Authenticate against a user in active directory?

Question

I do have a web application where i have a login page.How do i authenticate against the active directory users ?

As of now i am able to get some properties from the active directory,which concludes i am able to communicate with AD with LDAP string.I know its not possible to extract password from AD and authenticate against user entered password !!.

Is there a way i can authenticate against the active directory users ?

Here is my code so far

     public class Userdetails
{
    public static string ADPath = ConfigurationManager.AppSettings.Get(“ADPath”); // Get the ADAM Path from web config fiel
    public static string ADUser = ConfigurationManager.AppSettings.Get(“ADUser”); //ADAM Administrator
    public static string ADPassword = ConfigurationManager.AppSettings.Get(“ADPassword”); //ADAM Administrator  password

public static DirectoryEntry GetUserDetails(string userID)
{
        AuthenticationTypes AuthTypes;  // Authentication flags.
        // Set authentication flags.
        // For non-secure connection, use LDAP port and
        //  ADS_USE_SIGNING |
        //  ADS_USE_SEALING |
        //  ADS_SECURE_AUTHENTICATION
        // For secure connection, use SSL port and
        //  ADS_USE_SSL | ADS_SECURE_AUTHENTICATION
        AuthTypes = AuthenticationTypes.Signing |
            AuthenticationTypes.Sealing |
            AuthenticationTypes.Secure;
        DirectoryEntry De = new DirectoryEntry(ADPath, ADUser, ADPassword, AuthTypes);
    DirectorySearcher Ds = new DirectorySearcher(De);
    SearchResult Sr;
    Ds.SearchScope = SearchScope.Subtree;
    Ds.Filter = “(&(objectclass=*)(cn= ” + userID + “))”;
    Sr = Ds.FindOne();
    if (!(Sr == null))
    {
        De = new DirectoryEntry(Sr.Path, ADUser, ADPassword, AuthTypes);
        return De;
    }
    else
    {
        return null;
    }
}

Answer 1

http://msdn.microsoft.com/en-us/library/bb299745.aspx

http://msdn.microsoft.com/en-us/library/system.directoryservices.accountmanagement.aspx

http://msdn.microsoft.com/en-us/magazine/cc135979.aspx

    public bool Validate(string username, string password)
    {

        //ex PrincipalContext principalContext = new PrincipalContext(ContextType.ApplicationDirectory,"sea-dc-02.fabrikam.com:50001","ou=ADAM Users,o=microsoft,c=us",ContextOptions.SecureSocketLayer | ContextOptions.SimpleBind,"CN=administrator,OU=ADAM Users,O=Microsoft,C=US","P@55w0rd0987");

        try
        {
            using (PrincipalContext principalContext = new PrincipalContext(ContextType.Domain, Configuration.Config.ActiveDirectory.PrimaryServer, Configuration.Config.ActiveDirectory.Container, ContextOptions.Negotiate))
            {
                return principalContext.ValidateCredentials(username, password);
            }
        }
        catch (PrincipalServerDownException)
        {
            Debug.WriteLine("PrimaryServer={0};Container={1}", Configuration.Config.ActiveDirectory.PrimaryServer, Configuration.Config.ActiveDirectory.Container);
            Debug.WriteLine("LDAP://{0}/{1}", Configuration.Config.ActiveDirectory.PrimaryServer, Configuration.Config.ActiveDirectory.Container);
            throw;
        }