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fix(auth): validate OAuth state cookie to prevent CSRF attacks #171

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fix(auth): validate OAuth state cookie to prevent CSRF attacks #171

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121 changes: 79 additions & 42 deletions apps/backend/src/routes/auth.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -15,28 +15,47 @@ interface OAuthCallbackQuery {
export async function authRoutes(app: FastifyInstance) {
// ─── GitHub OAuth ───

app.get('/github', async (request: FastifyRequest, reply: FastifyReply) => {
const redirectUri = `${process.env.BACKEND_URL}/auth/github/callback`;
const clientState = (request.query as any).state || '';
const state = clientState ? `${clientState}_${generateState()}` : generateState();

const params = new URLSearchParams({
client_id: (process.env.GITHUB_CLIENT_ID || '').trim(),
redirect_uri: redirectUri,
scope: 'read:user user:email',
state,
});
const authUrl = `${GITHUB_AUTH_URL}?${params}`;
console.log('--- GITHUB OAUTH REDIRECT ---');
console.log('URL:', authUrl);
return reply.redirect(authUrl);
app.get('/github', async (request: FastifyRequest, reply: FastifyReply) => {
const redirectUri = `${process.env.BACKEND_URL}/auth/github/callback`;
const clientState = (request.query as any).state || '';
const state = clientState ? `${clientState}_${generateState()}` : generateState();

// Store state in a short-lived signed cookie before redirecting
reply.setCookie('oauth_state', state, {
httpOnly: true,
secure: process.env.NODE_ENV === 'production',
sameSite: 'lax',
path: '/',
maxAge: 600, // 10 minutes — plenty for a login round-trip
});

app.get('/github/callback', async (request: FastifyRequest<{ Querystring: OAuthCallbackQuery }>, reply: FastifyReply) => {
const { code } = request.query;
if (!code) {
return reply.status(400).send({ error: 'Missing authorization code' });
}
const params = new URLSearchParams({
client_id: (process.env.GITHUB_CLIENT_ID || '').trim(),
redirect_uri: redirectUri,
scope: 'read:user user:email',
state,
});
const authUrl = `${GITHUB_AUTH_URL}?${params}`;
console.log('--- GITHUB OAUTH REDIRECT ---');
console.log('URL:', authUrl);
return reply.redirect(authUrl);
});

app.get('/github/callback', async (request: FastifyRequest<{ Querystring: OAuthCallbackQuery }>, reply: FastifyReply) => {
const { code, state } = request.query;

// ── CSRF check ──────────────────────────────────────────────────────────────
const storedState = (request.cookies as any)?.oauth_state;
if (!state || !storedState || state !== storedState) {
return reply.status(400).send({ error: 'Invalid or missing OAuth state — possible CSRF attack' });
}
// Clear the state cookie immediately — prevents replay
reply.clearCookie('oauth_state', { path: '/' });
// ────────────────────────────────────────────────────────────────────────────

if (!code) {
return reply.status(400).send({ error: 'Missing authorization code' });
}

try {
// Exchange code for token
Expand Down Expand Up @@ -141,30 +160,48 @@ export async function authRoutes(app: FastifyInstance) {

// ─── Google OAuth ───

app.get('/google', async (request: FastifyRequest, reply: FastifyReply) => {
const redirectUri = `${process.env.BACKEND_URL}/auth/google/callback`;
const clientState = (request.query as any).state || '';
const state = clientState ? `${clientState}_${generateState()}` : generateState();

const params = new URLSearchParams({
client_id: (process.env.GOOGLE_CLIENT_ID || '').trim(),
redirect_uri: redirectUri,
response_type: 'code',
scope: 'openid email profile',
state,
access_type: 'offline',
});
const authUrl = `${GOOGLE_AUTH_URL}?${params}`;
console.log('--- GOOGLE OAUTH REDIRECT ---');
console.log('URL:', authUrl);
return reply.redirect(authUrl);
app.get('/google', async (request: FastifyRequest, reply: FastifyReply) => {
const redirectUri = `${process.env.BACKEND_URL}/auth/google/callback`;
const clientState = (request.query as any).state || '';
const state = clientState ? `${clientState}_${generateState()}` : generateState();

// Store state in a short-lived signed cookie before redirecting
reply.setCookie('oauth_state', state, {
httpOnly: true,
secure: process.env.NODE_ENV === 'production',
sameSite: 'lax',
path: '/',
maxAge: 600,
});

app.get('/google/callback', async (request: FastifyRequest<{ Querystring: OAuthCallbackQuery }>, reply: FastifyReply) => {
const { code } = request.query;
if (!code) {
return reply.status(400).send({ error: 'Missing authorization code' });
}
const params = new URLSearchParams({
client_id: (process.env.GOOGLE_CLIENT_ID || '').trim(),
redirect_uri: redirectUri,
response_type: 'code',
scope: 'openid email profile',
state,
access_type: 'offline',
});
const authUrl = `${GOOGLE_AUTH_URL}?${params}`;
console.log('--- GOOGLE OAUTH REDIRECT ---');
console.log('URL:', authUrl);
return reply.redirect(authUrl);
});

app.get('/google/callback', async (request: FastifyRequest<{ Querystring: OAuthCallbackQuery }>, reply: FastifyReply) => {
const { code, state } = request.query;

// ── CSRF check ──────────────────────────────────────────────────────────────
const storedState = (request.cookies as any)?.oauth_state;
if (!state || !storedState || state !== storedState) {
return reply.status(400).send({ error: 'Invalid or missing OAuth state — possible CSRF attack' });
}
reply.clearCookie('oauth_state', { path: '/' });
// ────────────────────────────────────────────────────────────────────────────

if (!code) {
return reply.status(400).send({ error: 'Missing authorization code' });
}

try {
const tokenRes = await fetch(GOOGLE_TOKEN_URL, {
Expand Down