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fix(mcp): RFC 9728 protected-resource metadata path + audience binding
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Codex/RFC review showed that Claude Desktop addresses the MCP resource
as <PUBLIC_URL>/mcp (the streamable-HTTP endpoint) rather than the
base URL. Per RFC 9728 the protected-resource metadata then lives at
.well-known/oauth-protected-resource inserted between host and path:

  https://mcp.buildmymcpserver.com/.well-known/oauth-protected-resource/<slug>/mcp

Runner template now:
  - publishes `resource: <PUBLIC_URL>/mcp`
  - sets WWW-Authenticate to the RFC 9728 well-known URL
  - serves /.well-known/oauth-protected-resource[/*] so the metadata
    answers at both the legacy and RFC paths during transition
  - accepts both audiences (<PUBLIC_URL>/mcp + <PUBLIC_URL>) during
    rollout so already-issued tokens keep working

API:
  - resolveServerByResource() tries port first, then path segment
    (production path-routing), with a guard against treating "mcp" as
    a tenant slug
  - AS metadata advertises resource_parameter_supported: true

nginx (scripts/setup-runner-tls.sh + scripts/bmm-mcp-runners.nginx):
  - new location matches /.well-known/oauth-protected-resource/<slug>/...
    and proxies to the slug's runner with the slug stripped, so the
    runner sees the local well-known path

Docs (oauth + api-reference) updated to the RFC paths.
This commit is contained in:
Marco Sadjadi
2026-05-28 20:54:27 +02:00
parent 1d845abf92
commit 4d136c4fb2
6 changed files with 161 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files

39
apps/generator/src/lib/render.ts
View File

@@ -59,9 +59,24 @@ import Fastify from 'fastify';
import { createRemoteJWKSet, jwtVerify } from 'jose';
import { randomUUID } from 'node:crypto';
const PUBLIC_URL = process.env.PUBLIC_URL ?? 'http://localhost:3000';
const CONTROL_PLANE_URL = process.env.CONTROL_PLANE_URL ?? 'http://host.docker.internal:4000';
const OAUTH_ISSUER = process.env.OAUTH_ISSUER ?? CONTROL_PLANE_URL + '/oauth';
function stripTrailingSlash(value) {
return value.replace(/\\/$/, '');
}
function protectedResourceMetadataUrl(resourceUrl) {
const url = new URL(resourceUrl);
const resourcePath = url.pathname === '/' ? '' : url.pathname;
url.pathname = '/.well-known/oauth-protected-resource' + resourcePath;
url.hash = '';
return url.toString();
}
const PUBLIC_URL = stripTrailingSlash(process.env.PUBLIC_URL ?? 'http://localhost:3000');
const CONTROL_PLANE_URL = stripTrailingSlash(process.env.CONTROL_PLANE_URL ?? 'http://host.docker.internal:4000');
const OAUTH_ISSUER = stripTrailingSlash(process.env.OAUTH_ISSUER ?? CONTROL_PLANE_URL + '/oauth');
const MCP_RESOURCE_URL = PUBLIC_URL + '/mcp';
const PROTECTED_RESOURCE_METADATA_URL = protectedResourceMetadataUrl(MCP_RESOURCE_URL);
const EXPECTED_AUDIENCES = Array.from(new Set([MCP_RESOURCE_URL, PUBLIC_URL]));
const PORT = Number.parseInt(process.env.PORT ?? '3000', 10);
const server = new McpServer(
@@ -75,15 +90,18 @@ const app = Fastify({ logger: { level: 'info' } });
app.get('/health', async () => ({ ok: true }));
app.get('/.well-known/oauth-protected-resource', async () => ({
resource: PUBLIC_URL,
const protectedResourceMetadata = async () => ({
resource: MCP_RESOURCE_URL,
authorization_servers: [OAUTH_ISSUER],
bearer_methods_supported: ['header'],
scopes_supported: ${JSON.stringify(spec.scopes)},
}));
});
app.get('/.well-known/oauth-protected-resource', protectedResourceMetadata);
app.get('/.well-known/oauth-protected-resource/*', protectedResourceMetadata);
app.get('/.well-known/oauth-authorization-server', async () => {
const r = await fetch(CONTROL_PLANE_URL + '/oauth/.well-known/oauth-authorization-server');
const r = await fetch(CONTROL_PLANE_URL + '/.well-known/oauth-authorization-server/oauth');
return await r.json();
});
@@ -96,16 +114,17 @@ app.all('/mcp', async (request, reply) => {
if (!auth || !auth.startsWith('Bearer ')) {
return reply
.code(401)
.header('WWW-Authenticate', \`Bearer resource_metadata="\${PUBLIC_URL}/.well-known/oauth-protected-resource"\`)
.header('WWW-Authenticate', \`Bearer resource_metadata="\${PROTECTED_RESOURCE_METADATA_URL}"\`)
.send({ error: 'unauthorized' });
}
const token = auth.slice(7);
try {
const { payload } = await jwtVerify(token, JWKS, {
issuer: OAUTH_ISSUER,
audience: PUBLIC_URL,
audience: EXPECTED_AUDIENCES,
});
if (payload.aud !== PUBLIC_URL) {
const audiences = Array.isArray(payload.aud) ? payload.aud : payload.aud ? [payload.aud] : [];
if (!audiences.some((aud) => EXPECTED_AUDIENCES.includes(aud))) {
return reply.code(403).send({ error: 'invalid_audience' });
}
} catch (e) {