@modelcontextprotocol/sdk
Version:
Model Context Protocol implementation for TypeScript
107 lines • 5.33 kB
JavaScript
import * as z from 'zod/v4';
import express from 'express';
import cors from 'cors';
import { verifyChallenge } from 'pkce-challenge';
import { authenticateClient } from '../middleware/clientAuth.js';
import { rateLimit } from 'express-rate-limit';
import { allowedMethods } from '../middleware/allowedMethods.js';
import { InvalidRequestError, InvalidGrantError, UnsupportedGrantTypeError, ServerError, TooManyRequestsError, OAuthError } from '../errors.js';
const TokenRequestSchema = z.object({
grant_type: z.string()
});
const AuthorizationCodeGrantSchema = z.object({
code: z.string(),
code_verifier: z.string(),
redirect_uri: z.string().optional(),
resource: z.string().url().optional()
});
const RefreshTokenGrantSchema = z.object({
refresh_token: z.string(),
scope: z.string().optional(),
resource: z.string().url().optional()
});
export function tokenHandler({ provider, rateLimit: rateLimitConfig }) {
// Nested router so we can configure middleware and restrict HTTP method
const router = express.Router();
// Configure CORS to allow any origin, to make accessible to web-based MCP clients
router.use(cors());
router.use(allowedMethods(['POST']));
router.use(express.urlencoded({ extended: false }));
// Apply rate limiting unless explicitly disabled
if (rateLimitConfig !== false) {
router.use(rateLimit({
windowMs: 15 * 60 * 1000, // 15 minutes
max: 50, // 50 requests per windowMs
standardHeaders: true,
legacyHeaders: false,
message: new TooManyRequestsError('You have exceeded the rate limit for token requests').toResponseObject(),
...rateLimitConfig
}));
}
// Authenticate and extract client details
router.use(authenticateClient({ clientsStore: provider.clientsStore }));
router.post('/', async (req, res) => {
res.setHeader('Cache-Control', 'no-store');
try {
const parseResult = TokenRequestSchema.safeParse(req.body);
if (!parseResult.success) {
throw new InvalidRequestError(parseResult.error.message);
}
const { grant_type } = parseResult.data;
const client = req.client;
if (!client) {
// This should never happen
throw new ServerError('Internal Server Error');
}
switch (grant_type) {
case 'authorization_code': {
const parseResult = AuthorizationCodeGrantSchema.safeParse(req.body);
if (!parseResult.success) {
throw new InvalidRequestError(parseResult.error.message);
}
const { code, code_verifier, redirect_uri, resource } = parseResult.data;
const skipLocalPkceValidation = provider.skipLocalPkceValidation;
// Perform local PKCE validation unless explicitly skipped
// (e.g. to validate code_verifier in upstream server)
if (!skipLocalPkceValidation) {
const codeChallenge = await provider.challengeForAuthorizationCode(client, code);
if (!(await verifyChallenge(code_verifier, codeChallenge))) {
throw new InvalidGrantError('code_verifier does not match the challenge');
}
}
// Passes the code_verifier to the provider if PKCE validation didn't occur locally
const tokens = await provider.exchangeAuthorizationCode(client, code, skipLocalPkceValidation ? code_verifier : undefined, redirect_uri, resource ? new URL(resource) : undefined);
res.status(200).json(tokens);
break;
}
case 'refresh_token': {
const parseResult = RefreshTokenGrantSchema.safeParse(req.body);
if (!parseResult.success) {
throw new InvalidRequestError(parseResult.error.message);
}
const { refresh_token, scope, resource } = parseResult.data;
const scopes = scope === null || scope === void 0 ? void 0 : scope.split(' ');
const tokens = await provider.exchangeRefreshToken(client, refresh_token, scopes, resource ? new URL(resource) : undefined);
res.status(200).json(tokens);
break;
}
// Additional auth methods will not be added on the server side of the SDK.
case 'client_credentials':
default:
throw new UnsupportedGrantTypeError('The grant type is not supported by this authorization server.');
}
}
catch (error) {
if (error instanceof OAuthError) {
const status = error instanceof ServerError ? 500 : 400;
res.status(status).json(error.toResponseObject());
}
else {
const serverError = new ServerError('Internal Server Error');
res.status(500).json(serverError.toResponseObject());
}
}
});
return router;
}
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