1 files changed, 285 insertions, 0 deletions
diff --git a/packages/core/src/mcp/oauth-utils.ts b/packages/core/src/mcp/oauth-utils.ts
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+++ b/packages/core/src/mcp/oauth-utils.ts
@@ -0,0 +1,285 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { MCPOAuthConfig } from './oauth-provider.js';
+import { getErrorMessage } from '../utils/errors.js';
+
+/**
+ * OAuth authorization server metadata as per RFC 8414.
+ */
+export interface OAuthAuthorizationServerMetadata {
+  issuer: string;
+  authorization_endpoint: string;
+  token_endpoint: string;
+  token_endpoint_auth_methods_supported?: string[];
+  revocation_endpoint?: string;
+  revocation_endpoint_auth_methods_supported?: string[];
+  registration_endpoint?: string;
+  response_types_supported?: string[];
+  grant_types_supported?: string[];
+  code_challenge_methods_supported?: string[];
+  scopes_supported?: string[];
+}
+
+/**
+ * OAuth protected resource metadata as per RFC 9728.
+ */
+export interface OAuthProtectedResourceMetadata {
+  resource: string;
+  authorization_servers?: string[];
+  bearer_methods_supported?: string[];
+  resource_documentation?: string;
+  resource_signing_alg_values_supported?: string[];
+  resource_encryption_alg_values_supported?: string[];
+  resource_encryption_enc_values_supported?: string[];
+}
+
+/**
+ * Utility class for common OAuth operations.
+ */
+export class OAuthUtils {
+  /**
+   * Construct well-known OAuth endpoint URLs.
+   */
+  static buildWellKnownUrls(baseUrl: string) {
+    const serverUrl = new URL(baseUrl);
+    const base = `${serverUrl.protocol}//${serverUrl.host}`;
+
+    return {
+      protectedResource: new URL(
+        '/.well-known/oauth-protected-resource',
+        base,
+      ).toString(),
+      authorizationServer: new URL(
+        '/.well-known/oauth-authorization-server',
+        base,
+      ).toString(),
+    };
+  }
+
+  /**
+   * Fetch OAuth protected resource metadata.
+   *
+   * @param resourceMetadataUrl The protected resource metadata URL
+   * @returns The protected resource metadata or null if not available
+   */
+  static async fetchProtectedResourceMetadata(
+    resourceMetadataUrl: string,
+  ): Promise<OAuthProtectedResourceMetadata | null> {
+    try {
+      const response = await fetch(resourceMetadataUrl);
+      if (!response.ok) {
+        return null;
+      }
+      return (await response.json()) as OAuthProtectedResourceMetadata;
+    } catch (error) {
+      console.debug(
+        `Failed to fetch protected resource metadata from ${resourceMetadataUrl}: ${getErrorMessage(error)}`,
+      );
+      return null;
+    }
+  }
+
+  /**
+   * Fetch OAuth authorization server metadata.
+   *
+   * @param authServerMetadataUrl The authorization server metadata URL
+   * @returns The authorization server metadata or null if not available
+   */
+  static async fetchAuthorizationServerMetadata(
+    authServerMetadataUrl: string,
+  ): Promise<OAuthAuthorizationServerMetadata | null> {
+    try {
+      const response = await fetch(authServerMetadataUrl);
+      if (!response.ok) {
+        return null;
+      }
+      return (await response.json()) as OAuthAuthorizationServerMetadata;
+    } catch (error) {
+      console.debug(
+        `Failed to fetch authorization server metadata from ${authServerMetadataUrl}: ${getErrorMessage(error)}`,
+      );
+      return null;
+    }
+  }
+
+  /**
+   * Convert authorization server metadata to OAuth configuration.
+   *
+   * @param metadata The authorization server metadata
+   * @returns The OAuth configuration
+   */
+  static metadataToOAuthConfig(
+    metadata: OAuthAuthorizationServerMetadata,
+  ): MCPOAuthConfig {
+    return {
+      authorizationUrl: metadata.authorization_endpoint,
+      tokenUrl: metadata.token_endpoint,
+      scopes: metadata.scopes_supported || [],
+    };
+  }
+
+  /**
+   * Discover OAuth configuration using the standard well-known endpoints.
+   *
+   * @param serverUrl The base URL of the server
+   * @returns The discovered OAuth configuration or null if not available
+   */
+  static async discoverOAuthConfig(
+    serverUrl: string,
+  ): Promise<MCPOAuthConfig | null> {
+    try {
+      const wellKnownUrls = this.buildWellKnownUrls(serverUrl);
+
+      // First, try to get the protected resource metadata
+      const resourceMetadata = await this.fetchProtectedResourceMetadata(
+        wellKnownUrls.protectedResource,
+      );
+
+      if (resourceMetadata?.authorization_servers?.length) {
+        // Use the first authorization server
+        const authServerUrl = resourceMetadata.authorization_servers[0];
+        const authServerMetadataUrl = new URL(
+          '/.well-known/oauth-authorization-server',
+          authServerUrl,
+        ).toString();
+
+        const authServerMetadata = await this.fetchAuthorizationServerMetadata(
+          authServerMetadataUrl,
+        );
+
+        if (authServerMetadata) {
+          const config = this.metadataToOAuthConfig(authServerMetadata);
+          if (authServerMetadata.registration_endpoint) {
+            console.log(
+              'Dynamic client registration is supported at:',
+              authServerMetadata.registration_endpoint,
+            );
+          }
+          return config;
+        }
+      }
+
+      // Fallback: try /.well-known/oauth-authorization-server at the base URL
+      console.debug(
+        `Trying OAuth discovery fallback at ${wellKnownUrls.authorizationServer}`,
+      );
+      const authServerMetadata = await this.fetchAuthorizationServerMetadata(
+        wellKnownUrls.authorizationServer,
+      );
+
+      if (authServerMetadata) {
+        const config = this.metadataToOAuthConfig(authServerMetadata);
+        if (authServerMetadata.registration_endpoint) {
+          console.log(
+            'Dynamic client registration is supported at:',
+            authServerMetadata.registration_endpoint,
+          );
+        }
+        return config;
+      }
+
+      return null;
+    } catch (error) {
+      console.debug(
+        `Failed to discover OAuth configuration: ${getErrorMessage(error)}`,
+      );
+      return null;
+    }
+  }
+
+  /**
+   * Parse WWW-Authenticate header to extract OAuth information.
+   *
+   * @param header The WWW-Authenticate header value
+   * @returns The resource metadata URI if found
+   */
+  static parseWWWAuthenticateHeader(header: string): string | null {
+    // Parse Bearer realm and resource_metadata_uri
+    const match = header.match(/resource_metadata_uri="([^"]+)"/);
+    if (match) {
+      return match[1];
+    }
+    return null;
+  }
+
+  /**
+   * Discover OAuth configuration from WWW-Authenticate header.
+   *
+   * @param wwwAuthenticate The WWW-Authenticate header value
+   * @returns The discovered OAuth configuration or null if not available
+   */
+  static async discoverOAuthFromWWWAuthenticate(
+    wwwAuthenticate: string,
+  ): Promise<MCPOAuthConfig | null> {
+    const resourceMetadataUri =
+      this.parseWWWAuthenticateHeader(wwwAuthenticate);
+    if (!resourceMetadataUri) {
+      return null;
+    }
+
+    console.log(
+      `Found resource metadata URI from www-authenticate header: ${resourceMetadataUri}`,
+    );
+
+    const resourceMetadata =
+      await this.fetchProtectedResourceMetadata(resourceMetadataUri);
+    if (!resourceMetadata?.authorization_servers?.length) {
+      return null;
+    }
+
+    const authServerUrl = resourceMetadata.authorization_servers[0];
+    const authServerMetadataUrl = new URL(
+      '/.well-known/oauth-authorization-server',
+      authServerUrl,
+    ).toString();
+
+    const authServerMetadata = await this.fetchAuthorizationServerMetadata(
+      authServerMetadataUrl,
+    );
+
+    if (authServerMetadata) {
+      console.log(
+        'OAuth configuration discovered successfully from www-authenticate header',
+      );
+      return this.metadataToOAuthConfig(authServerMetadata);
+    }
+
+    return null;
+  }
+
+  /**
+   * Extract base URL from an MCP server URL.
+   *
+   * @param mcpServerUrl The MCP server URL
+   * @returns The base URL
+   */
+  static extractBaseUrl(mcpServerUrl: string): string {
+    const serverUrl = new URL(mcpServerUrl);
+    return `${serverUrl.protocol}//${serverUrl.host}`;
+  }
+
+  /**
+   * Check if a URL is an SSE endpoint.
+   *
+   * @param url The URL to check
+   * @returns True if the URL appears to be an SSE endpoint
+   */
+  static isSSEEndpoint(url: string): boolean {
+    return url.includes('/sse') || !url.includes('/mcp');
+  }
+
+  /**
+   * Build a resource parameter for OAuth requests.
+   *
+   * @param endpointUrl The endpoint URL
+   * @returns The resource parameter value
+   */
+  static buildResourceParameter(endpointUrl: string): string {
+    const url = new URL(endpointUrl);
+    return `${url.protocol}//${url.host}`;
+  }
+}