GAE AttributeError：“凭据”对象没有属性“ with_subject”

问题内容：

我有一个要部署在App Engine（第二代Python 3.7）上的python应用程序，在该引擎上我使用了启用了域范围委派的服务帐户来访问用户数据。

我在本地做：

import google.auth
from apiclient.discovery import build

creds, project = google.auth.default(
    scopes=['https://www.googleapis.com/auth/admin.directory.user', ],
)
creds = creds.with_subject(GSUITE_ADMIN_USER)

service = build('admin', 'directory_v1', credentials=creds)

据我所知，这很好用，这是使用“应用默认凭据”（在本地，我定义了GOOGLE_APPLICATION_CREDENTIALS）时的当前方法。

问题出在GAE上，部署后with_subject会引发以下问题： AttributeError: 'Credentials' object has no attribute 'with_subject'

我已经在GAE服务帐户上启用了域范围的委派。

当我在本地使用的GOOGLE_APPLICATION_CREDENTIALS和GAE中的GOOGLE_APPLICATION_CREDENTIALS都是具有域范围委派的服务帐户时，有什么区别？

.with_subject()GAE在哪里？

creds收到的对象是类型compute_engine.credentials.Credentials。

完整回溯：

Traceback (most recent call last):
  File "/env/lib/python3.7/site-packages/gunicorn/arbiter.py", line 583, in spawn_worker
    worker.init_process()
  File "/env/lib/python3.7/site-packages/gunicorn/workers/gthread.py", line 104, in init_process
    super(ThreadWorker, self).init_process()
  File "/env/lib/python3.7/site-packages/gunicorn/workers/base.py", line 129, in init_process
    self.load_wsgi()
  File "/env/lib/python3.7/site-packages/gunicorn/workers/base.py", line 138, in load_wsgi
    self.wsgi = self.app.wsgi()
  File "/env/lib/python3.7/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/env/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 52, in load
    return self.load_wsgiapp()
  File "/env/lib/python3.7/site-packages/gunicorn/app/wsgiapp.py", line 41, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/env/lib/python3.7/site-packages/gunicorn/util.py", line 350, in import_app
    __import__(module)
  File "/srv/main.py", line 1, in <module>
    from config.wsgi import application
  File "/srv/config/wsgi.py", line 38, in <module>
    call_command('gsuite_sync_users')
  File "/env/lib/python3.7/site-packages/django/core/management/__init__.py", line 148, in call_command
    return command.execute(*args, **defaults)
  File "/env/lib/python3.7/site-packages/django/core/management/base.py", line 353, in execute
    output = self.handle(*args, **options)
  File "/srv/metanube_i4/users/management/commands/gsuite_sync_users.py", line 14, in handle
    gsuite_sync_users()
  File "/env/lib/python3.7/site-packages/celery/local.py", line 191, in __call__
    return self._get_current_object()(*a, **kw)
  File "/env/lib/python3.7/site-packages/celery/app/task.py", line 375, in __call__
    return self.run(*args, **kwargs)
  File "/srv/metanube_i4/users/tasks.py", line 22, in gsuite_sync_users
    creds = creds.with_subject(settings.GSUITE_ADMIN_USER)
AttributeError: 'Credentials' object has no attribute 'with_subject'"

套餐（部分清单）：

google-api-core==1.5.0
google-api-python-client==1.7.4
google-auth==1.5.1
google-auth-httplib2==0.0.3
google-cloud-bigquery==1.6.0
google-cloud-core==0.28.1
google-cloud-logging==1.8.0
google-cloud-storage==1.13.0
google-resumable-media==0.3.1
googleapis-common-protos==1.5.3
httplib2==0.11.3
oauthlib==2.1.0

问题答案：

的确，您不能使用with_subject具有GAE或GCE凭据的方法。但是，有一种解决方法可以在GCE服务器上工作，并且我认为这也适用于GAE默认服务帐户。解决方案是使用带有subject和的服务帐户标识来构建新的凭据scopes。可以在此处找到详细的指南，但下面还将介绍该过程。

首先，服务帐户需要权限才能为其自身创建服务帐户令牌。这可以通过转到项目IAM and admin > Service accounts页面来完成（确保信息面板可见，可以从右上角进行切换）。复制服务帐户的电子邮件地址，并通过选中复选框来选择有问题的服务帐户。现在信息面板上应该有ADD MEMBER按钮。单击它，然后将服务帐户电子邮件粘贴到New members文本框中。单击Select role下拉列表，然后选择角色Service Accounts -> Service Account Token Creator。您可以使用以下gcloud命令检查是否已分配角色：

gcloud iam service-accounts get-iam-policy [SERVICE_ACCOUNT_EMAIL]

现在到实际的Python代码。本示例是对上面链接的文档的略微修改。

from googleapiclient.discovery import build
from google.auth import default, iam
from google.auth.transport import requests
from google.oauth2 import service_account

TOKEN_URI = 'https://accounts.google.com/o/oauth2/token'
SCOPES = ['https://www.googleapis.com/auth/admin.directory.user']
GSUITE_ADMIN_USER = 'admin@example.com'

def delegated_credentials(credentials, subject, scopes):
    try:
        # If we are using service account credentials from json file
        # this will work
        updated_credentials = credentials.with_subject(subject).with_scopes(scopes)
    except AttributeError:
        # This exception is raised if we are using GCE default credentials

        request = requests.Request()

        # Refresh the default credentials. This ensures that the information
        # about this account, notably the email, is populated.
        credentials.refresh(request)

        # Create an IAM signer using the default credentials.
        signer = iam.Signer(
            request,
            credentials,
            credentials.service_account_email
        )

        # Create OAuth 2.0 Service Account credentials using the IAM-based
        # signer and the bootstrap_credential's service account email.
        updated_credentials = service_account.Credentials(
            signer,
            credentials.service_account_email,
            TOKEN_URI,
            scopes=scopes,
            subject=subject
        )
    except Exception:
        raise

    return updated_credentials


creds, project = default()
creds = delegated_credentials(creds, GSUITE_ADMIN_USER, SCOPES)

service = build('admin', 'directory_v1', credentials=creds)

try如果您GOOGLE_APPLICATION_CREDENTIALS设置的环境变量带有服务帐户文件的路径，则该块不会失败。如果该应用程序在Google
Cloud上运行，则会出现一个，AttributeError并通过创建具有subject和的新凭据来进行处理scopes。

您也可以通过None为subject对delegated_credentials功能，不受代表团创建凭证，以便该功能可有或无授权使用。

GAE AttributeError：“凭据”对象没有属性“ with_subject”

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