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

我想创建一个到存储桶的预签名上传 URL，并希望避免显式引用 json 密钥。

目前，我正在尝试使用默认 App Engine 服务帐户来执行此操作

我正在尝试跟随这个答案 https://stackoverflow.com/a/64245028/7385884但我收到此错误：

AttributeError：您需要私钥来签署凭据。 您当前使用的凭据 仅包含 令牌。看https://googleapis.dev/python/google-api-core/latest/auth.html#setting-up-a-service-account https://googleapis.dev/python/google-api-core/latest/auth.html#setting-up-a-service-account更多细节。

我的云函数代码如下所示：

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

当您使用签名 URL 的 v4 版本时，该方法的第一行 https://github.com/googleapis/python-storage/blob/9d5bb5622f17a0143fa6670406596e53d0068286/google/cloud/storage/_signing.py#L536 calls ensure_signed_credentials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）的方法。所以，这打破了当前的行为。

在函数的注释中，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，请使用 v2 版本。