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feat: add conformance tests for iss parameter (SEP-2468) #220
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228 changes: 228 additions & 0 deletions
228
examples/clients/typescript/auth-test-iss-validation.ts
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,228 @@ | ||
| #!/usr/bin/env node | ||
|
|
||
| /** | ||
| * Well-behaved client that validates the iss parameter in authorization responses. | ||
| * | ||
| * Per RFC 9207: | ||
| * - If the AS advertises authorization_response_iss_parameter_supported: true, | ||
| * the client MUST require iss in the redirect and MUST validate it against | ||
| * the AS metadata issuer. | ||
| * - If the AS does NOT advertise support, the client MUST reject any redirect | ||
| * that unexpectedly contains an iss parameter. | ||
| */ | ||
|
|
||
| import { createHash, randomBytes } from 'crypto'; | ||
| import { Client } from '@modelcontextprotocol/sdk/client/index.js'; | ||
| import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js'; | ||
| import { extractWWWAuthenticateParams } from '@modelcontextprotocol/sdk/client/auth.js'; | ||
| import type { FetchLike } from '@modelcontextprotocol/sdk/shared/transport.js'; | ||
| import type { Middleware } from '@modelcontextprotocol/sdk/client/middleware.js'; | ||
| import { runAsCli } from './helpers/cliRunner'; | ||
| import { logger } from './helpers/logger'; | ||
|
|
||
| interface OAuthTokens { | ||
| access_token: string; | ||
| token_type: string; | ||
| expires_in?: number; | ||
| refresh_token?: string; | ||
| scope?: string; | ||
| } | ||
|
|
||
| function generateCodeVerifier(): string { | ||
| return randomBytes(32) | ||
| .toString('base64') | ||
| .replace(/\+/g, '-') | ||
| .replace(/\//g, '_') | ||
| .replace(/=+$/, ''); | ||
| } | ||
|
|
||
| function computeS256Challenge(codeVerifier: string): string { | ||
| const hash = createHash('sha256').update(codeVerifier).digest(); | ||
| return hash | ||
| .toString('base64') | ||
| .replace(/\+/g, '-') | ||
| .replace(/\//g, '_') | ||
| .replace(/=+$/, ''); | ||
| } | ||
|
|
||
| /** | ||
| * OAuth flow that correctly validates the iss parameter per RFC 9207. | ||
| */ | ||
| async function oauthFlowWithIssValidation( | ||
| _serverUrl: string | URL, | ||
| resourceMetadataUrl: string | URL, | ||
| fetchFn: FetchLike | ||
| ): Promise<OAuthTokens> { | ||
| // 1. Fetch Protected Resource Metadata | ||
| const prmResponse = await fetchFn(resourceMetadataUrl); | ||
| if (!prmResponse.ok) { | ||
| throw new Error(`Failed to fetch PRM: ${prmResponse.status}`); | ||
| } | ||
| const prm = await prmResponse.json(); | ||
| const authServerUrl = prm.authorization_servers?.[0]; | ||
| if (!authServerUrl) { | ||
| throw new Error('No authorization server in PRM'); | ||
| } | ||
|
|
||
| // 2. Fetch Authorization Server Metadata | ||
| const asMetadataUrl = new URL( | ||
| '/.well-known/oauth-authorization-server', | ||
| authServerUrl | ||
| ); | ||
| const asResponse = await fetchFn(asMetadataUrl.toString()); | ||
| if (!asResponse.ok) { | ||
| throw new Error(`Failed to fetch AS metadata: ${asResponse.status}`); | ||
| } | ||
| const asMetadata = await asResponse.json(); | ||
|
|
||
| const expectedIssuer: string = asMetadata.issuer; | ||
| const issParameterSupported: boolean = | ||
| asMetadata.authorization_response_iss_parameter_supported === true; | ||
|
|
||
| // 3. Register client (DCR) | ||
| const dcrResponse = await fetchFn(asMetadata.registration_endpoint, { | ||
| method: 'POST', | ||
| headers: { 'Content-Type': 'application/json' }, | ||
| body: JSON.stringify({ | ||
| client_name: 'test-auth-client-iss-validation', | ||
| redirect_uris: ['http://localhost:3000/callback'] | ||
| }) | ||
| }); | ||
| if (!dcrResponse.ok) { | ||
| throw new Error(`DCR failed: ${dcrResponse.status}`); | ||
| } | ||
| const clientInfo = await dcrResponse.json(); | ||
|
|
||
| // 4. Build authorization URL with PKCE | ||
| const codeVerifier = generateCodeVerifier(); | ||
| const codeChallenge = computeS256Challenge(codeVerifier); | ||
|
|
||
| const authUrl = new URL(asMetadata.authorization_endpoint); | ||
| authUrl.searchParams.set('response_type', 'code'); | ||
| authUrl.searchParams.set('client_id', clientInfo.client_id); | ||
| authUrl.searchParams.set('redirect_uri', 'http://localhost:3000/callback'); | ||
| authUrl.searchParams.set('state', 'test-state'); | ||
| authUrl.searchParams.set('code_challenge', codeChallenge); | ||
| authUrl.searchParams.set('code_challenge_method', 'S256'); | ||
|
|
||
| // 5. Fetch authorization endpoint (simulates redirect) | ||
| const authResponse = await fetchFn(authUrl.toString(), { | ||
| redirect: 'manual' | ||
| }); | ||
| const location = authResponse.headers.get('location'); | ||
| if (!location) { | ||
| throw new Error('No redirect from authorization endpoint'); | ||
| } | ||
| const redirectUrl = new URL(location); | ||
| const authCode = redirectUrl.searchParams.get('code'); | ||
| if (!authCode) { | ||
| throw new Error('No auth code in redirect'); | ||
| } | ||
|
|
||
| // 6. Validate iss parameter per RFC 9207 | ||
| const issInRedirect = redirectUrl.searchParams.get('iss'); | ||
|
|
||
| if (issParameterSupported) { | ||
| // Server advertised support: iss MUST be present and MUST match metadata issuer | ||
| if (!issInRedirect) { | ||
| throw new Error( | ||
| 'Server advertised authorization_response_iss_parameter_supported but iss is absent from redirect' | ||
| ); | ||
| } | ||
| if (issInRedirect !== expectedIssuer) { | ||
| throw new Error( | ||
| `iss mismatch: expected '${expectedIssuer}', got '${issInRedirect}'` | ||
| ); | ||
| } | ||
| } else { | ||
| // Server did NOT advertise support: iss MUST NOT be present | ||
| if (issInRedirect) { | ||
| throw new Error( | ||
| `Unexpected iss parameter in redirect: server did not advertise authorization_response_iss_parameter_supported` | ||
| ); | ||
| } | ||
| } | ||
|
|
||
| // 7. Exchange code for token with PKCE code_verifier | ||
| const tokenResponse = await fetchFn(asMetadata.token_endpoint, { | ||
| method: 'POST', | ||
| headers: { 'Content-Type': 'application/x-www-form-urlencoded' }, | ||
| body: new URLSearchParams({ | ||
| grant_type: 'authorization_code', | ||
| code: authCode, | ||
| redirect_uri: 'http://localhost:3000/callback', | ||
| client_id: clientInfo.client_id, | ||
| code_verifier: codeVerifier | ||
| }).toString() | ||
| }); | ||
|
|
||
| if (!tokenResponse.ok) { | ||
| const error = await tokenResponse.text(); | ||
| throw new Error(`Token request failed: ${tokenResponse.status} - ${error}`); | ||
| } | ||
|
|
||
| return tokenResponse.json(); | ||
| } | ||
|
|
||
| /** | ||
| * Creates a fetch wrapper that uses OAuth with iss parameter validation. | ||
| */ | ||
| function withOAuthIssValidation(baseUrl: string | URL): Middleware { | ||
| let tokens: OAuthTokens | undefined; | ||
|
|
||
| return (next: FetchLike) => { | ||
| return async ( | ||
| input: string | URL, | ||
| init?: RequestInit | ||
| ): Promise<Response> => { | ||
| const makeRequest = async (): Promise<Response> => { | ||
| const headers = new Headers(init?.headers); | ||
| if (tokens) { | ||
| headers.set('Authorization', `Bearer ${tokens.access_token}`); | ||
| } | ||
| return next(input, { ...init, headers }); | ||
| }; | ||
|
|
||
| let response = await makeRequest(); | ||
|
|
||
| if (response.status === 401) { | ||
| const { resourceMetadataUrl } = extractWWWAuthenticateParams(response); | ||
| if (!resourceMetadataUrl) { | ||
| throw new Error('No resource_metadata in WWW-Authenticate'); | ||
| } | ||
| tokens = await oauthFlowWithIssValidation( | ||
| baseUrl, | ||
| resourceMetadataUrl, | ||
| next | ||
| ); | ||
| response = await makeRequest(); | ||
| } | ||
|
|
||
| return response; | ||
| }; | ||
| }; | ||
| } | ||
|
|
||
| export async function runClient(serverUrl: string): Promise<void> { | ||
| const client = new Client( | ||
| { name: 'test-auth-client-iss-validation', version: '1.0.0' }, | ||
| { capabilities: {} } | ||
| ); | ||
|
|
||
| const oauthFetch = withOAuthIssValidation(new URL(serverUrl))(fetch); | ||
|
|
||
| const transport = new StreamableHTTPClientTransport(new URL(serverUrl), { | ||
| fetch: oauthFetch | ||
| }); | ||
|
|
||
| await client.connect(transport); | ||
| logger.debug('Successfully connected to MCP server'); | ||
|
|
||
| await client.listTools(); | ||
| logger.debug('Successfully listed tools'); | ||
|
|
||
| await transport.close(); | ||
| logger.debug('Connection closed successfully'); | ||
| } | ||
|
|
||
| runAsCli(runClient, import.meta.url, 'auth-test-iss-validation <server-url>'); | ||
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I would have loved to add this behavior to the base
ConformanceOAuthProvider, but it looks like that provider doesn't have access to the AS Metadata currently, so it is not possible for us to do the checks there.runCrossAppAccessCompleteFlowsimilarly needs to fetch the metadata itself.Defer to maintainers on how best to incorporate this code.