azureIdentityCredentialAdapter.ts

import { ServiceClientCredentials } from "@azure/ms-rest-js";
import { DefaultAzureCredential, TokenCredential } from "@azure/identity";
import { Constants as MSRestConstants, WebResource } from "@azure/ms-rest-js";
import { TokenResponse } from "@azure/ms-rest-nodeauth/dist/lib/credentials/tokenClientCredentials";

const DEFAULT_AUTHORIZATION_SCHEME = "Bearer";

/**
 * This class provides a simple extension to use {@link TokenCredential} from com.azure:azure-identity library to
 * use with legacy Azure SDKs that accept {@link ServiceClientCredentials} family of credentials for authentication.
 */
export class AzureIdentityCredentialAdapter implements ServiceClientCredentials {
  private azureTokenCredential: TokenCredential;
  private scopes: string | string[];
  constructor(
      azureTokenCredential = new DefaultAzureCredential(),
      scopes: string | string[] = "https://management.azure.com/.default",
    ) { 
      this.azureTokenCredential = azureTokenCredential;
      this.scopes = scopes;
    }
 
  public async getToken(): Promise<TokenResponse>{
    const accessToken = (await this.azureTokenCredential.getToken(this.scopes));
    const result: TokenResponse = {
      accessToken: accessToken.token,
      tokenType: DEFAULT_AUTHORIZATION_SCHEME,
      expiresOn: accessToken.expiresOnTimestamp,
    };
    return result;
  }

  public async signRequest(webResource: WebResource) {
    const tokenResponse = await this.getToken();
    webResource.headers.set(MSRestConstants.HeaderConstants.AUTHORIZATION, `${tokenResponse.tokenType} ${tokenResponse.accessToken}`);
    return Promise.resolve(webResource);
  }
}