fix(comparison): also fix string comparison hashes in recovery codes

apps/server/src/routes/login.ts

@@ -1,3 +1,4 @@
+import crypto from "crypto";
 import utils from "../services/utils.js";
 import optionService from "../services/options.js";
 import myScryptService from "../services/encryption/my_scrypt.js";
@@ -160,7 +161,11 @@ function verifyPassword(submittedPassword: string) {
 
     const guess_hashed = myScryptService.getVerificationHash(submittedPassword);
 
-    return guess_hashed.equals(hashed_password);
+    // Use constant-time comparison to prevent timing attacks
+    if (hashed_password.length !== guess_hashed.length) {
+        return false;
+    }
+    return crypto.timingSafeEqual(guess_hashed, hashed_password);
 }
 
 function sendLoginError(req: Request, res: Response, errorType: 'password' | 'totp' = 'password') {

apps/server/src/services/encryption/recovery_codes.ts

@@ -56,13 +56,22 @@ function verifyRecoveryCode(recoveryCodeGuess: string) {
 
     const recoveryCodes = getRecoveryCodes();
     let loginSuccess = false;
-    recoveryCodes.forEach((recoveryCode) => {
+    let matchedCode: string | null = null;
+
+    // Check ALL codes to prevent timing attacks - do not short-circuit
+    for (const recoveryCode of recoveryCodes) {
         if (constantTimeCompare(recoveryCodeGuess, recoveryCode)) {
-            removeRecoveryCode(recoveryCode);
+            matchedCode = recoveryCode;
             loginSuccess = true;
-            return;
+            // Continue checking all codes to maintain constant time
         }
-    });
+    }
+
+    // Remove the matched code only after checking all codes
+    if (matchedCode) {
+        removeRecoveryCode(matchedCode);
+    }
+
     return loginSuccess;
 }
 

apps/server/src/services/utils.ts

@@ -82,8 +82,14 @@ export function hmac(secret: any, value: any) {
  * @param a First string to compare
  * @param b Second string to compare
  * @returns true if strings are equal, false otherwise
+ * @note Returns false for null/undefined/non-string inputs. Empty strings are considered equal.
  */
-export function constantTimeCompare(a: string, b: string): boolean {
+export function constantTimeCompare(a: string | null | undefined, b: string | null | undefined): boolean {
+    // Handle null/undefined/non-string cases safely
+    if (typeof a !== "string" || typeof b !== "string") {
+        return false;
+    }
+
     const bufA = Buffer.from(a, "utf-8");
     const bufB = Buffer.from(b, "utf-8");