在不使用顯式密鑰文件的情況下從 Google Cloud Function 生成 Cloud Storage Signed URL

Question

我想創建一個預簽名上傳 URL 到存儲桶，並希望避免明確引用 json 密鑰。

目前，我正在嘗試使用默認 App Engine 服務帳戶執行此操作

我正在嘗試遵循此答案，但收到此錯誤：

AttributeError：您需要一個私鑰來簽署憑證。您當前使用的憑證 <class 'google.auth.compute_engine.credentials.Credentials'> 只包含一個令牌。 有關更多詳細信息，請參閱https://googleapis.dev/python/google-api-core/latest/auth.html#setting-up-a-service-account 。

我的雲 Function 代碼如下所示：

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

當您使用簽名 URL 的 v4 版本時， 該方法的第一行調用ensure_signed_credentials方法檢查當前服務帳戶是否可以在獨立模式下生成簽名（因此使用私鑰）。 因此，這打破了當前的行為。

在 function 的注釋中，清楚地描述了需要服務帳戶 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，請改用 v2 版本。