Hernan de Lahitte's blog

# re: User Credentials CommandDialog with SecureString password

This is pretty neat! Just what I was looking for... My only comment is that the unmanaged interop might be easier from C++/CLI rather than C#...

# re: User Credentials CommandDialog with SecureString password

The C++/CLI version is ~433 lines compared to ~514 for C#. Here it is:
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// Port of C# code from: http://weblogs.asp.net/hernandl/archive/2005/11/21/usercredentialsdialog.aspx

#include "StdAfx.h"

#include <vcclr.h>

using namespace System;
using namespace System::Drawing;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Diagnostics;
using namespace System::Windows::Forms;
using namespace System::Security;
using namespace System::Security::Permissions;
using namespace System::Runtime::InteropServices;

namespace Security { namespace Windows { namespace Forms {

#pragma region UserCredentialsDialogFlags
/// <summary>
/// Specifies special behavior for this function.
/// This value can be a bitwise-OR combination of zero or more of the following values.
/// </summary>
// For more information of these flags see:
// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/secauthn/security/creduipromptforcredentials.asp
// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnnetsec/html/dpapiusercredentials.asp?frame=true
[Flags]
public enum class UserCredentialsDialogFlags
{
None = 0x0
, IncorrectPassword = CREDUI_FLAGS_INCORRECT_PASSWORD
, DoNotPersist = CREDUI_FLAGS_DO_NOT_PERSIST
, RequestAdministrator = CREDUI_FLAGS_REQUEST_ADMINISTRATOR
, ExcludesCertificates = CREDUI_FLAGS_EXCLUDE_CERTIFICATES
, RequireCertificate = CREDUI_FLAGS_REQUIRE_CERTIFICATE
, ShowSaveCheckbox = CREDUI_FLAGS_SHOW_SAVE_CHECK_BOX
, AlwaysShowUI = CREDUI_FLAGS_ALWAYS_SHOW_UI
, RequireSmartCard = CREDUI_FLAGS_REQUIRE_SMARTCARD
, PasswordOnlyOk = CREDUI_FLAGS_PASSWORD_ONLY_OK
, ValidateUsername = CREDUI_FLAGS_VALIDATE_USERNAME
, CompleteUserName = CREDUI_FLAGS_COMPLETE_USERNAME
, Persist = CREDUI_FLAGS_PERSIST
, ServerCredential = CREDUI_FLAGS_SERVER_CREDENTIAL
, ExpectConfirmation = CREDUI_FLAGS_EXPECT_CONFIRMATION
, GenericCredentials = CREDUI_FLAGS_GENERIC_CREDENTIALS
, UsernameTargetCredentials = CREDUI_FLAGS_USERNAME_TARGET_CREDENTIALS
, KeepUsername = CREDUI_FLAGS_KEEP_USERNAME
, Default = GenericCredentials |
ShowSaveCheckbox |
AlwaysShowUI |
ExpectConfirmation
, PromptValid = CREDUI_FLAGS_PROMPT_VALID
};
#pragma endregion

/// <summary>
/// Displays a dialog box and promts the user for login credentials.
/// </summary>
[ToolboxItem(true)]
[DesignerCategory("Dialogs")]
public ref class UserCredentialsDialog : public CommonDialog
{
#pragma region Fields

String^ user;
SecureString^ password;
String^ domain;
String^ target;
String^ message;
String^ caption;
Image^ banner;
BOOL saveChecked;

#pragma endregion

#pragma region Constructors
private:
void init(System::String^ target, System::String^ caption, System::String^ message, System::Drawing::Image^ banner)
{
Target = target;
Caption = caption;
Message = message;
Banner = banner;
}

public:
UserCredentialsDialog()
{
Reset();
}
UserCredentialsDialog(System::String^ target)
{
init(target, nullptr, nullptr, nullptr);
}
UserCredentialsDialog(System::String^ target, System::String^ caption)
{
init(target, caption, nullptr, nullptr);
}
UserCredentialsDialog(System::String^ target, System::String^ caption, System::String^ message)
{
init(target, caption, message, nullptr);
}
UserCredentialsDialog(System::String^ target, System::String^ caption, System::String^ message, System::Drawing::Image^ banner)
{
init(target, caption, message, banner);
}

#pragma endregion

#pragma region Properties

property System::String^ User
{
System::String^ get() { return user; }
void set(System::String^ value)
{
if (value != nullptr)
{
if (value->Length > CREDUI_MAX_USERNAME_LENGTH)
{
throw gcnew ArgumentException(String::Format(
"The user name has a maximum length of {0} characters.",
CREDUI_MAX_USERNAME_LENGTH), "User");
}
}
user = value;
}
}

property System::Security::SecureString^ Password
{
System::Security::SecureString^ get() { return password; }
void set(System::Security::SecureString^ value)
{
if (value != nullptr)
{
if (value->Length > CREDUI_MAX_PASSWORD_LENGTH)
{
throw gcnew ArgumentException(String::Format(
"The password has a maximum length of {0} characters.",
CREDUI_MAX_PASSWORD_LENGTH), "Password");
}
}
password = value;
}
}

property System::String^ Domain
{
System::String^ get() { return domain; }
void set(System::String^ value)
{
if (value != nullptr)
{
if (value->Length > CREDUI_MAX_DOMAIN_TARGET_LENGTH)
{
throw gcnew ArgumentException(String::Format(
"The domain name has a maximum length of {0} characters.",
CREDUI_MAX_DOMAIN_TARGET_LENGTH), "Domain");
}
}
domain = value;
}
}

property System::String^ Target
{
System::String^ get() { return target; }
void set(System::String^ value)
{
if (value != nullptr)
{
if (value->Length > CREDUI_MAX_GENERIC_TARGET_LENGTH)
{
throw gcnew ArgumentException(String::Format(
"The target has a maximum length of {0} characters.",
CREDUI_MAX_GENERIC_TARGET_LENGTH), "Target");
}
}
target = value;
}
}

property System::String^ Message
{
System::String^ get() { return message; }
void set(System::String^ value)
{
if (value != nullptr)
{
if (value->Length > CREDUI_MAX_MESSAGE_LENGTH)
{
throw gcnew ArgumentException(String::Format(
"The message has a maximum length of {0} characters.",
CREDUI_MAX_MESSAGE_LENGTH), "Message");
}
}
message = value;
}
}

property System::String^ Caption
{
System::String^ get() { return caption; }
void set(System::String^ value)
{
if (value != nullptr)
{
if (value->Length > CREDUI_MAX_CAPTION_LENGTH)
{
throw gcnew ArgumentException(String::Format(
"The caption has a maximum length of {0} characters.",
CREDUI_MAX_CAPTION_LENGTH), "Caption");
}
}
caption = value;
}
}

property System::Drawing::Image^ Banner
{
System::Drawing::Image^ get() { return banner; }
void set(System::Drawing::Image^ value)
{
if (value != nullptr)
{
if (value->Width != CREDUI_BANNER_WIDTH)
{
throw gcnew ArgumentException(
String::Format("The banner image width must be {0} pixels.",
CREDUI_BANNER_WIDTH), "Banner");
}
if (value->Height != CREDUI_BANNER_HEIGHT)
{
throw gcnew ArgumentException(
String::Format("The banner image height must be {0} pixels.",
CREDUI_BANNER_HEIGHT), "Banner");
}
}
banner = value;
}
}

property bool SaveChecked
{
bool get() { return saveChecked ? true : false; }
void set(bool value) { saveChecked = value; }
}

property UserCredentialsDialogFlags Flags;

#pragma endregion

#pragma region Public methods

void ConfirmCredentials(bool confirm)
{
(gcnew UIPermission(UIPermissionWindow::SafeSubWindows))->Demand();

pin_ptr<const wchar_t> pTarget = PtrToStringChars(target);
DWORD result = CredUIConfirmCredentialsW(pTarget, confirm);

if(result != NO_ERROR &&
result != ERROR_NOT_FOUND &&
result != ERROR_INVALID_PARAMETER)
{
throw gcnew InvalidOperationException(TranslateReturnCode(result));
}
}

/// <summary>
/// This method is for backward compatibility with APIs that does
/// not provide the <see cref="SecureString"/> type.
/// </summary>
/// <returns></returns>
String^ PasswordToString()
{
IntPtr ptr = Marshal::SecureStringToGlobalAllocUnicode(Password);
try
{
// Unsecure managed string
return Marshal::PtrToStringUni(ptr);
}
finally
{
Marshal::ZeroFreeGlobalAllocUnicode(ptr);
}
}


#pragma endregion

protected:
#pragma region CommonDialog overrides

protected: virtual bool RunDialog(IntPtr hwndOwner) override
{
if (System::Environment::OSVersion->Version->Major < 5)
{
throw gcnew PlatformNotSupportedException("The Credential Management API requires Windows XP / Windows Server 2003 or later.");
}

pin_ptr<const wchar_t> pCaption = PtrToStringChars(caption);
pin_ptr<const wchar_t> pMessage = PtrToStringChars(message);
CREDUI_INFO credInfo;
credInfo.cbSize = sizeof(CREDUI_INFO);
credInfo.hwndParent = static_cast<HWND>(hwndOwner.ToPointer());
credInfo.pszCaptionText = pCaption;
credInfo.pszMessageText = pMessage;
if (banner != nullptr)
{
IntPtr hBitmap = (gcnew Bitmap(banner,
CREDUI_BANNER_WIDTH, CREDUI_BANNER_HEIGHT))->GetHbitmap();
credInfo.hbmBanner = static_cast<HBITMAP>(hBitmap.ToPointer());
}
else
{
credInfo.hbmBanner = NULL;
}

WCHAR pszName[CREDUI_MAX_USERNAME_LENGTH+1];
WCHAR pszPwd[CREDUI_MAX_PASSWORD_LENGTH+1];
SecureZeroMemory(pszName, sizeof(pszName));
SecureZeroMemory(pszPwd, sizeof(pszPwd));

if (!String::IsNullOrEmpty(User))
{
if (!String::IsNullOrEmpty(Domain))
{
pin_ptr<const wchar_t> pDomain = PtrToStringChars(Domain + "\\");
wcscat_s(pszName, pDomain);
}
pin_ptr<const wchar_t> pUser = PtrToStringChars(User);
wcscat_s(pszName, pUser);
}
if (Password != nullptr)
{
pin_ptr<const wchar_t> pPassword = PtrToStringChars(PasswordToString());
wcscat_s(pszPwd, pPassword);
}

try
{
pin_ptr<const wchar_t> pTarget = PtrToStringChars(Target);
pin_ptr<BOOL> pSaveChecked = &saveChecked;
DWORD result = CredUIPromptForCredentials(
&credInfo, pTarget,
NULL /*Reserved*/, 0 /*dwAuthError*/,
pszName, CREDUI_MAX_USERNAME_LENGTH+1,
pszPwd, CREDUI_MAX_PASSWORD_LENGTH+1,
pSaveChecked, static_cast<DWORD>(Flags));
switch (result)
{
case NO_ERROR:
LoadUserDomainValues(pszName);
LoadPasswordValue(pszPwd);
return true;
case ERROR_CANCELLED:
User = nullptr;
Password = nullptr;
return false;
default:
throw gcnew InvalidOperationException(TranslateReturnCode(result));
}
}
finally
{
SecureZeroMemory(pszName, sizeof(pszName));
SecureZeroMemory(pszPwd, sizeof(pszPwd));
if (banner != nullptr)
{
DeleteObject(credInfo.hbmBanner);
}
}
}

/// <summary>
/// Set all properties to it's default values.
/// </summary>
public: virtual void Reset() override
{
target = Application::ProductName ? Application::ProductName : AppDomain::CurrentDomain->FriendlyName;
user = nullptr;
password = nullptr;
domain = nullptr;
caption = nullptr;// target as caption;
message = nullptr;
banner = nullptr;
SaveChecked = false;
Flags = UserCredentialsDialogFlags::Default;
}

#pragma endregion

#pragma region Private methods
private:
static const int CREDUI_BANNER_HEIGHT = 60; // "The bitmap size is limited to 320x60 pixels."
static const int CREDUI_BANNER_WIDTH = 320; // "The bitmap size is limited to 320x60 pixels."

static String^ UserCredentialsDialog::TranslateReturnCode(DWORD result)
{
return String::Format("Invalid operation: {0}", result.ToString());
}

void LoadPasswordValue(LPWSTR pPassword)
{
password = gcnew SecureString(pPassword, lstrlen(pPassword)); // avoid /w64 warning with wcslen()
password->MakeReadOnly();
}

void LoadUserDomainValues(LPCWSTR pPrincipalName)
{
WCHAR pszUser[CREDUI_MAX_USERNAME_LENGTH+1];
WCHAR pszDomain[CREDUI_MAX_DOMAIN_TARGET_LENGTH+1];
DWORD result = CredUIParseUserNameW(pPrincipalName,
pszUser, CREDUI_MAX_USERNAME_LENGTH+1, pszDomain, CREDUI_MAX_DOMAIN_TARGET_LENGTH+1);

if (result == NO_ERROR)
{
User = gcnew String(pszUser);
Domain = gcnew String(pszUser);
}
else
{
User = gcnew String(pPrincipalName);
Domain = Environment::MachineName;
}
}

#pragma endregion
};

}}}

# re: User Credentials CommandDialog with SecureString password

Great. Thanks for the translation. However, perhaps just a 16% difference between each version may let developers easly choose the one that better fit the language personal preference, considering that performance/memory consumption may not be a big deal in this context (UI client scenario).

# re: User Credentials CommandDialog with SecureString password

Yup, there isn't a whole lot of difference in lines-of-code. I like the C++/CLI version because it avoids duplicating Win32 structs/#defines in C#; otherwise the Interop is pretty much a wash in this sample.

What would be really neat is if there were a way for C# to read "simple" (say basic #defines and simple structs/classes) C++ .h files.

# Protect your passwords - The SecureString Class

Protect your passwords - The SecureString Class

# Protect your passwords - The SecureString Class

Protect your passwords - The SecureString Class

# re: User Credentials CommandDialog with SecureString password

Can u plese check the download link for the code it is not active or can u please send me the code at makhijani.sandeep@gmail.com. I am having the same problem and would like to use it.

thanks in advance

# re: User Credentials CommandDialog with SecureString password

Thanks a bunch for sharing. If I try to open the UserCredentialsDialog.cs in Designer I get: The designer must create an instance of type 'System.Windows.Forms.CommonDialog' but it cannot because the type is declared as abstract. It is compiling and working, but is there a solution to rid of this error?

# re: User Credentials CommandDialog with SecureString password

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# re: User Credentials CommandDialog with SecureString password

Is it possible to show a domain/machine selection (combobox) similar to the main Windows login?

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