login.ts

1import { createHash, randomBytes, timingSafeEqual } from "node:crypto";2import type { Context, Hono } from "hono";3import { deleteCookie, getCookie, setCookie } from "hono/cookie";4import { html } from "../pages/html.ts";5import { type PageContext, page } from "../pages/layout.ts";6import { clientIp } from "./client.ts";78const SESSION_SECONDS = 30 * 86400;9const SESSION_COOKIE = "kepr_session";10const SIGN_IN_COOKIE = "kepr_sign_in";11// Readable by kepr.js, and saying only that someone signed in here: public pages stay the same12// cacheable HTML for everyone, and the script asks the admin routes for the editing controls.13const EDITOR_COOKIE = "kepr_editor";14const COOKIE = { httpOnly: true, secure: true, sameSite: "Strict", path: "/" } as const;15const HEX64 = /^[0-9a-f]{64}$/;16const FAILURE_WINDOW_MS = 15 * 60 * 1000;17const FAILURES_PER_ADDRESS = 5;1819// Failed sign-ins, oldest first, in memory: a restart forgets them, but an attacker can't cause one.20const failures: { at: number; address: string }[] = [];21// Addresses are keyed hashes even in memory, as issue filings store them (§23).22const addressKey = randomBytes(32);2324const nowSeconds = () => Math.floor(Date.now() / 1000);25const sha256 = (text: string) => createHash("sha256").update(text).digest("hex");2627function sameText(a: string, b: string): boolean {28	const [x, y] = [Buffer.from(a), Buffer.from(b)];29	return x.length === y.length && timingSafeEqual(x, y);30}3132/** The session cookie's token when it names a live session in kepr.db, else null. */33function sessionToken(ctx: PageContext, c: Context): string | null {34	const token = getCookie(c, SESSION_COOKIE);35	if (!token || !HEX64.test(token)) return null;36	const row = ctx.kepr37		.query<{ n: number }, [string, number]>(38			"SELECT 1 AS n FROM sessions WHERE token_hash = ? AND expires_at > ?",39		)40		.get(sha256(token), nowSeconds());41	return row ? token : null;42}4344export function signedIn(ctx: PageContext, c: Context): boolean {45	return sessionToken(ctx, c) !== null;46}4748export async function adminPostRefusal(ctx: PageContext, c: Context): Promise<string> {49	if (c.req.header("origin") !== `https://${ctx.domain}`) return "Refused: wrong origin.";50	const form = (await c.req.parseBody()).form;51	return typeof form !== "string" || !sameText(form, formToken(c))52		? "Refused: this form expired. Reload and try again."53		: "";54}5556/**57 * The same-site token every admin form carries (§25): derived from the session's secret token, so58 * a page on another site can neither read nor guess it, and it dies with the session.59 */60export function formToken(c: Context): string {61	return sha256(`form:${getCookie(c, SESSION_COOKIE) ?? ""}`);62}6364/**65 * The refusal page behind every admin entry point, `/connect` included: one answer for a missing66 * session, a foreign origin, an expired form token or too many attempts, wherever it arrives.67 */68export function adminRefusal(69	c: Context,70	ctx: PageContext,71	status: 401 | 403 | 429,72	text: string,73): Response {74	c.header("Cache-Control", "no-store");75	const body = html`<h1 class="file-page-title">${text}</h1>`;76	return c.html(page(ctx, { title: "admin", description: "", path: c.req.path, body }), status);77}7879/**80 * §24's login at `/sign-in`, sessions, sign-out, and the guard in front of every81 * `/admin` route: a live session, and for anything but GET a matching `Origin` and form token.82 */83export function registerLogin(app: Hono, ctx: PageContext, passwordHash: string): void {84	const origin = `https://${ctx.domain}`;85	const refuse = (c: Context, status: 401 | 403 | 429, text: string) =>86		adminRefusal(c, ctx, status, text);8788	app.use("/admin/*", async (c, next) => {89		const token = sessionToken(ctx, c);90		if (!token) return refuse(c, 401, "Sign in first.");91		if (c.req.method !== "GET") {92			const error = await adminPostRefusal(ctx, c);93			if (error) return refuse(c, 403, error);94		}95		await next();96		c.header("Cache-Control", "no-store");97	});9899	app.get("/sign-in", (c) => signInPage(c, ctx, "", 200, nextPath(c.req.query("next"))));100101	app.post("/sign-in", async (c) => {102		const fields = await c.req.parseBody();103		const next = nextPath(fields.next);104		const cookie = getCookie(c, SIGN_IN_COOKIE) ?? "";105		const form = typeof fields.form === "string" ? fields.form : "";106		if (c.req.header("origin") !== origin || !HEX64.test(cookie) || !sameText(form, cookie)) {107			return refuse(c, 403, "Refused: this form expired. Reload and try again.");108		}109		const now = Date.now();110		while (failures[0] && failures[0].at <= now - FAILURE_WINDOW_MS) failures.shift();111		const address = createHash("sha256").update(addressKey).update(clientIp(c)).digest("hex");112		const mine = failures.filter((failure) => failure.address === address).length;113		if (mine >= FAILURES_PER_ADDRESS) {114			c.header("Retry-After", String(FAILURE_WINDOW_MS / 1000));115			return signInPage(c, ctx, "Too many attempts. Try again later.", 429, next);116		}117		const password = typeof fields.password === "string" ? fields.password : "";118		if (!(await Bun.password.verify(password, passwordHash))) {119			failures.push({ at: now, address });120			return signInPage(c, ctx, "That password is not right.", 401, next);121		}122		const token = randomBytes(32).toString("hex");123		const at = nowSeconds();124		ctx.kepr.query("DELETE FROM sessions WHERE expires_at <= ?").run(at);125		ctx.kepr126			.query("INSERT INTO sessions (token_hash, expires_at) VALUES (?, ?)")127			.run(sha256(token), at + SESSION_SECONDS);128		setCookie(c, SESSION_COOKIE, token, { ...COOKIE, maxAge: SESSION_SECONDS });129		setCookie(c, EDITOR_COOKIE, "1", { ...COOKIE, httpOnly: false, maxAge: SESSION_SECONDS });130		deleteCookie(c, SIGN_IN_COOKIE, COOKIE);131		return c.redirect(next, 303);132	});133134	app.post("/admin/sign-out", (c) => {135		ctx.kepr136			.query("DELETE FROM sessions WHERE token_hash = ?")137			.run(sha256(getCookie(c, SESSION_COOKIE) ?? ""));138		deleteCookie(c, SESSION_COOKIE, COOKIE);139		deleteCookie(c, EDITOR_COOKIE, { ...COOKIE, httpOnly: false });140		return c.redirect("/", 303);141	});142}143144/**145 * Where a sign-in goes on to: a path on this site, or `/admin`. `//host` and `/\host` are other146 * sites to a browser, and a control character could split the Location header.147 */148function nextPath(value: unknown): string {149	if (typeof value !== "string" || !value.startsWith("/")) return "/admin";150	if (value.startsWith("//") || value.startsWith("/\\")) return "/admin";151	if ([...value].some((char) => char.charCodeAt(0) <= 31 || char.charCodeAt(0) === 127))152		return "/admin";153	return value;154}155156// A double-submit token repeats a SameSite=Strict cookie that a cross-site post never has.157function signInPage(158	c: Context,159	ctx: PageContext,160	error: string,161	status: 200 | 401 | 429,162	next: string,163) {164	let cookie = getCookie(c, SIGN_IN_COOKIE) ?? "";165	if (!HEX64.test(cookie)) {166		cookie = randomBytes(32).toString("hex");167		setCookie(c, SIGN_IN_COOKIE, cookie, COOKIE);168	}169	c.header("Cache-Control", "no-store");170	const body = html`<h1 class="file-page-title">sign in</h1>171${error && html`<p class="issues-error mono" role="alert">${error}</p>`}172<form class="issues-form" method="post" action="/sign-in">173<input type="hidden" name="form" value="${cookie}">174<input type="hidden" name="next" value="${next}">175<label class="issues-label" for="password">password</label>176<input class="issues-input" id="password" name="password" type="password" required autocomplete="current-password" autofocus>177<button class="issues-submit" type="submit">sign in</button>178</form>`;179	return c.html(page(ctx, { title: "sign in", description: "", path: "/sign-in", body }), status);180}