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Get AD users and groups from client

Is there any way possible to access a clients AD users and groups outsite an intranet setting?
I am not looking for azure solutions.
The tech i am working with is .Net Core web api and Angular as frontend.
Retrieving AD information on my own domain is achievable and i could get UserPrincipals,
but if the web API and AD is not hosted on the same server, how does that work?

I can't tell you exactly how to do it, since I haven't done it with .NET Core yet, but I can tell you what you need to do and you can look up more details about each part.
Use forms authentication. You will need a login page that asks for their username and password.
Validate the credentials. There are several ways to do this. My favourite is in this answer, which uses LdapConnection from System.DirectoryServices.Protocols because it's the least amount of network requests needed to do the job and it will tell your why credentials fail (which would let you take the user to a "change password" page if their password has expired, for example). However, using DirectoryEntry/DirectorySearcher is easier for looking up groups, so you might want to also use that for validating too, by using the user's credentials in the constructor of DirectoryEntry (but you'd lose knowing the reason for failed attempts).
Look up the user's account. I prefer using DirectoryEntry/DirectorySearcher from System.DirectoryServices for this. Eldar's answer shows how to do that.
Find the user's groups. I wrote a whole article about this: Finding all of a user's groups. Assuming you only have one domain in your environment, and you already have a DirectoryEntry object for the user's account, this code will work:
private static IEnumerable<string> GetUserMemberOf(DirectoryEntry de) {
var groups = new List<string>();
//retrieve only the memberOf attribute from the user
de.RefreshCache(new[] {"memberOf"});
while (true) {
var memberOf = de.Properties["memberOf"];
foreach (string group in memberOf) {
var groupDe = new DirectoryEntry($"LDAP://{group.Replace("/", "\\/")}");
groupDe.RefreshCache(new[] {"cn"});
groups.Add(groupDe.Properties["cn"].Value as string);
}
//AD only gives us 1000 or 1500 at a time (depending on the server version)
//so if we've hit that, go see if there are more
if (memberOf.Count != 1500 && memberOf.Count != 1000) break;
try {
de.RefreshCache(new[] {$"memberOf;range={groups.Count}-*"});
} catch (COMException e) {
if (e.ErrorCode == unchecked((int) 0x80072020)) break; //no more results
throw;
}
}
return groups;
}
If you have more than one domain in your environment, then it'll be a bit more complicated.

var entry = new DirectoryEntry("LDAP://DC=DomainController,DC=com","UserName","P4$$w0Rd!???");
// userName password must be valid
var searcher = new DirectorySearcher(entry);
searcher.PropertiesToLoad.Add("sn");
var accName = "accNameToSearch"; // you can also use wildcart
// https://learn.microsoft.com/en-us/windows/win32/adsi/search-filter-syntax
searcher.Filter = $"(&(objectCategory=person)(objectClass=user)(sAMAccountName={accName}))";
var result = searcher.FindOne();
var sn = result.Properties["sn"];
There is no UserPrincipal class for that nuget package yet. But you can still query users and other stuff with ad query syntax like above.

C# access Active Directory as another user

I'd like to ask for your help with following issue. I am working on ad-hoc application, will be used only by me and just once.
Part of it is to perform password reset for over 3000 users in AD and send them new credentials.
I can read from AD as normal user, but I have to use privileged account to modify it. How can I do that? I know, I can use PowerShell and have it done in a seconds, but I'd like to learn how to do it in C#.
My code to search for user is simple
public class ADSecurity
{
public static string getUserName(string sam)
{
PrincipalContext ctx = new PrincipalContext(ContextType.Domain);
UserPrincipal user = UserPrincipal.FindByIdentity(ctx, IdentityType.SamAccountName, sam);
return user.Name;
}
}
How can I do the same, but as different user?
I've seen some guides, but none of them explained a-z ... just advice on how to impersonate, but nothing about how to use it. There was one article here about impersonation, but using LDAP protocol (DirectoryEntry). But as I understand, it is really slow.
Any advice appreciated. I need to run it 2 days from now, so in worst case scenario I use PowerShell to do it.
Thanks.

There are a few ways to do it:
Run your application under the needed credentials (Shift+right-click on the .exe file and use 'Run as a different user'). If you're just doing this once, this is the easiest.
Use the PrincipalContext constructor that accepts a username and password.
public class ADSecurity
{
public static string getUserName(string sam)
{
PrincipalContext ctx = new PrincipalContext(ContextType.Domain, null, username, password);
UserPrincipal user = UserPrincipal.FindByIdentity(ctx, IdentityType.SamAccountName, sam);
return user.Name;
}
}
Use the DirectoryEntry constructor that accepts a username and password.
I'm not sure which example you're talking about that's "slow", but in my experience, using DirectoryEntry directly is almost always faster, as long as you use it correctly. The System.DirectoryServices.AccountManagement namespace (what you are using in your example) uses DirectoryEntry behind the scenes anyway.
Of course, options 2 & 3 require you know the password.

How to integrate LDAP in WPF application that consumes WCF service

I will start by describing how my application works today without LDAP.
I have WPF application that consumes WCF services (authentication windows or UserName depends on users choice). This services allows communication with database.
I display to user a "Login screen" in order to allow him set her "user name" and "password" then application connects to service and consumes function that checks if UserName and Password exist in database. (see img below)
Now I need also to integrate LDAP for authenticating user accounts against their existing systems instead of having to create another login account.
I'm bit ignorant about LDAP and confused about many things. Please excuse the possible use of wrong terminology.
I googled but I still don't have answers of many questions.
1- What is the relation between users that exist in my database table "User" and profiles that I should be created in LDAP ?
2- What is the check I should do to allow user come from LDAP to access to my application and use all functionnalities of my service ?
3- Should I have service type "LDAP" like other authentications types I have today in my application ("Windows" and "UserName") ?
4- If I want to update my application architecture described in picture above where should I add LDAP ?

First I am going to answer your questions one by one,
The user on LDAP is the same on DB, you can hold LDAP's Username and it's domain in your Users Table,
but the profile on the LDAP may vary with your profile table, but it can be fetched from LDAP address.
It's enough to check username and password over LDAP, just need to hold LDAP addresses in a Table (example ExternalPath) and make a relation between User and ExternalPath tables. LDAP address is contains some specifications.
Yes, you have to have a separate mechanism for identifying LDAP Users which I will explain more further.
This is not hard if everything be atomic and designed right, in further steps you may see it is easy.
So let me tell about my experience in LDAP and Authenticate users on LDAP and DB and our architecture.
I was implemented a WCF service named Auth.svc, this service contains a method named AuthenticateAndAuthorizeUser this is transparent for user which came from LDAP or anywhere.
I hope you get the clue and architecture to Authenticate user over LDAP and DB in below steps:
1- First I have a table named Users which hold users info and one more field named ExternalPath as foreign key, if it is null specify UserName is in DB wit it's password otherwise it is came from UserDirectory.
2- In second step you have to hold LDAP address (in my case LDAP addresses are in ExternalPath table), all LDAP addresses are on port 389 commonly.
3- Implementing authenticate User, if is not found(with Username and Password) then check it's ExternalPath to verify over LDAP address.
4- The DB schema should be something like below screenshot.
As you can see ExternalPath field specify user is from LDAP or not.
5- In presentation layer I am defining LDAP servers like below screenshot also
6- In the other side while adding new user in system you can define LDAP for user in my case I am listing LDAP titles in a DropDown in adding User form (if admin select LDAP address then don't need to get password and save it in DB), as I mentioned just need to hold LDAP username not password.
7- But last thing is authenticating user on LDAP and DB.
So the authenticate method is something like:
User userLogin = User.Login<User>(username, password, ConnectionString, LogFile);
if (userLogin != null)
return InitiateToken(userLogin, sourceApp, sourceAddress, userIpAddress);
else//Check it's LDAP path
{
User user = new User(ConnectionString, LogFile).GetUser(username);
if (user != null && user.ExternalPath != null)
{
LDAPSpecification spec = new LDAPSpecification
{
UserName = username,
Password = password,
Path = user.ExternalPath.Path,
Domain = user.ExternalPath.Domain
};
bool isAthenticatedOnLDAP = LDAPAuthenticateUser(spec);
}
}
If userLogin does not exist in DB by entered UserName and Password then we should authenticate it over related LDAP address.
In else block find User from Users table and get it's ExternalPath if this field was not null means User is on LDAP.
8- The LDAPAuthenticateUser method is :
public bool LDAPAuthenticateUser(LDAPSpecification spec)
{
string pathDomain = string.Format("LDAP://{0}", spec.Path);
if (!string.IsNullOrEmpty(spec.Domain))
pathDomain += string.Format("/{0}", spec.Domain);
DirectoryEntry entry = new DirectoryEntry(pathDomain, spec.UserName, spec.Password, AuthenticationTypes.Secure);
try
{
//Bind to the native AdsObject to force authentication.
object obj = entry.NativeObject;
DirectorySearcher search = new DirectorySearcher(entry);
search.Filter = "(SAMAccountName=" + spec.UserName + ")";
search.PropertiesToLoad.Add("cn");
SearchResult result = search.FindOne();
if (null == result)
{
return false;
}
}
catch (Exception ex)
{
Logging.Log(LoggingMode.Error, "Error authenticating user on LDAP , PATH:{0} , UserName:{1}, EXP:{2}", pathDomain, spec.UserName, ex.ToString());
return false;
}
return true;
}
If exception raised in LDAPAuthenticateUser means User does not exist in User Directory.
The authentication code accepts a domain, a user name, a password, and a path to the tree in the Active Directory.
The above code uses the LDAP directory provider the authenticate method calls LDAPAuthenticateUser and passes in the credentials that are collected from the user. Then, a DirectoryEntry object is created with the path to the directory tree, the user name, and the password. The DirectoryEntry object tries to force the AdsObject binding by obtaining the NativeObject property. If this succeeds, the CN attribute for the user is obtained by creating a DirectorySearcher object and by filtering on the SAMAccountName. After the user is authenticated and exception not happened method returns true means user find on given LDAP address.
To see more info about Lightweight Directory Access Protocol and authenticate over it THIS Link can be useful which tells about specification more.
Hope will help you.

Redirect digest request to active directory

I am trying to redirect an http request with digest MD5 header information to an active directory to validate the credentials.
I do have the information given by the http header like nonce and username. My problem now is that I have no link to put this information into a PrincipalContext object.
I obviously can't use PrincipalContext.ValidateCredentials(username, password) cause it requires the password in plain text.
The only validation that I am able to use is UserPrincipal user = UserPrincipal.FindByIdentity(context, IdentityType.SamAccountName, username);, but this does not include the password.
I do have a HttpListenerContext object. But the user variable is null.

After I told my server to user AuthenticationSchemes.IntegratedWindowsAuthentication he automaticaly deliveres a WindowsPrincipal, which provides information from the AD.

Tim once you get the information you can do something like this to check if is Valid or not If I am understanding what you want to test properly then try something like this
if you are running this via code or a service you should have no issues with the password in regards to being exposed ..if you are concerned about that then you need to write something that will decrypt the MD5 Header Information where the pass word is.
using(PrincipalContext prContext= new PrincipalContext(ContextType.Domain, "Your Domain"))
{
bool isValid = prContext.ValidateCredentials("Username", "Password");
}

Is there a way to enable referral chasing for UserPrincipal.FindByIdentity()?

I have a .NET 3.5 web application that uses the System.DirectoryServices.AccountManagement classes. When I search for some users I get a PrincipalOperationException: A referral was returned from the server. If I did this the old school way with my own LDAP code I could enable chasing of referrals. Do I need to rewrite my code?
My code looks like this:
using (var principalContext = new PrincipalContext(ContextType.Domain, null, adPath))
{
// Find the principal object for which you wish to enumerate group
// membership.
using (var userPrincipal = UserPrincipal.FindByIdentity(principalContext, identity))
{
if (userPrincipal != null)
{
Name = userPrincipal.DisplayName;
DistinguishedName = userPrincipal.DistinguishedName;
EmailAddress = userPrincipal.EmailAddress;
Sid = userPrincipal.Sid.Value;
}
}
}
My adPath can be one of 2 values. One of the values is a domain that was recently joined, and can be accessed using different tools. I believe this is a problem with how this .NET library makes the LDAP calls.

Here is a partial Answer, as it's too long for a comment.
According to this Microsoft documentation, as you even know, Referrals are a hint that the client can chase. But concerning RODC they add "For example, in the case of an LDAP application, if chase referrals is enabled on the LDAP connection between the client and the RODC, the application never knows that the client received a referral from the RODC. The client is automatically redirected to the writable domain controller that is specified in the referral. ".
So I look how to enable LDAP chasing on a connexion in Microsoft site and I found this which means ADSI use. I'am very interested in the answer.
Do you try to query the global catalog like this :
/* Retreiving a principal context
*/
PrincipalContext domainContext = new PrincipalContext(ContextType.Domain, "YourGCServer:3268", "dc=dom,dc=fr", "User", "Password");
It's supposed to contains all the forest domain's datas.
I hope it helps.

Have you tried code of the form(put the domain in as the second argument):
var principalContext = new PrincipalContext(ContextType.Domain, "office.local", "OU=Users, DC=office, DC=local" ))
Also make sure that the adPath is from most specific to least specific.