🛡️ Sentinel: [High] Fix LaTeX RCE and DoS vulnerabilities

[anchapin]

🚨 Severity: HIGH
💡 Vulnerability: Potential Remote Code Execution (RCE) via pdflatex shell execution capabilities and Denial of Service (DoS) via hanging processes.
🎯 Impact: Untrusted LaTeX templates could execute arbitrary system commands or cause the application to hang indefinitely.
🔧 Fix: Added -no-shell-escape flags to pdflatex and pandoc commands and introduced timeout=30 with proper TimeoutExpired exception handling and process cleanup.
✅ Verification: Ran pytest tests/test_pdf_security.py to verify the timeout handling and -no-shell-escape injection on the mocked subprocesses.

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PR created automatically by Jules for task 8755560032578265345 started by @anchapin

Summary by Sourcery

Harden LaTeX-based PDF generation against RCE and hanging processes in the cover letter generator and PDF converter.

Bug Fixes:

• Disable LaTeX shell command execution by adding no-shell-escape options to pdflatex and pandoc invocations used for PDF generation.
• Prevent potential DoS from hanging LaTeX compilation by enforcing a 30-second timeout with proper process termination and error handling in PDF generation routines.

Documentation:

• Document the LaTeX compilation RCE and DoS vulnerability, its root cause, and the implemented mitigations in the Sentinel security notes.

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[sourcery-ai]

Reviewer's Guide

Adds shell-escape hardening and timeout-based DoS protection to LaTeX PDF generation via pdflatex and pandoc, and documents the vulnerability in Sentinel notes.

Sequence diagram for hardened LaTeX PDF compilation with timeout and no-shell-escape

sequenceDiagram
    participant Generator as CoverLetterGenerator
    participant Converter as PDFConverter
    participant Subprocess as subprocess
    participant Pdflatex as pdflatex/pandoc

    Generator->>Converter: _compile_pdf/_compile_pdflatex/_compile_pandoc
    Converter->>Subprocess: Popen(["pdflatex","-interaction=nonstopmode","-no-shell-escape",tex_path.name])
    Note over Converter,Subprocess: or Popen(["pandoc",tex_path,"-o",output_path,"--pdf-engine=xelatex","--pdf-engine-opt=-no-shell-escape"]) 
    Subprocess->>Pdflatex: start process

    alt within 30s
        Converter->>Subprocess: process.communicate(timeout=30)
        Subprocess-->>Converter: stdout, stderr
        Converter->>Converter: check process.returncode or output_path.exists()
        Converter-->>Generator: return True/False
    else timeout
        Converter->>Subprocess: process.communicate(timeout=30)
        Subprocess-->>Converter: TimeoutExpired
        Converter->>Subprocess: process.kill()
        Converter->>Subprocess: process.communicate()
        Converter-->>Generator: return False
    end

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File-Level Changes

Change	Details	Files
Harden CoverLetterGenerator LaTeX PDF compilation against RCE and hanging processes.	Add -no-shell-escape to pdflatex invocation arguments. Add --pdf-engine-opt=-no-shell-escape to pandoc-based PDF generation fallback. Wrap subprocess.communicate with a 30-second timeout and handle TimeoutExpired by killing the process, draining pipes, and returning failure. Keep existing success condition based on process returncode or output file existence.	cli/generators/cover_letter_generator.py
Apply the same LaTeX compilation hardening to the generic PDF converter.	Add -no-shell-escape to pdflatex invocation arguments in the converter. Add --pdf-engine-opt=-no-shell-escape to pandoc invocation. Use subprocess.communicate with a 30-second timeout and on timeout kill the process, drain output, and return False. Preserve existing return conditions on successful compilation or output file presence.	cli/pdf/converter.py
Document the LaTeX RCE and DoS vulnerability and its mitigations in Sentinel security notes.	Add a new dated section describing the RCE risk from pdflatex and pandoc shell execution. Explain the DoS risk from hanging LaTeX compilation processes. Document prevention measures including -no-shell-escape flags, communicate timeouts, and process cleanup.	.jules/sentinel.md

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[sourcery-ai]

Hey - I've left some high level feedback:

• The timeout and Popen handling logic for pdflatex/pandoc is duplicated in multiple places; consider extracting a shared helper (with a single DEFAULT_LATEX_TIMEOUT constant) to reduce repetition and keep behavior consistent across callers.
• On timeout or non-zero return codes, the stdout/stderr from pdflatex/pandoc are discarded; consider logging or surfacing these messages so it's easier to diagnose why PDF generation failed or hit the timeout.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The timeout and `Popen` handling logic for `pdflatex`/`pandoc` is duplicated in multiple places; consider extracting a shared helper (with a single `DEFAULT_LATEX_TIMEOUT` constant) to reduce repetition and keep behavior consistent across callers.
- On timeout or non-zero return codes, the stdout/stderr from `pdflatex`/`pandoc` are discarded; consider logging or surfacing these messages so it's easier to diagnose why PDF generation failed or hit the timeout.

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