/*
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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 { ManagedIdentityId } from "../../config/ManagedIdentityId.js";
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import { ManagedIdentityRequestParameters } from "../../config/ManagedIdentityRequestParameters.js";
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import { BaseManagedIdentitySource } from "./BaseManagedIdentitySource.js";
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import { CryptoProvider } from "../../crypto/CryptoProvider.js";
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import {
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HttpMethod,
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ManagedIdentityEnvironmentVariableNames,
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ManagedIdentityHeaders,
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ManagedIdentityIdType,
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ManagedIdentityQueryParameters,
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ManagedIdentitySourceNames,
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} from "../../utils/Constants.js";
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import { NodeStorage } from "../../cache/NodeStorage.js";
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import { ImdsRetryPolicy } from "../../retry/ImdsRetryPolicy.js";
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// Documentation for IMDS is available at https://docs.microsoft.com/azure/active-directory/managed-identities-azure-resources/how-to-use-vm-token#get-a-token-using-http
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const IMDS_TOKEN_PATH: string = "/metadata/identity/oauth2/token";
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const DEFAULT_IMDS_ENDPOINT: string = `http://169.254.169.254${IMDS_TOKEN_PATH}`;
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const IMDS_API_VERSION: string = "2018-02-01";
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/**
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* Managed Identity source implementation for Azure Instance Metadata Service (IMDS).
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*
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* IMDS is available on Azure Virtual Machines and Virtual Machine Scale Sets and provides
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* a REST endpoint to obtain OAuth tokens for managed identities. This implementation
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* handles both system-assigned and user-assigned managed identities.
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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/ImdsManagedIdentitySource.cs
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*/
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export class Imds extends BaseManagedIdentitySource {
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private identityEndpoint: string;
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/**
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* Constructs an Imds instance with the specified configuration.
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*
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* @param logger - Logger instance for recording debug information and errors
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* @param nodeStorage - NodeStorage instance used for token caching operations
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* @param networkClient - Network client implementation for making HTTP requests to IMDS
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* @param cryptoProvider - CryptoProvider for generating correlation IDs and other cryptographic operations
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* @param disableInternalRetries - When true, disables the built-in retry logic for IMDS requests
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* @param identityEndpoint - The complete IMDS endpoint URL including the token path
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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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) {
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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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}
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/**
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* Creates an Imds instance with the appropriate endpoint configuration.
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*
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* This method checks for the presence of the AZURE_POD_IDENTITY_AUTHORITY_HOST environment
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* variable, which is used in Azure Kubernetes Service (AKS) environments with Azure AD
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* Pod Identity. If found, it uses that endpoint; otherwise, it falls back to the standard
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* IMDS endpoint (169.254.169.254).
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*
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* @param logger - Logger instance for recording endpoint discovery and validation
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* @param nodeStorage - NodeStorage instance for token caching
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* @param networkClient - Network client for HTTP requests
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* @param cryptoProvider - CryptoProvider for cryptographic operations
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* @param disableInternalRetries - Whether to disable built-in retry logic
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*
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* @returns A configured Imds instance ready to make token requests
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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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): Imds {
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let validatedIdentityEndpoint: string;
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if (
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process.env[
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ManagedIdentityEnvironmentVariableNames
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.AZURE_POD_IDENTITY_AUTHORITY_HOST
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]
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) {
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logger.info(
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`[Managed Identity] Environment variable ${
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ManagedIdentityEnvironmentVariableNames.AZURE_POD_IDENTITY_AUTHORITY_HOST
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} for ${ManagedIdentitySourceNames.IMDS} returned endpoint: ${
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process.env[
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ManagedIdentityEnvironmentVariableNames
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.AZURE_POD_IDENTITY_AUTHORITY_HOST
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]
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}`,
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""
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);
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validatedIdentityEndpoint = Imds.getValidatedEnvVariableUrlString(
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ManagedIdentityEnvironmentVariableNames.AZURE_POD_IDENTITY_AUTHORITY_HOST,
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`${
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process.env[
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ManagedIdentityEnvironmentVariableNames
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.AZURE_POD_IDENTITY_AUTHORITY_HOST
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]
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}${IMDS_TOKEN_PATH}`,
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ManagedIdentitySourceNames.IMDS,
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logger
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);
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} else {
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logger.info(
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`[Managed Identity] Unable to find ${ManagedIdentityEnvironmentVariableNames.AZURE_POD_IDENTITY_AUTHORITY_HOST} environment variable for ${ManagedIdentitySourceNames.IMDS}, using the default endpoint.`,
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""
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);
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validatedIdentityEndpoint = DEFAULT_IMDS_ENDPOINT;
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}
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return new Imds(
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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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validatedIdentityEndpoint
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);
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}
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/**
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* Creates a properly configured HTTP request for acquiring an access token from IMDS.
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*
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* This method builds a complete request object with all necessary headers, query parameters,
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* and retry policies required by the Azure Instance Metadata Service.
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*
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* Key request components:
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* - HTTP GET method to the IMDS token endpoint
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* - Metadata header set to "true" (required by IMDS)
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* - API version parameter (currently "2018-02-01")
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* - Resource parameter specifying the target audience
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* - Identity-specific parameters for user-assigned managed identities
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* - IMDS-specific retry policy
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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.METADATA_HEADER_NAME] = "true";
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request.queryParameters[ManagedIdentityQueryParameters.API_VERSION] =
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IMDS_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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true // indicates source is IMDS
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)
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] = managedIdentityId.id;
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}
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// The bodyParameters are calculated in BaseManagedIdentity.acquireTokenWithManagedIdentity.
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request.retryPolicy = new ImdsRetryPolicy();
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return request;
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}
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}
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