User Impersonation on Win XP SP2

[vipleo]

I am having some issues, when I try to launch another process using
Process.Start(P rocessStartInfo psi) on win xp sp2 box (Other versions
of xp have no issue).

Here is the detail.
Main app checks for updates on startup and if updates are available, it
launches separate exe to copy files.

Before launching new process(exe), I am impersonating admin user as
main app is being launched by non-admin user.

User identity is changed after impersonation, but during update,
"Access is denied" win32Exception is being thrown when main code tries
to launch copier exe.

Impersonation is implemented using following win32 api.
<code>
string domainName = string.Empty;
try
{
// Get current windows identity
string currentWindowsI dentity = WindowsIdentity .GetCurrent().N ame;

domainName = currentWindowsI dentity.Substri ng(0,
currentWindowsI dentity.IndexOf ('\\'));

const int LOGON32_PROVIDE R_DEFAULT = 0;
//This parameter causes LogonUser to create a primary token.
const int LOGON32_LOGON_I NTERACTIVE = 2;
const int SecurityImperso nation = 2;
tokenHandle = IntPtr.Zero;
dupeTokenHandle = IntPtr.Zero;
// Call LogonUser to obtain a handle to an access token.
bool returnValue = LogonUser(_impe rsonationUserna me,
domainName,_imp ersonationPassw ord, LOGON32_LOGON_I NTERACTIVE,
LOGON32_PROVIDE R_DEFAULT,ref tokenHandle);

if (false == returnValue)
{
int ret = Marshal.GetLast Win32Error();
int errorCode = 0x5; //ERROR_ACCESS_DE NIED
throw new System.Componen tModel.Win32Exc eption(errorCod e);
}

// Check the identity.
bool retVal = DuplicateToken( tokenHandle, SecurityImperso nation, ref
dupeTokenHandle );
if (false == retVal)
{
CloseHandle(tok enHandle);
return;
}

// The token that is passed to the following constructor must
// be a primary token in order to use it for impersonation.
WindowsIdentity newId = new WindowsIdentity (dupeTokenHandl e);
_impersonatedUs er = newId.Impersona te();
}
catch(Exception ex)
{

}
</code>
I have enabled following security policies for non-admin user:

1) Replace a process level token.

2) Debug programs

3) Adjust memory quotas for a process

NOTE: 'Launching another exe' works fine, if no user impersonation is
used.

Any ideas, what might be wrong ?

~ViPuL

[JaredHite1]

I agree that the problem he's having right now is not related to the
solution I posted...Your advice of getting the process info before
impersonating is sound. What I'm saying is that even if he fixes his
current issue, a much larger one looms...Once the process is started,
it will be happily running under the process' permissions, not the
impersonated thread's, so he needs to consider another approach
altogether.

Jared

[Willy Denoyette [MVP]]

"JaredHite1 " <ja***@sharingd s.org> wrote in message
news:11******** *************@o 13g2000cwo.goog legroups.com...
|I agree that the problem he's having right now is not related to the
| solution I posted...Your advice of getting the process info before
| impersonating is sound. What I'm saying is that even if he fixes his
| current issue, a much larger one looms...Once the process is started,
| it will be happily running under the process' permissions, not the
| impersonated thread's, so he needs to consider another approach
| altogether.
|
| Jared
|

That's true, that's why I'm a bit scared when people start to impersonate an
admin, I always wonder why they need it, and most of the time they don't.
The same, here, now I see what the OP is trying to achieve, the only
solution, is or calling "runas.exe" through Process.Start or trying to use
System.Manageme nt and WMI, which is not guaranteed to be succesfull because
of a security issue in v1.1.

Willy.

[vipleo]

Interesting points, codefealls..:)
The reason I want to impersonate the admin is that app user doesn't
have write permission on app install dir and app uses auto-update
mechanism to get latest files from network share on start-up. Xcopy of
latest dlls is being done within app; so If exe itself need to be
updated, another copier exe will be launched to finish auto-update.

I didn't get chance to try your suggestion, willy.

I will try it today and post results.

Thanks for your help guys...

~ViPuL

[vipleo]

Interesting points, codefealls..:)
The reason I want to impersonate the admin is that app user doesn't
have write permission on app install dir and app uses auto-update
mechanism to get latest files from network share on start-up. Xcopy of
latest dlls is being done within app; so If exe itself need to be
updated, another copier exe will be launched to finish auto-update.

I didn't get chance to try your suggestion, willy.

I will try it today and post results.

Thanks for your help guys...

~ViPuL

[vipleo]

Good news & bad news..

Good news first, anothe exe is being launched with willy's suggestion
to get process info before doing impersonation.
But....(bad news begins), exe is getting following exception:

System.TypeInit ializationExcep tion: The type initializer for
"System.Runtime .Remoting.Ident ity" threw an exception. --->
System.Security .Cryptography.C ryptographicExc eption: CryptoAPI
cryptographic service provider (CSP) for this implementation could not
be acquired.
at
System.Security .Cryptography.R NGCryptoService Provider..ctor( CspParameters
cspParams)
at System.Security .Cryptography.R NGCryptoService Provider..ctor( )
at System.Runtime. Remoting.Identi ty..cctor()
--- End of inner exception stack trace ---
at
FHEG.Framework. AppUpdater.Copy FilesDelegate.B eginInvoke(Asyn cCallback
callback, Object object)
at FHEG.Framework. AppUpdater.Prog ressForm.BeginC opy()
at
FHEG.Framework. AppUpdater.Prog ressForm.Progre ssForm_Activate d(Object
sender, EventArgs e)
at System.Windows. Forms.Form.OnAc tivated(EventAr gs e)
at System.Windows. Forms.Form.set_ Active(Boolean value)
at System.Windows. Forms.Form.WmAc tivate(Message& m)
at System.Windows. Forms.Form.WndP roc(Message& m)
at System.Windows. Forms.ControlNa tiveWindow.OnMe ssage(Message& m)
at System.Windows. Forms.ControlNa tiveWindow.WndP roc(Message& m)
at System.Windows. Forms.NativeWin dow.Callback(In tPtr hWnd, Int32
msg, IntPtr wparam, IntPtr lparam)

[Willy Denoyette [MVP]]

"vipleo" <vn*****@gmail. com> wrote in message
news:11******** **************@ g44g2000cwa.goo glegroups.com.. .
| Good news & bad news..
|
| Good news first, anothe exe is being launched with willy's suggestion
| to get process info before doing impersonation.
| But....(bad news begins), exe is getting following exception:
|
| System.TypeInit ializationExcep tion: The type initializer for
| "System.Runtime .Remoting.Ident ity" threw an exception. --->
| System.Security .Cryptography.C ryptographicExc eption: CryptoAPI
| cryptographic service provider (CSP) for this implementation could not
| be acquired.
| at
| System.Security .Cryptography.R NGCryptoService Provider..ctor( CspParameters
| cspParams)
| at System.Security .Cryptography.R NGCryptoService Provider..ctor( )
| at System.Runtime. Remoting.Identi ty..cctor()
| --- End of inner exception stack trace ---
| at
| FHEG.Framework. AppUpdater.Copy FilesDelegate.B eginInvoke(Asyn cCallback
| callback, Object object)
| at FHEG.Framework. AppUpdater.Prog ressForm.BeginC opy()
| at
| FHEG.Framework. AppUpdater.Prog ressForm.Progre ssForm_Activate d(Object
| sender, EventArgs e)
| at System.Windows. Forms.Form.OnAc tivated(EventAr gs e)
| at System.Windows. Forms.Form.set_ Active(Boolean value)
| at System.Windows. Forms.Form.WmAc tivate(Message& m)
| at System.Windows. Forms.Form.WndP roc(Message& m)
| at System.Windows. Forms.ControlNa tiveWindow.OnMe ssage(Message& m)
| at System.Windows. Forms.ControlNa tiveWindow.WndP roc(Message& m)
| at System.Windows. Forms.NativeWin dow.Callback(In tPtr hWnd, Int32
| msg, IntPtr wparam, IntPtr lparam)
|

As was said before, when impersonating, you are only running the thread in
the impersonated context, not the process that you spawn from this thread,
that's exactly why I asked why you were impersonating.
The result is that:
1. won't be able to copy to the .exe directory, and
2. apparently the application you start this way needs to access the crypto
store of the administrator, which is impossible because, the store (assumed
it's registry based) is not loaded and if it was you won't be able to access
it anyway.

Really, the only thing you can do (on v1.1) it create the process to run as
an administrator by calling CreateProcessAs through PInvoke, or better
integrate the "update" into your application (while impersonating). But
honestly, do you really want to take all this overhead when starting a
client application, just because you do not want to grant write access to
the .exe directory?
Do you think, this is a real security measure? I would say it's not, think
of what can happen when the process crashes when impersonating an
administrator!

Willy.

[vipleo]

I was able to launch another exe successsfully using CreateProcessAU ser
but ran into other issue. So I gave up.

Thanks a lot for your help guys. I really appreciate it.

~ViPuL

[JaredHite1]

I remember trying createprocessas user and not having any success
either...

I still think your best bet is to do File.Copy operations while
impersonating. In my case, I didn't have the option of granting the
user write rights to the folder since it was in an enterprise
environment where all that stuff was way out of my control.

Good luck,
Jared