Add Optional 2FA Support (#61)

* Add TOTP MFA Support

* Add Passkey MFA Support

It's not impossible I missed some minor cleanup, but most things make sense and there isn't a lot of obvious duplication anymore.

---------

Co-authored-by: Bruno Bernardino <me@brunobernardino.com>

routes/api/auth/multi-factor/passkey/verify.ts

@@ -0,0 +1,99 @@
+import { Handlers } from 'fresh/server.ts';
+import { AuthenticationResponseJSON } from '@simplewebauthn/server';
+
+import { FreshContextState } from '/lib/types.ts';
+import { PasskeyModel } from '/lib/models/multi-factor-auth/passkey.ts';
+import { UserModel } from '/lib/models/user.ts';
+import { AppConfig } from '/lib/config.ts';
+import { createSessionResponse } from '/lib/auth.ts';
+
+export interface RequestBody {
+  email: string;
+  challenge: string;
+  authenticationResponse: AuthenticationResponseJSON;
+  redirectUrl?: string;
+}
+
+export interface ResponseBody {
+  success: boolean;
+  error?: string;
+}
+
+export const handler: Handlers<unknown, FreshContextState> = {
+  async POST(request) {
+    const isMultiFactorAuthEnabled = await AppConfig.isMultiFactorAuthEnabled();
+
+    if (!isMultiFactorAuthEnabled) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'Multi-factor authentication is not enabled on this server',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 403 });
+    }
+
+    const body = await request.clone().json() as RequestBody;
+    const { email, challenge, authenticationResponse, redirectUrl } = body;
+
+    if (!email || !challenge || !authenticationResponse) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'Email, challenge, and authentication response are required',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 400 });
+    }
+
+    const user = await UserModel.getByEmail(email);
+    if (!user) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'User not found',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 404 });
+    }
+
+    const config = await AppConfig.getConfig();
+    const expectedOrigin = config.auth.baseUrl;
+    const expectedRPID = new URL(config.auth.baseUrl).hostname;
+
+    const userCredentials = PasskeyModel.getCredentialsFromUser(user);
+    const credentialID = authenticationResponse.id;
+
+    const credential = userCredentials.find((credential) => credential.credentialID === credentialID);
+    if (!credential) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'Credential not found for this user',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 400 });
+    }
+
+    const verification = await PasskeyModel.verifyAuthentication(
+      authenticationResponse,
+      challenge,
+      expectedOrigin,
+      expectedRPID,
+      credential,
+    );
+
+    if (!verification.verified) {
+      const responseBody: ResponseBody = {
+        success: false,
+        error: 'Passkey authentication verification failed',
+      };
+
+      return new Response(JSON.stringify(responseBody), { status: 400 });
+    }
+
+    // Update the counter to protect against replay attacks
+    PasskeyModel.updateCounterForUser(user, credentialID, verification.authenticationInfo.newCounter);
+    await UserModel.update(user);
+
+    return await createSessionResponse(request, user, {
+      urlToRedirectTo: redirectUrl || '/',
+    });
+  },
+};