🛡️ Sentinel: [CRITICAL] Fix command option injection

.jules/sentinel.md

@@ -2,3 +2,8 @@
 **Vulnerability:** API endpoints in `backend/src/server.ts` taking user input (`projectId`, `jobId`) were directly joined with paths using `join` in `backend/src/store/localStore.ts` without proper sanitization. This allowed attackers to escape the project directory context and overwrite or read arbitrary files by sending payload containing `../` sequences.
 **Learning:** Even internal backend services handling project resources must securely sanitize all parameter values used for file operations to prevent path traversal outside expected boundaries.
 **Prevention:** Always use safe path sanitization utilities, like the implemented `safeJoin` and `toSafeRelativePath` in `backend/src/utils/path.ts`, to securely construct file paths and ensure the final path remains within the intended boundaries.
+
+## 2025-03-28 - [Command Option Injection in compileQueue]
+**Vulnerability:** The `mainFile` parameter in `backend/src/services/compileQueue.ts` was used directly in a `latexmk` shell command within the Rust compile worker without sanitizing for malicious option flags (e.g., `-shell-escape`).
+**Learning:** External processes executed with array-based arguments (like `Command::new().arg()` or Node's `spawn`) are still vulnerable to Option Injection if user-provided positional arguments start with a hyphen (`-`) and are interpreted as flags by the underlying binary.
+**Prevention:** Explicitly validate and reject any user-provided inputs that start with a hyphen (`-`) when they are intended to be used as positional arguments (such as filenames) in external binary execution.

backend/src/services/compileQueue.ts

@@ -101,6 +101,11 @@ export class CompileQueueService {
     const settings = await this.store.getSettings();
     const projectId = request.projectId.trim();
     const mainFile = request.mainFile?.trim() || "main.tex";
+
+    // Prevent command option injection in latexmk (e.g., -shell-escape)
+    if (mainFile.startsWith("-")) {
+      throw new HttpError(400, "mainFile cannot start with a hyphen.");
+    }
     const timeoutMs = request.timeoutMs ?? settings.compileTimeoutMs;
     const jobId = createId("job");