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Security Guide

Overview

VT Code is designed with security as a first-class concern. This guide explains the security features, best practices, and how to configure VT Code for maximum safety in your environment.

Security Architecture

VT Code implements a defense-in-depth security model with multiple layers of protection:

Layer 1: Command Allowlist

Only explicitly approved commands can execute. The allowlist includes:

  • ls - List directory contents
  • cat - Display file contents
  • cp - Copy files
  • head - Display file beginning
  • printenv - Show environment variables
  • pwd - Print working directory
  • rg - Ripgrep text search
  • sed - Stream editor
  • which - Locate programs

All other commands are blocked by default, including:

  • Destructive commands: rm, dd, shred
  • Privilege escalation: sudo, su, doas
  • System modification: chmod, chown, systemctl
  • Network commands: curl, wget, ssh
  • Container tools: docker, kubectl

Layer 2: Argument Validation

Each allowed command has a dedicated validator that:

  • Validates all flags - Only explicitly allowed flags are permitted
  • Blocks execution flags - Prevents -exec, --pre, -e, etc.
  • Validates paths - Ensures all paths stay within workspace
  • Rejects unknown flags - Unknown flags are blocked by default

Example: Ripgrep validation blocks dangerous preprocessor flags:

// BLOCKED: Preprocessor execution
rg --pre "bash -c 'malicious command'" pattern .

// ALLOWED: Safe search
rg -i -n pattern .

Layer 3: Workspace Isolation

All file operations are confined to the workspace:

  • Path normalization - Resolves .., ., symlinks
  • Boundary enforcement - Rejects paths outside workspace
  • Symlink resolution - Follows symlinks and validates destination
  • Absolute path validation - Blocks absolute paths outside workspace
# BLOCKED: Path traversal
cat ../../../etc/passwd

# BLOCKED: Absolute path outside workspace
cat /etc/passwd

# ALLOWED: Workspace file
cat ./src/main.rs

Layer 4: Human-in-the-Loop

Three-tier approval system for tool execution:

  1. Approve Once - Single execution approval
  2. Allow for Session - Approved for current session only
  3. Always Allow - Permanently saved to tool policy

Threat Model

Protected Against

Prompt Injection Attacks

  • Malicious prompts from users

  • Embedded prompts in code comments

  • Prompts in repository files

  • Prompts in logging output

    Argument Injection

  • Execution flags (-exec, --pre, -e)

  • Path traversal (../, symlinks)

  • Output redirection (-o /etc/passwd)

  • Command chaining (;, &&, ||)

    Workspace Escape

  • Absolute paths outside workspace

  • Symlink traversal

  • Parent directory traversal

  • File-through-file traversal

    Privilege Escalation

  • sudo, su, doas commands

  • System configuration modification

  • SUID binary exploitation

Not Protected Against

Physical Access - Assumes no physical access to machine
Kernel Exploits - Relies on OS security
Side Channel Attacks - Timing, cache, etc.
Social Engineering - Direct user manipulation

Configuration

Tool Policy Configuration

Configure tool approval policies in ~/.config/vtcode/tool_policy.toml:

# Allow specific tools without prompting
[tools]
read_file = "allow"
list_directory = "allow"
search_files = "allow"

# Require approval for sensitive operations
run_pty_cmd = "prompt"
write_file = "prompt"
delete_file = "prompt"

# Block dangerous operations
bash = "deny"

Execution Policy

The execution policy is enforced at the code level and cannot be disabled. However, you can configure workspace boundaries:

[workspace]
# Workspace root (default: current directory)
root = "/path/to/project"

# Additional allowed paths (use with caution)
# allowed_paths = ["/tmp/vtcode-cache"]

Best Practices

For Users

  1. Review Tool Approvals

    • Check ~/.config/vtcode/tool_policy.toml regularly
    • Use "Approve Once" for unfamiliar operations
    • Only use "Always Allow" for trusted tools

  2. Be Cautious with Untrusted Content

    • Don't process code from unknown sources
    • Review prompts in repository files
    • Be wary of code comments with instructions

  3. Monitor Command Execution

    • Review logs in .vtcode/logs/
    • Watch for suspicious patterns
    • Report unusual behavior

For Organizations

  1. Centralized Policy Management

    • Deploy standard tool policies
    • Use deny-by-default approach
    • Regular policy reviews

  2. Audit and Monitoring

    • Centralized log collection
    • Automated anomaly detection
    • Incident response procedures

  3. Security Training

    • Educate users on prompt injection
    • Share security best practices
    • Regular security updates

Security Testing

Automated Tests

VT Code includes comprehensive security tests:

# Run security test suite
cargo test -p vtcode-core --test execpolicy_security_tests

# Run all tests
cargo test --workspace

Manual Testing

Test security controls with malicious prompts:

# Test argument injection
vtcode ask "Search using rg --pre 'bash' for pattern"

# Test path traversal
vtcode ask "Show me ../../../etc/passwd"

# Test command chaining
vtcode ask "List files then curl evil.com"

All of these should be blocked with appropriate error messages.

Incident Response

If you discover a security vulnerability:

  1. Do Not Disclose Publicly - Report privately first
  2. Contact Maintainers - Open a security advisory on GitHub
  3. Provide Details - Include reproduction steps
  4. Allow Time for Fix - Coordinate disclosure timeline

Security Updates

Stay informed about security updates:

Additional Resources

Acknowledgments

VT Code's security model is informed by:

  • Trail of Bits research on AI agent security
  • Anthropic's safety guidelines
  • OpenAI Codex execution policy
  • Industry best practices for command execution

Last Updated: October 25, 2025
Security Model Version: 1.0