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MCP Security Architecture

Overview

The MCP (Model Context Protocol) implementation includes a secure credential management system designed to eliminate password exposure in API calls and system logs while maintaining security best practices.

Solution Architecture

SharedCredentialManager

The system uses a SharedCredentialManager class that implements secure credential storage using /dev/shm (RAM-based filesystem):

Key Security Features:

  1. RAM-Only Storage: Credentials stored in /dev/shm (memory filesystem)

    • No persistent disk storage
    • Automatically cleared on container restart
    • No password files left on filesystem

  2. Multi-Worker Support: Works across Gunicorn worker processes

    • File-based locking for thread/process safety
    • Shared storage accessible by all workers
    • Consistent token access across load-balanced requests

  3. Secure Token Generation:

    • Cryptographically secure tokens using secrets.token_urlsafe(32)
    • 256-bit entropy tokens
    • Unpredictable token values

  4. File Security:

    • Restrictive permissions (600 - owner read/write only)
    • Atomic file operations with exclusive locking
    • Temporary file patterns for safe writes

  5. Automatic Cleanup:

    • Expired tokens automatically removed
    • Cleanup on token access and creation
    • Manual revocation support

Workflow

Token Creation

1. User calls create_credential_token with username/password/database
2. System generates secure 32-byte token
3. Credentials stored in /dev/shm/mcp_credentials/token_<hash>.json
4. File permissions set to 600 (owner only)
5. Token returned to user

Token Usage

1. User calls execute_sql with token (no password needed)
2. System looks up token in /dev/shm storage
3. Credentials retrieved and used for database connection
4. No password exposure in logs or API calls

Token Cleanup

1. Automatic cleanup on expired tokens
2. Manual revocation available
3. All files cleared on container restart
4. No persistent credential storage

Configuration

  • Default Expiry: 30 minutes
  • Storage Location: /dev/shm/mcp_credentials/
  • File Permissions: 600 (owner read/write only)
  • Thread Safety: File locking with fcntl

Production Deployment

The system is designed for multi-worker Gunicorn deployments:

CMD gunicorn --worker-tmp-dir /dev/shm --workers=2 --threads=4 \
    --worker-class=gthread --bind 0.0.0.0:5000 "sql2csv:create_app()"

Key requirements:

  • /dev/shm must be available (standard in Docker containers)
  • Multiple workers supported via shared filesystem storage
  • Workers share credential tokens seamlessly

MCP Tool Usage

create_credential_token

Creates a secure token for database credentials:

{
  "name": "create_credential_token",
  "arguments": {
    "database": "pdb21",
    "username": "RNTMGR2",
    "password": "secretpassword",
    "expiry_minutes": 30
  }
}

execute_sql

Executes SQL using the secure token:

{
  "name": "execute_sql",
  "arguments": {
    "database": "pdb21",
    "credential_token": "abc123...",
    "sql": "SELECT * FROM users"
  }
}

revoke_credential_token

Immediately revokes a token:

{
  "name": "revoke_credential_token",
  "arguments": {
    "credential_token": "abc123..."
  }
}