Question

我已经写了下面的代码来获取带缓存到期令牌的blob url，实际上已经设置了2个小时来使blob url到期，

            CloudStorageAccount storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageConnectionString"));
           CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
                         CloudBlobContainer container = blobClient.GetContainerReference(containerName);
            CloudBlockBlob blockBlob = container.GetBlockBlobReference("blobname");
            //Create an ad-hoc Shared Access Policy with read permissions which will expire in 2 hours
            SharedAccessBlobPolicy policy = new SharedAccessBlobPolicy()
            {
                Permissions = SharedAccessBlobPermissions.Read,
                SharedAccessExpiryTime = DateTime.UtcNow.AddHours(2),
            };

            SharedAccessBlobHeaders headers = new SharedAccessBlobHeaders()
            {
                ContentDisposition = string.Format("attachment;filename=\"{0}\"", "blobname"),
            };
            var sasToken = blockBlob.GetSharedAccessSignature(policy, headers);
            blobUrl = blockBlob.Uri.AbsoluteUri + sasToken;

使用上面的代码我得到带有效到期令牌的blob url，现在我想在一个客户端应用程序中检查blob url是否有效。我通过传递URL并获取响应状态代码来尝试Web请求和http客户端方法。如果响应代码是404，那么我假设URL已过期，如果URL仍然有效，但这种方法需要更多时间。

请以其他方式建议我。

Answer 1

我尝试运行与你的代码非常相似的代码，我收到403错误，这实际上是在这种情况下的预期。根据您的问题，我不确定403是否比404更有帮助。以下是在控制台应用程序中运行的代码，返回403：

class Program
{
    static void Main(string[] args)
    {
        string blobUrl = CreateSAS();
        CheckSAS(blobUrl);

        Console.ReadLine();
    }

    //This method returns a reference to the blob with the SAS, and attempts to read it.
    static void CheckSAS(string blobUrl)
    {
        CloudBlockBlob blob = new CloudBlockBlob(new Uri(blobUrl));

        //If the DownloadText() method is run within the two minute period that the SAS is valid, it succeeds.
        //If it is run after the SAS has expired, it returns a 403 error.
        //Sleep for 3 minutes to trigger the error.
        System.Threading.Thread.Sleep(180000);
        Console.WriteLine(blob.DownloadText());
    }

    //This method creates the SAS on the blob.
    static string CreateSAS()
    {
        string containerName = "forum-test";
        string blobName = "blobname";
        string blobUrl = "";

        CloudStorageAccount storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageConnectionString"));
        CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
        CloudBlobContainer container = blobClient.GetContainerReference(containerName);
        container.CreateIfNotExists();

        CloudBlockBlob blockBlob = container.GetBlockBlobReference(blobName + DateTime.Now.Ticks);
        blockBlob.UploadText("Blob for forum test");

        //Create an ad-hoc Shared Access Policy with read permissions which will expire in 2 hours
        SharedAccessBlobPolicy policy = new SharedAccessBlobPolicy()
        {
            Permissions = SharedAccessBlobPermissions.Read,
            SharedAccessExpiryTime = DateTime.UtcNow.AddMinutes(2),
        };

        SharedAccessBlobHeaders headers = new SharedAccessBlobHeaders()
        {
            ContentDisposition = string.Format("attachment;filename=\"{0}\"", blobName),
        };
        var sasToken = blockBlob.GetSharedAccessSignature(policy, headers);
        blobUrl = blockBlob.Uri.AbsoluteUri + sasToken;

        return blobUrl;
    }
}

在某些情况下，SAS故障确实会返回404，这可能会导致使用SAS进行故障排除操作时出现问题。 Azure存储团队了解此问题，在将来的版本中，SAS故障可能会返回403。有关解决404错误的帮助，请参阅http://azure.microsoft.com/en-us/documentation/articles/storage-monitoring-diagnosing-troubleshooting/#SAS-authorization-issue。

Answer 2

几天前我也遇到了同样的问题。我实际上期望存储服务在SAS令牌过期时返回403错误代码，但存储服务返回404错误。

鉴于我们没有任何其他选项，您执行此操作的方式是唯一可行的方法，但仍然不正确，因为如果存储帐户中不存在blob，则可能会出现404错误。 / p>

Answer 3

也许您可以从生成的SAS中解析“se”参数，这意味着到期时间，例如“SE = 2013-04-30T02％3A23％3A26Z”。但是，由于服务器时间可能与客户端时间不同，因此解决方案可能不稳定。

http://azure.microsoft.com/en-us/documentation/articles/storage-dotnet-shared-access-signature-part-1/

Answer 4

您使用的是SharedAccessExpiryTime的UTC时间（请参阅https://docs.microsoft.com/en-us/azure/storage/common/storage-dotnet-shared-access-signature-part-1#parameters-common-to-account-sas-and-service-sas-tokens中的“到期时间”）。

然后将到期时间记录在令牌中的se索赔下，可以在实际使用令牌之前对照客户端的当前UTC时间检查其值。这样一来，您就不必再对Blob存储进行额外的调用，而只需查找令牌是否已过期即可。

如何找到共享访问令牌过期的bloburl？

4 个答案: