使用访问令牌签署谷歌云存储 blob

Question

目标：使用 OAuth2.0 访问令牌生成签名 URL

我找到的用于签署 Google Cloud Storage Blob 的示例和源代码都需要服务帐户凭据文件（具体来说是私钥）。例如：

https://cloud.google.com/storage/docs/access-control/signing-urls-with-helpers#storage-signed-url-get-object-python

但是，由于我关注the authorization flow discussed here，因此我只有 OAuth2.0 访问令牌（并且我没有有权访问 GCS 存储桶/对象的服务帐户的凭据文件和私钥）。因此，我想知道如何使用 OAuth2.0 访问令牌对 blob 进行签名。

使用的代码：

我使用以下方式对 blob 进行签名：

# First, get access token:
service_account = "<email address of a service account>"
access_token = build(
    serviceName='iamcredentials',
    version='v1',
    http=http
).projects().serviceAccounts().generateAccessToken(
    name="projects/{}/serviceAccounts/{}".format(
        "-",
        service_account),
    body=body
).execute()["accessToken"]

credentials = AccessTokenCredentials(access_token, "MyAgent/1.0", None)

# Second, use the access token to sign a blob
url = "https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/{}:signBlob".format(service_account)
encoded = base64.b64encode(blob)
sign_blob_request_body = {"payload": encoded}

response = requests.post(url,
                         data=json.dumps(sign_blob_request_body),
                         headers={
                             'Content-Type': 'application/json',
                             'Authorization': 'Bearer {}'.format(credentials.access_token)})
signature = response.json()["signedBlob"]

# Third, use the signature to create signed URL:
encoded_signature = base64.b64encode(signature)
signed_url = "https://storage.googleapis.com/<BUCKET>/<OBJECT>?" \
             "GoogleAccessId={}&" \
             "Expires={}&" \
             "Signature={}".format(service_account, 
                                   expiration, 
                                   encoded_signature)

收到的错误信息：

<Error>
    <Code>SignatureDoesNotMatch</Code>
    <Message>
        The request signature we calculated does not match the signature you provided. Check your Google secret key and signing method.
    </Message>
    <StringToSign>GET 1561832204 /<BUCKET>/<OBJECT></StringToSign>
</Error>

Answer 1

如果您不想使用 API 密钥，follow procedure described in this sample 正在使用 iamcredentials.signBlob() API 为无需分发 API 密钥的服务帐户“远程”签名 URL。

签名字符串（必须签名）具有以下格式：

signature_string = ('{verb}\n'
                    '{content_md5}\n'
                    '{content_type}\n'
                    '{expiration}\n'
                    '{resource}')