Files
gemini-cli/packages/core/src/mcp/oauth-utils.ts

431 lines
13 KiB
TypeScript

/**
* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import type { MCPOAuthConfig } from './oauth-provider.js';
import { getErrorMessage } from '../utils/errors.js';
import { debugLogger } from '../utils/debugLogger.js';
/**
* Error thrown when the discovered resource metadata does not match the expected resource.
*/
export class ResourceMismatchError extends Error {
constructor(message: string) {
super(message);
this.name = 'ResourceMismatchError';
}
}
/**
* 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[];
}
export const FIVE_MIN_BUFFER_MS = 5 * 60 * 1000;
/**
* Utility class for common OAuth operations.
*/
export class OAuthUtils {
/**
* Construct well-known OAuth endpoint URLs.
* By default, uses standard root-based well-known URLs.
* If includePathSuffix is true, appends any path from the base URL to the well-known endpoints.
*/
static buildWellKnownUrls(baseUrl: string, includePathSuffix = false) {
const serverUrl = new URL(baseUrl);
const base = `${serverUrl.protocol}//${serverUrl.host}`;
if (!includePathSuffix) {
// Standard discovery: use root-based well-known URLs
return {
protectedResource: new URL(
'/.well-known/oauth-protected-resource',
base,
).toString(),
authorizationServer: new URL(
'/.well-known/oauth-authorization-server',
base,
).toString(),
};
}
// Path-based discovery: append path suffix to well-known URLs
const pathSuffix = serverUrl.pathname.replace(/\/$/, ''); // Remove trailing slash
return {
protectedResource: new URL(
`/.well-known/oauth-protected-resource${pathSuffix}`,
base,
).toString(),
authorizationServer: new URL(
`/.well-known/oauth-authorization-server${pathSuffix}`,
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) {
debugLogger.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) {
debugLogger.debug(
`Failed to fetch authorization server metadata from ${authServerMetadataUrl}: ${getErrorMessage(error)}`,
);
return null;
}
}
/**
* Convert authorization server metadata to OAuth configuration.
*
* @param metadata The authorization server metadata
* @returns The OAuth configuration
*/
static metadataToOAuthConfig(
metadata: OAuthAuthorizationServerMetadata,
): MCPOAuthConfig {
return {
authorizationUrl: metadata.authorization_endpoint,
tokenUrl: metadata.token_endpoint,
scopes: metadata.scopes_supported || [],
registrationUrl: metadata.registration_endpoint,
};
}
/**
* Discover Oauth Authorization server metadata given an Auth server URL, by
* trying the standard well-known endpoints.
*
* @param authServerUrl The authorization server URL
* @returns The authorization server metadata or null if not found
*/
static async discoverAuthorizationServerMetadata(
authServerUrl: string,
): Promise<OAuthAuthorizationServerMetadata | null> {
const authServerUrlObj = new URL(authServerUrl);
const base = `${authServerUrlObj.protocol}//${authServerUrlObj.host}`;
const endpointsToTry: string[] = [];
// With issuer URLs with path components, try the following well-known
// endpoints in order:
if (authServerUrlObj.pathname !== '/') {
// 1. OAuth 2.0 Authorization Server Metadata with path insertion
endpointsToTry.push(
new URL(
`/.well-known/oauth-authorization-server${authServerUrlObj.pathname}`,
base,
).toString(),
);
// 2. OpenID Connect Discovery 1.0 with path insertion
endpointsToTry.push(
new URL(
`/.well-known/openid-configuration${authServerUrlObj.pathname}`,
base,
).toString(),
);
// 3. OpenID Connect Discovery 1.0 with path appending
endpointsToTry.push(
new URL(
`${authServerUrlObj.pathname}/.well-known/openid-configuration`,
base,
).toString(),
);
}
// With issuer URLs without path components, and those that failed previous
// discoveries, try the following well-known endpoints in order:
// 1. OAuth 2.0 Authorization Server Metadata
endpointsToTry.push(
new URL('/.well-known/oauth-authorization-server', base).toString(),
);
// 2. OpenID Connect Discovery 1.0
endpointsToTry.push(
new URL('/.well-known/openid-configuration', base).toString(),
);
for (const endpoint of endpointsToTry) {
const authServerMetadata =
await this.fetchAuthorizationServerMetadata(endpoint);
if (authServerMetadata) {
return authServerMetadata;
}
}
debugLogger.debug(
`Metadata discovery failed for authorization server ${authServerUrl}`,
);
return null;
}
/**
* 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 {
// First try standard root-based discovery
const wellKnownUrls = this.buildWellKnownUrls(serverUrl, false);
// Try to get the protected resource metadata at root
let resourceMetadata = await this.fetchProtectedResourceMetadata(
wellKnownUrls.protectedResource,
);
// If root discovery fails and we have a path, try path-based discovery
if (!resourceMetadata) {
const url = new URL(serverUrl);
if (url.pathname && url.pathname !== '/') {
const pathBasedUrls = this.buildWellKnownUrls(serverUrl, true);
resourceMetadata = await this.fetchProtectedResourceMetadata(
pathBasedUrls.protectedResource,
);
}
}
if (resourceMetadata) {
// RFC 9728 Section 7.3: The client MUST ensure that the resource identifier URL
// it is using as the prefix for the metadata request exactly matches the value
// of the resource metadata parameter in the protected resource metadata document.
const expectedResource = this.buildResourceParameter(serverUrl);
if (resourceMetadata.resource !== expectedResource) {
throw new ResourceMismatchError(
`Protected resource ${resourceMetadata.resource} does not match expected ${expectedResource}`,
);
}
}
if (resourceMetadata?.authorization_servers?.length) {
// Use the first authorization server
const authServerUrl = resourceMetadata.authorization_servers[0];
const authServerMetadata =
await this.discoverAuthorizationServerMetadata(authServerUrl);
if (authServerMetadata) {
const config = this.metadataToOAuthConfig(authServerMetadata);
if (authServerMetadata.registration_endpoint) {
debugLogger.log(
'Dynamic client registration is supported at:',
authServerMetadata.registration_endpoint,
);
}
return config;
}
}
// Fallback: try well-known endpoints at the base URL
debugLogger.debug(`Trying OAuth discovery fallback at ${serverUrl}`);
const authServerMetadata =
await this.discoverAuthorizationServerMetadata(serverUrl);
if (authServerMetadata) {
const config = this.metadataToOAuthConfig(authServerMetadata);
if (authServerMetadata.registration_endpoint) {
debugLogger.log(
'Dynamic client registration is supported at:',
authServerMetadata.registration_endpoint,
);
}
return config;
}
return null;
} catch (error) {
if (error instanceof ResourceMismatchError) {
throw error;
}
debugLogger.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
const match = header.match(/resource_metadata="([^"]+)"/);
if (match) {
return match[1];
}
return null;
}
/**
* Discover OAuth configuration from WWW-Authenticate header.
*
* @param wwwAuthenticate The WWW-Authenticate header value
* @param mcpServerUrl Optional MCP server URL to validate against the resource metadata
* @returns The discovered OAuth configuration or null if not available
*/
static async discoverOAuthFromWWWAuthenticate(
wwwAuthenticate: string,
mcpServerUrl?: string,
): Promise<MCPOAuthConfig | null> {
const resourceMetadataUri =
this.parseWWWAuthenticateHeader(wwwAuthenticate);
if (!resourceMetadataUri) {
return null;
}
const resourceMetadata =
await this.fetchProtectedResourceMetadata(resourceMetadataUri);
if (resourceMetadata && mcpServerUrl) {
// Validate resource parameter per RFC 9728 Section 7.3
const expectedResource = this.buildResourceParameter(mcpServerUrl);
if (resourceMetadata.resource !== expectedResource) {
throw new ResourceMismatchError(
`Protected resource ${resourceMetadata.resource} does not match expected ${expectedResource}`,
);
}
}
if (!resourceMetadata?.authorization_servers?.length) {
return null;
}
const authServerUrl = resourceMetadata.authorization_servers[0];
const authServerMetadata =
await this.discoverAuthorizationServerMetadata(authServerUrl);
if (authServerMetadata) {
return this.metadataToOAuthConfig(authServerMetadata);
}
return null;
}
/**
* Extract base URL from an MCP server URL.
*
* @param mcpServerUrl The MCP server URL
* @returns The base URL
*/
static extractBaseUrl(mcpServerUrl: string): string {
const serverUrl = new URL(mcpServerUrl);
return `${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}//${url.host}${url.pathname}`;
}
/**
* Parses a JWT string to extract its expiry time.
* @param idToken The JWT ID token.
* @returns The expiry time in **milliseconds**, or undefined if parsing fails.
*/
static parseTokenExpiry(idToken: string): number | undefined {
try {
const payload = JSON.parse(
Buffer.from(idToken.split('.')[1], 'base64').toString(),
);
if (payload && typeof payload.exp === 'number') {
return payload.exp * 1000; // Convert seconds to milliseconds
}
} catch (e) {
debugLogger.error(
'Failed to parse ID token for expiry time with error:',
e,
);
}
// Return undefined if try block fails or 'exp' is missing/invalid
return undefined;
}
}