Introducing Ayeixa MCP Guardian: Capability Fencing & Parameter Sanitization for MCP

Ayeixa has released MCP Guardian, an open-source middleware that adds capability fencing and parameter sanitization to Model Context Protocol servers, blocking directory traversal and dangerous shell commands. The tool includes RBAC, an audit logger with SHA-256 hash chaining, and a sandboxed execution wrapper, verified by six passing unit tests.

Introducing Ayeixa MCP Guardian: Capability Fencing & Parameter Sanitization for MCP Model Context Protocol MCP empowers language models to interact directly with databases, filesystems, and CLI utilities. However, exposing tool APIs creates security vulnerabilities: unauthorized directory traversal ../../etc/passwd , destructive shell commands rm -rf , and untracked actions. Ayeixa MCP Guardian @ayeixa/mcp-guardian is a runtime capability fence and parameter sanitization middleware for Model Context Protocol servers and client tool invocations. 1. Core Architecture MCP Guardian operates as an interceptor middleware: - ToolPermissionFence : Enforces granular Role-Based Access Control RBAC and explicit tool allowlists/denylists. - InvocationSanitizer : Sanitizes parameter arguments, blocking directory traversal patterns ../ and dangerous system commands sudo , rm -rf , chmod 777 . - RuntimeAuditLogger : Records every invocation payload, argument set, and permission verdict into a tamper-evident SHA-256 cryptographic hash chain. - GuardianSandbox : Permission-gated execution wrapper evaluating authorization rules and logging audit records before dispatching to tool executors. 2. Implemented Capabilities & Test Verification Verified with hermetic unit tests: - Permission Fencing : RBAC and denied command enforcement tests/permission.test.ts . - Audit Ledger : Cryptographic hash chain validation tests/audit.test.ts . - Execution Wrapper : Permission-gated dispatch and error containment tests/sandbox.test.ts . Verification: 6/6 hermetic unit tests passing 0 failures . 3. Local Quick Start Usage Example 4. Limitations & Contributing - Pre-release v0.1.0-alpha . Provides application-level permission gating and parameter sanitization. - Public npm publication is pending. - We encourage security developers and researchers to contribute. See open good first issue tags on GitHub. License: Apache-2.0