Tag Archives: Windows Server

Microsoft exposes a security issue that affects millions of Windows 10 computers, RDP and DHCP on win2008R2

Windows 10 Crypto API Spoofing

Microsoft has released a new security patch for a vulnerability that could affect millions of Windows 10 Users world wide.

A decades old API

The decades old CryptoAPI tool validates and signs packages/software which could be utilized by hackers/developers to sign and execute illegitimate software thus would allow users to run anything without user’s nor Antivirus/Internet Security software’s notice.

Microsoft mentioned that the vulnerability could also allow hackers to change or modify encrypted communications.

It’s important to mention that CryptoAPI is a legacy API that’s being replaced by a new CNG (Cryptography Next Generation API) which also supports CryptoAPI.

CryptoAPI Key Storage Architecture

cryptoapi architecture

Download Patch

Direct Download

https://www.catalog.update.microsoft.com/Search.aspx?q=KB4528760

CVE

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0601

Windows 2008 R2, Windows 7 RDP

A day ago Microsoft released two very important security patches on May 14, 2019.

One of these patches has been detected in the RDP service (CVE-2019-0708) which affects Windows 7 and Windows 2008 R2.

According to MS’s Article a remote code execution vulnerability exists in Remote Desktop Services – formerly known as Terminal Services – when an unauthenticated attacker connects to the target system using RDP and sends specially crafted requests.

No Authentication or Interaction needed

This vulnerability is pre-authentication and requires no user interaction. An attacker who successfully exploited this vulnerability could execute arbitrary code on the target system.

An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

When look at CVE-2019-0708, which is related to the RDP service, we see that attackers are able to run code on systems by sending specially produced packages without any user interaction and authentication and manage to install malware like Ransomware or other execution files.

Download Patch

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0708

Windows 2008R2, 2012R2, 2016 and 2019 DHCP

The other one is in the DHCP service (CVE-2019-0725), and both vulnerabilities are very critical.

A memory corruption vulnerability exists in the Windows Server DHCP service when processing specially crafted packets. An attacker who successfully exploited the vulnerability could run arbitrary code on the DHCP server.

Download Patch

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0725

Sources:

Microsoft, NSA, Other Security Researchers

Upgrade FRS (File Replication Service) to DFSR (Distributed File System Replication) Guide through

Upgrade FRS to DFSR:

You might be searching on how to do this due to many reasons, Migrating your DCs to Windows 2016 or Windows 2019, The steps to do this type of migration is pretty easy and straightforward.

First Let’s explain a bit about what does FRS and DFSR do and what is the difference?

Windows Server 2003 and 2003 R2 uses File Replication Service (FRS) to replicate SYSVOL folder content to other domain controllers.

SYSVOL is a folder shared by domain controller to hold its logon scripts, group policies and other items related to AD.

All the domain controllers in the network will replicate the content of SYSVOL folder. The default path for SYSVOL folder is %SystemRoot%\SYSVOL. This folder path can be defined when you install the active directory.

How does DFS Works?

In Windows server 2008 and later Active Directory uses Distributed File System (DFS) for the replication.  DFS Replication uses a compression algorithm known as remote differential compression (RDC). RDC detects changes to the data in a file and enables DFS Replication to replicate only the changed file blocks instead of the entire file.

Although FRS has been deprecated Since Windows server 2008 most people still looking to migrate to latest version.

Migration Starts Here

In this guide, I am going to explain how to do this kind of migration step by step.

I am going to run the migration on Windows 2008 R2 Servers. however the process is exactly the same on Windows 2012 R2.

To start, I need to check the service console to see which services are running the replication. From run type services.msc and enter

As you can see there, File Replication Service is running

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In the same manner DFS service is also started and functioning, But that doesn’t mean that RFS is not being used.

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Health Check

Before starting any migration, I prefer to do a check on Eventviewer just to make sure nothing critical is being reported. In the same way I would like to see if there any warning being reported.
Below you can see errors are being reported from File Replication Service by the Domain Controller SRV01, So the time is convenient to start this kind of migration as this would fix the errors being reported.

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Prerequirements:

The first part of the process for migrating SYSVOL replication from File Replication Service (FRS) to Distributed File System (DFS) Replication is to raise the functional level of the domain to Windows Server 2008 and to set the global migration state to Prepared.

Make sure your Domain Function Level is raised to 2008 at least for this process to work.

Migration:

To start migration, Run Powershell as an administrator from the DC And type the following command to prepare DCs for the migration.

dfsrmig /getglobalstate

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Preparing to migrate

dfsrmig /setglobalstate 1

When this is done, you might have to wait sometime (5 mins or less for small environments). When done waiting type dfsrmig /getglobalstate to verify that the global migration state is Prepared. The following output appears if the global migration state is Prepared.

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You will be able to see an event ID 8014 showing you the success of this command.  Which means you can move to the next stage.

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Migrate the domain to the Redirected state

From a command prompt or PowerShell window on a writeable domain controller (not a read-only domain controller) in the domain that you want to migrate, type dfsrmig /setglobalstate 2 to set the global migration state to Redirected.

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2. Type dfsrmig /getglobalstate to verify that the global migration state is Redirected. The following output appears if the global migration state is Redirected.

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After doing this, Checking event viewer you can see event ID 8017 showing you the current state, in my case it’s showing DFSR has successfully Migrated the DC to “Redirected” state. so it means we are good to go to the next step.

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Migrating to the Eliminated State

Log on to a writeable domain controller (if you are not logged on already).

Open a command prompt window and then type dfsrmig /setglobalstate 3 to set the global migration state to Eliminated.

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2. At a command prompt, type dfsrmig /getmigrationstate to verify that all the domain controllers are at the Redirected state. The following output appears when all domain controllers are at the Redirected state.

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In the event viewer you can see the state of the DCs reporting that DC will now migrate to the “Eliminated” state. with event ID 8018

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Once everything is finished, You will be able to confirm by two things, First on the Service console the File Replication Service should be disabled since it’s no longer going to be used.

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Second thing is by using Command line or Powershel, Type Net Share an you can see the new Shares being published with new names “Sysvol_DFSR”.

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Ref:

https://docs.microsoft.com/en-us/windows-server/storage/dfs-replication/migrate-sysvol-to-dfsr

https://docs.microsoft.com/en-us/windows/win32/win7appqual/file-replication-service–frs–is-deprecated-in-windows-server-2008-r2

Migrating DFS from 2000 Mode to 2008 step by step

The Story

Few months ago I have got a request from one of my clients regarding migrating DFS from 2012R2 to 2016.

2012R2 was migrated from 2008r2 and was based on 2000 Mode. To do this you’ve got a list of requirements as it can be migrated but certain features won’t be supported if you continue to use the 2000 Mode in DFS on Windows 2016 server.

How to Start

In this tutorial I will explain how to do this migration by doing a demo step by step and guide you through this Migration with screenshots and the required commands.

I have added a tiny comparison also to make it clear why are we going to use this particular method of migrating DFS mode and Server.

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To migrate a domain-based namespace to Windows Server 2008 mode

  1. Open a Command Prompt window and type the following command to export the namespace to a file, where \\ domain \ namespace is the name of the appropriate domain and namespace and path\filename is the path and file name of the export file:
On the source DC/DFS Server

Dfsutil root export \\domain\namespace C:\filename.xml

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  1. Write down the path (\\ server \ share ) for each namespace server. You must manually add namespace servers to the recreated namespace because Dfsutil cannot import namespace servers.

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  1. In DFS Management, right-click the namespace and then click Delete , or type the following command at a command prompt, where \\ domain \ namespace is the name of the appropriate domain and namespace:
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    Dfsutil root remove \\domain\namespace

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Let’s go refresh the console and see if it’s deleted there

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Next remove

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I will remove the rest of the name spaces

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All have been removed, Now lets remove the name spaces from the display and observe what happens to the replication groups

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NOTE:

Replication groups didn’t get affected

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  1. In DFS Management, recreate the namespace with the same name, but use the Windows Server 2008 mode, or type the following command at a command prompt, where \\ server \ namespace is the name of the appropriate server and share for the namespace root:
    Dfsutil root adddom \\server\namespace v2
I will use the UI instead of the command

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Although we raised the forest and domain function forest but still the 2008 is still greyed out. Lets try to restart the DFS services on the FSMO server

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After restarting

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Next, I will copy all the xml files to the new server and import them there

My new server is 2016

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  1. To import the namespace from the export file, type the following command at a command prompt, where \\ domain \ namespace is the name of the appropriate domain and namespace and path\filename is the path and file name of the file to import:
    Dfsutil root import merge path\filename.xml \\domain\namespace

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After the Import

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I will continue to import the rest of the namespaces

First we need to create them with their matching namespaces from the GUI

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Now I will import and merge the xml file

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After adding the NEW folder which has replicating group existing already from the previous mode. First it didn’t show up

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but after navigating to the NewFolder and clicking on Replication tab then Navigate to the replication group showed the replication group underneath the Replication

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What has changed?

The only noticeable thing which has changed is the NameSpace Servers everything else like ( Folder targets still the same, replication is identical to previous settings)

See this screenshot

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Let’s check the access to the new namespace

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Finally, Let’s import the latest namespace and its configuration (PublicFolder)

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Let’s check the result on GUI

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Notice the replication group for the PF didn’t come, so let’s do as we have explained before to show the replication group

Here we go

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Right after this process finishes, the command creates some kind of a report with time, importing status and other related settings such as site cost, timeout.. Etc

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Note

To minimize the time that is required to import a large namespace, run the Dfsutil root import command locally on a namespace server.

Add any remaining namespace servers to the recreated namespace by right-clicking the namespace in DFS Management and then clicking Add Namespace Server , or by typing the following command at a command prompt, where \\ server \ share is the name of the appropriate server and share for the namespace root:
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Dfsutil target add \\server\share

Note

You can add namespace servers before importing the namespace, but doing so causes the namespace servers to incrementally download the metadata for the namespace instead of immediately downloading the entire namespace after being added as a namespace server.

Ref:

https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/cc753875(v=ws.11)