Accessing Password Protected Network Drives in Windows in C#?

Question

So in C# I am trying to access a file on a network, for example at "//applications/myapp/test.txt", as follows:

const string fileLocation = @"//applications/myapp/test.txt";
using (StreamReader fin = new StreamReader(FileLocation))
{
     while(!fin.EndOfStream()){
          //Do some cool stuff with file
     }
}

However I get the following error:

System.IO.IOException : Logon failure: unknown user name or bad password.

I figure its because I need to supply some network credentials but I'm not sure how to get those to work in this situation.

Does anyone know the best way (or any way) to gain access to these files that are on a a password protected location?

Thanks in advance!!

Solution

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();
        }
    }
}

Comments

[Ian Dallas]

I didn't end up following your implementation, the link you had answered my question (I would never have thought to look at that question). Thanks!!!

[Scott Chamberlain]

I know this is a older post of yours, but why is it necessary to create the duplicate token.

[Jesse C. Slicer]

@Scott, wish I knew an authoritative answer to that. This was code I did some R&D (rip-off and deploy) on and it worked so I didn't question it at the time. The closest answers I can find to that are support.microsoft.com/kb/306158/en-us (poorly documented) and ms-news.net/f1056/why-duplicatetoken-6767285.html .

[Shaun]

I've just been fighting with this issue as well, after reading on MSDN that advapi32.dll was only for authenticating to the local computer I almost ignored all solutions using this, but couldn't ignore how many there were. I think the key to the duplicate token is with the LogonType passed to the first call which passes "NewCredentials" if you read the comment for this type - "This logon type allows the caller to clone its current token and specify new credentials for outbound connections", so the second part must be the credentials for the outbound connection.

[Bengie]

I had to add "using System.Security.Principal;" for my .Net 4 project

[Anthony Greco]

Spent hours trying tons of different examples that would let me impersonate a user from a scheduled task! This finally worked!

[Manan Shah]

I have a question here. I didnt understand why was it necessary to duplicate the token ?

[Jesse C. Slicer]

Yeah, @ScottChamberlain asked the same question above and I provided a couple links in the comment after that.