2

目标

我构建了一个在 Google App Engine 上运行的 REST API,受Google Cloud IAP(身份识别代理)保护。我的目标是使用服务帐户从 Salesforce 向此 API 发出请求(使用外部服务功能)。

语境

感谢上一个问题,我知道我需要为此流程使用JWT 令牌交换来请求OIDC令牌。所以下一步是了解如何填写 Salesforce 的命名凭据定义:

Salesforce 命名凭证 JWT 令牌交换

命名凭据的属性如下:

  1. 证书:不适用于我的用例。
  2. 身份类型:是为每个访问的 Salesforce 用户使用不同的凭据,还是全面使用单个凭据。我将使用Named Principal
  3. 身份验证协议:现在意识到需要 JWT 令牌交换。
  4. 令牌端点 URL:为服务帐户下载的 JSON 指定https://oauth2.googleapis.com/token.
  5. 范围:我不确定这个属性的正确值,也许应该是openid email
  6. 发行人:不知道这应该是什么。
  7. 命名主体主题:我认为这应该是服务帐户中的client_email值。但是,此文档说“为受 IAP 保护的客户端 ID 请求 OIDC 令牌”。这是否意味着我应该改用 IAP Client ID for Web 应用程序页面中的客户端 ID?
  8. 受众:我能找到的唯一可能合适的值来自 GCP 控制台的 HTTPS 资源部分中的 IAP 签名标头 JWT,格式为/projects/NNNNN/apps/XXXXXXX
  9. 令牌有效期:我相信这应该是 1 小时。
  10. JWT 签名证书:服务帐户私钥
  11. 生成授权标头:应启用。

问题:

  1. 任何人都可以确认我的理解并协助处理范围、发行人和指定的主要主题字段吗?
  2. IAP 文档谈到需要 JWT附加声明target_audience最终结果如何?
4

1 回答 1

0

我认为target_audience云是位于您的 IAP 仪表板上的 iapClientId。就像这里提到的一样。

import google.auth
import google.auth.app_engine
import google.auth.compute_engine.credentials
import google.auth.iam
from google.auth.transport.requests import Request
import google.oauth2.credentials
import google.oauth2.service_account
import requests
import requests_toolbelt.adapters.appengine


IAM_SCOPE = 'https://www.googleapis.com/auth/iam'
OAUTH_TOKEN_URI = 'https://www.googleapis.com/oauth2/v4/token'


def make_iap_request(url, client_id, method='GET', **kwargs):
    """Makes a request to an application protected by Identity-Aware Proxy.

    Args:
      url: The Identity-Aware Proxy-protected URL to fetch.
      client_id: The client ID used by Identity-Aware Proxy.
      method: The request method to use
              ('GET', 'OPTIONS', 'HEAD', 'POST', 'PUT', 'PATCH', 'DELETE')
      **kwargs: Any of the parameters defined for the request function:
                https://github.com/requests/requests/blob/master/requests/api.py
                If no timeout is provided, it is set to 90 by default.

    Returns:
      The page body, or raises an exception if the page couldn't be retrieved.
    """
    # Set the default timeout, if missing
    if 'timeout' not in kwargs:
        kwargs['timeout'] = 90

    # Figure out what environment we're running in and get some preliminary
    # information about the service account.
    bootstrap_credentials, _ = google.auth.default(
        scopes=[IAM_SCOPE])
    if isinstance(bootstrap_credentials,
                  google.oauth2.credentials.Credentials):
        raise Exception('make_iap_request is only supported for service '
                        'accounts.')
    elif isinstance(bootstrap_credentials,
                    google.auth.app_engine.Credentials):
        requests_toolbelt.adapters.appengine.monkeypatch()

    # For service account's using the Compute Engine metadata service,
    # service_account_email isn't available until refresh is called.
    bootstrap_credentials.refresh(Request())

    signer_email = bootstrap_credentials.service_account_email
    if isinstance(bootstrap_credentials,
                  google.auth.compute_engine.credentials.Credentials):
        # Since the Compute Engine metadata service doesn't expose the service
        # account key, we use the IAM signBlob API to sign instead.
        # In order for this to work:
        #
        # 1. Your VM needs the https://www.googleapis.com/auth/iam scope.
        #    You can specify this specific scope when creating a VM
        #    through the API or gcloud. When using Cloud Console,
        #    you'll need to specify the "full access to all Cloud APIs"
        #    scope. A VM's scopes can only be specified at creation time.
        #
        # 2. The VM's default service account needs the "Service Account Actor"
        #    role. This can be found under the "Project" category in Cloud
        #    Console, or roles/iam.serviceAccountActor in gcloud.
        signer = google.auth.iam.Signer(
            Request(), bootstrap_credentials, signer_email)
    else:
        # A Signer object can sign a JWT using the service account's key.
        signer = bootstrap_credentials.signer

    # Construct OAuth 2.0 service account credentials using the signer
    # and email acquired from the bootstrap credentials.
    service_account_credentials = google.oauth2.service_account.Credentials(
        signer, signer_email, token_uri=OAUTH_TOKEN_URI, additional_claims={
            'target_audience': client_id
        })

    # service_account_credentials gives us a JWT signed by the service
    # account. Next, we use that to obtain an OpenID Connect token,
    # which is a JWT signed by Google.
    google_open_id_connect_token = get_google_open_id_connect_token(
        service_account_credentials)

    # Fetch the Identity-Aware Proxy-protected URL, including an
    # Authorization header containing "Bearer " followed by a
    # Google-issued OpenID Connect token for the service account.
    resp = requests.request(
        method, url,
        headers={'Authorization': 'Bearer {}'.format(
            google_open_id_connect_token)}, **kwargs)
    if resp.status_code == 403:
        raise Exception('Service account {} does not have permission to '
                        'access the IAP-protected application.'.format(
                            signer_email))
    elif resp.status_code != 200:
        raise Exception(
            'Bad response from application: {!r} / {!r} / {!r}'.format(
                resp.status_code, resp.headers, resp.text))
    else:
        return resp.text


def get_google_open_id_connect_token(service_account_credentials):
    """Get an OpenID Connect token issued by Google for the service account.

    This function:

      1. Generates a JWT signed with the service account's private key
         containing a special "target_audience" claim.

      2. Sends it to the OAUTH_TOKEN_URI endpoint. Because the JWT in #1
         has a target_audience claim, that endpoint will respond with
         an OpenID Connect token for the service account -- in other words,
         a JWT signed by *Google*. The aud claim in this JWT will be
         set to the value from the target_audience claim in #1.

    For more information, see
    https://developers.google.com/identity/protocols/OAuth2ServiceAccount .
    The HTTP/REST example on that page describes the JWT structure and
    demonstrates how to call the token endpoint. (The example on that page
    shows how to get an OAuth2 access token; this code is using a
    modified version of it to get an OpenID Connect token.)
    """

    service_account_jwt = (
        service_account_credentials._make_authorization_grant_assertion())
    request = google.auth.transport.requests.Request()
    body = {
        'assertion': service_account_jwt,
        'grant_type': google.oauth2._client._JWT_GRANT_TYPE,
    }
    token_response = google.oauth2._client._token_endpoint_request(
        request, OAUTH_TOKEN_URI, body)
    return token_response['id_token']

于 2020-02-13T18:49:45.097 回答