerUserId,
						teamID: machine.teamId
					}
				},
				next
			);
		}
		return Actor.with({ type: 'public', properties: {} }, next);
	}

	const authHeader = c.req.header('authorization');
	if (!authHeader) {
		return Actor.with({ type: 'public', properties: {} }, next);
	}

	const match = authHeader.match(/^Bearer (.+)$/);
	if (!match) {
		return Actor.with({ type: 'public', properties: {} }, next);
	}

	const token = match[1];

	// A personal access token is resolved from the database, never through JWT
	// verification. The prefix decides which, so a PAT does not pay for a
	// well-known lookup and a JWT does not pay for a query.
	if (AccessToken.looksLikeToken(token)) {
		const pat = await AccessToken.authenticate(token);
		if (!pat) {
			return Actor.with({ type: 'public', properties: {} }, next);
		}
		await AccessToken.touchLastUsed(pat.id);

		if (pat.teamId) {
			// The team grant is re-checked against live membership rather than
			// trusted from the row, so someone removed from a team loses what
			// their old token carried without anyone remembering to revoke it.
			const membership = await Member.findByTeamAndUser({
				teamId: pat.teamId,
				userId: pat.ownerUserId
			});
			if (!membership) {
				return Actor.with({ type: 'public', properties: {} }, next);
			}
			return Actor.with(
				{
					type: 'member',
					properties: {
						userID: pat.ownerUserId,
						role: membership.role,
						teamID: pat.teamId
					}
				},
				next
			);
		}

		return Actor.with(
			{
				type: 'user',
				properties: {
					userID: pat.ownerUserId,
					// A PAT is tied to neither a Steam account nor a device, so
					// it carries neither. A route needing those must read them
					// from the user rather than assume the caller came by SSH.
					linkedAccountID: '',
					fingerprint: undefined
				}
			},
			next
		);
	}

	// A token that cannot be verified — malformed, expired, or because the
	// auth service is unreachable — makes the caller unauthenticated, not the
	// request a server fault. `verify` reports the first two in `err` and
	// *throws* the third, and an uncaught throw turned a bad token into a 500.
	let verified;
	try {
		verified = await getClient(c.env).verify(subjects, token);
	} catch (error) {
		// eslint-disable-next-line no-console
		console.error('token verification failed:', error);
		return Actor.with({ type: 'public', properties: {} }, next);
	}
	if (verified.err) {
		return Actor.with({ type: 'public', properties: {} }, next);
	}

	const { subject } = verified;
	if (subject.type === 'user') {
		const teamID = c.req.header('x-nestri-team');
		if (teamID) {
			const membership = await Member.findByTeamAndUser({
				teamId: teamID,
				userId: subject.properties.userID
			});
			if (membership) {
				return Actor.with(
					{
						type: 'member',
						properties: {
							userID: subject.properties.userID,
							role: membership.role,
							teamID
						}
					},
					next
				);
			}
		}
		return Actor.with(
			{
				type: 'user',
				properties: {
					userID: subject.properties.userID,
					linkedAccountID: subject.properties.linkedAccountID,
					fingerprint: subject.properties.fingerprint
				}
			},
			next
		);
	}

	return Actor.with({ type: 'public', properties: {} }, next);
};

/**
 * Requires an authenticated caller of any kind, machines included.
 *
 * It deliberately does *not* single machines out: `/games` applies this to the
 * whole group, and download-state — the one route a box exists to call — sits
 * inside it. What stops a box from acting as its owner is `Actor.userID`,
 * which refuses a machine outright, so a route written for a human cannot
 * silently accept a box no matter which guard it sits behind.
 */
export const notPublic: MiddlewareHandler = async (_, next) => {
	const actor = Actor.use();
	if (actor.type === 'public') {
		throw new VisibleError(
			'authentication',
			ErrorCodes.Authentication.UNAUTHORIZED,
			'Missing authorization header'
		);
	}
	return next();
};

/** Requires credentials belonging to a registered nessh host. */
export const machineOnly: MiddlewareHandler = async (_, next) => {
	const actor = Actor.use();
	if (actor.type !== 'machine') {
		throw new VisibleError(
			'forbidden',
			ErrorCodes.Permission.INSUFFICIENT_PERMISSIONS,
			'Machine credentials required'
		);
	}
	return next();
};