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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Feature Proposal: Secure Tool/Resource/Prompt Decorators with Auth + Encrypted I/O","articleBody":"### Description\n\n🚀 Feature Request\n\nI would like to propose adding a secure wrapper layer to @mcp.tool, @mcp.resource, and @mcp.prompt that supports:\n\n1. Authentication (Auth)\n\nAbility to pass an auth function (e.g. verify_identity()) that can validate JWT, Certs, or TEE Attestation before executing the function.\n\nAuthentication should be bidirectional - we need to verify both:\n  1. Client authentication - Is the client authorized to use the tool?\n  2. Tool/Server authentication - Is the tool legitimate and trustworthy?\n\n\nIf authentication fails, return a proper MCP Error (e.g. 403 Forbidden).\n\n2. Key Negotiation Mechanism\n\nClient provides a public key (PK) or session token.\n\nServer performs Diffie-Hellman (ECDH) or TLS/mTLS handshake to derive a session key.\n\nSession key is stored in context and used for symmetric encryption/decryption of I/O.\n\n3. Unified Secure Interface\n\nDevelopers could write secure MCP functions like this:\n\n```\n@mcp.secure_tool(auth=verify_identity, encrypt=True)\nasync def trade(symbol: str, amount: float) -\u003e str:\n    return f\"Trade {amount} {symbol} executed\"\n\n```\nAnd the same approach could apply to resource and prompt.\n\n🔹 Example Implementation\n\n```\nimport functools\nfrom mcp.server.fastmcp import FastMCP, tool, resource, prompt\nfrom mcp.server.models import Error\nfrom cryptography.hazmat.primitives.ciphers.aead import AESGCM\nimport os, base64\n\nmcp = FastMCP(\"SecureApp\")\n\n# ========== Simple Key Management ==========\nSESSION_KEY = AESGCM.generate_key(bit_length=128)\naesgcm = AESGCM(SESSION_KEY)\nNONCE_SIZE = 12\n\ndef encrypt(data: str) -\u003e str:\n    nonce = os.urandom(NONCE_SIZE)\n    ct = aesgcm.encrypt(nonce, data.encode(), None)\n    return base64.b64encode(nonce + ct).decode()\n\ndef decrypt(token: str) -\u003e str:\n    raw = base64.b64decode(token)\n    nonce, ct = raw[:NONCE_SIZE], raw[NONCE_SIZE:]\n    pt = aesgcm.decrypt(nonce, ct, None)\n    return pt.decode()\n\n# ========== Auth Function ==========\ndef verify_identity() -\u003e bool:\n    # TODO: implement JWT / CERT / Attestation validation\n    return True\n\n# ========== Decorator Factory ==========\ndef secure_wrapper(deco, auth=None, encrypt_io=False, *args, **kwargs):\n    def decorator(func):\n        @deco(*args, **kwargs)   # wrap original MCP decorator\n        @functools.wraps(func)\n        async def wrapper(*f_args, **f_kwargs):\n            # Auth check\n            if auth and not auth():\n                raise Error(code=403, message=\"Authentication failed\")\n\n            # Decrypt inputs\n            if encrypt_io:\n                f_kwargs = {k: decrypt(v) if isinstance(v, str) else v \n                            for k, v in f_kwargs.items()}\n\n            # Execute\n            result = await func(*f_args, **f_kwargs) if callable(func) else func\n\n            # Encrypt outputs\n            if encrypt_io and isinstance(result, str):\n                result = encrypt(result)\n\n            return result\n        return wrapper\n    return decorator\n\n# Three secure variants\ndef secure_tool(auth=None, encrypt_io=False, *args, **kwargs):\n    return secure_wrapper(tool, auth, encrypt_io, *args, **kwargs)\n\ndef secure_resource(auth=None, encrypt_io=False, *args, **kwargs):\n    return secure_wrapper(resource, auth, encrypt_io, *args, **kwargs)\n\ndef secure_prompt(auth=None, encrypt_io=False, *args, **kwargs):\n    return secure_wrapper(prompt, auth, encrypt_io, *args, **kwargs)\n\n# ========== Usage Example ==========\n@secure_tool(auth=verify_identity, encrypt_io=True)\nasync def add(a: int, b: int) -\u003e str:\n    return f\"sum={a+b}\"\n\n@secure_resource(\"secure://greet/{name}\", auth=verify_identity, encrypt_io=True)\ndef greeting(name: str) -\u003e str:\n    return f\"Hello, {name}!\"\n\n@secure_prompt(auth=verify_identity, encrypt_io=True)\ndef greet_user(name: str) -\u003e str:\n    return f\"Write a secure greeting for {name}\"\n\n```\n\n🔹 Encrypted I/O Flow\n\nInput: client encrypts arguments with session key → sends\n\nServer: decrypts args → executes function\n\nOutput: result encrypted → returned to client\n\nClient: decrypts result with the same session key\n\n\n✅ Summary\n\ntool, resource, and prompt can all uniformly support auth + encrypted I/O.\n\nImplemented via decorator factory pattern, keeping code clean.\n\nSupports pluggable JWT, Cert, TEE Attestation validation.\n\nSession key negotiation can use TLS/mTLS or ECDH.\n\nThis would make MCP safer to use in environments where sensitive data and secure tool execution are required.\n\n\n\n### References\n\n[_MR_](https://github.com/modelcontextprotocol/python-sdk/pull/1309) https://github.com/modelcontextprotocol/python-sdk/pull/1309","author":{"url":"https://github.com/wenhuizhang","@type":"Person","name":"wenhuizhang"},"datePublished":"2025-08-25T03:58:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/1305/python-sdk/issues/1305"}