feat(login): pagina pubblica /login con next sicuro

src/lib/safe-next.ts

@@ -0,0 +1,7 @@
+// Path interno sicuro per il redirect post-login: deve iniziare con "/", non essere
+// protocol-relative ("//"), non puntare alle API. Tutto il resto → home.
+export function safeNext(next: string | null): string {
+  if (!next || !next.startsWith('/') || next.startsWith('//')) return '/';
+  if (next.startsWith('/api/')) return '/';
+  return next;
+}

src/pages/login.astro

@@ -0,0 +1,53 @@
+---
+import Base from '../layouts/Base.astro';
+import { getDb } from '../lib/db';
+import { login, getSessionUser, SESSION_COOKIE } from '../lib/auth';
+import { rateLimit } from '../lib/rate-limit';
+import { safeNext } from '../lib/safe-next';
+export const prerender = false;
+
+const dest = safeNext(Astro.url.searchParams.get('next'));
+
+// Già loggato → via dal login.
+const existing = Astro.cookies.get(SESSION_COOKIE)?.value;
+if (existing && getSessionUser(getDb(), existing)) return Astro.redirect(dest);
+
+let error = '';
+if (Astro.request.method === 'POST') {
+  if (!rateLimit(`login:${Astro.clientAddress}`, 5, 15 * 60 * 1000)) {
+    error = 'Troppi tentativi: riprova tra 15 minuti.';
+  } else {
+    const form = await Astro.request.formData();
+    const token = login(getDb(), String(form.get('username') ?? ''), String(form.get('password') ?? ''));
+    if (token) {
+      Astro.cookies.set(SESSION_COOKIE, token, {
+        httpOnly: true, sameSite: 'lax', path: '/',
+        secure: import.meta.env.PROD, maxAge: 7 * 24 * 3600,
+      });
+      return Astro.redirect(safeNext(String(form.get('next') ?? '') || dest));
+    }
+    error = 'Credenziali non valide.';
+  }
+}
+---
+<Base title="Accedi" description="Area riservata InsanityLab">
+  <section class="section">
+    <div class="container login-wrap">
+      <h1 class="section-heading">Accedi</h1>
+      {error && <p class="login-err">{error}</p>}
+      <form method="post" class="login-form">
+        <input type="hidden" name="next" value={dest} />
+        <input class="login-field" name="username" placeholder="Utente" required autocomplete="username" />
+        <input class="login-field" type="password" name="password" placeholder="Password" required autocomplete="current-password" />
+        <button class="btn btn--dark" type="submit">Entra</button>
+      </form>
+    </div>
+  </section>
+</Base>
+
+<style>
+  .login-wrap { max-width: 380px; margin: 0 auto; }
+  .login-form { display: grid; gap: 14px; margin-top: 20px; }
+  .login-field { padding: 12px; border: 1px solid #ccc; font: inherit; }
+  .login-err { color: #a33; }
+</style>

tests/safe-next.test.ts

@@ -0,0 +1,18 @@
+import { describe, it, expect } from 'vitest';
+import { safeNext } from '../src/lib/safe-next';
+
+describe('safeNext', () => {
+  it('accetta path interni', () => {
+    expect(safeNext('/about')).toBe('/about');
+    expect(safeNext('/blog/x?y=1')).toBe('/blog/x?y=1');
+  });
+  it('rifiuta esterni, protocol-relative, api e vuoti', () => {
+    expect(safeNext(null)).toBe('/');
+    expect(safeNext('')).toBe('/');
+    expect(safeNext('//evil.com')).toBe('/');
+    expect(safeNext('https://evil.com')).toBe('/');
+    expect(safeNext('/api/admin/posts')).toBe('/');
+    expect(safeNext('javascript:alert(1)')).toBe('/');
+    expect(safeNext('not-a-path')).toBe('/');
+  });
+});