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how to validate domain credentials

I need to validate a suite of credentials towards the domain controller. e.g.:

Username: STACKOVERFLOW\joelPassword: splotchy Method 1. Query Active Directory with Impersonation

A lot of different people suggest querying the Active Directory for one thing. If an exception is thrown, then the credentials aren't valid - as is usually recommended on this stackoverflow query.

There are a few critical drawbacks to this means on the other hand:

  1. You are not only authenticating a domain account, but you are also doing an implicit authorization check. That is, you are reading properties from the AD using an impersonation token. What if the otherwise valid account has no rights to read from the AD? By default all users have read access, but domain policies can be set to disable access permissions for restricted accounts (and or groups).

  2. Binding against the AD has a serious overhead, the AD schema cache has to be loaded at the client (ADSI cache in the ADSI provider used by DirectoryServices). This is both network, and AD server, resource consuming - and is too expensive for a simple operation like authenticating a user account.

  3. You're relying on an exception failure for a non-exceptional case, and assuming that means invalid username and password. Other problems (e.g. network failure, AD connectivity failure, memory allocation error, etc) are then mis-intrepreted as authentication failure.

Method 2. LogonUser Win32 API

Others have recommended the use of the LogonUser() API serve as. This sounds great, however sadly the calling user once in a while wishes a permission on a regular basis best given to the operating system itself:

The process calling LogonUser requires the SE_TCB_NAME privilege. If the calling process does not have this privilege, LogonUser fails and GetLastError returns ERROR_PRIVILEGE_NOT_HELD.

In some cases, the process that calls LogonUser must also have the SE_CHANGE_NOTIFY_NAME privilege enabled; otherwise, LogonUser fails and GetLastError returns ERROR_ACCESS_DENIED. This privilege is not required for the local system account or accounts that are members of the administrators group. By default, SE_CHANGE_NOTIFY_NAME is enabled for all users, but some administrators may disable it for everyone.

Handing out the "Act as part of the working machine" privilege isn't one thing you wish to must do willy-nilly - as Microsoft issues out in a data base article:

...the process that is calling LogonUser must have the SE_TCB_NAME privilege (in User Manager, this is the "Act as part of the Operating System" right). The SE_TCB_NAME privilege is very powerful and should not be granted to any arbitrary user just so that they can run an application that needs to validate credentials.

Additionally, a decision to LogonUser() will fail if a clean password is targeted.

What is the correct strategy to authenticate a collection of domain credentials?

I occur to be calling from controlled code, however this can be a a common Windows query. It can be assumed that the shoppers have the .NET Framework put in.

#c #windows #security #authentication
Last update on March 20, 6:46 pm by francesco2366.

C# in .NET three.five the use of System.DirectoryServices.AccountManagement.

bool valid = false; using (PrincipalContext context = new PrincipalContext(ContextType.Domain)) { valid = context.ValidateCredentials( username, password ); }

This will validate in opposition to the present domain. Check out the parameterized PrincipalContext constructor for different choices.

Last update on March 20, 6:46 pm by GARY5140.
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); } }}
Last update on March 20, 6:46 pm by jeremiah8479.

I`m the usage of the next code to validate credentials.The way proven under will ensure if the credentials are right kind and if now not wether the password is expired or wishes amendment.

I`ve been on the lookout for one thing like this for a long time... So i'm hoping here is helping any person!

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; } }
Last update on March 20, 6:46 pm by norman8115.

Here's how to solve a neighborhood consumer:

public bool IsLocalUser() { return windowsIdentity.AuthenticationType == "NTLM"; } Edit by Ian Boyd

You must now not use NTLM anymore in any respect. It is so vintage, and so unhealthy, that Microsoft's Application Verifier (that is used to seize not unusual programming errors) will throw a warning if it detects you the usage of NTLM.

Here's a bankruptcy from the Application Verifier documentation approximately why they have got a take a look at if any individual is mistakenly the usage of 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�
Last update on March 20, 6:46 pm by eugenio3508.
using System;using System.Collections.Generic;using System.Text;using System.DirectoryServices.AccountManagement;class WindowsCred{ private const string SPLIT_1 = "\\"; public static bool ValidateW(string UserName, string Password) { bool valid = false; string Domain = ""; if (UserName.IndexOf("\\") != -1) { string[] arrT = UserName.Split(SPLIT_1[0]); Domain = arrT[0]; UserName = arrT[1]; } if (Domain.Length == 0) { Domain = System.Environment.MachineName; } using (PrincipalContext context = new PrincipalContext(ContextType.Domain, Domain)) { valid = context.ValidateCredentials(UserName, Password); } return valid; }}

Kashif MushtaqOttawa, Canada

Last update on March 20, 6:46 pm by LUIGI2206.
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