Access files from network share in c# web app


Answers

I've had no problems connecting to network shares transparently as if they were local drives. The only issue you may have is what you mentioned: having the aspnet account gain access to the share. Impersonation is probably the best way to do this.

You should be able to use any filestream objects to access the network share as long as it has a drive letter on the server machine.

Question

I have a web application that needs to read (and possibly write) files from a network share. I was wondering what the best way to do this would be?

I can't give the network service or aspnet accounts access to the network share. I could possibly use impersonation.

The network share and the web application are both hosted on the same domain and I can create a new user on the domain specifically for this purpose however I'm not quite sure how to join the dots between creating the filestream and specifying the credentials to use in the web application.


Unfortunately the drive isn't mapped as a network drive on the machine, it's only available to me as a network share so unfortunately I can't make a transparent call.

There is one problem I can think of with impersonation... I can only impersonate one user per application domain I think but I'm happy to be corrected. I may need to write this file to several different shares which means I may have to impersonate several users.

I like the idea of creating a token... if I can do that I'll be able to ask the use up front for their credentials and then dynamically apply the security and give them meaningful error messages if access is denied... I'm off to play but I'll be back with an update.




you'll need to impersonate the user see this question

Effectivly you'll need to call logon to create windows identity which you can use to access the file system with

there is some more descussion on the subject here




Check your IIS directory security settings. You need to have anonymous authentication turned off and Windows authentication turned on.




Accessing Password Protected Network Drives in Windows in C#?

This question got me to where I needed to be pretty quickly in the same case.

Here's how I adapted the code:

using System;
using System.Runtime.InteropServices;

/// <summary>
/// Implements P/Invoke Interop calls to the operating system.
/// </summary>
internal static class NativeMethods
{
    /// <summary>
    /// The type of logon operation to perform.
    /// </summary>
    internal enum LogonType : int
    {
        /// <summary>
        /// This logon type is intended for users who will be interactively
        /// using the computer, such as a user being logged on by a
        /// terminal server, remote shell, or similar process.
        /// This logon type has the additional expense of caching logon
        /// information for disconnected operations; therefore, it is
        /// inappropriate for some client/server applications, such as a
        /// mail server.
        /// </summary>
        Interactive = 2,

        /// <summary>
        /// This logon type is intended for high performance servers to
        /// authenticate plaintext passwords.
        /// The LogonUser function does not cache credentials for this
        /// logon type.
        /// </summary>
        Network = 3,

        /// <summary>
        /// This logon type is intended for batch servers, where processes
        /// may be executing on behalf of a user without their direct
        /// intervention.  This type is also for higher performance servers
        /// that process many plaintext authentication attempts at a time,
        /// such as mail or Web servers.
        /// The LogonUser function does not cache credentials for this
        /// logon type.
        /// </summary>
        Batch = 4,

        /// <summary>
        /// Indicates a service-type logon.  The account provided must have
        /// the service privilege enabled.
        /// </summary>
        Service = 5,

        /// <summary>
        /// This logon type is for GINA DLLs that log on users who will be
        /// interactively using the computer.
        /// This logon type can generate a unique audit record that shows
        /// when the workstation was unlocked.
        /// </summary>
        Unlock = 7,

        /// <summary>
        /// This logon type preserves the name and password in the
        /// authentication package, which allows the server to make
        /// connections to other network servers while impersonating the
        /// client.  A server can accept plaintext credentials from a
        /// client, call LogonUser, verify that the user can access the
        /// system across the network, and still communicate with other
        /// servers.
        /// NOTE: Windows NT:  This value is not supported.
        /// </summary>
        NetworkCleartext = 8,

        /// <summary>
        /// This logon type allows the caller to clone its current token
        /// and specify new credentials for outbound connections.  The new
        /// logon session has the same local identifier but uses different
        /// credentials for other network connections.
        /// NOTE: This logon type is supported only by the
        /// LOGON32_PROVIDER_WINNT50 logon provider.
        /// NOTE: Windows NT:  This value is not supported.
        /// </summary>
        NewCredentials = 9
    }

    /// <summary>
    /// Specifies the logon provider.
    /// </summary>
    internal enum LogonProvider : int
    {
        /// <summary>
        /// Use the standard logon provider for the system.
        /// The default security provider is negotiate, unless you pass
        /// NULL for the domain name and the user name is not in UPN format.
        /// In this case, the default provider is NTLM.
        /// NOTE: Windows 2000/NT:   The default security provider is NTLM.
        /// </summary>
        Default = 0,

        /// <summary>
        /// Use this provider if you'll be authenticating against a Windows
        /// NT 3.51 domain controller (uses the NT 3.51 logon provider).
        /// </summary>
        WinNT35 = 1,

        /// <summary>
        /// Use the NTLM logon provider.
        /// </summary>
        WinNT40 = 2,

        /// <summary>
        /// Use the negotiate logon provider.
        /// </summary>
        WinNT50 = 3
    }

    /// <summary>
    /// The type of logon operation to perform.
    /// </summary>
    internal enum SecurityImpersonationLevel : int
    {
        /// <summary>
        /// The server process cannot obtain identification information
        /// about the client, and it cannot impersonate the client.  It is
        /// defined with no value given, and thus, by ANSI C rules,
        /// defaults to a value of zero.
        /// </summary>
        Anonymous = 0,

        /// <summary>
        /// The server process can obtain information about the client,
        /// such as security identifiers and privileges, but it cannot
        /// impersonate the client.  This is useful for servers that export
        /// their own objects, for example, database products that export
        /// tables and views.  Using the retrieved client-security
        /// information, the server can make access-validation decisions
        /// without being able to use other services that are using the
        /// client's security context.
        /// </summary>
        Identification = 1,

        /// <summary>
        /// The server process can impersonate the client's security
        /// context on its local system.  The server cannot impersonate the
        /// client on remote systems.
        /// </summary>
        Impersonation = 2,

        /// <summary>
        /// The server process can impersonate the client's security
        /// context on remote systems.
        /// NOTE: Windows NT:  This impersonation level is not supported.
        /// </summary>
        Delegation = 3
    }

    /// <summary>
    /// Logs on the user.
    /// </summary>
    /// <param name="userName">Name of the user.</param>
    /// <param name="domain">The domain.</param>
    /// <param name="password">The password.</param>
    /// <param name="logonType">Type of the logon.</param>
    /// <param name="logonProvider">The logon provider.</param>
    /// <param name="token">The token.</param>
    /// <returns>True if the function succeeds, false if the function fails.
    /// To get extended error information, call GetLastError.</returns>
    [DllImport("advapi32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    internal static extern bool LogonUser(
        string userName,
        string domain,
        string password,
        LogonType logonType,
        LogonProvider logonProvider,
        out IntPtr token);

    /// <summary>
    /// Duplicates the token.
    /// </summary>
    /// <param name="existingTokenHandle">The existing token
    /// handle.</param>
    /// <param name="securityImpersonationLevel">The security impersonation
    /// level.</param>
    /// <param name="duplicateTokenHandle">The duplicate token
    /// handle.</param>
    /// <returns>True if the function succeeds, false if the function fails.
    /// To get extended error information, call GetLastError.</returns>
    [DllImport("advapi32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    internal static extern bool DuplicateToken(
        IntPtr existingTokenHandle,
        SecurityImpersonationLevel securityImpersonationLevel,
        out IntPtr duplicateTokenHandle);

    /// <summary>
    /// Closes the handle.
    /// </summary>
    /// <param name="handle">The handle.</param>
    /// <returns>True if the function succeeds, false if the function fails.
    /// To get extended error information, call GetLastError.</returns>
    [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    internal static extern bool CloseHandle(IntPtr handle);
}

followed by

    IntPtr token;

    if (!NativeMethods.LogonUser(
        this.userName,
        this.domain,
        this.password,
        NativeMethods.LogonType.NewCredentials,
        NativeMethods.LogonProvider.Default,
        out token))
    {
        throw new Win32Exception();
    }

    try
    {
        IntPtr tokenDuplicate;

        if (!NativeMethods.DuplicateToken(
            token,
            NativeMethods.SecurityImpersonationLevel.Impersonation,
            out tokenDuplicate))
        {
            throw new Win32Exception();
        }

        try
        {
            using (WindowsImpersonationContext impersonationContext =
                new WindowsIdentity(tokenDuplicate).Impersonate())
            {
                // Do stuff with your share here.

                impersonationContext.Undo();
                return;
            }
        }
        finally
        {
            if (tokenDuplicate != IntPtr.Zero)
            {
                if (!NativeMethods.CloseHandle(tokenDuplicate))
                {
                    // Uncomment if you need to know this case.
                    ////throw new Win32Exception();
                }
            }
        }
    }
    finally
    {
        if (token != IntPtr.Zero)
        {
            if (!NativeMethods.CloseHandle(token))
            {
                // Uncomment if you need to know this case.
                ////throw new Win32Exception();
            }
        }
    }