Question

我正在与Microsoft Health Cloud API接口，并已成功请求访问令牌和刷新令牌。与RESTful API的通信按预期工作，尽管我很难搞清楚如何可靠地确定过期的访问令牌。

我有以下代码：

fire_and_forget read_profile()
{
    HttpClient httpClient{};
    httpClient.DefaultRequestHeaders().Authorization({ L"bearer", access_token_ });
    try
    {
        auto const response{ co_await httpClient.GetStringAsync({ L"https://api.microsofthealth.net/v1/me/Profile" }) };
        // Raise event passing the response along.
        // Code left out for brevity.
        co_return;
    }
    catch (hresult_error const& e)
    {
        if (e.code() != 0x80190191) // Magic value for "unauthorized access (401)"
        {
            throw;
        }
        // This is an "unauthorized access (401)" error. Continue with requesting a new
        // access token from the refresh token.
        // Code left out for brevity.
    }

虽然它似乎有用，但出于这么多原因感觉不对。这不仅仅是神奇的价值，而且还有这个特定的错误代码可能用于其他错误模式的事实。

是否有更强大的方法来确定访问令牌是否已过期？

注意：据我所知，我可以使用到期时间间隔，并检查系统时间。我不想走这条路，因为它也不完全可靠，并且为跨设备漫游这些信息带来了额外的复杂性。

Answer 1

据我所知，我可以使用到期时间间隔，并检查系统时间。

Microsoft Health Cloud API已提供expires_in字段以验证令牌是否有效。通常，我们可以检查系统时间，如果系统时间是人为修改的，那么它并不完全可靠。所以我们可以使用NTP服务器时间，而不是使用系统时间。

 public async static Task<DateTime> GetNetworkTime()
 {
     //default Windows time server
     const string ntpServer = "time.windows.com";

     // NTP message size - 16 bytes of the digest (RFC 2030)
     var ntpData = new byte[48];

     //Setting the Leap Indicator, Version Number and Mode values
     ntpData[0] = 0x1B; //LI = 0 (no warning), VN = 3 (IPv4 only), Mode = 3 (Client Mode)

     var addresses = await Dns.GetHostAddressesAsync(ntpServer);
     //The UDP port number assigned to NTP is 123
     var ipEndPoint = new IPEndPoint(addresses[0], 123);
     //NTP uses UDP

     using (var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp))
     {
         socket.Connect(ipEndPoint);

         //Stops code hang if NTP is blocked
         socket.ReceiveTimeout = 3000;

         socket.Send(ntpData);
         socket.Receive(ntpData);
         socket.Dispose();
     }

     //Offset to get to the "Transmit Timestamp" field (time at which the reply 
     //departed the server for the client, in 64-bit timestamp format."
     const byte serverReplyTime = 40;

     //Get the seconds part
     ulong intPart = BitConverter.ToUInt32(ntpData, serverReplyTime);

     //Get the seconds fraction
     ulong fractPart = BitConverter.ToUInt32(ntpData, serverReplyTime + 4);

     //Convert From big-endian to little-endian
     intPart = SwapEndianness(intPart);
     fractPart = SwapEndianness(fractPart);

     var milliseconds = (intPart * 1000) + ((fractPart * 1000) / 0x100000000L);

     //**UTC** time
     var networkDateTime = (new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc)).AddMilliseconds((long)milliseconds);

     return networkDateTime.ToLocalTime();
 }

 // stackoverflow.com/a/3294698/162671
 static uint SwapEndianness(ulong x)
 {
     return (uint)(((x & 0x000000ff) << 24) +
                    ((x & 0x0000ff00) << 8) +
                    ((x & 0x00ff0000) >> 8) +
                    ((x & 0xff000000) >> 24));
 }

如何确定过期的访问令牌？

1 个答案: