Blog - Title

January, 2013

  • Configuring Change Notification on a MANUALLY created Replication partner

    Hello. Jim here again to elucidate on the wonderment of change notification as it relates to Active Directory replication within and between sites. As you know Active Directory replication between domain controllers within the same site (intrasite) happens instantaneously. Active Directory replication between sites (intersite) occurs every 180 minutes (3 hours) by default. You can adjust this frequency to match your specific needs BUT it can be no faster than fifteen minutes when configured via the AD Sites and Services snap-in.

    Back in the old days when remote sites were connected by a string and two soup cans, it was necessary in most cases to carefully consider configuring your replication intervals and times so as not to flood the pipe (or string in the reference above) with replication traffic and bring your WAN to a grinding halt. With dial up connections between sites it was even more important. It remains an important consideration today if your site is a ship at sea and your only connectivity is a satellite link that could be obscured by a cloud of space debris.

    Now in the days of wicked fast fiber links and MPLS VPN Connectivity, change notification may be enabled between site links that can span geographic locations. This will make Active Directory replication instantaneous between the separate sites as if the replication partners were in the same site. Although this is well documented on TechNet and I hate regurgitating existing content, here is how you would configure change notification on a site link:

    1. Open ADSIEdit.msc.
    2. In ADSI Edit, expand the Configuration container.
    3. Expand Sites, navigate to the Inter-Site Transports container, and select CN=IP.

      Note: You cannot enable change notification for SMTP links.
    4. Right-click the site link object for the sites where you want to enable change notification, e.g. CN=DEFAULTSITELINK, click Properties.
    5. In the Attribute Editor tab, double click on Options.
    6. If the Value(s) box shows <not set>, type 1.

    There is one caveat however. Change notification will fail with manual connection objects. If your connection objects are not created by the KCC the change notification setting is meaningless. If it's a manual connection object, it will NOT inherit the Options bit from the Site Link. Enjoy your 15 minute replication latency.

    Why would you want to keep connection objects you created manually, anyway? Why don't you just let the KCC do its thing and be happy? Maybe you have a Site Link costing configuration that you would rather not change. Perhaps you are at the mercy of your networking team and the routing of your network and you must keep these manual connections. If, for whatever reason you must keep the manually created replication partners, be of good cheer. You can still enjoy the thrill of change notification.

    Change Notification on a manually created replication partner is configured by doing the following:

    1. Open ADSIEDIT.msc.
    2. In ADSI Edit, expand the Configuration container.
    3. Navigate to the following location:

      \Sites\SiteName\Server\NTDS settings\connection object that was manually created
    4. Right-click on the manually created connection object name.
    5. In the Attribute Editor tab, double click on Options.
    6. If the value is 0 then set it to 8.

    If the value is anything other than zero, you must do some binary math. Relax; this is going to be fun.

    On the Site Link object, it's the 1st bit that controls change notification. On the Connection object, however, it's the 4th bit. The 4th bit is highlighted in RED below represented in binary (You remember binary don't you???)

    Binary Bit

    8th

    7th

    6th

    5th

    4th

    3rd

    2nd

    1st

    Decimal Value

    128

    64

    32

    16

    8

    4

    2

    1

     

    NOTE: The values represented by each bit in the Options attribute are documented in the Active Directory Technical Specification. Fair warning! I'm only including that information for the curious. I STRONGLY recommend against setting any of the options NOT discussed specifically in existing documentation or blogs in your production environment.

    Remember what I said earlier? If it's a manual connection object, it will NOT inherit the Options value from the Site Link object. You're going to have to enable change notifications directly on the manually created connection object.

    Take the value of the Options attribute, let's say it is 16.

    Open Calc.exe in Programmer mode, and paste the contents of your options attribute.

    Click on Bin, and count over to the 4th bit starting from the right.

    That's the bit that controls change notification on your manually created replication partner. As you can see, in this example it is zero (0), so change notifications are disabled.

    Convert back to decimal and add 8 to it.

    Click on Bin, again.

    As you can see above, the bit that controls change notification on the manually created replication partner is now 1. You would then change the Options value in ADSIEDIT from 16 to 24.

    Click on Ok to commit the change.

    Congratulations! You have now configured change notification on your manually created connection object. This sequence of events must be repeated for each manually created connection object that you want to include in the excitement and instantaneous gratification of change notification. Keep in mind that in the event something (or many things) gets deleted from a domain controller, you no longer have that window of intersite latency to stop inbound replication on a downstream partner and do an authoritative restore. Plan the configuration of change notifications accordingly. Make sure you take regular backups, and test them occasionally!

    And when you speak of me, speak well…

    Jim "changes aren't permanent, but change is" Tierney

     

  • ADAMSync + (AD Recycle Bin OR searchFlags) = "FUN"

    Hello again ADAMSyncers! Kim Nichols here again with what promises to be a fun and exciting mystery solving adventure on the joys of ADAMSync and AD Recycle Bin (ADRB) for AD LDS. The goal of this post is two-fold:

    1. Explain AD Recycle Bin for AD LDS and how to enable it
    2. Highlight an issue that you may experience if you enable AD Recycle Bin for AD LDS and use ADAMSync

    I'll start with some background on AD Recycle Bin for AD LDS and then go through a recent mind-boggling scenario from beginning to end to explain why you may not want (or need) to enable AD Recycle Bin if you are planning on using ADAMSync.

    Hold on to your hats!

    AD Recycle Bin for ADLDS

    If you're not familiar with AD Recycle Bin and what it can do for you, check out Ned's prior blog posts or the content available on TechNet.

    The short version is that AD Recycle Bin is a feature added in Windows Server 2008 R2 that allows Administrators to recover deleted objects without restoring System State backups and performing authoritative restores of those objects.  

    Requirements for AD Recycle Bin

       

    To enable AD Recycle Bin (ADRB) for AD DS your forest needs to meet some basic requirements:

       

    1. Have extended your schema to Windows Server 2008 R2.
    2. Have only Windows Server 2008 R2 DC's in your forest.
    3. Raise your domain(s) functional level to Windows Server 2008 R2.
    4. Raise your forest's functional level to Windows Server 2008 R2.

       

    What you may not be aware of is that AD LDS has this feature as well. The requirements for implementing ADRB in AD LDS are the same as AD DS although they are not as intuitive for AD LDS instances.

     

    Schema must be Windows Server 2008 R2

       

    If your AD LDS instance was originally built as an ADAM instance, then you may or may not have extended the schema of your instance to Windows Server 2008 R2. If not, upgrading the schema is a necessary first step in order to support ADRB functionality.

       

    To update your AD LDS schema to Windows Server 2008 R2, run the following command from your ADAM installation directory on your AD LDS server:

       

    Ldifde.exe –i –f MS-ADAM-Upgrade-2.ldf –s server:port –b username domain password –j . -$ adamschema.cat

       

    You'll also want to update your configuration partition:

       

    ldifde –i –f ms-ADAM-Upgrade-1.ldf –s server:portnumber –b username domain password –k –j . –c "CN=Configuration,DC=X" #configurationNamingContext

       

    Information on these commands can be found on TechNet:

    Decommission any Windows Server 2003 ADAM servers in the Replica set

       

    In an AD DS environment, ADRB requires that all domain controllers in the forest be running Windows Server 2008 R2. Translating this to an AD LDS scenario, all servers in your replica set must be running Windows Server 2008 R2. So, if you've been hanging on to those Windows Server 2003 ADAM servers for some reason, now is the time to decommission them.

     

    LaNae's blog "How to Decommission an ADAM/ADLDS server and Add Additional Servers" explains the process for removing a replica member. The process is pretty straightforward and just involves uninstalling the instance, but you will want to check FSMO role ownership, overall instance health, and application configurations before blindly uninstalling. Now is not the time to discover applications have been hard-coded to point to your Windows Server 2003 server or that you've been unknowingly been having replication issues.

       

    Raise the functional level of the instance

       

    In AD DS, raising the domain and forest functional levels is easy; there's a UI -- AD Domains and Trusts. AD LDS doesn't have this snap-in, though, so it is a little more complicated. There's a good KB article (322692) that details the process of raising the functional levels of AD and gives us insight into what we need to do raise our AD LDS functional level since we can't use the AD Domains and Trusts MMC.

       

    AD LDS only has the concept of forest functional levels. There is no domain functional level in AD LDS. The forest functional level is controlled by the msDS-Behavior-Version attribute on the CN=Partitions object in the Configuration naming context of your AD LDS instance.

       

       

    Simply changing the value of msDS-Behavior-Version from 2 to 4 will update the functional level of your instance from Windows Server 2003 to Windows Server 2008 R2. Alternatively, you can use Windows PowerShell to upgrade the functional level of your AD LDS instance. For AD DS, there is a dedicated Windows PowerShell cmdlet for raising the forest functional level called Set-ADForestMode, but this cmdlet is not supported for AD LDS. To use Windows PowerShell to raise the functional level for AD LDS, you will need to use the Set-ADObject cmdlet to specify the new value for the msDS-Behavior-Version attribute.

       

    To raise the AD LDS functional level using Windows PowerShell, run the following command (after loading the AD module):

       

    Set-ADObject -Identity <path to Partitions container in Configuration Partition of instance> -Replace @{'msds-Behavior-Version'=4} -Server <server:port>

       

    For example in my environment, I ran:

       

    Set-ADObject -Identity 'CN=Partitions,CN=Configuration,CN={A1D2D2A9-7521-4068-9ACC-887EDEE90F91}' -Replace @{'msDS-Behavior-Version'=4} -Server 'localhost:50000'

       

     

     

       

       

    As always, before making changes to your production environment:

    1. Test in a TEST or DEV environment
    2. Have good back-ups
    3. Verify the general health of the environment (check replication, server health, etc)

       

    Now we're ready to enable AD Recycle Bin! 

    Enabling AD Recycle Bin for AD LDS

       

    For Windows Server 2008 R2, the process for enabling ADRB in AD LDS is nearly identical to that for AD DS. Either Windows PowerShell or LDP can be used to enable the feature. Also, there is no UI for enabling ADRB for AD LDS in Windows Server 2008 R2 or Windows Server 2012. Windows Server 2012 does add the ability to enable ADRB and restore objects through the AD Administrative Center for AD DS (you can read about it here), but this UI does not work for AD LDS instances on Windows Server 2012.

       

    Once the feature is enabled, it cannot be disabled. So, before you continue, be certain you really want to do this. (Read this whole post to help you decide.)

       

    The ADRB can be enabled in both AD DS and AD LDS using a PowerShell cmdlet, but the syntax is slightly different between the two. The difference is fully documented in TechNet.

       

    In my lab, I used the PowerShell cmdlet to enable the feature rather than using LDP. Below is the syntax for AD LDS:

       

    Enable-ADOptionalFeature 'recycle bin feature' -Scope ForestOrConfigurationSet -Server <server:port> -Target <DN of configuration partition>

       

    Here's the actual cmdlet I used and a screenshot of the output. The cmdlet asks you confirm that you want to enable the feature since this is an irreversible process.

       

     

     

       

    You can verify that the command worked by checking the msDS-EnabledFeature attribute on the Partitions container of the Configuration NC of your instance.

       

     

    Seemed like a good idea at the time. . .

       

    Now, on to what prompted this post in the first place.

       

    Once ADRB is enabled, there is a change to how deleted objects are handled when they are removed from the directory. Prior to enabling ADRB when an object is deleted, it is moved to the Deleted Objects container within the application partition of your instance (CN=Deleted Objects, DC=instance1, DC=local or whatever the name of your instance is) and most of the attributes are deleted. Without Recycle Bin enabled, a user object in the Deleted Object container looks like this in LDP:

       

       

    After enabling ADRB, a deleted user object looks like this in LDP:

       

       

    Notice that after enabling ADRB, givenName, displayName, and several other attributes including userPrincipalName (UPN) are maintained on the object while in the Deleted Objects container. This is great if you ever need to restore this user: most of the data is retained and it's a pretty simple process using LDP or PowerShell to reanimate the object without the need to go through the authoritative restore process. But, retaining the UPN attribute specifically can cause issues if ADAMSync is being used to synchronize objects from AD DS to AD LDS since the userPrincipalName attribute must be unique within an AD LDS instance.

       

    In general, the recommendation when using ADAMSync, is to perform all user management (additions/deletions) on the AD DS side of the sync and let the synchronization process handle the edits in AD LDS. There are times, though, when you may need to remove users in AD LDS in order to resolve synchronization issues and this is where having ADRB enabled will cause problems.

       

    For example:

       

    Let's say that you discover that you have two users with the same userPrincipalName in AD and this is causing issues with ADAMSync: the infamous ATT_OR_VALUE_EXISTS error in the ADAMSync log.

       

    ====================================================

    Processing Entry: Page 67, Frame 1, Entry 64, Count 1, USN 0 Processing source entry <guid=fe36238b9dd27a45b96304ea820c82d8> Processing in-scope entry fe36238b9dd27a45b96304ea820c82d8.

       

    Adding target object CN=BillyJoeBob,OU=User Accounts,dc=fabrikam,dc=com. Adding attributes: sourceobjectguid, objectClass, sn, description, givenName, instanceType, displayName, department, sAMAccountName, userPrincipalName, Ldap error occurred. ldap_add_sW: Attribute Or Value Exists. Extended Info: 0000217B: AtrErr: DSID-03050758, #1:

    0: 0000217B: DSID-03050758, problem 1006 (ATT_OR_VALUE_EXISTS), data 0, Att 90290 (userPrincipalName)

       

    . Ldap error occurred. ldap_add_sW: Attribute Or Value Exists. Extended Info: 0000217B: AtrErr: DSID-03050758, #1:

    0: 0000217B: DSID-03050758, problem 1006 (ATT_OR_VALUE_EXISTS), data 0, Att 90290 (userPrincipalName)

    ===============================================

       

       

    Upon further inspection of the users, you determine that at some point a copy was made of the user's account in AD and the UPN was not updated. The old account is not needed anymore but was never cleaned up either. To get your ADAMSync working, you:

    1. Delete the user account that synced to AD LDS.
    2. Delete the extra account in AD (or update the UPN on one of the accounts).
    3. Try to sync again

       

    BWAMP!

       

    The sync still fails with the ATT_OR_VALUE_EXISTS error on the same user. This doesn't make sense, right? You deleted the extra user in AD and cleaned up AD LDS by deleting the user account there. There should be no duplicates. The ATT_OR_VALUE_EXISTS error is not an ADAMSync error. ADAMSync is making LDAP calls to the AD LDS instance to create or modify objects. This error is an LDAP error from the AD LDS instance and is telling you already have an object in the directory with that same userPrincipalName. For what it's worth, I've never seen this error logged if the duplicate isn't there. It is there; you just have to find it!

       

    At this point, it's not hard to guess where the duplicate is coming from, since we've already discussed ADRB and the attributes maintained on deletion. The duplicate userPrincipalName is coming from the object we deleted from the AD LDS instance and is located in the Deleted Objects container. The good news is that LDP allows you to browse the container to find the deleted object. If you've never used LDP before to look through the Deleted Objects container, TechNet provides information on how to browse for deleted objects via LDP.

     

    It's great that we know why we are having the problem, but how do we fix it? Now that we're already in this situation, the only way to fix it is to eliminate the duplicate UPN from the object in CN=Deleted Objects. To do this:

       

    1. Restore the deleted object in AD LDS using LDP or PowerShell
    2. After the object is restored, modify the UPN to something bogus that will never be used on a real user
    3. Delete the object again
    4. Run ADAMSync again

       

    Now your sync should complete successfully!

    Not so fast, you say . . .

       

    So, I was feeling pretty good about myself on this case. I spent hours figuring out ADRB for AD LDS and setting up the repro in my lab and proving that deleting objects with ADRB enabled could cause ATT_OR_VALUE_EXISTS errors during ADAMSync. I was already patting myself on the back and starting my victory lap when I got an email back from my customer stating the msDS-BehaviorVersion attribute on their AD LDS instance was still set to 2.

       

    Huh?!

       

    I'll admit it, I was totally confused. How could this be? I had LDP output from the customer's AD LDS instance and could see that the userPrincipalName attribute was being maintained on objects in the Deleted Objects container. I knew from my lab that this is not normal behavior when ADRB is disabled. So, what the heck is going on?

       

    I know when I'm beat, so decided to use one of my "life lines" . . . I emailed Linda Taylor. Linda is an Escalation Engineer in the UK Directory Services team and has been working with ADAM and AD LDS much longer than I have. This is where I should include a picture of Linda in a cape because she came to the rescue again!

       

    Apparently, there is more than one way for an attribute to be maintained on deletion. The most obvious was that ADRB had been enabled. The less obvious requires a better understanding of what actually happens when an object is deleted. Transformation into a Tombstone documents this process in more detail. The part that is important to us is:

    The Schema Management snap-in doesn't allow us to see attributes on attributes, so to verify the value of searchFlags on the userPrincipalName attribute we need to ADSIEdit or LDP.

       

    WARNING: Modifying the schema can have unintended consequences. Please be certain you really need to do this before proceeding and always test first!

       

    By default, the searchFlags attribute on userPrincipalName should be set to 0x1 (INDEX).

       

       

       

    My customer's searchFlags attribute was set to 0x1F (31 decimal) = (INDEX |CONTAINER_INDEX |ANR |PRESERVE_ON_DELETE |COPY).

       

       

    Apparently these changes to the schema had been made to improve query efficiency when searching on the userPrincipalName attribute.

     

    Reminder: Manually modifying the schema in this way is not something you should doing unless are certain you know what you are doing or have been directed to by Microsoft Support.

     

    The searchFlags attribute is a bitwise attribute containing a number of different options which are outlined here. This attribute can be zero or a combination of one or more of the following values:

    Value

    Description

    1 (0x00000001)

    Create an index for the attribute.

    2 (0x00000002)

    Create an index for the attribute in each container.

    4 (0x00000004)

    Add this attribute to the Ambiguous Name Resolution (ANR) set. This is used to assist in finding an object when only partial information is given. For example, if the LDAP filter is (ANR=JEFF), the search will find each object where the first name, last name, email address, or other ANR attribute is equal to JEFF. Bit 0 must be set for this index take affect.

    8 (0x00000008)

    Preserve this attribute in the tombstone object for deleted objects.

    16 (0x00000010)

    Copy the value for this attribute when the object is copied.

    32 (0x00000020)

    Supported beginning with Windows Server 2003. Create a tuple index for the attribute. This will improve searches where the wildcard appears at the front of the search string. For example, (sn=*mith).

    64(0x00000040)

    Supported beginning with ADAM. Creates an index to greatly help VLV performance on arbitrary attributes.

       

    To remove the PRESERVE_ON_DELETE flag, we subtracted 8 from customer's value of 31, which gave us a value of 23 (INDEX | CONTAINER | ANR | COPY). 

     

    Once we removed the PRESERVE_ON_DELETE flag, we created and deleted a test account to confirm our modifications changed the tombstone behavior of the userPrincipalName attribute. UPN was no longer maintained!

       

    Mystery solved!! I think we all deserve a Scooby Snack now!

       

    Nom nom nom!

     

    Lessons learned

       

    1. ADRB is a great feature for AD. It can even be useful for AD LDS if you aren't synchronizing with AD. If you are synchronizing with AD, then the benefits of ADRB are limited and in the end it can cause you more problems than it solves.
    2. Manually modifying the schema can have unintended consequences.
    3. PowerShell for AD LDS is not as easy as AD
    4. AD Administrative Center is for AD and not AD LDS
    5. LDP Rocks!

       

    This wraps up the "More than you really ever wanted to know about ADAMSync, ADRB & searchFlags" Scooby Doo edition of AskDS. Now, go enjoy your Scooby Snacks!

     
    - Kim "That Meddling Kid" Nichols

       

       

  • Intermittent Mail Sack: Must Remember to Write 2013 Edition

    Hi all, Jonathan here again with the latest edition of the Intermittent Mail Sack. We've had some great questions over the last few weeks so I've got a lot of material to cover. This sack, we answer questions on:

    Before we get started, however, I wanted to share information about a new service available to Premier customers through Microsoft Services Premier Support. Many Premier customers will be familiar with the Risk Assessment Program (RAP). Premier Support is now rolling out an online offering called the RAP as a Service (or RaaS for short). Our colleagues over on the Premier Field Engineering (PFE) blog have just posted a description of the new offering, and I encourage you to check it out. I've been working on the Active Directory RaaS offering since the early beta, and we've gotten really good feedback. Unfortunately, the offering is not yet available to non-Premier customers; look at RaaS as yet one more benefit to a Premier Support contract.

     

    Now on to the Mail Sack!

    Question

    I'm considering upgrading my DFSR hub servers to Server 2012. Is there anything I should know before I hit the easy button and do an upgrade?

    Answer

    The most important thing to note is that Microsoft strongly discourages mixing Windows Server 2012 and legacy operating system DFSR. You just mentioned upgrading your hub servers, and make no mention of any branch servers. If you're going to upgrade your DFSR servers then you should upgrade all of them.

    Check out Ned's post over on the FileCab blog: DFS Replication Improvements in Windows Server. Specifically, review the section that discusses Dynamic Access Control Support.

    Also, there is a minor issue that has been found that we are still tracking. When you upgrade from Windows Server 2008 R2 to Windows Server 2012 the DFS Management snap-in stops working. The workaround is to just uninstall and then reinstall the DFS Management tools:

    You can also do this with PowerShell:

    Uninstall-WindowsFeature -name RSAT-DFS-Mgmt-Con
    Install-WindowsFeature -name RSAT-DFS-Mgmt-Con

     

    Question

    From our SharePoint site, when users click on log-off then they get sent to this page: https://your_sts_server/adfs/ls/?wa=wsignout1.0.

    We configured the FedAuth cookie to be session based after we did this:

    $sts = Get-SPSecurityTokenServiceConfig 
    $sts.UseSessionCookies = $true 
    $sts.Update() 

     

    The problem is, unless the user closes all their browsers then when they go to the log-in page the browser remembers their credentials. This is not acceptable for some PC's are shared by people. Also, closing all browsers is not acceptable as they run multiple web applications.

    Answer

    (Courtesy of Adam Conkle)

    Great question! I hope the following details help you in your deployment:

    Moving from a persistent cookie to a session cookie with SharePoint 2010 was the right move in this scenario in order to guarantee that closing the browser window would terminate the session with SharePoint 2010.

    When you sign out via SharePoint 2010 and are redirected to the STS URL containing the query string: wa=wsignout1.0, this is what we call a WS-Federation sign-out request. This call is sufficient for signing out of the STS as well as all relying parties signed into during the session.

    However, what you are experiencing is expected behavior for how Integrated Windows Authentication (IWA) works with web browsers. If your web browser client experienced either a no-prompt sign-in (using Kerberos authentication for the currently signed in user), or NTLM, prompted sign-in (provided credentials in a Windows Authentication "401" credential prompt), then the browser will remember the Windows credentials for that host for the duration of the browser session.

    If you were to collect a HTTP headers trace (Fiddler, HTTPWatch, etc.) of the current scenario, you will see that the wa=wsignout1.0 request is actually causing AD FS and SharePoint 2010 (and any other RPs involved) to clean up their session cookies (MSISAuth and FedAuth) as expected. The session is technically ending the way it should during sign-out. However, if the client keeps the current browser session open, browsing back to the SharePoint site will cause a new WS-Federation sign-in request to be sent to AD FS (wa=wsignin1.0). When the sign-in request is sent to AD FS, AD FS will attempt to collect credentials with a HTTP 401, but, this time, the browser has a set of Windows credentials ready to provide to that host.

    The browser provides those Windows credentials without a prompt shown to the user, and the user is signed back into AD FS, and, thus, is signed back into SharePoint 2010. To the naked eye, it appears that sign-out is not working properly, while, in reality, the user is signing out and then signing back in again.

    To conclude, this is by-design behavior for web browser clients. There are two workarounds available:

    Workaround 1

    Switch to forms-based authentication (FBA) for the AD FS Federation Service. The following article details this quick and easy process: AD FS 2.0: How to Change the Local Authentication Type

    Workaround 2

    Instruct your user base to always close their web browser when they have finished their session

    Question

    Are the attributes for files and folders used by Dynamic Access Control are replicated with the object? That is, using DFSR, if I replicate the file to another server which uses the same policy will the file have the same effective permissions on it?

    Answer

    (Courtesy of Mike Stephens)

    Let me clarify some aspects of your question as I answer each part

    When enabling Dynamic Access Control on files and folders there are multiple aspects to consider that are stored on the files and folders.

    Resource Properties

    Resource Properties are defined in AD and used as a template to stamp additional metadata on a file or folder that can be used during an authorization decision. That information is stored in an alternate data stream on the file or folder. This would replicate with the file, the same as the security descriptor.

    Security Descriptor

    The security descriptor replicates with the file or folder. Therefore, any conditional expression would replicate in the security descriptor.

    All of this occurs outside of Dynamic Access Control -- it is a result of replicating the file throughout the topology, for example, if using DFSR. Central Access Policy has nothing to do with these results.

    Central Access Policy

    Central Access Policy is a way to distribute permissions without writing them directly to the DACL of a security descriptor. So, when a Central Access Policy is deployed to a server, the administrator must then link the policy to a folder on the file system. This linking is accomplished by inserting a special ACE in the auditing portion of the security descriptor informs Windows that the file/folder is protected by a Central Access Policy. The permissions in the Central Access Policy are then combined with Share and NTFS permissions to create an effective permission.

    If the a file/folder is replicated to a server that does not have the Central Access Policy deployed to it then the Central Access Policy is not valid on that server. The permissions would not apply.

    Question

    I read the post located here regarding the machine account password change in Active Directory.

    Based on what I read, if I understand this correctly, the machine password change is generated by the client machine and not AD. I have been told, (according to this post, inaccurately) that AD requires this password reset or the machine will be dropped from the domain.

    I am a Macintosh systems administrator, and as you probably know, this issue does indeed occur on Mac systems.

    I have reset the password reset interval to be various durations from fourteen days which is the default, to one day.

    I have found that if I disjoin and rejoin the machine to the domain it will generate a new password and work just fine for 30 days. At that time, it will be dropped from the domain and have to be rejoined. This is not 100% of the time, however it is often enough to be a problem for us as we are a higher education institution which in addition to our many PCs, also utilizes a substantial number of Macs. Additionally, we have a script which runs every 60 days to delete machine accounts from AD to keep it clean, so if the machine has been turned off for more than 60 days, the account no longer exists.

    I know your forte is AD/Microsoft support, however I was hoping that you might be able to offer some input as to why this might fail on the Macs and if there is any solution which we could implement.

    Other Mac admins have found workarounds like eliminating the need for the pw reset or exempting the macs from the script, but our security team does not want to do this.

    Answer

    (Courtesy of Mike Stephens)

    Windows has a security policy feature named Domain member: Disable machine account password change, which determines whether the domain member periodically changes its computer account password. Typically, a mac, linux, or unix operating system uses some version of Samba to accomplish domain interoperability. I'm not familiar with these on the mac; however, in linux, you would use the command

    Net ads changetrustpw 

     

    By default, Windows machines initiate a computer password change every 30 days. You could schedule this command to run every 30 days once it completes successfully. Beyond that, basically we can only tell you how to disable the domain controller from accepting computer password changes, which we do not encourage.

    Question

    I recently installed a new server running Windows 2008 R2 (as a DC) and a handful of client computers running Windows 7 Pro. On a client, which is shared by two users (userA and userB), I see the following event on the Event Viewer after userA logged on.

    Event ID: 45058 
    Source: LsaSrv 
    Level: Information 
    Description: 
    A logon cache entry for user userB@domain.local was the oldest entry and was removed. The timestamp of this entry was 12/14/2012 08:49:02. 

     

    All is working fine. Both userA and userB are able to log on on the domain by using this computer. Do you think I have to worry about this message or can I just safely ignore it?

    Fyi, our users never work offline, only online.

    Answer

    By default, a Windows operating system will cache 10 domain user credentials locally. When the maximum number of credentials is cached and a new domain user logs onto the system, the oldest credential is purged from its slot in order to store the newest credential. This LsaSrv informational event simply records when this activity takes place. Once the cached credential is removed, it does not imply the account cannot be authenticated by a domain controller and cached again.

    The number of "slots" available to store credentials is controlled by:

    Registry path: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    Setting Name: CachedLogonsCount
    Data Type: REG_SZ
    Value: Default value = 10 decimal, max value = 50 decimal, minimum value = 1

    Cached credentials can also be managed with group policy by configuring:

    Group Policy Setting path: Computer Configuration\Policies\Windows Settings\Security Settings\Local Policies\Security Options.
    Group Policy Setting: Interactive logon: Number of previous logons to cache (in case domain controller is not available)

    The workstation the user must have physical connectivity with the domain and the user must authenticate with a domain controller to cache their credentials again once they have been purged from the system.

    I suspect that your CachedLogonsCount value has been set to 1 on these clients, meaning that that the workstation can only cache one user credential at a time.

    Question

    In Windows 7 and Server 2008 Kerberos DES encryption is disabled by default.

    At what point will support for DES Kerberos encryption be removed? Does this happen in Windows 8 or Windows Server 2012, or will it happen in a future version of Windows?

    Answer

    DES is still available as an option on Windows 8 and Windows Server 2012, though it is disabled by default. It is too early to discuss the availability of DES in future versions of Windows right now.

    There was an Advisory Memorandum published in 2005 by the Committee on National Security Systems (CNSS) where DES and all DES-based systems (3DES, DES-X) would be retired for all US Government uses by 2015. That memorandum, however, is not necessarily a binding document. It is expected that 3DES/DES-X will continue to be used in the private sector for the foreseeable future.

    I'm afraid that we can't completely eliminate DES right now. All we can do is push it to the back burner in favor of newer and better algorithms like AES.

    Question

    I have two Issuing certification authorities in our corporate network. All our approved certificate templates are published on both issuing CAs. We would like to enable certificate renewals from Internet with our Internet-facing CEP/CES configured for certificate authentication in Certificate Renewal Mode Only. What we understand from the whitepaper is that it's not going to work when the CA that issues the certificate must be the same CA used for certificate renewal.

    Answer

    First, I need to correct an assumption made based on your reading of the whitepaper. There is no requirement that, when a certificate is renewed, the renewal request be sent to the same CA as that that issued the original certificate. This means that your clients can go to either enrollment server to renew the certificate. Here is the process for renewal:

    1. When the user attempts to renew their certificate via the MMC, Windows sends a request to the Certificate Enrollment Policy (CEP) server URL configured on the workstation. This request includes the template name of the certificate to be renewed.
    2. The CEP server queries Active Directory for a list of CAs capable of issuing certificates based on that template. This list will include the Certificate Enrollment Web Service (CES) URL associated with that CA. Each CA in your environment should have one or more instances of CES associated with it.
    3. The list of CES URLs is returned to the client. This list is unordered.
    4. The client randomly selects a URL from the list returned by the CEP server. This random selection ensures that renewal requests are spread across all returned CAs. In your case, if both CAs are configured to support the same template, then if the certificate is renewed 100 times, either with or without the same key, then that should result in a nearly 50/50 distribution between the two CAs.

    The behavior is slightly different if one of your CAs goes down for some reason. In that case, should clients encounter an error when trying to renew a certificate against one of the CES URIs then the client will failover and use the next CES URI in the list. By having multiple CAs and CES servers, you gain high availability for certificate renewal.

    Other Stuff

    I'm very sad that I didn't see this until after the holidays. It definitely would have been on my Christmas list. A little pricey, but totally geek-tastic.

    This was also on my list, this year. Go Science!

    Please do keep those questions coming. We have another post in the hopper going up later in the week, and soon I hope to have some Windows Server 2012 goodness to share with you. From all of us on the Directory Services team, have a happy and prosperous New Year!

    Jonathan "13th baktun" Stephens