@modelcontextprotocol/sdk
Version:
Model Context Protocol implementation for TypeScript
143 lines • 6.6 kB
JavaScript
import { z } from "zod";
import express from "express";
import { rateLimit } from "express-rate-limit";
import { allowedMethods } from "../middleware/allowedMethods.js";
import { InvalidRequestError, InvalidClientError, InvalidScopeError, ServerError, TooManyRequestsError, OAuthError } from "../errors.js";
// Parameters that must be validated in order to issue redirects.
const ClientAuthorizationParamsSchema = z.object({
client_id: z.string(),
redirect_uri: z.string().optional().refine((value) => value === undefined || URL.canParse(value), { message: "redirect_uri must be a valid URL" }),
});
// Parameters that must be validated for a successful authorization request. Failure can be reported to the redirect URI.
const RequestAuthorizationParamsSchema = z.object({
response_type: z.literal("code"),
code_challenge: z.string(),
code_challenge_method: z.literal("S256"),
scope: z.string().optional(),
state: z.string().optional(),
resource: z.string().url().optional(),
});
export function authorizationHandler({ provider, rateLimit: rateLimitConfig }) {
// Create a router to apply middleware
const router = express.Router();
router.use(allowedMethods(["GET", "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: 100, // 100 requests per windowMs
standardHeaders: true,
legacyHeaders: false,
message: new TooManyRequestsError('You have exceeded the rate limit for authorization requests').toResponseObject(),
...rateLimitConfig
}));
}
router.all("/", async (req, res) => {
var _a;
res.setHeader('Cache-Control', 'no-store');
// In the authorization flow, errors are split into two categories:
// 1. Pre-redirect errors (direct response with 400)
// 2. Post-redirect errors (redirect with error parameters)
// Phase 1: Validate client_id and redirect_uri. Any errors here must be direct responses.
let client_id, redirect_uri, client;
try {
const result = ClientAuthorizationParamsSchema.safeParse(req.method === 'POST' ? req.body : req.query);
if (!result.success) {
throw new InvalidRequestError(result.error.message);
}
client_id = result.data.client_id;
redirect_uri = result.data.redirect_uri;
client = await provider.clientsStore.getClient(client_id);
if (!client) {
throw new InvalidClientError("Invalid client_id");
}
if (redirect_uri !== undefined) {
if (!client.redirect_uris.includes(redirect_uri)) {
throw new InvalidRequestError("Unregistered redirect_uri");
}
}
else if (client.redirect_uris.length === 1) {
redirect_uri = client.redirect_uris[0];
}
else {
throw new InvalidRequestError("redirect_uri must be specified when client has multiple registered URIs");
}
}
catch (error) {
// Pre-redirect errors - return direct response
//
// These don't need to be JSON encoded, as they'll be displayed in a user
// agent, but OTOH they all represent exceptional situations (arguably,
// "programmer error"), so presenting a nice HTML page doesn't help the
// user anyway.
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;
}
// Phase 2: Validate other parameters. Any errors here should go into redirect responses.
let state;
try {
// Parse and validate authorization parameters
const parseResult = RequestAuthorizationParamsSchema.safeParse(req.method === 'POST' ? req.body : req.query);
if (!parseResult.success) {
throw new InvalidRequestError(parseResult.error.message);
}
const { scope, code_challenge, resource } = parseResult.data;
state = parseResult.data.state;
// Validate scopes
let requestedScopes = [];
if (scope !== undefined) {
requestedScopes = scope.split(" ");
const allowedScopes = new Set((_a = client.scope) === null || _a === void 0 ? void 0 : _a.split(" "));
// Check each requested scope against allowed scopes
for (const scope of requestedScopes) {
if (!allowedScopes.has(scope)) {
throw new InvalidScopeError(`Client was not registered with scope ${scope}`);
}
}
}
// All validation passed, proceed with authorization
await provider.authorize(client, {
state,
scopes: requestedScopes,
redirectUri: redirect_uri,
codeChallenge: code_challenge,
resource: resource ? new URL(resource) : undefined,
}, res);
}
catch (error) {
// Post-redirect errors - redirect with error parameters
if (error instanceof OAuthError) {
res.redirect(302, createErrorRedirect(redirect_uri, error, state));
}
else {
const serverError = new ServerError("Internal Server Error");
res.redirect(302, createErrorRedirect(redirect_uri, serverError, state));
}
}
});
return router;
}
/**
* Helper function to create redirect URL with error parameters
*/
function createErrorRedirect(redirectUri, error, state) {
const errorUrl = new URL(redirectUri);
errorUrl.searchParams.set("error", error.errorCode);
errorUrl.searchParams.set("error_description", error.message);
if (error.errorUri) {
errorUrl.searchParams.set("error_uri", error.errorUri);
}
if (state) {
errorUrl.searchParams.set("state", state);
}
return errorUrl.href;
}
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