1. Security Overview
2. Threat Model
3. Security Features
4. Known Limitations
5. Best Practices
6. Vulnerability Reporting

Todo CLI is designed with a security-first mindset for local, single-user task management. The application follows the principle of least privilege and maintains an air-gapped architecture with no network communication.

Core Security Principles:

• 🔒 Local-First: All data stays on the user's machine
• 🚫 No Network: Zero external communication
• ✅ Input Validation: All user inputs are validated and sanitized
• 🔐 File Permissions: Appropriate Unix permissions on data files (0644)
• 📦 Minimal Dependencies: Limited attack surface (4 direct dependencies)
• 🔍 Transparency: Open source for security audits

graph TB
    subgraph "Protected ✅"
        A[Path Traversal]
        B[Command Injection]
        C[SQL Injection]
        D[Network Attacks]
    end

    subgraph "Partial Protection ⚠️"
        E[Data at Rest]
        F[Physical Access]
        G[Memory Dumps]
    end

    subgraph "User Responsibility ❌"
        H[Malicious Binary]
        I[Compromised OS]
        J[Backup Security]
    end

    style A fill:#4caf50
    style B fill:#4caf50
    style C fill:#4caf50
    style D fill:#4caf50
    style E fill:#ff9800
    style F fill:#ff9800
    style G fill:#ff9800
    style H fill:#ef5350
    style I fill:#ef5350
    style J fill:#ef5350

Zero Network Communication - The application never makes network calls, eliminating entire classes of vulnerabilities:

• ✅ No data exfiltration risk
• ✅ No remote code execution
• ✅ No dependency on external services
• ✅ Works completely offline

All user inputs are validated before processing:

Example Validation:

func validateTitle(title string) error {
    if strings.TrimSpace(title) == "" {
        return errors.New("title cannot be empty")
    }
    if len(title) > 200 {
        return errors.New("title too long")
    }
    // Check for control characters
    for _, r := range title {
        if unicode.IsControl(r) && r != '\n' && r != '\t' {
            return errors.New("invalid characters")
        }
    }
    return nil
}

Secure Defaults:

# Data directory permissions
~/.todo-cli/          # drwxr-xr-x (0755)
  tasks.json          # -rw-r--r-- (0644)
  backups/            # drwxr-xr-x (0755)
    backup_*.json     # -rw-r--r-- (0644)

Path Sanitization:

• All paths resolved to absolute
• Restricted to ~/.todo-cli/ directory
• No path traversal allowed
• Atomic file writes for data integrity

Only 4 direct dependencies from trusted sources:

• spf13/cobra - CLI framework (used by kubectl, Hugo)
• fatih/color - Terminal colors
• manifoldco/promptui - Interactive prompts
• gopkg.in/yaml.v3 - YAML parser

All dependencies are version-pinned in go.mod with checksums in go.sum.

Recommended Mitigations:

# Enable full-disk encryption
# macOS: sudo fdesetup enable
# Linux: Use LUKS during installation
# Windows: Enable BitLocker

# Prevent command history leakage
export HISTIGNORE="todo*"

# Restrict data directory access
chmod 700 ~/.todo-cli

Data Security:

# Restrict access to data directory
chmod 700 ~/.todo-cli

# Encrypt backups for external storage
tar czf - ~/.todo-cli/backups | \
    gpg -c > todo-backups-$(date +%Y%m%d).tar.gz.gpg

Task Content:

• ✅ Use code names for sensitive projects
• ✅ Be mindful when sharing screen
• ❌ Don't store passwords or API keys
• ❌ Avoid highly sensitive personal data without encryption

Secure Coding Checklist:

• All user inputs validated
• File paths sanitized
• No shell command execution
• Errors don't leak sensitive info
• Dependencies kept up to date
• Appropriate file permissions set

Security Testing:

# Static analysis
go vet ./...
staticcheck ./...

# Dependency vulnerabilities
go list -json -m all | nancy sleuth

# Build with security flags
go build -race -buildmode=pie

If you discover a security vulnerability:

1. DO NOT open a public GitHub issue
2. Email: gouranga.samrat@gmail.com
3. Include:
   • Description of vulnerability
   • Steps to reproduce
   • Potential impact
   • Suggested fix (if any)

Response Timeline:

• 24 hours: Initial acknowledgment
• 72 hours: Preliminary assessment
• 7 days: Detailed response with timeline
• 30 days: Fix released (critical issues)

We follow responsible disclosure - vulnerabilities are fixed privately before public disclosure.

Todo CLI Security Strengths:

• ✅ Air-gapped (no network)
• ✅ Input validation throughout
• ✅ Minimal dependencies
• ✅ Secure file permissions
• ✅ Open source & auditable

User Responsibilities:

• Enable OS-level encryption
• Secure backup storage
• Keep dependencies updated
• Follow security best practices

Remember: Security is a shared responsibility between the application and its users.

Last Updated: 2024-03-12 Security Contact: gouranga.samrat@com