🛡️ Sentinel: [HIGH] 로그인 사용자 열거 타이밍 공격 방어

.jules/sentinel.md

@@ -30,3 +30,7 @@
 **Vulnerability:** Known high-severity vulnerabilities discovered by the audit in `js-yaml` and `nanoid` packages.
 **Learning:** Deeply nested dependencies (`js-yaml` via `eslint`, `nanoid` via `vitest/vite`) may expose the application to DoS or logic loops.
 **Prevention:** Use `pnpm.overrides` in the root `package.json` to enforce patched versions across all transitive paths in a pnpm workspace.
+## 2025-03-09 - [Fix User Enumeration via Timing Attack]
+**Vulnerability:** User enumeration timing attack in the login route where non-existent users return immediately while existent users incur a ~100ms bcrypt overhead.
+**Learning:** Early returns before expensive operations like bcrypt allow attackers to enumerate valid users based on response times. When mitigating this, hardcoding a dummy hash for bcrypt.compare triggers SAST rules (detected-bcrypt-hash).
+**Prevention:** Use await bcrypt.hash(password, 10) for non-existent users to safely simulate the required processing delay without failing SAST checks.

packages/web/src/lib/server/auth-actions.ts

@@ -64,7 +64,10 @@ export async function loginUser(
   const { email, password } = input
 
   const user = await db.user.findUnique({ where: { email } })
-  if (!user) return null
+  if (!user) {
+    await bcrypt.hash(password, 10)
+    return null
+  }
 
   const valid = await bcrypt.compare(password, user.passwordHash)
   if (!valid) return null