In Azure DevOps services, when you connect an agent to the server, you have different types of ways to authenticate to the server. You can see here for example, about connecting a Linux agent, that you have these 4 types:
Alternate (Basic authentication)
PAT
Negotiate - Connect as a user other than the signed-in user via a scheme such as Kerberos or NTLM.
Integrated - Not supported in Linux
The integrated type is mentioned in the page about connecting a Windows agent as "Windows default credentials"
Bare with me please.
In my organization, we have a Active Directory domain with a Single-Sign-On, I suppose it uses Kerberos as the authentication protocol. Sometimes I use Powershell scripts to access the API of our internal Azure DevOps Server, and I use the -UseDefaultCredentials flag so the user won't have to enter username and password - it will just authenticate based on the logged-in user.
That got me thinking that the -UseDefaultCredentials flag is using Kerberos to authenticate.
But from the above, it seems that Integrated is using "Default credentials", which is something else than "Negotiate" which uses Kerberos.
Can someone help me understand this?
The UseDefaultCredentials flag tells the underlying system to try and use the caller's SSO credentials, which in most cases is the credential used to log into the system interactively or otherwise.
Strictly speaking it does not indicate which protocol to use. What it's actually saying is "dear system internals: please figure it out for me". The way this works is by selecting the negotiate protocol, which as it's name suggests negotiates the use of specific authentication protocols based on the client credentials as well as information from the server. This is called the SPNEGO protocol. It is transparent to the caller.
SPNEGO is fairly simple in nature. The client has a list of known authentication protocols (Kerberos, NTLM, etc.) and will send that list to the server saying 'pick one please'. The server can select any of them and respond telling them what to use, and the client then goes and uses it. Fin.
SPNEGO is also relatively smart because it can reasonably predict what it thinks the server will accept and will attempt to optimistically provide a token up front using the first protocol in the list. So if it thinks it needs Kerberos it'll go and get a Kerberos ticket up front and send it first. The server might think that's fine, or it might fail and return a response saying
"no, I really need NTLM", and so the client tries again with NTLM.
I work as a React Developer for a company that chose to use IIS and SQL as their backend. The API calls don't use JWT but rather use Kerberos tickets.
This already presents an issue that I have to run chrome with --auth-server-whitelist="*" in order to get a ticket from kerberos at all. However, I am still unable to make API calls.
The best we can tell is my kerberos ticket (which can be viewed by issuing klist to terminal. The only difference between one that works on a PC and mine is that theirs has the ok-as-delegate flag and mine does not.
Surely there is a configuration issue on the backend or with IIS preventing my ticket from attaining this flag? Any help would be greatly appreciated.
Given a windows domain, and two win7 systems, how can I establish a user verified connection from the first computer to the second without prompting for the user to re-enter credentials.
A good summary of this is: A TCP connection, server-side, has no idea what user is originating the connection. How can implementing a TCP based program permit user validation.
Work around ideas:
- I could write a WMI provider and use the underlying WMI infrastructure to verify the user.
I'd prefer not to get a work-around, as I've been working around not really understanding how to authenticate over the network using Windows for many years. Please help me to understand how Windows is actually performing this step so that I can implement the technique. If the answer is kerberos some example code on how to generate/send something from the client (without prompting for credentials, just use the logged in user) that the server can process/validate.
I think this may have already been answered here: Windows authentication token C++
(Will need some time to implement/test before I will be sure.)
The magic answer I was looking for back then was SSPI (Kerberos). A similar solution exists with OpenSSL. For others looking for this you will also be interested in SSL, TLS (the new SSL), and SASL (a mechanism for deciding on the fly which identification algorithm to use) and it's Microsoft counterpart SSPI.
In a corporate desktop scenario, where the user is logged in to an Active Directory domain, I'd like my application to issue HTTP requests using the same proxy as Internet Explorer uses. The problem is that the proxy requires NTLM authentication using the credentials of the currently logged in user, which is something I don't know how my application could acquire.
Besides asking the user for his/her password (for which I found a lot of solutions), is there a way to do it the right, like using some native API? I'm not picky about programming languages in this case, if it works in this scenario, I accept it, although I'd prefer C/C++.
Since you are on Windows, and you are using domain logins, you should rather rely on Kerberos. Anyway, you now several options:
If you use WinHTTP , you simple have to enable it.
Use libcurl on Windows and it will compile with SSPI support by default.
If you use sockets by yourself, you have to call SSPI with the Negotiate package and exchange tokens per HTTP all by yourself.
I heard that on Windows you can login from a web browser to the web server without going through the usual login entering username and password but using instead the credentials from Windows directly, using the NTLM protocol.
How is this achieved? Does the web server need to support some additional authentication?
Update: I'm asking for a generic web server, not just IIS. How to do that on Apache for instance?
The webserver just needs to be configured to support Windows authentication (which will be NTLM, or - better - Kerberos if both client and server are W2K or later). I believe that IIS or Apache can be configured to do that.
The browser also has to support this - at least IE does so (not sure about the others, it may be possible). edit: looks like firefox has some support for this too, and safari on MacOS
edit: for details on apache, google modules for NTLM authentication. Kerberos modules also exist. as per other answers, this really only works on an Intranet - not just because the browser needs to be in an Intranet zone (only applies to IE), but because any intervening firewall will typically stop this working, and because the necessary interdomain trusts will probably not exist. It's also a bit trickier to make work if the apache server is on UNIX, and especially if you also have Kerberos servers on UNIX in the mix, but still possible.
It will only be seamless in a specific situation; namely the webserver needs to support NTLM (for example, IIS), and it needs to be in a zone that the client is configured to trust (The "Intranet Zone" in IE parlance, unless the end user has tweaked their settings)
If your webserver and client pc's are on a network secured by Active Directory or similar, you can set 'Windows Integrated Security' in IIS on the web server for the website which automatically logs in all I.E clients (That are allowed).
As stated previously, NTLM is typically used if your back end is Windows Managed (MS Active Directory). However, there are also modules available for Apache that will tie into this: mod_ntlm.
Since this is it's own protocol, it is required that the browser is able to understand this protocol and reply to the authentication challenges. I don't know which browsers support this off hand, but my assumption would be that most do.
From my experience, kerberos is more of a prefered method, but I have not worked with it much, so unfortunately, I don't have much advise as far as that goes.
On a side note, I recall reading somewhere that the JRE also has ways of tying into NTLM on your web server in order to obtain identity information for the authenticated user. As stated previously, .NET has support for this as well.
Also, Firefox does not support NTLM by default but it can be configured using the following tut: http://www.crossedconnections.org/w/?p=89
If you set the IIS settings to require authentication then your users will need to log in to access the page. They then have any rights (if not an interface) to anything on that server that they would if they logged in the normal way (from the console).
Other than this, I am not sure what you are referring to.
Yes this is possible. It is often used in intranet applications where users are. windows uses NTLM or Kerberos to authorize the user against a central service, typically Active Directory on the windows platform. On the .NET platform the current user information can be accessed through the System.Threading.Thread.CurrentPrincipal.Identity instance.
You might also want to look into Jespa. It seems a little bit more straight forward than Kerberos but provides good ntlm sso capabilities.
I was looking for more information about Kerberos (because NTLM, even v2, become deprecated with AD 2008), and I found this article, explaining how make it work with Apache (as you mentionned it).
http://blog.scottlowe.org/2006/08/10/kerberos-based-sso-with-apache/
This question is probably outdated (or at least solved), but if it can help someone ...