From a454e6610d021a2398ef6ba5a971d749babfa6f9 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Thu, 16 Jul 2026 20:55:29 +0000
Subject: [PATCH] =?UTF-8?q?=F0=9F=9B=A1=EF=B8=8F=20Sentinel:=20[CRITICAL]?=
 =?UTF-8?q?=20Fix=20timing=20attack=20vulnerability=20in=20auth=20token=20?=
 =?UTF-8?q?validation?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .jules/sentinel.md        | 4 ++++
 src/cli/commands/serve.ts | 9 +++------
 2 files changed, 7 insertions(+), 6 deletions(-)
 create mode 100644 .jules/sentinel.md

diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 00000000..02434c99
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2024-07-25 - Timing Attack Fast Path in Token Comparison
+**Vulnerability:** The authentication validation used a short-circuit buffer length check (`tokenBuffer.length === authTokenBuffer.length`) before calling `crypto.timingSafeEqual()`.
+**Learning:** Checking the length of secrets before a constant-time comparison creates a fast path that leaks the length of the expected secret via timing differences, rendering the constant-time check partially ineffective.
+**Prevention:** Always hash both secrets to a fixed length (e.g., using `crypto.createHash('sha256')`) before comparison to ensure true constant-time evaluation and avoid short-circuiting logic based on length.
\ No newline at end of file
diff --git a/src/cli/commands/serve.ts b/src/cli/commands/serve.ts
index 2c37293e..e20ec168 100644
--- a/src/cli/commands/serve.ts
+++ b/src/cli/commands/serve.ts
@@ -346,13 +346,10 @@ export async function handleServeCommand(_options: unknown, command: Command) {
 
           let isAuthenticated = false;
           if (scheme?.toLowerCase() === 'bearer' && token) {
-            const tokenBuffer = Buffer.from(token);
+            const tokenHash = crypto.createHash('sha256').update(token).digest();
             for (const authToken of authTokens) {
-              const authTokenBuffer = Buffer.from(authToken);
-              if (
-                tokenBuffer.length === authTokenBuffer.length &&
-                crypto.timingSafeEqual(tokenBuffer, authTokenBuffer)
-              ) {
+              const authTokenHash = crypto.createHash('sha256').update(authToken).digest();
+              if (crypto.timingSafeEqual(tokenHash, authTokenHash)) {
                 isAuthenticated = true;
                 break;
               }