Introduction Granularidad Password

IntroductionIn previous versions of Active Directory (AD) we had only one password and account lockout policy for the entire domain. Some companies had to use multiple domains to place different password policies on different users; others had to develop their own password filters or buy third party solutions. With Windows Server 2008 we have the option to specify different password policies for different users and groups out-of-the-box.This first of two articles is a walkthrough on creating a password policy in addition to the usual one we have in the Default Domain Policy Group Policy placed on the domain level.New in classIn short the new functionality, referred to as Granular Password Settings or Fine-Grained Password Policy, is based on the introduction of two new object classes in the AD schema: the Password Settings Container and Password Setting objects. These objects basically provide us the option to introduce multiple password policies into a single AD domain. But let us take a look at what else we needThe tools and prerequisitesThis is a quick view on the tools and prerequisites needed for creating additional password policies.ADUCFirst of all the Active Directory domain functional level must be Windows Server 2008. This can be checked using Active Directory Users and Computers (ADUC) Right click the domain > choose Raise domain functional level the current domain functional level should read Windows Server 2008 (below is a screenshot from the beta 3 version of Windows Server 2008 build 6001):

Figure 1GPMCWe will still have to use the Group Policy Management Console (GPMC) to set the default password policy for the entire domain (the fallback policy you could say). If you have forgotten how to set the default domain password and lockout settings, they can be found in GPMC on the domain level under Default Domain Policy > Computer Configuration > Windows Settings > Security Settings > Account Policies > Password Policy/Account Lockout Policy.By the way, the GPMC is included with Windows Server 2008 (like with Windows Vista), but must be added as a Feature choose Add Feature in Server Manager, select Group Policy Management and after a few moments you are Group Policy Ready ADSI EditThe most important tool for this exercise is actually a tool that most administrators have feared through the years because whenever you have to use it it is normally when something bad has happened well, I am referring to the ADSI Edit utility (adsiedit.msc). Most of the granular password policy settings are created and configured from within this tool. ADSI Edit is part of the standard Windows Server 2008 installation so you do not have to add it afterwards.The stepsThis is a quick view on the steps required to configure Granular Password Settings in Windows Server 2008:1. Create a Password Settings Object (PSO) in the Password Settings Container (PSC) using ADSI Edit 2. Configure the PSO options by completing the primitive wizard within ADSI Edit 3. Assign the PSO to a user account or a global security group 4. Confirm that the settings actually appliedNow that we know what steps we have to take, lets get going!Lets get startedFirst, let us fire up ADSI Edit by clicking Start > Run > adsiedit.msc and click OK (or press Enter). Right click the ADSI Edit root and select Connect to

Figure 2Select OK to choose the default options in the Connection Settings dialog:

Figure 3In ADSI Edit you should now be able to expand the domain, expand the System container and finally right click the new Password Settings Container (PSC) and choose New > Object....

Figure 4You will now have to select a class for the new object, but you are given one choice only (sometimes it is nice not to have too many options, right?). Select msDS-PasswordSettings and click Next:

Figure 5From now on a pretty basic wizard is started that guides us though the process of creating a Password Settings Object (PSO). We will have to specificy a value for each of the following 11 attributes. Type in the values as shown in the table below (be sure to type the minus sign in front of values where it is required) or come up with your own.AttributeValueQuick explanation

CnPassPolAdminsThis is the name of the policy. Try to come up with a naming convention for these policies if you will have lots of them.

msDS-PasswordSettingsPrecedence10This number is used as a cost for priority between different policies in case a user is hit by multiple PSOs. Be sure to leave space below and above for future use. The stronger the PSO password settings are, the lower the cost should be.

msDS-PasswordReversibleEncryptionEnabledFalseBoolean value to select if passwords should be stored with reversible encryption (usually not a good idea).

msDS-PasswordHistoryLength32How many previously used passwords should the system remember?

msDS-PasswordComplexityEnabledTrueShould the users use a complex password? (Boolean value)

msDS-MinimumPasswordLength16What should be the minimum number of characters in the user accounts password?

msDS-MinimumPasswordAge-864000000000(9 zeros)What is the minimum password age? (in this case 1 day) NB! Minus sign

msDS-MaximumPasswordAge-36288000000000(9 zeros)What is the maximum password age? (in this case 42 days) NB! Minus sign

msDS-LockoutTreshold30How many failed attempts before the user account will be locked?

msDS-LockoutObservationWindow-18000000000(9zeros)After how long should the counter for failed attempts be reset? (in this case 6 minutes) NB! Minus sign

msDS-LockoutDuration-18000000000(9zeros)For how long should the user account object be locked in case of too many bad passwords entered? (in this case 6 minutes) NB! Minus sign

Table 1When all that typing is done you should see the following dialog just click Finish.

Figure 6Make it happenNow the PSO is created and it should be visible below the PSC in both ADSI Edit and ADUC/Server Manager (just remember to enable Advanced Features in the View menu), it should look like this:

Figure 7From this point all we have to do is to assign the new policy to a specific user, multiple users, a global security group, multiple global security groups or a combination of users and global security groups.To do this, right click the PSO in ADUC (or ADSI Edit) and select Properties click Filter and make sure you have the following options selected/de-selected:

Figure 8If you cannot see the picture I can tell you that the following options are selected: Mandatory, Optional, Constructed, Backlinks and System-only. The Show only attributes that have values is NOT selected.Now browse to msDS-PSOAppliesTo, select it and click Edit.

Figure 9In the Multi-valued String Editor insert the distinguished name of a user or a global security group in the Value to add field and click Add. You can add multiple distinguished names in this dialog when done just click OK.

Figure 10In the example above I have added a global security group named Admins (with the distinguished name of CN=Admins,CN=Users,DC=Contoso,DC=Local). Every user account that is a member of this group is now hit by the new PassPolAdmins password policy instead of the one defined in the Default Domain Policy. Cool, right!At this point you might wonder what happens if the user is hit by multiple conflicting password policies. I will get back to this in detail in the next article in this series, but let me remind you we defined a precedence value during the PSO creation. Did you notice the change?When you browsed around in ADUC just before, did you then notice the new Attribute Editor tab we now have on most objects (View > Advanced Features must be enabled)?

Figure 11This is really cool because it enables administrator to view or edit lots of stuff which should normally be done within the ADSI Edit tool. With this tab we can take properties on the PSOs in the domain and modify the msDS-PSOAppliesTo attribute to easily set the password policy on a user or group (or move a user or group from that policy). Please notice that you cannot set the password policy from properties on the user or group objects information about what policy applies to which users or groups is in other words set on the Password Settings Object itself!Where can I see what policy wins?It can be hard to determine what policy wins for a specific user object (probably the one with the lowest cost AKA precedence value) the Resultant Set of Policy (RSoP) you could say. But I am happy to tell you that Microsoft thought about this by introducing the msDS-ResultantPSO attribute on user objects (only).

Figure 12This value determines what policy applies to the specific user (in my example a user named Windows Admin). This is in other word the active password and lockout policy for the selected user.Both group and user objects have another new attribute, msDS-PSOApplied, which holds (in a multi-valued string) all the policies that the group or user is hit by - either directly or through group membership. In the example below the group called Admins is hit by 2 different password policies.

Figure 13NB! If you cannot see the values mentioned here, be sure to set the Attribute Editor tabs filtering options to the ones described in the Make it happen section above.

ConclusionWe have now seen how to add a password and lockout policy in addition to the existing policy which is defined on the domain level by default.To be honest I sometimes wonder why Microsoft was not able to make the procedure for this as easy as it is with for example Specops Password Policy (with Windows 200x AD) where everything is handled within GPEDIT, but at least we have a free option built-in to Active Directory now. I guess Microsoft wants the security group approach instead of the OU approach most likely based on requests from costumers out there.It is just a matter of getting used to this new approach and I am sure we will see some easy-to-use tools and scripts within short time to make the described process even easier to complete. Despite the nerdy management of these policies I think it is going to be used a great deal out there lets hope so anyway! Please also read Configuring Granular Password Settings in Windows Server 2008 part 2 when it is published in short time.

We have now seen how to create PSOs and assign them to users and/or groups, but why do we need multiple password and account lockout policies you might ask? Well, there are many reason for doing this one could be hosting scenarios where multiple companies are present in a single AD domain, another more common reason is where we need stricter settings to apply to a specific group of people with privileged accounts (like domain administrators, help desk personnel etc.). Those privileged accounts can have a complexity requirement and a requirement of defining a minimum of 16 characters in their passwords and other, more limited accounts, can have more user friendly requirements - although I would recommend everyone to use passwords of that strength (more about this in a later article).Who can hit what?At the riskof repeating myself I must say this to make sure it is 100% clear. The new multiple password policy functionality in Windows Server 2008 (Codename Longhorn) allows us to set individual password policies and account lockout policies on user objects, interOrgPerson objects and global security groups.Fine-grained password policies cannot be applied to an OU directly now we must apply these policies to groups instead. Not any kind of group it must be security groups set to the global scope. Its possible to set the options/attributes on other groups; however it will not work as expected (the settings are ignored).If we really want to handle password policies within the OU structure, theShadow Groups can be useful see the section Shadow Groups and how to script them later in this article.By default only members of the Domain Admins group can set, create and delete fine-grained password policies better known as Password Setting Objects (PSO). However, these permissions can be delegated and tweaked if required, but the default settings should be fine for most environments. To be more specific, only members of the Domain Admins group have the required Create Child and Delete Child permissions on the Password Settings Container (PSC) object. To apply a PSO to a user or a group object, you must have Write permissions on the PSO object members of the Domain Admins group are the only ones with this permission by default. The funny thing is that you dont have to have permissions on the user or group object itself, as these are set by a background directory process.Take a look at those attributesI just have to mention some of the attributes that make all of this possible.msDS-PSOAppliesTo Every PSO has a multi-valued attribute named msDS-PSOAppliesTo which is known as a forward link, linking to user or group objects. It can link to a single user, a single group, multiple users, multiple groups or multiple users and groups. These links are actually just the distinguished names (Eg. CN=GroupA,OU=MyGoups,DC=Contoso,DC=Local) of the associated objects. You might ask: What if we rename or move a user or group object (to another OU or container), will the PSOs follow the objects? Yes - the PSOs msDS-PSOAppliesTo attribute is automatically updated by the directory service in the background, to point to the new location (distinguished name) of the changed object.msDS-PSOAppliedThe just mentioned msDS-PSOAppliesTo attribute on the PSOs can be edited as opposed to the back link attribute msDS-PSOApplied which is present on user and group objects. The latter attribute is view only and handled by the directory service in the background.The msDS-PSOApplied attribute contains a back link to the PSO/PSOs pointing at its parent object as users and groups can have multiple PSOs applied to them this attribute is multi-valued too. msDS-ResultantPSOThe msDS-ResultantPSO attribute is present on user objects only. It contains a calculated value, also referred to as the Resultant Set of Policy (RSoP). This is a link to the single lucky PSO that is active on the specific user object. This value is calculated by the directory service process in the background from the rules mentioned in the next section of this article (The Design).You might ask: When is the password policy active on a user who is added to a group? As soon as a user is added to the group the resultant PSO is also calculated for the user object by the directory service. It is the same story if you remove a user account from a group - the change takes effect immediately.msDS-PasswordSettingsPrecedenceThe msDS-PasswordSettingsPrecedence attribute is present on the PSO objects. A lower value for this attribute indicates that the PSO has a higher priority. This attribute is used when multiple PSOs are applied to a user object i.e. the lowest cost is chosen . If you assign a unique precedence value to each of your PSOs in the domain, it will always be easy to determine the effective password policy for a certain user object.The designBefore implementing multiple password policies in the domain it is recommended to get an overview of what policies are needed and to finish the overall design of those policies and their interaction. You can have multiple policies assigned to a single user, directly or through group memberships (even nested security groups are addressed), but only one PSO can be effective for a certain user object at any given time, and password or lockout settings cannot be merged like with Group Policies it is one or the other policy that takes effect.Therefore we need some rules and a priority calculation when multiple PSOs are present for a user.The simple rulesThe resultant PSO is determined as follows:1. A PSO that is linked directly to the user object will take effect unless multiple PSOs are linked directly to the user object. If more than one PSO is linked, the PSO with the lowest precedence value (msDS-PasswordSettingsPrecedence) is the resultant PSO. If the system should spot two or more PSOs applied directly to a given user, all with the exact same msDS-PasswordSettingsPrecedence value, the PSO with the smallest Global Unique Identifier (GUID) is applied. 2. If no PSOs are linked to the user object, the global security group memberships of the userare taken into consideration. If the user is a member of multiple security groups with different PSOs applied, the PSO with the lowest precedence value is the resultant PSO. If the system should spot two or more PSOs applied by group membership to a given user, all with the exact same msDS-PasswordSettingsPrecedence value, the PSO with the smallest GUID is applied.If no PSO is obtained from conditions 1 and 2, the password and lockout settings from the Default Domain Policy are applied, just like it was with earlier versions of Active Directory (AD) environments.

So, to make a long story short: PSOs set on user objects will win over PSOs set on group objects and the lower precedence value will win over the higher if that fails the result is based on GUID numbers and if nothing applies we are back to where we started: The Default Domain Policy!As more general recommendations I will mention these:The Description field can be used to specify the password and lockout settings that are enabled in the PSO. Use it for a quick wrap-up of the PSO configuration and intended use.Create a naming convention for PSOs like you have for other AD objects etc.Assign PSOs to groups, instead of directly on user objects, for better overview and easier manageability.Assign a unique precedence value to each of the PSOs in your domain, it will then be much easier to determine the effective password policy for a certain user object.The Default Deny All ruleWell, I know this might not be a popular thing to say, but I would recommend you set the password settings contained in the Default Domain Policy to a very high (almost annoying) level of security. This is because you or somebody else might forget to include a user in one of the password security groups. In that case the user accounts password policy will fallback to the one defined in this default policy set on the domain level.Look at the security policy in the Default Domain Policy as the Default Deny All rule in a firewall if no specific rule/policy is available for the user (or one of the groups of which he is a member) then we should place a very strict policy on the users head. The user will probably call help desk to get this fixed ASAP - if we give the user a very relaxed password policy instead he/she will, in most cases, never complain.Another way to do this would be to set a granular password policy on the Domain Users group with the lowest priority used - but again, at some point an account might slip out of this group for some reason My choice is definitely the Default Deny All rule as always!Shadow groups and how to script themIf you have never heard about Shadow Groups, do not worry neither had Itwo months ago. A Shadow Group (SG) is a security group (in this case a Global security group) that contains the objects within a given OU as members. A SG is a security group that is logically mapped to an OU you could say.For instance you might have an OU, OU=Sales,OU=CorpUsers,DC=Contoso,DC=Local, with the user accounts for the entire sales department a SG would be a group that matched that content 100%. For password policies this can be a really good thing if we want the password policies to follow the OU structure virtually, instead of following the Security Group structure.You can probably imagine that this would mean a great deal of work if we had to update the SGs manually every hour or so that is why I have written a small and simple VBS script to automate this process by using a scheduled task.The script collects the user accounts from a specific OU - specified as an argument to the script and places those into a dictionary object. The script then collects the users within a specific group - specified as an argument to the script - and places those into another dictionary object. By comparing those dictionaries, the script adds or removes users from the shadows group. The script is designed to be scheduled as a task and should be used with the following syntax: ShadowGroup.vbs "Target OU" "Shadow Group"Example:ShadowGroup.vbs "OU=Test,DC=Contoso,DC=Local" "CN=Shadow,OU=Test,DC=Contoso,DC=Local"The script can be downloaded here, but use in a production environment is at your own risk. It is recommended to put in some error handling routines and maybe reporting functionality. Also support for sublevel OUs would be a good idea to implement. I might provide such a script later on, but so far we have the basic functionality included.ScriptingIt is actually possible to script the creation and modification of granular password policies and assigning those policies to specific users or groups. However, this article will not deal with these possibilities in detail. We can use the good old LDIFDE tool and of course, the new Sheriff in town, Mr. PowerShell. Windows PowerShell is included with Windows Server 2008 and must be added as a Feature choose Add Feature in the new and shiny Server Manager, select Windows PowerShell and after a few moments you are PowerShell ReadyI will recommend you trying out the Quest AD Cmdlets and to check out PowerGui.org.A free command line tool, PSOmgr, already exists from Joeware. With this tool you can manage Password Settings Objects in Windows Server 2008 very easily, eg. display the applied policies and the effective policy of a given user, display the PSOs in the domain/forest, add or remove a user from a PSO, create/rename/delete/modify PSOs and much more