🛡️ Sentinel: [CRITICAL] Fix LaTeX injection RCE vulnerability in PDF compilation

.jules/sentinel.md

@@ -7,3 +7,8 @@
 **Vulnerability:** The `CoverLetterGenerator` used a standard Jinja2 environment (intended for HTML/XML or plain text) to render LaTeX templates. This allowed malicious user input (or AI hallucinations) containing LaTeX control characters (e.g., `\input{...}`) to be injected directly into the LaTeX source, leading to potential Local File Inclusion (LFI) or other exploits.
 **Learning:** Jinja2's default `autoescape` is context-aware based on file extensions, but usually only for HTML/XML. It does NOT automatically escape LaTeX special characters. Relying on manual filters (like `| latex_escape`) in templates is error-prone and brittle, as developers might forget to apply them to every variable.
 **Prevention:** Always use a dedicated Jinja2 environment for LaTeX generation that enforces auto-escaping via a `finalize` hook (e.g., `tex_env.finalize = latex_escape`). This ensures *all* variable output is sanitized by default, providing defense-in-depth even if the template author forgets explicit filters.
+
+## 2026-04-29 - [Critical] LaTeX Injection RCE in PDF Compilation
+**Vulnerability:** The `cli/pdf/converter.py` and `cli/generators/cover_letter_generator.py` modules used `subprocess.Popen` to call `pdflatex` and `pandoc` without the `-no-shell-escape` flags. Additionally, these subprocess calls lacked a timeout, making them susceptible to Remote Code Execution (RCE) and infinite hang vulnerabilities if untrusted input (e.g., from an AI hallucination or malicious user input in a template) contained LaTeX control characters or external commands.
+**Learning:** External compilation tools like `pdflatex` have unsafe defaults that allow them to execute shell commands during rendering. Without explicitly restricting these permissions, untrusted input passed to these tools can easily lead to a full system compromise. Missing timeouts also expose the system to Denial of Service via compilation loops.
+**Prevention:** Always append `-no-shell-escape` to `pdflatex` and `--pdf-engine-opt=-no-shell-escape` to `pandoc` commands to enforce sandboxing. Furthermore, always specify a robust timeout when calling external executables via `subprocess` (e.g., `communicate(timeout=30)`) and explicitly kill the process if the timeout is reached.

cli/generators/cover_letter_generator.py

@@ -771,14 +771,19 @@ def _compile_pdf(self, output_path: Path, tex_content: str) -> bool:
         try:
             # Use Popen with explicit cleanup to avoid double-free issues
             process = subprocess.Popen(
-                ["pdflatex", "-interaction=nonstopmode", tex_path.name],
+                ["pdflatex", "-interaction=nonstopmode", "-no-shell-escape", tex_path.name],
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,
                 cwd=tex_path.parent,
             )
-            stdout, stderr = process.communicate()
-            if process.returncode == 0 or output_path.exists():
-                pdf_created = True
+            try:
+                stdout, stderr = process.communicate(timeout=30)
+                if process.returncode == 0 or output_path.exists():
+                    pdf_created = True
+            except subprocess.TimeoutExpired:
+                process.kill()
+                process.communicate()
+                pdf_created = False
         except (subprocess.CalledProcessError, FileNotFoundError):
             # Check if PDF was created anyway
             if output_path.exists():
@@ -787,13 +792,25 @@ def _compile_pdf(self, output_path: Path, tex_content: str) -> bool:
                 # Fallback to pandoc
                 try:
                     process = subprocess.Popen(
-                        ["pandoc", str(tex_path), "-o", str(output_path), "--pdf-engine=xelatex"],
+                        [
+                            "pandoc",
+                            str(tex_path),
+                            "-o",
+                            str(output_path),
+                            "--pdf-engine=xelatex",
+                            "--pdf-engine-opt=-no-shell-escape",
+                        ],
                         stdout=subprocess.PIPE,
                         stderr=subprocess.PIPE,
                     )
-                    stdout, stderr = process.communicate()
-                    if process.returncode == 0 or output_path.exists():
-                        pdf_created = True
+                    try:
+                        stdout, stderr = process.communicate(timeout=30)
+                        if process.returncode == 0 or output_path.exists():
+                            pdf_created = True
+                    except subprocess.TimeoutExpired:
+                        process.kill()
+                        process.communicate()
+                        pdf_created = False
                 except (subprocess.CalledProcessError, FileNotFoundError):
                     pass
 

cli/pdf/converter.py

@@ -86,12 +86,17 @@ def _compile_pdflatex(
         """
         try:
             process = subprocess.Popen(
-                ["pdflatex", "-interaction=nonstopmode", tex_path.name],
+                ["pdflatex", "-interaction=nonstopmode", "-no-shell-escape", tex_path.name],
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,
                 cwd=working_dir,
             )
-            stdout, stderr = process.communicate()
+            try:
+                stdout, stderr = process.communicate(timeout=30)
+            except subprocess.TimeoutExpired:
+                process.kill()
+                process.communicate()
+                return False
 
             if process.returncode == 0 or output_path.exists():
                 return True
@@ -121,12 +126,24 @@ def _compile_pandoc(
         """
         try:
             process = subprocess.Popen(
-                ["pandoc", str(tex_path), "-o", str(output_path), "--pdf-engine=xelatex"],
+                [
+                    "pandoc",
+                    str(tex_path),
+                    "-o",
+                    str(output_path),
+                    "--pdf-engine=xelatex",
+                    "--pdf-engine-opt=-no-shell-escape",
+                ],
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,
                 cwd=working_dir,
             )
-            stdout, stderr = process.communicate()
+            try:
+                stdout, stderr = process.communicate(timeout=30)
+            except subprocess.TimeoutExpired:
+                process.kill()
+                process.communicate()
+                return False
 
             if process.returncode == 0 or output_path.exists():
                 return True