This document outlines the security measures implemented in the Claude Gemini MCP Integration project to protect against common vulnerabilities and ensure safe operation.

Files affected:

• gemini_helper.py:80 (shell=True with user input)
• gemini_mcp_server.py:158 (create_subprocess_shell with user input)
• .claude/scripts/slim_gemini_hook.py:117 (subprocess arguments)

Fix implemented:

• Replaced shell=True with argument lists
• Added input validation for model names and prompts
• Implemented strict character validation for command arguments
• Used minimal environment variables in subprocess calls

Security impact: Prevents arbitrary command execution via malicious input

Files affected:

• gemini_helper.py:178 (unrestricted file access)
• gemini_mcp_server.py:276-277 (direct path checking)
• Hook scripts file validation

Fix implemented:

• Added validate_path_security() function across all modules
• Implemented path resolution and boundary checking
• Restricted file access to current directory tree only
• Added file type validation with allowlist approach

Security impact: Prevents access to files outside project directory

Files affected: All prompt construction areas

Fix implemented:

• Added sanitize_for_prompt() function to all modules
• Filters dangerous prompt injection patterns
• Escapes control characters
• Limits input length to prevent buffer overflow
• Validates input types before processing

Security impact: Prevents manipulation of AI model behavior via malicious prompts

Files affected: Error handling and logging throughout codebase

Fix implemented:

• Added API key validation with minimum length checks
• Implemented regex-based secret redaction in error messages
• Sanitized subprocess environment variables
• Removed sensitive data from logs and error outputs

Security impact: Prevents API keys and tokens from being leaked in logs or errors

Files affected: All parameter handling functions

Fix implemented:

• Added comprehensive type checking for all inputs
• Implemented bounds checking for strings and numeric values
• Added enumeration validation for analysis types and scopes
• Enhanced error handling with secure failure modes

Security impact: Prevents various attack vectors through malformed input

1. Input Validation Layer

   • Type checking at entry points
   • Length limits and bounds checking
   • Enumeration validation
   • Character set restrictions

2. Sanitization Layer

   • Prompt injection pattern filtering
   • Path normalization and validation
   • Secret redaction in outputs
   • Control character filtering

3. Execution Layer

   • Subprocess argument lists (no shell execution)
   • Minimal environment variables
   • Path boundary enforcement
   • File type restrictions

4. Output Layer

   • Error message sanitization
   • Log data filtering
   • Response size limits
   • Structured error responses

Purpose: Prevents prompt injection attacks Features:

• Filters dangerous instruction patterns
• Removes control characters
• Enforces length limits
• Case-insensitive pattern matching

Purpose: Prevents path traversal attacks Features:

• Path resolution and normalization
• Directory boundary checking
• File existence validation
• Type validation (file vs directory)

Purpose: Secure credential handling Features:

• Minimum length validation
• Type checking
• Secret pattern redaction in errors
• Environment isolation

ALLOWED_EXTENSIONS = {
    '.py', '.js', '.ts', '.java', '.cpp', '.c', '.rs',     # Programming
    '.vue', '.html', '.css', '.scss', '.sass', '.jsx', '.tsx',  # Frontend
    '.json', '.yaml', '.toml', '.md', '.txt'               # Configuration
}

• Maximum file size: 80KB (81,920 bytes)
• Maximum lines: 800 lines per file
• Maximum prompt: 1MB (1,000,000 characters)

• Allowed access: Current directory tree only
• Blocked patterns: ../, symbolic links outside tree
• Validation: Path resolution and boundary checking

# SECURE: Use argument lists
process = subprocess.Popen(
    ["gemini", "-m", model_name, "-p", prompt],
    shell=False,  # Critical: Never use shell=True
    env={"PATH": os.environ.get("PATH", "")}  # Minimal environment
)

# INSECURE: Never use shell commands
# cmd = f"gemini -m {model_name} -p {prompt}"  # VULNERABLE
# subprocess.run(cmd, shell=True)              # NEVER DO THIS

• Minimal environment: Only PATH variable passed
• No shell expansion: Argument lists prevent injection
• Process isolation: Limited subprocess permissions

# API key patterns automatically redacted
error_message = re.sub(r'AIzaSy[A-Za-z0-9_-]{33}', '[API_KEY_REDACTED]', error_message)
error_message = re.sub(r'sk-[A-Za-z0-9_-]{32,}', '[API_KEY_REDACTED]', error_message)
error_message = re.sub(r'Bearer [A-Za-z0-9_.-]{10,}', '[TOKEN_REDACTED]', error_message)

• Generic error messages for security failures
• No sensitive information in user-facing errors
• Detailed logging for debugging (sanitized)
• Graceful degradation on security violations

1. Input Validation

   • Always validate input types and ranges
   • Use allowlists instead of blocklists when possible
   • Implement fail-secure defaults

2. Path Handling

   • Always use validate_path_security() before file operations
   • Never trust user-provided paths
   • Use absolute paths internally

3. Subprocess Calls

   • Never use shell=True with user input
   • Always use argument lists
   • Validate command arguments before execution

4. Prompt Construction

   • Always use sanitize_for_prompt() for user inputs
   • Never interpolate user data directly into prompts
   • Validate AI model responses

5. Error Handling

   • Sanitize error messages before logging
   • Never expose internal paths or configurations
   • Use structured error responses

1. Environment Security

   • Keep API keys secure and rotate regularly
   • Use environment variables for sensitive configuration
   • Monitor for unusual activity in logs

2. File Organization

   • Keep sensitive files outside project directory
   • Use appropriate file permissions
   • Regularly review file access patterns

3. Update Management

   • Keep dependencies updated
   • Monitor security advisories
   • Test security updates in isolated environments

• CWE-22: Path Traversal - ✅ Fixed with boundary validation
• CWE-78: Command Injection - ✅ Fixed with argument lists
• CWE-94: Code Injection - ✅ Fixed with input sanitization
• CWE-200: Information Exposure - ✅ Fixed with secret redaction
• CWE-20: Input Validation - ✅ Fixed with comprehensive validation

All security improvements are tracked in git history with detailed commit messages:

• Path validation functions added
• Input sanitization implemented
• Subprocess security hardened
• Error handling secured

1. Static Analysis

   • Run security scanners on codebase
   • Check for hardcoded secrets
   • Validate input handling patterns

2. Dynamic Testing

   • Test with malicious file paths
   • Attempt prompt injection attacks
   • Verify error message sanitization

3. Integration Testing

   • Test security boundaries
   • Verify access control enforcement
   • Validate error handling paths

For security issues or questions:

• Create issue in project repository (for non-sensitive issues)
• Review security documentation before implementation
• Follow secure coding practices in all contributions

• CRITICAL: Fixed 5 major security vulnerabilities
• Added comprehensive input validation framework
• Implemented secure subprocess handling
• Added path traversal protection
• Enhanced error handling security
• Created comprehensive security documentation

Last Updated: 2025-01-12 Security Review Status: ✅ Current Next Review Due: 2025-04-12