/*
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* Copyright (c) Microsoft Corporation. All rights reserved.
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* Licensed under the MIT License.
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*/
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import { INetworkModule, Logger } from "@azure/msal-common/node";
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import { BaseManagedIdentitySource } from "./BaseManagedIdentitySource.js";
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import {
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HttpMethod,
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ManagedIdentityEnvironmentVariableNames,
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ManagedIdentitySourceNames,
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ManagedIdentityIdType,
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ManagedIdentityQueryParameters,
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ManagedIdentityHeaders,
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} from "../../utils/Constants.js";
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import { CryptoProvider } from "../../crypto/CryptoProvider.js";
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import { ManagedIdentityRequestParameters } from "../../config/ManagedIdentityRequestParameters.js";
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import { ManagedIdentityId } from "../../config/ManagedIdentityId.js";
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import { NodeStorage } from "../../cache/NodeStorage.js";
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// MSI Constants. Docs for MSI are available here https://docs.microsoft.com/azure/app-service/overview-managed-identity
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const APP_SERVICE_MSI_API_VERSION: string = "2019-08-01";
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/**
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* Azure App Service Managed Identity Source implementation.
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*
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* This class provides managed identity authentication for applications running in Azure App Service.
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* It uses the local metadata service endpoint available within App Service environments to obtain
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* access tokens without requiring explicit credentials.
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*
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* Original source of code: https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/identity/Azure.Identity/src/AppServiceManagedIdentitySource.cs
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*/
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export class AppService extends BaseManagedIdentitySource {
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private identityEndpoint: string;
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private identityHeader: string;
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/**
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* Creates a new instance of the AppService managed identity source.
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*
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* @param logger - Logger instance for diagnostic output
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* @param nodeStorage - Node.js storage implementation for caching
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* @param networkClient - Network client for making HTTP requests
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* @param cryptoProvider - Cryptographic operations provider
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* @param disableInternalRetries - Whether to disable internal retry logic
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* @param identityEndpoint - The App Service identity endpoint URL
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* @param identityHeader - The secret header value required for authentication
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*/
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constructor(
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logger: Logger,
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nodeStorage: NodeStorage,
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networkClient: INetworkModule,
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cryptoProvider: CryptoProvider,
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disableInternalRetries: boolean,
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identityEndpoint: string,
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identityHeader: string
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) {
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super(
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logger,
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nodeStorage,
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networkClient,
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cryptoProvider,
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disableInternalRetries
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);
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this.identityEndpoint = identityEndpoint;
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this.identityHeader = identityHeader;
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}
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/**
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* Retrieves the required environment variables for App Service managed identity.
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*
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* App Service managed identity requires two environment variables:
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* - IDENTITY_ENDPOINT: The URL of the local metadata service
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* - IDENTITY_HEADER: A secret header value for authentication
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*
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* @returns An array containing [identityEndpoint, identityHeader] values from environment variables.
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* Either value may be undefined if the environment variable is not set.
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*/
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public static getEnvironmentVariables(): Array<string | undefined> {
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const identityEndpoint: string | undefined =
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process.env[
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ManagedIdentityEnvironmentVariableNames.IDENTITY_ENDPOINT
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];
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const identityHeader: string | undefined =
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process.env[
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ManagedIdentityEnvironmentVariableNames.IDENTITY_HEADER
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];
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return [identityEndpoint, identityHeader];
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}
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/**
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* Attempts to create an AppService managed identity source if the environment supports it.
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*
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* This method checks for the presence of required environment variables and validates
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* the identity endpoint URL. If the environment is not suitable for App Service managed
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* identity (missing environment variables or invalid endpoint), it returns null.
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*
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* @param logger - Logger instance for diagnostic output
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* @param nodeStorage - Node.js storage implementation for caching
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* @param networkClient - Network client for making HTTP requests
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* @param cryptoProvider - Cryptographic operations provider
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* @param disableInternalRetries - Whether to disable internal retry logic
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*
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* @returns A new AppService instance if the environment is suitable, null otherwise
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*/
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public static tryCreate(
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logger: Logger,
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nodeStorage: NodeStorage,
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networkClient: INetworkModule,
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cryptoProvider: CryptoProvider,
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disableInternalRetries: boolean
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): AppService | null {
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const [identityEndpoint, identityHeader] =
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AppService.getEnvironmentVariables();
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// if either of the identity endpoint or identity header variables are undefined, this MSI provider is unavailable.
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if (!identityEndpoint || !identityHeader) {
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logger.info(
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`[Managed Identity] ${ManagedIdentitySourceNames.APP_SERVICE} managed identity is unavailable because one or both of the '${ManagedIdentityEnvironmentVariableNames.IDENTITY_HEADER}' and '${ManagedIdentityEnvironmentVariableNames.IDENTITY_ENDPOINT}' environment variables are not defined.`,
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""
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);
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return null;
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}
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const validatedIdentityEndpoint: string =
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AppService.getValidatedEnvVariableUrlString(
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ManagedIdentityEnvironmentVariableNames.IDENTITY_ENDPOINT,
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identityEndpoint,
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ManagedIdentitySourceNames.APP_SERVICE,
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logger
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);
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logger.info(
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`[Managed Identity] Environment variables validation passed for ${ManagedIdentitySourceNames.APP_SERVICE} managed identity. Endpoint URI: ${validatedIdentityEndpoint}. Creating ${ManagedIdentitySourceNames.APP_SERVICE} managed identity.`,
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""
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);
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return new AppService(
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logger,
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nodeStorage,
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networkClient,
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cryptoProvider,
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disableInternalRetries,
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identityEndpoint,
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identityHeader
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);
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}
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/**
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* Creates a managed identity token request for the App Service environment.
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*
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* This method constructs an HTTP GET request to the App Service identity endpoint
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* with the required headers, query parameters, and managed identity configuration.
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* The request includes the secret header for authentication and appropriate API version.
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*
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* @param resource - The target resource/scope for which to request an access token (e.g., "https://graph.microsoft.com/.default")
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* @param managedIdentityId - The managed identity configuration specifying whether to use system-assigned or user-assigned identity
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*
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* @returns A configured ManagedIdentityRequestParameters object ready for network execution
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*/
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public createRequest(
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resource: string,
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managedIdentityId: ManagedIdentityId
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): ManagedIdentityRequestParameters {
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const request: ManagedIdentityRequestParameters =
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new ManagedIdentityRequestParameters(
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HttpMethod.GET,
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this.identityEndpoint
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);
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request.headers[ManagedIdentityHeaders.APP_SERVICE_SECRET_HEADER_NAME] =
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this.identityHeader;
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request.queryParameters[ManagedIdentityQueryParameters.API_VERSION] =
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APP_SERVICE_MSI_API_VERSION;
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request.queryParameters[ManagedIdentityQueryParameters.RESOURCE] =
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resource;
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if (
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managedIdentityId.idType !== ManagedIdentityIdType.SYSTEM_ASSIGNED
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) {
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request.queryParameters[
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this.getManagedIdentityUserAssignedIdQueryParameterKey(
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managedIdentityId.idType
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)
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] = managedIdentityId.id;
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}
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// bodyParameters calculated in BaseManagedIdentity.acquireTokenWithManagedIdentity
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return request;
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}
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}
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