I'm having some trouble calling a web service from within a web application and I was hoping someone here might be able to help. From what I can tell, this seems to have something to do with the Kerberos double-hop issue. However, if it is, I'm not sure what to do to actually fix the problem. To make things harder, I don't have the proper permissions to make changes to Active Directory accounts, so I need to know what to ask for when requesting changes. In my situation, I need to pass the credentials (Integrated Windows Authentication) from a web application onto a backend web service so that the web service runs under the proper user context.
Here's my exact issue:
This works
This doesn't work
The only difference between the working scenario and the non-working scenario is that the working scenario is running the application on localhost (whether a developer's PC or on the server in question) and the non-working example is running on another machine. The code between both scenarios is exactly the same.
What I've tried
Adding an SPN to the domain account that runs the app pool for each server setspn -a http/server1 DOMAIN\account
Different methods of impersonation
Removing the impersonation code using(...) and executing the web service call as the app pool account. This works as expected.
Does anyone have any idea on what I might be able to do in order to fix this problem?
The intermediate server must be trusted for delegation. Otherwise no credential will be delegated and the intermediate server cannot impersonate the original client.
More often than not the reason is that Server 1 does not pass a delegation token to Server 2. So when Server 2 tries to use that authentication ticket to go somewhere else (probably a SQL server) it fails.
You should set the impersonation level for the WCF call
ClientCredentials.Windows.AllowedImpersonationLevel = TokenImpersonationLevel.Delegation
http://msdn.microsoft.com/en-us/library/system.servicemodel.security.windowsclientcredential.allowedimpersonationlevel.aspx
Related
We've recently released the latest version of our intranet application, which now uses windows authentication as standard, and needs to be able to connect to a configured SQL server with the end-user's domain credentials.
Lately we've found that on a couple of customer deployments, although IIS can see the user's domain credentials, it will not pass these on to SQL server. Instead, it seems to use the anonymous account. This is in spite of following all the correct steps (changing the directory security to Win Auth, updating Web.Config to use Win Auth and denying anonymous users).
I've been doing a lot of reading that suggests we need to make sure that Kerberos is in place, but I'm not sure (a) how valid this is (i.e. is it really a requirement?) or (b) how to go about investigating if it's set up or how to go about setting it up.
We're in a situation where we need to be able to either configure IIS or the application to work for the customer, or explain to the customer exactly what they need to do to get it working.
We've managed to reproduce this on our internal network with a test SQL server and a developer's IIS box, so we're going to mess around with this set up and see if we can come up with a solution, but if anyone has any bright ideas, I'd be most happy to hear them!
I'd especially like to hear people's thoughts or advice in terms of Kerberos. Is this a requirement, and if it is, how do I outline to customers how it should be configured?
Oh, and I've also seen a couple of people mention the 'classic one-hop rule' for domains and passing windows credentials around, but I don't know how much weight this actually holds?
Thanks!
Matt
This is called the Double-Hop Problem and prohibits the forwarding of user's credentials to third parties. This occurs when they browse from one machine, against a site on another (first hop), and forwarding the credentials to a third machine (second hop).
The problem will not appear if you host IIS and SQL Server on the same machine.
There's alot more technical details published on this at How to use the System.DirectoryServices namespace in ASP.NET, which explains the double-hop issue, and primary and secondary tokens.
To run your application under the user's Active Directory or Windows credentials, ensure these:
the IIS application is set to NOT allow anonymous access
the IIS application uses Integrated Windows authentication
your connection string should have Integrated Security=SSPI to ensure the user's Windows/AD credentials are passed to SQL Server.
i.e. Data Source=myServerAddress;Initial Catalog=myDataBase;Integrated Security=SSPI;
You state you're not sure "how to go about investigating if it's set up or how to go about setting it up".
For this I'd heartily recommend a tool called DelegConfig. It's a very handy app that you can tell you if kerberos is setup properly.
Unzip it into a directory, configure a virtual directory in IIS to point to it. Browse to the main page and you tell it which backend server you want to allow access to (e.g. UNC, SQL, HTTP etc..) and it tell you its setup correctly or not and explain why.
It even has the abilty to recongiure the kerberos to fix the issue if you so desire (although I've not used this - I'd rather reconfiguire it myself to understand what I've done in future)
I realise this comes too late for your particular problem but thought it worth sharing for others that follow - especially the tools ability to explain why delegation is or is not working. I've found it invaluble.
I am trying to write to a file on a server (web05) from a classic asp site running on Windows 2008 serer on IIS7 (webadmin). This fails and web05 logs an anonymous logon attempt during the course of the save operation.
Webadmin's site is running on an app pool in classic mode with a domain user as the process account. The process account has rights to "Trust this user for delegation to any service (Kerberos only)". The same applies for the web05 and webadmin servers.
The site is using Windows Authentication and the idea is that when I log on the site with my domain user, the rights of my user should define what I am allowed to do in the context of the IIS site. If I turn on Basic Authentication, everything works fine.
I have also used setspn.exe to add an SPN for the URL. If I type setspn.exe -L webadmin, I get:
HTTP/webadmin.companyname.com
TERMSRV/webadmin
TERMSRV/webadmin.companypub.local
HOST/webadmin
HOST/webadmin.companypub.local
So from what I understand the SPNs are set up correctly.
If I run processmonitor on webadmin while the save operation is executed, it says that the process is indeed impersonating my domain user - but getting "Access denied" (and as I said before, web05 logs an anonymous logon attempt).
Any idea what causes this?
Kind regards,
Simon
It sounds to me like you're a little confused over impersonation. The process isn't impersonating the domain user account its simply running as that user. There is a difference.
When a request arrives into ASP it will then impersonate a user and the thread handling the request will be running under the security token of the impersonated user. Its quite possible to have the same process impersonating multiple different users in multiple threads. In most cases where the anonymous user access is enabled this user is the Guest level IUSR account. Its most likely that its under this user your code is attempting and failing to run.
However if anonymous is turned off for the resource being accessed or the IUSR account does not have access to the resource then the a 401 response is sent back, with some indication of what authentication protocols it will accept. The browser may then attempt to authenticate the connection using either the current users credentials or request some credentials from the user.
You don't specify exactly how you are attempting to save file. Its worth pointing out couple of things though.
ASP code exection which may subsequently result in an access denied will not use the above mechanism to try to resolve the user.
Once a connection is authenticated it often continues to be re-used for subsequent requests (which is counter-intuative to the knowledge the HTTP is a "connection-less" protocol).
I am trying to clean up my previous questions. This answer is not sufficient to answer the question above, but I concluded that it is better to provide some insight than none. If op disagrees, please take necessary action.
This is a way back - but I recall wanting to run kerberos authentication on this app. The problem turned out to be that I tried to do kerberos outside the firewall. The app would work fine within the domain and firewall of the server's home domain but failed whenever requests came from outside.
I did a lot of chatting with an Irish technician in Microsoft, and he taught me a little about the limitations when using Kerberos. The reason I wanted to use Kerberos was that I didn't like the thought of Basic Windows authentication being unencrypted.
Good luck with your Kerberos quest :-)
I ran into this same issue and it turned out to be a simple change to the application pool. If enable 32-bit applications is set to FALSE then I recieved a prompt to login to the machine. Setting this value to true fixed the issue.
I'm getting a 401 (access denied) calling a method on an internal web service. I'm calling it from an ASP.NET page on our company intranet. I've checked all the configuration and it should be using integrated security with an account that has access to that service, but I'm trying to figure out how to confirm which account it's connecting under. Unfortunately I can't debug the code on the production network. In our dev environment everything is working fine. I know there has to be a difference in the settings, but I'm at a loss with where to start. Any recommendations?
Have you looked in the IIS logs?
I would also recommend looking in the Security event log on the server for authentication failures. You should find a footprint of the failed authorisation attempt here. Be warned though - it is not unusual to get 10s of security events a second, so ideally you need to be able to access the event log as the requests are failing.
If you do not specify which credentials to use in your ASP.NET page when you instantiate the web service then I believe it defaults to NT_Authority\Anonymous.
If you're using System.Net.CredentialCache then your web service needs to be in a trusted domain, accessed over HTTPS and using either NTLM, Kerberos or Digest Auth otherwise it does not pass the credentials from the cache.
http://msdn.microsoft.com/en-us/library/system.net.credentialcache.defaultcredentials.aspx
http://msdn.microsoft.com/en-us/library/system.net.credentialcache.defaultnetworkcredentials.aspx
http://msdn.microsoft.com/en-us/library/system.net.credentialcache.defaultcredentials.aspx
Perhaps the production server uses a different user for its application pool than your dev environment? I once spent a day figuring that one out. Another option would be the (lack of) impersonation in the web.config
Here's the situaiton. I'm working on developing a new website to access an old database. This is a DoD installation so there's lots of security around.
The current application is written in classic ASP, VBScript and some javascript. The new systems is ASP.NET.
Accessing the database in the old system meant hitting the server with your own credentials (domainname\username). Now I'm trying to test some of the early development I've done. When I used Cassini (under VS2008), I had no trouble getting to the database because ourdomain\myusername registered with the SQL Server instance as a trusted connection. Due to security aspects that I have to write, Cassini can't serve as a test server anymore - I have to use IIS (we have security card readers here). Cassini can't handle them.
So when I went through all the problems of getting the appropriate accounts added to Administrators on my local pc so that I could debug in VS2008 while using IIS, I tried to connect to the database and I was rejected because MYPC\ASPNET was not a trusted connection.
Altering the existing database is out of the question. Hard coding usernames and passwords for access to the database is out of the question.
I asked the DBA if he could add MYPC\ASPNET to of the domain groups so that SQL Server could see it as a trusted connection (since MYDOMAIN\MYNAME was in a group that was seen as a trusted connection). He tells me that is not technically possible.
In the end there are going to be three or four machines (mine, another developer, the eventual live web server and a future test web server) who's ASPNET accounts are going to be hitting our two SQL servers (live and test).
What do I have to do to make the existing SQL server see me as Friend and not Foe? I looked at impersonation but I get the impression it's not compatible with our system - the business rules make a call to a common routine to create a SqlConnection object and open it (maybe even a SqlTransaction object to go with it) and this object is used for the rest of the business rules and data-access layer until it's done. It didn't look like impersonation would persist once the SqlConnection was opened (and passed, ByRef back to the calling routine)
Thanks in advance for any advice.
You have two options:
Run your web application in an application pool configured to run in the context of a domain account
Use impersonation and configure your web application to use windows authentication only
Use Impersonation
As has already been suggested you should use impersonation.
However if your SQL Server is running on a different machine than your web server then impersonation will not suffice as the credentials of the user will not be delegated to the SQL Server (server hop). In that case you will have to either enable delegation in the AD or create a non-Windows login on your SQL Server and use that instead (this will not work if your SQL Server actually uses the Windows login for access control to tables etc.).
Sounds like you want to impersonate the client who is accessing your web site correct? Have you tried to use impersonation or are you assuming it won't work?
Edit
As Albert points out, impersonation requires the user to be authenticated using Windows authentication. You will want to disable Anonymous Access, and enable Windows Authentication in IIS Management tool.
Please note: In each step I describe below I'm logged in as the same domain user account.
I have a web application that controls a service on a remote machine (via ServiceController). When I connect to the website remotely and attempt to control the service, I get an InvalidOperationException: Access is denied.
I know it CAN work, because when I connect to the website from the web server (remote desktop in, login as my domain user, then open the webpage), it works as expected.
I have configured IIS and ASP.NET to require windows authentication and impersonation. I log the current thread's principal when this fails, and I see that the thread is running under my identity whether I'm connecting remotely or from the server itself.
I have tried forcing IIS to use Kerberos authentication, NTLM authentication and both at the same time; whether my principal reports its AuthenticationType as "Negotiate" or "NTLM" it doesn't matter. None of them work when I connect remotely (from my local machine)
ANOTHER weird thing about this is that if I'm debugging from my local machine/connecting to the remote server, it works every time! But I'm NOT debugging, it fails every time!
What in the heck could be going on here?
Your scenario is delegation and not impersonation. Delegation is hard to achieve and it depends on many thing that are done right.
A place to start would be Kerberos authentication and troubleshooting delegation issues
David Wang blog is a very useful resource on thous issues.
"ANOTHER weird thing about this is that if I'm debugging from my local machine/connecting to the remote server, it works every time! But I'm NOT debugging, it fails every time!"
That's a clear indication that you have permission issues. When you run in the debugger you're running as the logged on user, when you're not debugging it runs as whatever IIS is set to use (NETWORK SERVICE by default). Try setting (temporarily!) the Enable anonymous access using your domain account as the user and see if that works. If it does then it means your IIS is not setup properly to impersonate (and it's probably running as NETWORK SERVICE).
Permissions in IIS can be a bitch to fine tune properly...
Good luck!
P/S: This looks more like a network administration question than a programming one (see https://stackoverflow.com/questions/321618/stackoverflow-is-for-programming-questions-here-are-some-better-forums-for-your#321756)