Labs: Securing Multi-protocol File Access (NFS/CIFS) on NAS (NetApp) Using Centrify and Windows Security Groups

Background

In the previous post, we discussed how to overcome identity limitations in NAS sharing scenarios.  In heterogeneous environments the main issue is about Identity - the filer is unable to consistently translate the Windows identity to a UNIX identity.  With Centrify Zones and the LDAP Proxy we solved the issue providing a unified identity consistently across Windows, Unix, Linux and Macs.

In Summary, here's what we accomplished:

The LDAP Proxy present's user information for the filer with consistency.  The UNIX information corresponds to what the AD user has in the Centrify Zone.

Now, we can let the NetApp filer do it's magic.  Let's look at a very simple example:

Testing Mixed Share Permissions

Set up the NetApp share

1. Create a new qtree
   qtree create /vol/vol0/mixed
2. Change the security model as mixed
   qtree security mixed
3. Export the newly created qtree
   exportfs -p rw /vol/vol0/mixed

Create a New AD Security Group for the Mixed Share Access

1. Open ADUC browse to an OU for groups
2. Select New > Group
3. Give it a name  (e.g. "Mixed-Share-Access")
4. Add a test user to the newly created share.

Publish the share in Windows

1. Open Computer Managemetnt
2. Connect to your NetApp filer
3. Navigate to System Tools > Shared folders
4. Follow the wizard to create your share
5. In the Share Permissions, remove Everyone and add your previously-created AD Group

Now you have:

• A CIFS share that is a shared folder protected by a Security Group in AD.  Access is governed by group membership and the permissions on the share.  NTFS permissions will be assigned at file/folder creation based on the user's identity.
• An NFS share that can be mounted from any Unix, Linux or Mac system;  UNIX file permissions will be assigned at folder/file creation based on the user's identity.  We'll leverage the NETGROUPS option with Centrify-exposed options to accomplish this.

Let's see this in action

Improvements

As outlined in the latter part of the video, there's definitely improvements that can be implemented:

• On the NetApp side, Kerberos can be implemented for additional security.  Remember that Centrify already provides "hands-off" Kerberos environment optimized for Microsoft's Kerberos.
• The AD Group used to control access can be UNIX-enabled, this opens the possibility of leveraging the group's UNIX identity as a group owner on the UNIX side.

Key benefits

• Process consolidation - now a single AD group can be leveraged to control access.
• Better Security - there's a better grasp on who has access to what.

Business Problems: Conquering the NAS multiprotocol (CIFS/NFS) file sharing in a mixed (Unix, Linux, Windows, Mac) environment using Centrify

Background

Network Attached Storage (NAS) is a key part of any enterprise today; they provide flexibility and an abstraction layer from an infrastructure perspective.  In the heterogeneous enterprise, the easy part is the infrastructure piece;  the hard part has to do with the diversity of platforms and the multiple file-sharing protocols in use.  This post and a series of labs will illustrate how leveraging Active Directory, Centrify Zones, the Centrify agent for UNIX, Linux & Mac and the Centrify LDAP Proxy we can ensure consistency with multi-protocol CIFS/NFS shares and enhance operational efficiency.

In previous posts, we have addressed how to to solve the consistency issue individually:

• Centrify and NFS Basics  (video lab)
• Centrify and Samba (CIFS) basics  (lab1, lab2)

This posts uses a NetApp filer as an example(*).  The concepts outlined here can be used on any NAS device that supports LDAP.  We will assume that you understand that the fundamental problem is how to solve the issue of identity across multiple platforms and how we accomplish that with the Centrify Agent and Active Directory (I highly recommend that you read the previous links).

The Issues (or variations of it)

• We have a NAS device, we integrated it with AD and it works great as long as the user is performing file operations on Windows.  However, we have to keep separate NFS shares.  We also have to manage permissions in multiple groups (Windows or UNIX) and that takes a lot of effort.
  Note, in my example with NetApp, the appliance does a great job at discovering LDAP servers:
  
  netapp1> Sat Jul  5 11:26:52 EST [netapp1:auth.ldap.trace.LDAPConnection.statusMsg:info]: AUTH: TraceLDAPServer- AD LDAP server address discovery for CORP.CONTOSO.COM complete. 2 unique addresses found.
  
  However, although it can resolve the AD portion, it is plain wrong about the Unix UID:
• We have a multi-protocol share (CIFS/NFS), everything is great on Windows, when the user wants to access their files over NFS he has to call to have the file/folder ownership taken care of
• We are tired of having to resolve file ownership issues.  Our organization is globally very diverse and each time we have a new visitor we spend significant amount of time helping them get access.
• We have a combination of Unix, Linux, Mac and Windows users and although we had it down in individual servers, when we moved to filers now we have all these new issues.
• I have a filer in my environment and we have Centrify as well, I know it can help but I don't now where to start.

Example of one of the issues

Let's look at an example.  In my environment with a domain-joined Netapp the appliance does a great job at discovering LDAP servers (this happened once I searched for one of my users):

netapp1> Sat Jul  5 11:26:52 EST [netapp1:auth.ldap.trace.LDAPConnection.statusMsg:info]: AUTH: TraceLDAPServer- AD LDAP server address discovery for CORP.CONTOSO.COM complete. 2 unique addresses found.

netapp1> wcc -s george.constanza

(NT - UNIX) account name(s):  (CORP\george.constanza - pcuser)

        ***************

        UNIX uid = 65534

        NT membership

                CORP\george.constanza

                CORP\UNIX-Model-Samba Users

                CORP\UNIX-Model-All Users

                CORP\UNIX-Model-dbaadmin

                CORP\Domain Users

                CORP\UNIX-Model-Sysadmins

                CORP\UNIX-Model-webadmin

                CORP\UNIX-Model-All UNIX Groups

                BUILTIN\Users

        User is also a member of Everyone, Network Users,

        Authenticated Users

        ***************

This is great from a Windows perspective, however, look at the Unix UID (65534), when you look at the options, this means that the user is being assigned a "nobody" user from a UNIX perspective.  We can further confirm this with this command:

netapp1> wcc -u george.constanza

no passwd entry for george.constanza

The way I have my system configured, although I can derive the user's identity leveraging the DCs, I can't see the user's Unix identity.  It is stored in the zone. See the output from a centrified system:

george@ubu1:/etc/centrifydc/openldap$ adquery user george.constanza -A

unixname:george

uid:1149240406

gid:1149240406

gecos:George Constanza

home:/home/george

shell:/bin/bash

auditLevel:AuditIfPossible

isAlwaysPermitLogin:false

dn:CN=George Constanza,OU=Staff,DC=corp,DC=contoso,DC=com

samAccountName:george.constanza

displayName:George Constanza

sid:S-1-5-21-2180375406-786980114-1643973036-1110

userPrincipalName:george.constanza@corp.contoso.com

canonicalName:corp.contoso.com/Staff/George Constanza

passwordHash:x

accountExpires:Never

passwordExpires:Wed Aug 13 11:28:48 2014

passwordWillExpire:39

nextPasswordChange:Thu Jul  3 11:28:48 2014

lastPasswordChange:Wed Jul  2 11:28:48 2014

accountLocked:false

accountDisabled:false

zoneEnabled:true

unixGroups:dbaadmin,george,webadmin

memberOf:corp.contoso.com/UNIX/Provisioning/UNIX-Model-All UNIX Groups,corp.contoso.com/UNIX/Provisioning/UNIX-Model-All Users,corp.contoso.com/UNIX/RBAC/UNIX-Model-Samba Users,corp.contoso.com/UNIX/RBAC/UNIX-Model-Sysadmins,corp.contoso.com/UNIX/UNIX Groups/UNIX-Model-dbaadmin,corp.contoso.com/UNIX/UNIX Groups/UNIX-Model-webadmin,corp.contoso.com/Users/Domain Users

Our goal is to make sure that our filer (or application) gets the correct Identity information for the purposes of proper file/folder ownership, access and permissions.

Who's affected

As you can see, the variety of problems outlines have multiple constituents:

• Security needs to make sure that users have access to what they need and to comply with policies
• IT (business) need to make sure that users can do their jobs
• IT (operations) wants to be efficient and make sure that an army of people is not needed
• The End User just wants to get their job done

As with all Business Problems, we'll use the Plan, Do, Check, Adjust methodology.

Planning

As discussed in previous posts, the key to this issue is Identity.  In this case, the NAS appliance needs to know not only the user's AD information, but the extended attributes (RFC2307) like unixname, UID, GID, Home, GECOS, Shell, etc., and unlike other approaches, Centrify stores this information in the zone.  This makes the solution more flexible because an AD principal can have multiple Unix identities.

Note:  If you've read this blog, you know that I've been very vocal about overrides (what enables multiple identities and roles).  Every process needs to have constraints; constraints make solutions simpler.  Having a normalized UNIX namespace is the goal and destination of any enterprise, even if Centrify allows you to put off this goal.  

Identity and Access Planning

1. Do the best you can to have a normalized namespace.  Leverage Centrify's ability to assign users a unique UID by generating it from the AD SID (using Centrify or Apple's Scheme).
2. Perform a migration if necessary (this post talks about strategies and Centrify tools for that purpose)
3. Leverage the power of hierarchical zones:  provision all identities at the top-most zone.  This will ensure that all pertinent systems will know the user's identities.
4. Continue to enforce the least-access principle:  Use the "listed" role to make users known to the systems (e.g. the LDAP proxies) and ensure that they can't sign-in to the systems.

Planning your LDAP Proxies

The Centrify LDAP proxy leverages the Centrify client (adclient) to present AD information to clientless devices or programs.  The benefits of leveraging the proxy are:

• It flattens AD for the application:  depending on the enterprise, AD can be complex.  There may be multiple forests, child domains, one-way, two-way trusts, etc.
• It leverages the agent's built-in capabilities:  optimal DC selection, site-awareness and offline cache.

Plan for high-availability:  the NAS (or application) is going to require redundancy, plan to deploy and configure multiple proxies.

Plan for confidentiality:  make sure that only authenticated connections over secure transports (TLS, SSL, etc) in case your appliance or application does not do it natively.

Plan for high-performance:  As always, have NSCD on the Centrified system, and plan for co-location near the appliance, application and be close to Global Catalog servers in complex environments.

Plan for your file-sharing use case

This section varies based on what you want to accomplish.  Planning for home directories is not the same as planning for a workgroup share.  

Implement (Do)

1. Unix-enable all your relevant users (you don't need to Unix-enable users that won't ever access via NFS).  You can do this manually, with ZPA or with your own IdM solution.   
2. Assign roles as required:  keep the least-access principle intact by leveraging the "listed" role.
3. Install the LDAP Proxy(es):
1. Copy the Centrify LDAP proxy binaries to the platfrom.
   e.g. for Ubuntu on 2014:  centrifydc-ldapproxy-5.1.3-deb5-x86_64.deb
2. Log in and install the package
   e.g. dpkg - i centrifydc-ldapproxy-5.1.3-deb5-x86_64.deb
   The LDAP proxy binary is on /usr/share/centrifydc/libexec
   The config files and schemas are in /etc/centrifydc/openldap
   The LDAP utilities (like ldapsearch)  are on /usr/share/centrifydc/bin
3. Modify the RFC 2307 map
1. Edit the /etc/centrifydc/openldap/rfc2307.map file
2. Add the following line (for NetApp compatibility):
   # Added for NetApp
   posixAccount.userPassword: _userPassword
4. For testing only, start slapd manually:
   dzdo /usr/share/centrifydc/libexec/slapd -f /etc/centrifydc/openldap/ldapproxy.slapd.conf -h ldap://ubu1.corp.contoso.com
5. Check that the proxy is running
   $ ps -ef | grep slapd
   root     23192     1  0 Jul04 ?        00:00:00 ./slapd -f /etc/centrifydc/openldap/ldapproxy.slapd.conf -h ldap://ubu1.corp.contoso.com
6. Verify that the proxy is responding to queries (e.g. check the Administrator account)
   $ /usr/share/centrifydc/bin/ldapsearch -h ubu1.corp.contoso.com-x -b "dc=corp,dc=contoso,dc=com" "(cn=Administrator)"
   # extended LDIF
   #
   # LDAPv3
   # base <dc=corp,dc=contoso,dc=com> with scope sub
   # filter: (cn=Administrator)
   # requesting: ALL
   # with pagedResults control: size=100
   ## Administrator, Users, corp.contoso.comdn: cn=Administrator,cn=Users,dc=corp,dc=contoso,dc=comaccountExpires: 0
   (output truncated***)
4. Configure your NAS appliance (e.g. on NetApp Ontap v 8.1.2)
1. Housekeeping:  Make sure that the name of the appliance is resolvable (add an A record for it) and that all Centrified systems, Windows Systems can resolve it.  The NetApp system should resolve all systems as well.  E.g.
   netapp1> ping ubu1
   ubu1.corp.contoso.com is alive
   netapp1> options dns
   dns.cache.enable             on
   dns.domainname               corp.contoso.com
   dns.enable                   on
   dns.update.enable            off
   dns.update.ttl               24h
2. Housekeeping:  Make sure that CIFS and NFS are licensed, enabled and the NetApp filer is joined to the domain.  (use the license command, the cifs setup command )
3. Verify that there's a computer object for the netapp device and that you can (as a Domain Admin) connect to it via Computer Management.  E.g. using ldapsearch:
   george@ubu1:/etc/centrifydc/openldap$ /usr/share/centrifydc/bin/ldapsearch -h
   ubu1.corp.contoso.com -x -b "dc=corp,dc=contoso,dc=com" "(cn=NETAPP1)"
   <truncated>
   # NETAPP1, Appliances, corp.contoso.com
   dn: cn=NETAPP1,ou=Appliances,dc=corp,dc=contoso,dc=com
   <truncated>
4. Optional:  Make sure that Domain Administrators are not mapped to root the NetApp filer:
   netapp1> options wafl.nt_admin_priv_map_to_root off
5. Configure NetApp to use the LDAP Proxy (Example corp.contoso.com;  ubu1)
1. Set up the LDAP base container
   netapp1> options ldap.base dc=corp,dc=contoso,dc=com
2. Set up the LDAP server(s) to be used by the NetApp appliance
   netapp1> options ldap.servers ubu1.corp.contoso.com
3. Set up the name of the Active Directory Domain
   netapp1> options ldap.ADdomain corp.contoso.com
4. Map the userPassword attribute to avoid null results
   netapp1> options ldap.nssmap.attribute.userPassword cn
5. Enable LDAP
   netapp1> options ldap.enable on
6. Modify the /etc/nsswitch.conf to make LDAP the first source for user, group and shadow entries.
   netapp1> wrfile /etc/nsswitch.conf
   hosts:  files  dns
   passwd:  ldap files
   group: ldap files
   netgroup:  files nis
   shadow:  files nis
7. Verify the results
1. Query and note the UID from Windows
   wcc -s jerry.seinfeld 
2. Query and note the UID from UNIX
   wcc -u jerry.seinfeld
3. Advanced query using NSS
   priv set diag
   getXXbyYY getpwbyname_r jerry.seinfeld
   
   Compare the results with the zone information.  At this point it should match the UNIX identity on Access Manager

Check the Results

To verify the results, use a multi-protocol (CIFS/NFS) share and make sure that the identity information is consistent.

1. From a Windows system in the target domain, map or browse to the share via CIFS.  Create a file.
2. From a Unix/Linux or Mac system, mount the share as an NFS mount and issue the ls -la and ls -lan.  Compare the results from before.

Adjustments to the Implementation

Adjustments are based on your existing environment, however, based on ours here are some key modifications:

• There's only one LDAP proxy, we need several for high-availability
• The LDAP Proxy is accepting anonymous connections, we need to make sure that only authenticated connections are accepted.
• Ideally we would use Secure LDAP or implement TLS or IPSec for additional confidentiality controls.
• Operations needs to monitor the health and status of the LDAP Proxies

Lab Videos

What you'll need to follow along:

• Active Directory
• Centrify Standard Edition
• A Centrify zone
• Client for Unix, Linux or Mac
• Centrify's LDAP Proxy
• A Multi-protocol filer (we'll use NetApp's  ONTAP Simulator)

Installing, Configuring and Testing the Centrify LDAP Proxy

Configuring the NetApp appliance to use the Centrify LDAP Proxy


Verifying the NetApp CIFS/NFS share provides consistent identities

Mac OS X Extras: Computer Certificate Auto-enrollment

Background

Digital Certificates have an important place in a properly managed enterprise.  From an infrastructure perspective, they can enhance authentication and provide encryption for Ethernet and Wifi Networks.
Centrify for Mac OS X has built-in capabilities to enable 802.1x authentication leveraging Group Policy but it does require that the computer has a digital certificate.

PKI Disclaimer:  As in all PKI-related posts and videos, I make the caveat that Public Key Infrastructure is no joke.  There are policy, people, process, security and technology implications to your enterprise, so all PKI deployments need to provide a high-level of assurance.  You may have landed here due to a google search or reference, feel free to use these posts for testing purposes, but again, when it comes to PKI, any production deployment should conform to best practices.

Centrify uses GPOs to configure computer or user-based 802.1x settings on the Mac OS X platform

Configuring Computer AutoEnrollment for Mac OS X

The Centrify adclient is capable of leveraging Windows certificate auto enrollment with the Microsoft CA. The basic steps are:

On the AD side (with a Domain or Cert Admin)

1. Configure the certificate template based on your needs (using the Certificate Templates MMC)
• Subject  (typically common name based on the User Principal Name)
• Security (set it to an AD group containing your Mac Systems and check to Enroll and AutoEnroll)
• Extensions (add what you need)
  If using it for 802.1x - usage should be Client and Server Authentication.
2. Configure your CA to issue Certificates based on that template (using the Certificate Authority MMC)
3. Modify your GPO to enable the PKI policies for auto-enrollment
   Enabling the Computer Configuration > Windows Settings > Security Settings > Public Key Policies > "Certificate Services Client - Auto-Enrollment Settings" GPO

On the Mac (domain-joined)

1. Flush the cache with adflush (or wait the cache flush interval)  [sudo adflush]
2. Refresh the group policies (with adgpupdate) or wait for the GP refresh interval
3. Verify the Certificates on the Keychain Access app.

Video Lab