c# - 从远程文件共享下载文件会引发访问被拒绝

Question

我在 ASP.Net 通用处理程序中有以下代码来下载文件。

// generate you file
// set FilePath and FileName variables
string stFile = FilePath + FileName;
try {
    response.Clear();
    response.ContentType = "application/pdf";
    response.AppendHeader("Content-Disposition", "attachment; filename=" + FileName + ";");
    response.TransmitFile(stFile);
} catch (Exception ex) {
    // any error handling mechanism
} finally {
    response.End();
}

它适用于本地路径 - 例如“D:\Files\Sample.pdf”或“\localserver\Files\Sample.pdf”。

但它在尝试访问“\anotherServer\Files\Sample.pdf”等网络文件共享时抛出并拒绝访问错误。

和双跳有关系吗？我是否可以使用 spsecurity.runwithelevatedprivileges 来解决此问题？或者还有哪些其他选择？

根据这篇文章 https://weblogs.asp.net/owscott/iis-windows-authentication-and-the-double-hop-issue这似乎是一个双跳问题。我该如何解决这个问题？我想要的只是最终用户应该能够使用 asp.net 通用处理程序下载远程资源。

Answer 1

我必须处理一次类似的事情，并通过将网络共享映射到特定驱动器来让它工作。

在尝试访问之前向您的网络共享添加凭据的解决方案不起作用(但您可以作为第一次尝试尝试)

NetworkCredential nc = new NetworkCredential("<login>", "<pass>");
CredentialCache cache = new CredentialCache();
cache.Add(new Uri("<your network share>"), "Basic", nc);

如果这不起作用，请使用将网络共享映射到驱动器的组合解决方案。使用 NetworkDrive 类对 WNetAddConnection2 和 WNetCancelConnection2 进行 WinApi 调用:

public class NetworkDrive
{
    public enum ResourceScope
    {
        RESOURCE_CONNECTED = 1,
        RESOURCE_GLOBALNET,
        RESOURCE_REMEMBERED,
        RESOURCE_RECENT,
        RESOURCE_CONTEXT
    }

    public enum ResourceType
    {
        RESOURCETYPE_ANY,
        RESOURCETYPE_DISK,
        RESOURCETYPE_PRINT,
        RESOURCETYPE_RESERVED
    }

    public enum ResourceUsage
    {
        RESOURCEUSAGE_CONNECTABLE = 0x00000001,
        RESOURCEUSAGE_CONTAINER = 0x00000002,
        RESOURCEUSAGE_NOLOCALDEVICE = 0x00000004,
        RESOURCEUSAGE_SIBLING = 0x00000008,
        RESOURCEUSAGE_ATTACHED = 0x00000010,
        RESOURCEUSAGE_ALL = (RESOURCEUSAGE_CONNECTABLE | RESOURCEUSAGE_CONTAINER | RESOURCEUSAGE_ATTACHED),
    }

    public enum ResourceDisplayType
    {
        RESOURCEDISPLAYTYPE_GENERIC,
        RESOURCEDISPLAYTYPE_DOMAIN,
        RESOURCEDISPLAYTYPE_SERVER,
        RESOURCEDISPLAYTYPE_SHARE,
        RESOURCEDISPLAYTYPE_FILE,
        RESOURCEDISPLAYTYPE_GROUP,
        RESOURCEDISPLAYTYPE_NETWORK,
        RESOURCEDISPLAYTYPE_ROOT,
        RESOURCEDISPLAYTYPE_SHAREADMIN,
        RESOURCEDISPLAYTYPE_DIRECTORY,
        RESOURCEDISPLAYTYPE_TREE,
        RESOURCEDISPLAYTYPE_NDSCONTAINER
    }

    [StructLayout(LayoutKind.Sequential)]
    private class NETRESOURCE
    {
        public ResourceScope dwScope = 0;
        public ResourceType dwType = 0;
        public ResourceDisplayType dwDisplayType = 0;
        public ResourceUsage dwUsage = 0;
        public string lpLocalName = null;
        public string lpRemoteName = null;
        public string lpComment = null;
        public string lpProvider = null;
    }

    [DllImport("mpr.dll")]
    private static extern int WNetAddConnection2(NETRESOURCE lpNetResource, string lpPassword, string lpUsername, int dwFlags);

    [DllImport("mpr.dll")]
    static extern int WNetCancelConnection2(string lpName, Int32 dwFlags, bool bForce);

    private const int CONNECT_UPDATE_PROFILE = 0x1;
    private const int NO_ERROR = 0;

    public int MapNetworkDrive(string unc, string drive, string user, string password)
    {
        NETRESOURCE myNetResource = new NETRESOURCE();
        myNetResource.lpLocalName = drive;
        myNetResource.lpRemoteName = unc;
        myNetResource.lpProvider = null;
        int result = WNetAddConnection2(myNetResource, password, user, 0);
        if (result == 0)
            return result;
        else
            throw new Win32Exception(Marshal.GetLastWin32Error());
    }

    public int UnmapNetworkDrive(string drive)
    {
        int result = WNetCancelConnection2(drive, CONNECT_UPDATE_PROFILE, true);
        if (result != NO_ERROR)
        {
            throw new Win32Exception(Marshal.GetLastWin32Error());
        }
        return result;
    }
}

然后像这样使用它:

NetworkDrive nd = new NetworkDrive();

try
{
    if (nd.MapNetworkDrive("<your network share>", "Z:", "<login>", "<pass>") == 0)
    {
        NetworkCredential nc = new NetworkCredential("<login>", "<pass>");
        CredentialCache cache = new CredentialCache();
        cache.Add(new Uri("<your network share>"), "Basic", nc);

        // access network share using UNC path (not your drive letter)
    }
}
finally
{
    nd.UnmapNetworkDrive("Z:");
}