We are in the process of turning off NTLM in our environment for both inbound and outbound traffic via GPO. In our lab testing we have encountered the following when blocking inbound NTLM on a remote host:
RDP'ing to the remote host with inbound NTLM blocked via cross-forest generated a CredSSP error message.
Setting Encryption Oracle Remediation to either Mitigated or Vulnerable as a workaround did not work.
Turning off NLA on the remote host as a workaround will allow cross-forest RDP
I have tried applying "Allow delegating fresh credentials" via policy on the remote host but it is still getting the CredSSP error
I have also tried setting the policy on the remote host to use SSL for "Require use of specific security layer for remote (RDP) connections", and I still got the same CredSSP error.
What did work is if I try to RDP from the same forest to the remote host, it will allow the connection and I can confirm it is using Kerberos for RDP instead of NTLM.
Another observation is once the same forest RDP worked on the remote host, cross-forest RDP connection on the remote host with the blocked inbound NTLM will now work.
Has anyone encountered something similar like this before?
If so, has anyone found a solution for cross-forest RDP to work on a remote host with blocked inbound NTLM without the need to pre-auth on the remote host in the same forest?
The Encryption Oracle Remediation error is a red herring because it uses the same error code as the NTLM is not available error. Unless you haven't patched in 3 years it'll likely never be the Encryption Oracle Remediation issue. It's really just that it tried to fallback to NTLM and policy said no.
In all likelihood the issue is that the client can't find or communicate with a domain controller to do NLA.
The client must find the user's domain first (domain A). From there it authenticates their password. It then asks to get a ticket to the machine. The machine isn't in the user's domain so it creates a referral ticket to where it thinks the machine is (domain B).
The referral is handed back to the client and the client tries to find a DC to where the referral is supposed to go (domain B). The client sends the referral to domain B and asks for a ticket to the machine. The domain controller either finds the machine and issues a ticket for it, or says it doesn't know and offers a referral to another domain (domain C) and you try again, or it just fails saying no machine can be found.
All of this occurs from the client's perspective, not the target machine's perspective. This happens before the client even pings the target machine (ish). This is why disabling NLA appears to resolve the issue.
So there are a handful of reasons why this happens:
You used an IP address -- this is a straight-to-NTLM scenario. Kerberos doens't do IP addresses by default. You can turn it on, but it won't scale.
Client can't communicate with a DC in user's domain (domain A). Networking issue, client needs line of sight to domain controller, plus DNS.
Client can't communicate a with DC in the target machine's domain (domain B). Still a networking issue, client needs line of sight to domain controller, plus DNS.
You're not providing a proper fully qualified name and the user's DC can't figure out what forest it should refer to. You can enable Forest Search Order and it'll maybe help, or you can type in the fully qualified machine name.
This isn't an exhaustive list but these are the most common causes.
References:
https://syfuhs.net/windows-and-domain-trusts
https://syfuhs.net/how-authentication-works-when-you-use-remote-desktop
I also had a similar issue when using the DOMAIN\username login ; using the UPN (username#domaine.com) worked for me.
My understanding is using the UPN allows the client to know the DNS domain name, which then allows it to discover the DC of the remote domain through DNS resolution.
NB : my setup was from a workgroup server so not exactly the same as yours; YMMV.
Related
I have a program on my computer that runs as SYSTEM and it is trying to launch an exe(opc server) on a remote machine x.x.x.x. But I get a DCOM error in my machine's eventviewer.
DCOM got error "2147942405" from the computer x.x.x.x when attempting to activate the server: yyyyy
I followed almost all the suggestions on the internet about opening dcomcnfg and adding users limits.default for launch and activation and Everyone,system,interactive,network from link (ftp://ftp.softing.com/pub/outgoing/opc/DCOM/DCOM-Settings-en.pdf) but nothing works.
Would anybody have nay other ideas on how to make this work.
According to MS Technet:
https://social.technet.microsoft.com/Forums/Azure/en-US/8bb5807f-73ba-4092-abc8-283d8fced6c4/request-a-certificate-from-certificate-service-fails-dcom-error-2147942405?forum=winserversecurity
With my VERY limited understanding of Certificate servers you may have one of the scenarios:
Client PC's are trying to connect to a Certificate server that no longer exists
Client PC's have a certificate that is valid but the Certificate server no longer exists
A Certificate server is broken
Clients do not have the proper authority to request the Certificate
I say this is limited knowledge as I am currently trying to remove AD Certificate services from a Domain Controller and I can see that in the System event log the exact same messages are being logged as I have stopped the Certificate services to asses the impact. If I get further information I will post back.
I have a issue on connecting to a clustered sql server instance using wcf-sql adapter.
The sql cluster infrastructure is :
We have 2 servers, SVR1 and SVR2, each have a named SQL instance INST1 installed and these 2 servers are clustered. In SRV1, a clustered MSDTC installed and assigned a NETBIOS name as DTCCLUSTER1. SRV1/SRV2 and DTCCLUSTER1 have its own IP address.
When I try to connect to this SQL Server using WCF-SQL Adapter, I got a timeout error and finally find out this is caused by a MSDTC connection issue. DTCPing test failed in both SRV1 to BizTalk server and BizTalk to SRV1.
The SRV1 hosting DTCCLUSTER1 have been configured to allow both inbound and outbound connections. For security reason, we cannot allow "No Auth" in MSDTC but choosed "Mutual Auth required" in both SRV1 and BizTalk server side.
On server side, the firewall was configured to allow DCE RPC inbound and outbound. We even disabled the firewall in BizTalk server side. Also no port blocking by network.
We are still doing the troubleshooting now, but my question here is kind of more general: what's the proper configuration of the MSDTC for a clustered SQL Server?
For now, there MIGHT be a workaround by setting the UseAmbientTransaction property to false.
Off course, the MSDTC issue is your main concern :)
Are you sure you checked the Network DTC access checkbox as described here:
http://msdn.microsoft.com/en-us/library/dd897483(v=bts.10).aspx
For more information on troubleshooting these specific issues, please see here: http://msdn.microsoft.com/en-us/library/aa561924(v=bts.10).aspx
This link provides you with some good advice on how to set these properties.
More specifically, if you enable the mutual auth required option, take a look at this paragraph:
If either the Mutual Authentication Required or the Incoming Caller
Authentication Required configuration options are enabled then the
client(s) computer account must be granted the Access this computer
from the network user right. If the computer account for a client
computer is not granted the Access this computer from the network user
right, or is included in the Deny access to this computer from the
network user right, then DTC communication between the client and
server computer will fail.
Typically I always set no auth. It might be worth it to try the setting and see if this makes it work. Also be aware that MSDTC settings need to be the same across your BizTalk and SQL servers, including your MSDTC cluster (IIRC: if you have a windows 2008 R2 msdtc cluster).
I've recently purchased a cloud server which has public IP and I am using it to host an xmpp server.
My first task was to ensure my users connected using my subdomain - as an example m.chat.com.
In my configuration I have the following:
%% Hostname
{hosts, ["m.chat.com"]}.
I then created an admin user with that domain.
In parrellel I have created the following DNS record with my host provider, hostgator for my subdomain m.chat.com
Name TTL Class Type Record
m.chat.com 14400 IN A [IP of the server]
One thing that puzzled me was my ability to access the ejabberd web admin console. This was achieved via: [IP of the server]:5280/admin however I could not access it via m.chat.com:5280/admin
That aside, inside the web console, under "Virtual Hosts" I could see the host "m.chat.com". I created a user "user#m.chat.com" and tried to connect via Adium.
Inside Adium, simply typing in user#m.chat.com with the password did not work. Instead I had to also specify the "Connect server" which in this case was the [IP of the server].
It has connected fine and I have registered other users to check everything is working and it is.
Then I thought I'd go back to the ejabberd configuration and start messing around. I changed the hostname to the following:
%% Hostname
{hosts, ["m.chat.com", "facebook.com"]}.
I registered a user with that domain and restarted ejabberd. Upon checking the web console, to my surprise, I could see the Virtual host "facebook.com". I tested this user in Adium with the [IP of the server] defined in the "Connect server" section and it connected fine. I asked other people with their own internet connections to use this account on their PCs and they were able to connect too.
Story over - my question to everyone is how is this possible? Am I missing something? Is there no domain authentication. After searching online, it seems you can even use fake domains.
If I am to operate my own service in the future (iOS chat app) I do not want anyone using my domain names with their own public servers.
Can someone shine some light.
Thanks!
Edit: A second question - Preferably I do not want to have to define the "Connect Server" upon using a client. I would like the client to recognise the #m.chat.com domain and establish a connection to the Servers IP automatically. Have I configured my DNS record correctly? For anyone else using Hostgator, is there an additional task I must do?
Edit: I can now access the web console via m.chat.com:5280/admin and I no longer have to specify the Connect server when using a client. I didnt do anything, I think it was a case of Hostgater updating the DNS or something, they say it usually takes 4 hours. However I am still slightly puzzled as to why I can create accounts with the facebook.com domain. I understand that because I can not access the DNS admin for this domain I can not create any records but that does not prevent me from using the domain and just specifying a Connect server.
Your initial problems (unable to access the server by using m.chat.com) were almost certainly DNS issues, and it seems you have isolated that down to the time taken to update the record.
Your second question - about the fact that you can name virtual hosts without restriction, is simple but interesting. What makes you think there should be any kind of restriction? It would be like you dictating that I can't save "m.chat.com" in a file on my disk, or that I can't send "m.chat.com" in a message across the internet.
This is why DNS exists and is structured the way it is. Although I can tell my server that it hosts facebook.com, nobody will connect to it because the DNS record for facebook.com does not point at my server (users generally don't set the "connect host" manually). Which begs the question... why would I want to tell my server it hosts facebook.com, and if I did, why should Facebook care?
An additional, but relevant, identity layer on top of DNS are certificates - which clients should validate for the virtual host name in spite of any "connect host" set. Since it's not possible to have a certificate for facebook.com, clients should generally pop up warnings or fail to connect at all. If they don't, they're probably not validating the certificate correctly.
I have an application that can connect to the Principal, but can't connect to the Mirror during a failover.
(Note to moderator: please let me know if this question is more appropriate for serverfault. I posted it here because I found more questions similar to this issue than on serverfault.)
This is the error I receive when my application attempts to connect to the Mirror after a failover:
Named Pipes Provider: Could not open a connection to SQL Server [53].
Cannot open database "MY_DB_NAME" requested by the login. The login failed.
I am familiar with the fact that when initially connected to the Principal, the name of the Mirror server is cached to be used during the failover and that the failover partner I specify in my connection string is only used if the initial connection to the Principal fails.
This clearly describes the problem I'm having:
http://blogs.msdn.com/b/spike/archive/2010/12/15/running-a-database-mirror-setup-with-the-sqlbrowser-service-off-may-produce-unexpected-results.aspx
...but the SQL Browser Service is running and I can't figure out why the name won't resolve when connecting to the mirror.
I'm assuming there is a service that must be running to enable NetBIOS name resolution that is not running, because this is what I see in WireShark consistently without a response from the Mirror:
Source Destination Protocol Length Info
10.200.3.111 10.200.5.255 NBNS 92 Name query NB SQL-02-SVR-<00>
Question 1: What could be causing the problem? ;-)
Question 2: I really don't want to enable NetBIOS (for security reasons) and I'm using IP addresses (no FQDNs) in the mirror configuration and in the connection string. Given the caching behavior of the mirror partner when connecting to the Principal, is there a way to force TCP/IP to be used so the value that is cached is the IP address and not the name? Do I need to run the SQL Server Browser/Computer Browser services?
The configuration:
App Is Delphi XE2 using SDAC 6.5.9 (I don't think this is relevant to the component I'm using because it works in other installations with mirroring and has no issues)
SQL Server 2012 Enterprise installed as a default instance on Principal, Mirror and Witness in a non-domain configuration using certificate authentication.
Windows Server 2008 R2 SP1 64-bit on all machines
Firewalls disabled on Principal, Mirror and Client (where app is running)
TCP/IP and Named Pipes enabled on Principal and Mirror
SQL Server Browser service running on Mirror
Computer Browser service running on Mirror
Mirroring is configured for automatic failover with a witness and works properly (I can fail back and forth between mirror and principal without issue)
SQL Native Client 2012 installed on Client machine
Same app login (with same SID and user rights) exists on both Principal and Mirror
Correct server, failover partner, database name, user name and password verified in my app log
In connection string, principal server is 'tcp:10.200.3.15,1433' and failover partner is 'tcp:10.200.3.16,1433' using the SQL Native client
I can ping both servers from the Client machine
NetBIOS over TCP/IP has been enabled in the adapter under the WINS tab (on the Mirror and Client machines)
I've been able to get the application working with mirroring on several other installations, but this one is baffling me.
I found the problem, which was that the customer had the Principal and Mirror in one VLAN and the Client(s) in another. Although the IP addressing scheme was the same, the policy for communication between the VLANs prevented broadcast messages, which is why the NetBIOS query was failing on the client. A WINS or DNS server will be implemented to resolve this issue.
However, I am still interested in an answer to my Question #2, above.
Recently we got a new server at the office purely for testing purposes. It is set up so that we can access it from any computer.
However today our ip got blocked from one of our other sites saying that our ip has been suspected of having a virus that sends spam emails. we learned this from the cbl http://cbl.abuseat.org/
So of course we turned the server off to stop this. The problem is the server must be on to continue developing our application and to access the database that is installed on it. Our normal admin is on vacation and is unreachable, and the rest of us are idiots(me included) in this area.
We believe that the best solution is to remove it from connecting to the internet but still access it on the lan. If that is a valid solution how would this be done or is there a better way? say blocking specified ports or whatever.
I assume that this server is behind a router? You should be able to block WAN connections to the server on the router and still leave it open to accepting LAN connection. Or you could restrict the IPs that can connect to the server to the development machines on the network.