User based tool filter

Trusted Header Public Key Configuration¶

The MCP Broker can filter tools based on a signed JWT in the x-authorized-tools header. This enables identity-based tool filtering when integrated with an external authorization system.

How It Works¶

An upstream authorization system validates the user's identity
It creates a signed JWT containing the user's allowed tools in an allowed-tools claim
This JWT is passed to the broker via the x-authorized-tools header
The broker validates the JWT signature and filters tools/list responses accordingly

JWT Payload Format¶

The allowed-tools claim should contain a JSON object mapping server routes to tool arrays:

{
  "allowed-tools": "{\"mcp-test/server1-route\":[\"tool_a\",\"tool_b\"],\"mcp-test/server2-route\":[\"tool_c\"]}",
  "exp": 1760004918,
  "iat": 1760004618
}

Example Key Pair Generation¶

Generate an ECDSA P-256 key pair:

# Generate private key
openssl ecparam -name prime256v1 -genkey -noout -out private-key.pem

# Extract public key
openssl ec -in private-key.pem -pubout -out public-key.pem

Create Kubernetes Secret¶

kubectl create secret generic trusted-headers-public-key \
  --from-file=key=public-key.pem \
  -n mcp-system

Configure the Broker¶

Reference the secret in the broker deployment:

env:

  - name: TRUSTED_HEADER_PUBLIC_KEY
    valueFrom:
      secretKeyRef:
        name: trusted-headers-public-key
        key: key

When this environment variable is set, the broker will validate any x-authorized-tools header using ES256 and filter the tools list accordingly. If validation fails, an empty tools list is returned.

Example AuthPolicy that uses this method¶

An example AuthPolicy that implements the x-authorized-tools can be found at Sample Tool Filtering