implement session via cloudflare kv

app/src/app.d.ts

@@ -1,9 +1,13 @@
+import { KVNamespace } from '@cloudflare/workers-types';
 // See https://svelte.dev/docs/kit/types#app.d.ts
 // for information about these interfaces
 declare global {
 	namespace App {
         interface Platform {
-            env: Env
+            env: {
+                GH_MEDIA: R2Bucket;
+				GH_SESSIONS: KVNamespace;
+            };
             cf: CfProperties
             ctx: ExecutionContext
         }

app/src/lib/server/session.ts

@@ -0,0 +1,79 @@
+import type { KVNamespace } from "@cloudflare/workers-types";
+import { encodeBase32, encodeHexLowerCase } from "@oslojs/encoding";
+import { sha256 } from "@oslojs/crypto/sha2";
+
+import type { RequestEvent } from "@sveltejs/kit";
+
+// in seconds
+const EXPIRATION_TTL: number = 60 * 60 * 24 * 7;
+
+export async function validateSessionToken(token: string, sessions: KVNamespace): Promise<SessionValidationResult> {
+	const sessionId = encodeHexLowerCase(sha256(new TextEncoder().encode(token)));
+	const session: Session | null = await sessions.get(sessionId, { type: "json" });
+
+	if (!session) {
+		return null;
+	}
+
+	if (Date.now() >= session.expiresAt.getTime() - 1000 * 60 * 60 * 24 * 15) {
+		await sessions.put(sessionId, JSON.stringify(session), { expirationTtl: EXPIRATION_TTL });
+	}
+	return session;
+}
+
+export async function invalidateSession(sessionId: string, sessions: KVNamespace): Promise<void> {
+	await sessions.delete(sessionId);
+}
+
+export async function invalidateUserSessions(userId: number, sessions: KVNamespace): Promise<void> {
+	const keys = await sessions.list({ prefix: `${userId}:` });
+	for (const key of keys.keys) {
+		await sessions.delete(key.name);
+	}
+}
+
+export function setSessionTokenCookie(event: RequestEvent, token: string, expiresAt: Date): void {
+	event.cookies.set("session", token, {
+		httpOnly: true,
+		path: "/",
+		secure: import.meta.env.PROD,
+		sameSite: "lax",
+		expires: expiresAt
+	});
+}
+
+export function deleteSessionTokenCookie(event: RequestEvent): void {
+	event.cookies.set("session", "", {
+		httpOnly: true,
+		path: "/",
+		secure: import.meta.env.PROD,
+		sameSite: "lax",
+		maxAge: 0
+	});
+}
+
+export function generateSessionToken(): string {
+	const tokenBytes = new Uint8Array(20);
+	crypto.getRandomValues(tokenBytes);
+	const token = encodeBase32(tokenBytes).toLowerCase();
+	return token;
+}
+
+export async function createSession(token: string, userId: number, sessions: KVNamespace): Promise<Session> {
+	const sessionId = `${userId}:${encodeHexLowerCase(sha256(new TextEncoder().encode(token)))}`;
+	const session: Session = {
+		id: sessionId,
+		userId,
+		expiresAt: new Date(Date.now() + 1000 * EXPIRATION_TTL)
+	};
+	await sessions.put(sessionId, JSON.stringify(session), { expirationTtl: EXPIRATION_TTL });
+	return session;
+}
+
+export interface Session {
+	id: string;
+	expiresAt: Date;
+	userId: number;
+}
+
+type SessionValidationResult = Session | null;

app/src/routes/login/+page.server.ts

@@ -0,0 +1,10 @@
+import { redirect } from "@sveltejs/kit";
+
+import type { RequestEvent } from "./$types";
+
+export async function load(event: RequestEvent) {
+	if (event.locals.session !== null && event.locals.user !== null) {
+		return redirect(302, "/");
+	}
+	return {};
+}