How to validate domain credentials?
C# in .NET 3.5 using System.DirectoryServices.AccountManagement.
bool valid = false;
using (PrincipalContext context = new PrincipalContext(ContextType.Domain))
{
valid = context.ValidateCredentials( username, password );
}
This will validate against the current domain. Check out the parameterized PrincipalContext constructor for other options.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security;
using System.DirectoryServices.AccountManagement;
public struct Credentials
{
public string Username;
public string Password;
}
public class Domain_Authentication
{
public Credentials Credentials;
public string Domain;
public Domain_Authentication(string Username, string Password, string SDomain)
{
Credentials.Username = Username;
Credentials.Password = Password;
Domain = SDomain;
}
public bool IsValid()
{
using (PrincipalContext pc = new PrincipalContext(ContextType.Domain, Domain))
{
// validate the credentials
return pc.ValidateCredentials(Credentials.Username, Credentials.Password);
}
}
}
I`m using the following code to validate credentials. The method shown below will confirm if the credentials are correct and if not wether the password is expired or needs change.
I`ve been looking for something like this for ages... So i hope this helps someone!
using System;
using System.DirectoryServices;
using System.DirectoryServices.AccountManagement;
using System.Runtime.InteropServices;
namespace User
{
public static class UserValidation
{
[DllImport("advapi32.dll", SetLastError = true)]
static extern bool LogonUser(string principal, string authority, string password, LogonTypes logonType, LogonProviders logonProvider, out IntPtr token);
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool CloseHandle(IntPtr handle);
enum LogonProviders : uint
{
Default = 0, // default for platform (use this!)
WinNT35, // sends smoke signals to authority
WinNT40, // uses NTLM
WinNT50 // negotiates Kerb or NTLM
}
enum LogonTypes : uint
{
Interactive = 2,
Network = 3,
Batch = 4,
Service = 5,
Unlock = 7,
NetworkCleartext = 8,
NewCredentials = 9
}
public const int ERROR_PASSWORD_MUST_CHANGE = 1907;
public const int ERROR_LOGON_FAILURE = 1326;
public const int ERROR_ACCOUNT_RESTRICTION = 1327;
public const int ERROR_ACCOUNT_DISABLED = 1331;
public const int ERROR_INVALID_LOGON_HOURS = 1328;
public const int ERROR_NO_LOGON_SERVERS = 1311;
public const int ERROR_INVALID_WORKSTATION = 1329;
public const int ERROR_ACCOUNT_LOCKED_OUT = 1909; //It gives this error if the account is locked, REGARDLESS OF WHETHER VALID CREDENTIALS WERE PROVIDED!!!
public const int ERROR_ACCOUNT_EXPIRED = 1793;
public const int ERROR_PASSWORD_EXPIRED = 1330;
public static int CheckUserLogon(string username, string password, string domain_fqdn)
{
int errorCode = 0;
using (PrincipalContext pc = new PrincipalContext(ContextType.Domain, domain_fqdn, "ADMIN_USER", "PASSWORD"))
{
if (!pc.ValidateCredentials(username, password))
{
IntPtr token = new IntPtr();
try
{
if (!LogonUser(username, domain_fqdn, password, LogonTypes.Network, LogonProviders.Default, out token))
{
errorCode = Marshal.GetLastWin32Error();
}
}
catch (Exception)
{
throw;
}
finally
{
CloseHandle(token);
}
}
}
return errorCode;
}
}
Here's how to determine a local user:
public bool IsLocalUser()
{
return windowsIdentity.AuthenticationType == "NTLM";
}
Edit by Ian Boyd
You should not use NTLM anymore at all. It is so old, and so bad, that Microsoft's Application Verifier (which is used to catch common programming mistakes) will throw a warning if it detects you using NTLM.
Here's a chapter from the Application Verifier documentation about why they have a test if someone is mistakenly using NTLM:
Why the NTLM Plug-in is Needed
NTLM is an outdated authentication protocol with flaws that potentially compromise the security of applications and the operating system. The most important shortcoming is the lack of server authentication, which could allow an attacker to trick users into connecting to a spoofed server. As a corollary of missing server authentication, applications using NTLM can also be vulnerable to a type of attack known as a “reflection” attack. This latter allows an attacker to hijack a user’s authentication conversation to a legitimate server and use it to authenticate the attacker to the user’s computer. NTLM’s vulnerabilities and ways of exploiting them are the target of increasing research activity in the security community.
Although Kerberos has been available for many years many applications are still written to use NTLM only. This needlessly reduces the security of applications. Kerberos cannot however replace NTLM in all scenarios – principally those where a client needs to authenticate to systems that are not joined to a domain (a home network perhaps being the most common of these). The Negotiate security package allows a backwards-compatible compromise that uses Kerberos whenever possible and only reverts to NTLM when there is no other option. Switching code to use Negotiate instead of NTLM will significantly increase the security for our customers while introducing few or no application compatibilities. Negotiate by itself is not a silver bullet – there are cases where an attacker can force downgrade to NTLM but these are significantly more difficult to exploit. However, one immediate improvement is that applications written to use Negotiate correctly are automatically immune to NTLM reflection attacks.
By way of a final word of caution against use of NTLM: in future versions of Windows it will be possible to disable the use of NTLM at the operating system. If applications have a hard dependency on NTLM they will simply fail to authenticate when NTLM is disabled.
How the Plug-in Works
The Verifier plug detects the following errors:
The NTLM package is directly specified in the call to AcquireCredentialsHandle (or higher level wrapper API).
The target name in the call to InitializeSecurityContext is NULL.
The target name in the call to InitializeSecurityContext is not a properly-formed SPN, UPN or NetBIOS-style domain name.
The latter two cases will force Negotiate to fall back to NTLM either directly (the first case) or indirectly (the domain controller will return a “principal not found” error in the second case causing Negotiate to fall back).
The plug-in also logs warnings when it detects downgrades to NTLM; for example, when an SPN is not found by the Domain Controller. These are only logged as warnings since they are often legitimate cases – for example, when authenticating to a system that is not domain-joined.
NTLM Stops
5000 – Application Has Explicitly Selected NTLM Package
Severity – Error
The application or subsystem explicitly selects NTLM instead of Negotiate in the call to AcquireCredentialsHandle. Even though it may be possible for the client and server to authenticate using Kerberos this is prevented by the explicit selection of NTLM.
How to Fix this Error
The fix for this error is to select the Negotiate package in place of NTLM. How this is done will depend on the particular Network subsystem being used by the client or server. Some examples are given below. You should consult the documentation on the particular library or API set that you are using.
APIs(parameter) Used by Application Incorrect Value Correct Value ===================================== =============== ======================== AcquireCredentialsHandle (pszPackage) “NTLM” NEGOSSP_NAME “Negotiate”