Module rbac 

Role-based access control (RBAC) middleware for the proxy.

This module enforces per-role tool access policies on authenticated requests. It reads JWT claims from RouterRequest extensions, maps claim values to named roles via a configurable mapping, and applies per-role allow/deny lists to both tools/call and tools/list requests.

How role resolution works

1. The auth layer (JWT or introspection) validates the token and inserts TokenClaims into the request extensions.
2. RbacConfig reads a configured claim (e.g. "scope", "role", "groups") from those claims.
3. The claim value is matched against role_mapping.mapping to resolve a role name (e.g. "read-only" -> "reader").
4. The resolved role’s allow_tools and deny_tools lists determine access.

If no TokenClaims are present in the request extensions (e.g. unauthenticated or bearer-token-only requests), the RBAC layer passes the request through without restriction.

Allow/deny list semantics

Each role can define an allow list, a deny list, or both:

• Allow list only: only the listed tools are accessible. All others are denied.
• Deny list only: all tools are accessible except those listed.
• Both: a tool must appear in the allow list AND not appear in the deny list.
• Neither (empty lists): the role has unrestricted access (e.g. an admin role).

Interaction with capability filtering

RBAC runs on top of the static capability filter configured per backend. The final set of visible tools is the intersection of what the backend exposes and what the role permits – RBAC can only further restrict, never widen, the tools a client can see or call.

Configuration example

[auth]
type = "jwt"
issuer = "https://auth.example.com"
audience = "mcp-proxy"
jwks_uri = "https://auth.example.com/.well-known/jwks.json"

[[auth.roles]]
name = "admin"
# Empty allow/deny = unrestricted access

[[auth.roles]]
name = "reader"
allow_tools = ["files/read_file", "files/list_dir"]

[[auth.roles]]
name = "developer"
deny_tools = ["admin/restart", "admin/shutdown"]

[auth.role_mapping]
claim = "scope"

[auth.role_mapping.mapping]
admin = "admin"
read-only = "reader"
dev = "developer"

Enforcement

RbacService is a Tower middleware that wraps the proxy’s inner service. On tools/call requests, it checks the tool name against the resolved role before forwarding. On tools/list responses, it filters out tools the role cannot access. Denied calls receive a JSON-RPC InvalidParams error with a message identifying the role and tool.

Structs

RbacConfig

Resolved RBAC rules.

RbacService

Middleware that enforces RBAC on tool calls and list responses.