feat: Open More Endpoints for Customization (#1721)

* feat: Allow custom STS Access Token URL for Downscoped Clients

* feat: Open More Endpoints for Customization

* docs: Update

* docs: Update

* docs: Update

* chore: remove unrelated

* refactor: base endpoints on universe domain

src/auth/baseexternalclient.ts

@@ -53,12 +53,13 @@ export const EXPIRATION_TIME_OFFSET = 5 * 60 * 1000;
  * 3. external_Account => non-GCP service (eg. AWS, Azure, K8s)
  */
 export const EXTERNAL_ACCOUNT_TYPE = 'external_account';
-/** Cloud resource manager URL used to retrieve project information. */
+/**
+ * Cloud resource manager URL used to retrieve project information.
+ *
+ * @deprecated use {@link BaseExternalAccountClient.cloudResourceManagerURL} instead
+ **/
 export const CLOUD_RESOURCE_MANAGER =
   'https://cloudresourcemanager.googleapis.com/v1/projects/';
-/** The workforce audience pattern. */
-const WORKFORCE_AUDIENCE_PATTERN =
-  '//iam\\.googleapis\\.com/locations/[^/]+/workforcePools/[^/]+/providers/.+';
 
 // eslint-disable-next-line @typescript-eslint/no-var-requires
 const pkg = require('../../../package.json');
@@ -88,6 +89,12 @@ export interface BaseExternalAccountClientOptions
   client_id?: string;
   client_secret?: string;
   workforce_pool_user_project?: string;
+  scopes?: string[];
+  /**
+   * @example
+   * https://cloudresourcemanager.googleapis.com/v1/projects/
+   **/
+  cloud_resource_manager_url?: string | URL;
 }
 
 /**
@@ -150,6 +157,13 @@ export abstract class BaseExternalAccountClient extends AuthClient {
   public projectNumber: string | null;
   private readonly configLifetimeRequested: boolean;
   protected credentialSourceType?: string;
+  /**
+   * @example
+   * ```ts
+   * new URL('https://cloudresourcemanager.googleapis.com/v1/projects/');
+   * ```
+   */
+  protected cloudResourceManagerURL: URL | string;
   /**
    * Instantiate a BaseExternalAccountClient instance using the provided JSON
    * object loaded from an external account credentials file.
@@ -195,6 +209,11 @@ export abstract class BaseExternalAccountClient extends AuthClient {
       serviceAccountImpersonation
     ).get('token_lifetime_seconds');
 
+    this.cloudResourceManagerURL = new URL(
+      opts.get('cloud_resource_manager_url') ||
+        `https://cloudresourcemanager.${this.universeDomain}/v1/projects/`
+    );
+
     if (clientId) {
       this.clientAuth = {
         confidentialClientType: 'basic',
@@ -204,22 +223,11 @@ export abstract class BaseExternalAccountClient extends AuthClient {
     }
 
     this.stsCredential = new sts.StsCredentials(tokenUrl, this.clientAuth);
-    // Default OAuth scope. This could be overridden via public property.
-    this.scopes = [DEFAULT_OAUTH_SCOPE];
+    this.scopes = opts.get('scopes') || [DEFAULT_OAUTH_SCOPE];
     this.cachedAccessToken = null;
     this.audience = opts.get('audience');
     this.subjectTokenType = subjectTokenType;
     this.workforcePoolUserProject = workforcePoolUserProject;
-    const workforceAudiencePattern = new RegExp(WORKFORCE_AUDIENCE_PATTERN);
-    if (
-      this.workforcePoolUserProject &&
-      !this.audience.match(workforceAudiencePattern)
-    ) {
-      throw new Error(
-        'workforcePoolUserProject should not be set for non-workforce pool ' +
-          'credentials.'
-      );
-    }
     this.serviceAccountImpersonationUrl = serviceAccountImpersonationUrl;
     this.serviceAccountImpersonationLifetime =
       serviceAccountImpersonationLifetime;
@@ -360,7 +368,7 @@ export abstract class BaseExternalAccountClient extends AuthClient {
       const headers = await this.getRequestHeaders();
       const response = await this.transporter.request<ProjectInfo>({
         headers,
-        url: `${CLOUD_RESOURCE_MANAGER}${projectNumber}`,
+        url: `${this.cloudResourceManagerURL.toString()}${projectNumber}`,
         responseType: 'json',
       });
       this.projectId = response.data.projectId;
@@ -576,11 +584,9 @@ export abstract class BaseExternalAccountClient extends AuthClient {
     // be normalized.
     if (typeof this.scopes === 'string') {
       return [this.scopes];
-    } else if (typeof this.scopes === 'undefined') {
-      return [DEFAULT_OAUTH_SCOPE];
-    } else {
-      return this.scopes;
     }
+
+    return this.scopes || [DEFAULT_OAUTH_SCOPE];
   }
 
   private getMetricsHeaderValue(): string {

src/auth/downscopedclient.ts

@@ -39,8 +39,6 @@ const STS_REQUEST_TOKEN_TYPE = 'urn:ietf:params:oauth:token-type:access_token';
  * The requested token exchange subject_token_type: rfc8693#section-2.1
  */
 const STS_SUBJECT_TOKEN_TYPE = 'urn:ietf:params:oauth:token-type:access_token';
-/** The STS access token exchange end point. */
-const STS_ACCESS_TOKEN_URL = 'https://sts.googleapis.com/v1/token';
 
 /**
  * The maximum number of access boundary rules a Credential Access Boundary
@@ -75,6 +73,13 @@ export interface CredentialAccessBoundary {
   accessBoundary: {
     accessBoundaryRules: AccessBoundaryRule[];
   };
+  /**
+   * An optional STS access token exchange endpoint.
+   *
+   * @example
+   * 'https://sts.googleapis.com/v1/token'
+   */
+  tokenURL?: string | URL;
 }
 
 /** Defines an upper bound of permissions on a particular resource. */
@@ -135,6 +140,12 @@ export class DownscopedClient extends AuthClient {
     quotaProjectId?: string
   ) {
     super({...additionalOptions, quotaProjectId});
+
+    // extract and remove `tokenURL` as it is not officially a part of the credentialAccessBoundary
+    this.credentialAccessBoundary = {...credentialAccessBoundary};
+    const tokenURL = this.credentialAccessBoundary.tokenURL;
+    delete this.credentialAccessBoundary.tokenURL;
+
     // Check 1-10 Access Boundary Rules are defined within Credential Access
     // Boundary.
     if (
@@ -162,7 +173,10 @@ export class DownscopedClient extends AuthClient {
       }
     }
 
-    this.stsCredential = new sts.StsCredentials(STS_ACCESS_TOKEN_URL);
+    this.stsCredential = new sts.StsCredentials(
+      tokenURL || `https://sts.${this.universeDomain}/v1/token`
+    );
+
     this.cachedDownscopedAccessToken = null;
   }
 

src/auth/googleauth.ts

@@ -1073,9 +1073,20 @@ export class GoogleAuth<T extends AuthClient = JSONClient> {
    * Sign the given data with the current private key, or go out
    * to the IAM API to sign it.
    * @param data The data to be signed.
+   * @param endpoint A custom endpoint to use.
+   *
+   * @example
+   * ```
+   * sign('data', 'https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/');
+   * ```
    */
-  async sign(data: string): Promise<string> {
+  async sign(data: string, endpoint?: string): Promise<string> {
     const client = await this.getClient();
+    const universe = await this.getUniverseDomain();
+
+    endpoint =
+      endpoint ||
+      `https://iamcredentials.${universe}/v1/projects/-/serviceAccounts/`;
 
     if (client instanceof Impersonated) {
       const signed = await client.sign(data);
@@ -1093,24 +1104,24 @@ export class GoogleAuth<T extends AuthClient = JSONClient> {
       throw new Error('Cannot sign data without `client_email`.');
     }
 
-    return this.signBlob(crypto, creds.client_email, data);
+    return this.signBlob(crypto, creds.client_email, data, endpoint);
   }
 
   private async signBlob(
     crypto: Crypto,
     emailOrUniqueId: string,
-    data: string
+    data: string,
+    endpoint: string
   ): Promise<string> {
-    const url =
-      'https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/' +
-      `${emailOrUniqueId}:signBlob`;
+    const url = new URL(endpoint + `${emailOrUniqueId}:signBlob`);
     const res = await this.request<SignBlobResponse>({
       method: 'POST',
-      url,
+      url: url.href,
       data: {
         payload: crypto.encodeBase64StringUtf8(data),
       },
     });
+
     return res.data.signedBlob;
   }
 }