在不使用显式密钥文件的情况下从 Google Cloud Function 生成 Cloud Storage Signed URL

Question

我想创建一个预签名上传 URL 到存储桶，并希望避免明确引用 json 密钥。

目前，我正在尝试使用默认 App Engine 服务帐户执行此操作

我正在尝试遵循此答案，但收到此错误：

AttributeError：您需要一个私钥来签署凭证。您当前使用的凭证 <class 'google.auth.compute_engine.credentials.Credentials'> 只包含一个令牌。 有关更多详细信息，请参阅https://googleapis.dev/python/google-api-core/latest/auth.html#setting-up-a-service-account 。

我的云 Function 代码如下所示：

from google.cloud import storage
import datetime
import google.auth

def generate_upload_url(blob_name, additional_metadata: dict = {}):
    credentials, project_id = google.auth.default()
    # Perform a refresh request to get the access token of the current credentials (Else, it's None)
    from google.auth.transport import requests

    r = requests.Request()
    credentials.refresh(r)

    client = storage.Client()
    bucket = client.get_bucket("my_bucket")
    blob = bucket.blob(blob_name)
    
    service_account_email = credentials.service_account_email
    print(f"attempting to create signed url for {service_account_email}")
    url = blob.generate_signed_url(
        version="v4",
        service_account_email=service_account_email,
        access_token=credentials.token,
        # This URL is valid for 120 minutes
        expiration=datetime.timedelta(minutes=120),
        # Allow PUT requests using this URL.
        method="PUT",
        content_type="application/octet-stream",
        
    )
    return url


def get_upload_url(request):
    blob_name = get_param(request, "blob_name")
    url = generate_upload_url(blob_name)
    return url

Answer 1

当您使用签名 URL 的 v4 版本时， 该方法的第一行调用ensure_signed_credentials方法检查当前服务帐户是否可以在独立模式下生成签名（因此使用私钥）。 因此，这打破了当前的行为。

在 function 的注释中，清楚地描述了需要服务帐户 JSON 文件

        If you are on Google Compute Engine, you can't generate a signed URL.
        Follow `Issue 922`_ for updates on this. If you'd like to be able to
        generate a signed URL from GCE, you can use a standard service account
        from a JSON file rather than a GCE service account.

因此，请改用 v2 版本。