Security Best Practices For Latex Installations On Linux
Restricting System Access
LaTeX installations on Linux consist of sensitive source code and documents that should only be accessed by authorized users. To prevent unwanted modifications, the system administrator can configure user permissions to limit which users can view, edit, execute, or delete LaTeX files.
The first step is to create a separate Linux user account specifically for running the LaTeX installation. Give this LaTeX user account the most restrictive permissions necessary for LaTeX to function properly. Avoid granting the LaTeX user sudo or root privileges.
Use Linux filesystem permissions to control LaTeX user account access. Set the umask to 007 or 027 to remove read and execute permissions for newly created files and directories. Configure POSIX ACLs to enforce least privilege file access policies.
Enable Linux security modules like SELinux to provide mandatory access controls so all system files and resources are isolated and cannot be tampered with by unauthorized users or processes. SELinux policies will be covered later in the article.
In addition to restricting user permissions, configure iptables firewall rules to limit network access to the system running LaTeX. Restrict inbound connections only to essential protocols and services needed for LaTeX, while denying everything else. This will prevent remote attackers from accessing the system.
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Safeguarding Source Code
The LaTeX installation depends on critical source code and custom configuration files that should be protected from data loss scenarios. Use a version control system (VCS) like Git to track all source code changes in case they need to be rolled back.
Configure daily Git commits to backup the latest version of the LaTeX code repositories. Then mirror the Git repository to an offsite location to safeguard against infrastructure failures. Potential offsite repositories include GitHub, GitLab, Bitbucket, or an internal file server at another data center.
In addition to version control, establish backup policies like scheduled rsync jobs to copy the entire LaTeX directory, custom configs, and generated documents to a secure storage server or cloud storage provider on a nightly basis.
Store backups in an encrypted format using utilities like gpg or 7zip to prevent unauthorized access. Validate the backup integrity by periodically restoring copies to test servers. Destroy old backups after 30 days since LaTeX documents often change frequently.
Implementing version control, encrypted offsite backups, and restoration testing ensures the LaTeX source code and outputs can be recovered in a disaster scenario.
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Verifying Packages and Dependencies
The LaTeX installation relies on many open source TeX packages and dependencies from repositories like CTAN to implement advanced typesetting functionality. Only install packages from trusted sources, otherwise a compromised LaTeX dependency could lead to remote code execution or data leakage risks.
Only enable official TeX repositories that cryptographically sign packages with GPG keys to validate authenticity. Custom repositories should go through similar signing and auditing procedures before use.
Continuously monitor all enabled TeX repositories for newly discovered vulnerabilities that get disclosed in packages LaTeX depends on. Outdated LaTeX distributions like TeX Live can contain hundreds of old vulnerable packages.
Use tools like the Debian Security Tracker to monitor relevant CVEs across LaTeX package dependencies that may require updating. Establish policies to promptly patch vulnerable Linux packages that LaTeX integrates with like Python, Perl, Ghostscript, ImageMagick, etc.
Understand the downstream impact of updating LaTeX packages since dependencies and compilation procedures often break with new package versions. Test LaTeX functionality after updates on staging servers before deployment.
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Enabling Security Features
Linux offers many built-in security modules that add protection for LaTeX installations against suspicious activities if properly configured. Take advantage of these security features beyond just relying on filesystem permissions.
Enable nightly unattended security updates using standard Linux package managers to always keep LaTeX package dependencies fully updated. Monitor update logs for info on applied fixes.
Configure the SELinux mandatory access control system in enforcing mode for all LaTeX processes and files to implement least privilege confinement. Customize strict SELinux policies using Booleans, file contexts, ports, etc. This will prevent attackers who compromise the LaTeX user account from doing extensive damage if they manage to break out.
Use the Linux Audit system to monitor critical LaTeX files and binaries. Audit watched LaTeX resources like /usr/bin/pdflatex and trigger alerts for access attempts or modification. Auditctl rules provide deep visibility into LaTeX system activities.
Consider sandboxing some LaTeX processing functions within containers to isolate processes from the underlying server. Docker configs allow custom restrictions around LaTeX container resources and capabilities.
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Monitoring Activity
Detecting security issues with LaTeX requires going beyond just preventing vulnerabilities and actively monitoring the environment for signs of breach or failure. Analyze Linux and application logs on a continuous basis to uncover anomalous LaTeX behaviors.
Centralize LaTeX server logs into aggregation platforms like Elastic, Splunk, or LogRhythm for advanced correlation and pattern recognition abilities. Trigger alerts if pdflatex crash events surge indicating a bad Tex package. Detect brute force attacks against the LaTeX user account via SSH logs.
Implement file integrity monitoring tools like Tripwire, AIDE, or Osiris to generate checksums of critical LaTeX files like texmf.cnf so any unauthorized changes are detected indicating foul play. Diff file integrity reports and investigate the root causes of latex binary or configuration alterations.
Graph relevant LaTeX server performance metrics over time as another data source, watching for resource exhaustion issues across CPU, memory, disks, network that hurt availability. Set performance baselines so anomalies indicate problems.
Export Nginx access logs from LaTeX front-end servers to identify attempted exploitation of any exposed web APIs using techniques like SQLi or RCE. Fail2ban can help block malicious requests.
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Testing and Validation
Assess the security posture of LaTeX deployments through both static analysis testing and active penetration exercises to validate the configurations and uncover potential issues.
Leverage SAST/DAST tools like Checkmarx, Veracode, or OWASP ZAP to scan LaTeX web servers and repositories for risky coding flaws around injections, authentications, encryptions, etc. that may impact the installations.
Dynamically test LaTeX's attack surface and configurations using penetration testing exercises mimicking threat actors to find security gaps. Attempt privilege escalations, service exploits, vulnerability scans on internal/external networks. Validate firewall , SELinux, and system hardening protections.
Build a matrix of CIS Linux Benchmark controls and map coverage to LaTeX servers. Perform audits against the benchmark to validate 70% or more adherence across system settings like access restrictions, logging, malware defense, and other host protections.
Construct LaTeX regression testing suites that run Tex test cases after system changes to ensure continuity of document building workflows. The LaTeX installation has many integration touch points that can unintentionally break.
Ongoing security testing provides confidence in the LaTeX deployment protections against both external and insider threats attempting to manipulate sensitive documents or pivot laterally to other assets.
