🛡️ Sentinel: [CRITICAL] Fix pdflatex RCE and DoS vulnerabilities

[anchapin]

Severity: CRITICAL
Vulnerability: PDF compilation via pdflatex and pandoc in cli/pdf/converter.py and cli/generators/cover_letter_generator.py omitted the -no-shell-escape flag and did not enforce an execution timeout.
Impact: This allowed malicious untrusted input to execute arbitrary shell commands via LaTeX (\write18), leading to Remote Code Execution (RCE), as well as infinite compilation loops leading to Denial of Service (DoS).
Fix: Explicitly added -no-shell-escape (or --pdf-engine-opt=-no-shell-escape for pandoc) to all execution commands. Additionally added timeout=30 to process.communicate() to prevent hangs, and correctly caught subprocess.TimeoutExpired to kill the zombie processes and safely skip completion logic.
Verification: Verified via manual source checking via sed and ran full test suite (python -m pytest tests/) to ensure no regressions. All 681 tests passed successfully.

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PR created automatically by Jules for task 8184241153704705132 started by @anchapin

Summary by Sourcery

Harden PDF generation against RCE and DoS via external LaTeX tools.

Bug Fixes:

• Disable LaTeX shell escape in pdflatex and pandoc PDF compilation to prevent command execution vulnerabilities.
• Add timeouts and proper timeout handling for pdflatex and pandoc subprocesses to avoid hanging and DoS during PDF generation.

Documentation:

• Document the pdflatex/pandoc RCE and DoS vulnerability, its root cause, and required mitigations in the Sentinel security log.

[google-labs-jules]

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[sourcery-ai]

Reviewer's Guide

Hardened LaTeX/PDF generation by disabling shell escape and adding timeouts around pdflatex/pandoc subprocesses, plus documenting the security issue in Sentinel notes.

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

sequenceDiagram
    participant Caller as PdfConverter
    participant Converter as _compile_pdflatex
    participant Subproc as subprocess.Popen
    participant Proc as process

    Caller->>Converter: _compile_pdflatex(tex_path, working_dir, output_path)
    Converter->>Subproc: Popen(["pdflatex", "-interaction=nonstopmode", "-no-shell-escape", tex_path.name])
    Note right of Subproc: returns process
    Subproc-->>Converter: process

    alt process completes within 30s
        Converter->>Proc: communicate(timeout=30)
        Proc-->>Converter: stdout, stderr
        Converter->>Caller: return True or False based on
        Note right of Converter: True if returncode==0 or output_path.exists()
    else subprocess.TimeoutExpired
        Converter->>Proc: kill()
        Converter->>Proc: communicate()
        Proc-->>Converter: stdout, stderr
        Converter->>Caller: return False
    end

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File-Level Changes

Change	Details	Files
Harden pdflatex invocation in cover letter generator against RCE and hangs.	Added -no-shell-escape flag to pdflatex command to prevent shell execution via LaTeX. Wrapped process.communicate() with a 30-second timeout and handled subprocess.TimeoutExpired by killing the process and avoiding success flags. Applied the same timeout-and-kill pattern to the pandoc fallback path, including not marking PDF creation as successful on timeout.	cli/generators/cover_letter_generator.py
Secure core PDF converter’s pdflatex and pandoc pipelines with shell-escape restrictions and timeouts.	Added -no-shell-escape to pdflatex invocation to disable LaTeX shell escapes. Configured pandoc to pass --pdf-engine-opt=-no-shell-escape through to xelatex. Introduced a 30-second timeout when waiting on subprocesses and treated timeouts as failures after killing the child process.	cli/pdf/converter.py
Document the pdflatex RCE/DoS vulnerability and mitigation in Sentinel security notes.	Added a new Sentinel entry describing the missing -no-shell-escape and timeout as a critical issue. Documented learnings about dangerous defaults in external build tools and the need for explicit timeouts. Recorded prevention guidelines for always using -no-shell-escape and timeouts in PDF compilation pipelines.	.jules/sentinel.md

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[sourcery-ai]

Hey - I've left some high level feedback:

• The subprocess timeout/kill logic is duplicated across pdflatex and pandoc calls; consider extracting a small helper (e.g., run_with_timeout(cmd, cwd, timeout=30)) to centralize behavior and make future changes less error-prone.
• The hardcoded timeout=30 value is repeated in multiple places; promoting this to a shared constant (or configuration option) would make it easier to adjust globally if needed and keep the timeout policy consistent.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The subprocess timeout/kill logic is duplicated across pdflatex and pandoc calls; consider extracting a small helper (e.g., `run_with_timeout(cmd, cwd, timeout=30)`) to centralize behavior and make future changes less error-prone.
- The hardcoded `timeout=30` value is repeated in multiple places; promoting this to a shared constant (or configuration option) would make it easier to adjust globally if needed and keep the timeout policy consistent.

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