I’m creating an Xaml/C# application and I would like it to popup with a Login Prompt.
I would like to know if its possible to use CredUIPromptForWindowsCredentials.
- Show Windows Security Dialog
- Get the entered username & password
- Perform Custom validation
- If validation succes -> continue app
- else if validation failed -> -inform user of invalid username or password
I have already looked at Windows Security login form? and http://www.pinvoke.net/default.aspx/credui/creduipromptforwindowscredentials.html?diff=y but they don’t explain how to handle the validation.
I would really like a small example, where if the user enters username = “Bo” and password = “123” then succes else display error message and allow the user to try again.
The App is going to be installed on multiple computers.
Or is this simply not possible?
Update
Inspired by the answer in this question Show Authentication dialog in C# for windows Vista/7
I have modified the code to work as expected.
Please not, that the validation part is only for proof of concept.
WindowsSecurityDialog.cs
public class WindowsSecurityDialog
{
public string CaptionText { get; set; }
public string MessageText { get; set; }
[DllImport("ole32.dll")]
public static extern void CoTaskMemFree(IntPtr ptr);
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
private struct CREDUI_INFO
{
public int cbSize;
public IntPtr hwndParent;
public string pszMessageText;
public string pszCaptionText;
public IntPtr hbmBanner;
}
[DllImport("credui.dll", CharSet = CharSet.Auto)]
private static extern bool CredUnPackAuthenticationBuffer(int dwFlags,
IntPtr pAuthBuffer,
uint cbAuthBuffer,
StringBuilder pszUserName,
ref int pcchMaxUserName,
StringBuilder pszDomainName,
ref int pcchMaxDomainame,
StringBuilder pszPassword,
ref int pcchMaxPassword);
[DllImport("credui.dll", CharSet = CharSet.Auto)]
private static extern int CredUIPromptForWindowsCredentials(ref CREDUI_INFO notUsedHere,
int authError,
ref uint authPackage,
IntPtr InAuthBuffer,
uint InAuthBufferSize,
out IntPtr refOutAuthBuffer,
out uint refOutAuthBufferSize,
ref bool fSave,
int flags);
public bool ValidateUser()
{
var credui = new CREDUI_INFO
{
pszCaptionText = CaptionText,
pszMessageText = MessageText
};
credui.cbSize = Marshal.SizeOf(credui);
uint authPackage = 0;
IntPtr outCredBuffer;
uint outCredSize;
bool save = false;
const int loginErrorCode = 1326; //Login Failed
var authError = 0;
while (true)
{
var result = CredUIPromptForWindowsCredentials(ref credui,
authError,
ref authPackage,
IntPtr.Zero,
0,
out outCredBuffer,
out outCredSize,
ref save,
1 /* Generic */);
var usernameBuf = new StringBuilder(100);
var passwordBuf = new StringBuilder(100);
var domainBuf = new StringBuilder(100);
var maxUserName = 100;
var maxDomain = 100;
var maxPassword = 100;
if (result == 0)
{
if (CredUnPackAuthenticationBuffer(0, outCredBuffer, outCredSize, usernameBuf, ref maxUserName,
domainBuf, ref maxDomain, passwordBuf, ref maxPassword))
{
//TODO: ms documentation says we should call this but i can't get it to work
//SecureZeroMem(outCredBuffer, outCredSize);
//clear the memory allocated by CredUIPromptForWindowsCredentials
CoTaskMemFree(outCredBuffer);
var networkCredential = new NetworkCredential()
{
UserName = usernameBuf.ToString(),
Password = passwordBuf.ToString(),
Domain = domainBuf.ToString()
};
//Dummy Code replace with true User Validation
if (networkCredential.UserName == "Bo" && networkCredential.Password == "1234")
return true;
else //login failed show dialog again with login error
{
authError = loginErrorCode;
}
}
}
else return false;
}
}
}
App.xaml.cs
protected override void OnStartup(StartupEventArgs e)
{
var windowsSecurityDialog = new WindowsSecurityDialog
{
CaptionText = "Enter your credentials",
MessageText = "These credentials will be used to connect to YOUR APP NAME";
};
if (windowsSecurityDialog.ValidateUser())
base.OnStartup(e);
}
You’ll find a complete implementation for WPF and WinForms using CredUIPromptForWindowsCredentials at Ookii dialogs.