A Comparison – AWS Managed Microsoft AD and Azure Active Directory Domain Services

A Comparison – AWS Managed Microsoft AD and Azure Active Directory Domain Services

Over the past year I’ve done deep dives into both Amazon’s AWS Managed Microsoft Active Directory and Microsoft’s Azure Active Directory Domain Services.  These services represent each vendor’s offering of a managed Windows Active Directory (AD) service.  I extensively covered the benefits of a service over the course of the posts, so today I’m going to cover the key features of each service.  I’m also going to include two tables.  One table will outline the differences in general features while the other outlines the differences in security-related features.

Let’s hit on the key points first.

  • Amazon provides a legacy (Windows AD is legacy folks) managed service while Microsoft provides a modernized service (Azure AD) which has been been integrated with a legacy service.
  • Microsoft synchronizes users, passwords hashes, and groups from the Azure AD to a managed instance of Windows Active Directory.  The reliance on this synchronization means the customer has to be comfortable synchronizing both directory data and password hashes to Azure AD.  Amazon does not require any data be synchronized.
  • Amazon provides the capability to leverage the identities in the managed instance of Windows AD or in a forest that has a trust with the managed instance to be leveraged in managing AWS resources.  In this instance Amazon is taking a legacy service and enabling it for management of the modern cloud management plane.
  • The pricing model for the services differs where Amazon bills on a per domain controller basis while Microsoft bills on the number of objects in the directory.
  • Amazon’s service is eligible to be used in solutions that require PCI DSS Level 1 or HIPAA.
  • Both services use a delegated model where the customer has full control over an OU rather the directory itself.  Highly privileged roles such as Schema Admin, Enterprise Admins, and Domain Admins are maintained by the cloud provider.
  • Both services provide LDAP for legacy applications customers may be trying to lift and shift.  Microsoft limits LDAP to read operations while Amazon supports both read and write operations.
  • Both services support LDAPS.  At this time Amazon requires an instance of Active Directory Certificate Services be deployed to act as a Certificate Authority and provide certificates to the managed domain controllers.
  • Both services do not allow the customer to modify the Default Domain Policy or Default Domain Controller Policies.  This means the customer cannot modify the password or lockout policy applied to the domain.  Amazon provides a method of enforcing custom password and lockout policies through Fine Grained Password Policies.  Additionally, the customer does not have the ability to harden the OS of the domain controllers for either service so it is important to review the vendor documentation.
  • Amazon’s service supports Active Directory forest trusts and external trusts.  Microsoft’s service doesn’t support trusts at this time.

Here is a table showing the comparison of general features:

Features AWS Managed Microsoft AD Azure Active Directory Domain Services
Cost Basis Number of Domain Controllers Number of Directory Objects
Schema Extensions Yes, with limitations No
Trusts Yes, with limitations No
Domain Controller Log Access Security and DNS Server Event Logs No
DNS Management Yes Yes
Snapshots Yes No
Limit of Managed Forests 10 per account 1 per Azure AD tenant
Supports being used on-premises Yes with Direct Connect or VPN No, within VNet only
Scaled By Customer Yes No
Max number of Domain Controller 20 per directory Unknown how service is scaled

Here is a table of security capabilities:

Features AWS Managed Microsoft AD Azure Active Directory Domain Services
Requires Directory Synchronization No Yes, including password
Fine-Grained Password Policies Yes, limited to seven No
Smart Card Authentication Not native, requires RADIUS No
LDAPS Yes, with special requirements Yes, but LDAP operations are limited to read
LDAPS Protocols SSLv3, TLS 1.0, TLS 1.2 TLS 1.0, TLS 1.2
LDAPS Cipher Suites RC4, 3DES, AES128, AES256 RC4, 3DES, AES128, AES256
Kerberos Delegation Account-Based and Resource-Based Resource-Based
Kerberos Encryption RC4, AES128, AES256 RC4, AES128, AES256
NTLM Support NTLMv1, NTLMv2 NTLMv1, NTLMv2

Well folks that sums it up.  As you can see from both of the series as well as this summary post both vendors have taken very different approaches in providing the service.  It will be interesting to see how these offerings evolve over the next few years.  As much as we’d love to see Windows Active Directory go away, it will still be here for years to come.

Until next time my fellow geeks!

AWS Managed Microsoft AD Deep Dive Part 7 – Trusts and Domain Controller Event Logs

AWS Managed Microsoft AD Deep Dive  Part 7 – Trusts and Domain Controller Event Logs

Welcome back fellow geek.  Today I’m continuing my deep dive series into AWS Managed Microsoft AD.  This will represent the seventh post in the series and I’ve covered some great content over the series including:

  1. An overview of the service
  2. How to setup the service
  3. The directory structure, pre-configured security principals, group policies and the delegated security model
  4. How to configure LDAPS and the requirements that pop up due to Amazon’s delegation model
  5. Security of the service including supported secure transport protocols, ciphers, and authentication protocols
  6. How do schema extensions work and what are the limitations

Today I’m going cover three additional capabilities of AWS Managed Microsoft AD which includes the creation of trusts, access to the Domain Controller event logs, and scalability.

I’ll first cover the capabilities around Active Directory trusts.  Providing this capability opens up the possibility a number of scenarios that aren’t possible in managed Windows Active Directory (Windows AD) services that don’t support trusts such as Microsoft’s Azure Active Directory Domain Services.  Some of the scenarios that pop up in my head are resource forest, trusts with trusted partners to maintain collaboration for legacy applications (applications dependent on legacy protocols such as Kerberos/NTLM/LDAP), trusts between development, QA, and production forests, and the usage of features features such as selective authentication to mitigate the risk to on-premises infrastructure.

For many organizations, modernization of an entire application catalog isn’t feasible but those organizations still want to take advantage of the cost and security benefits of cloud services.  This is where AWS Managed Microsoft AD can really shine.  It’s capability to support Active Directory forests trusts opens up the opportunity for those organizations to extend their identity boundary to the cloud while supporting legacy infrastructure.  Existing on-premises core infrastructure services such as PKI and SIEM can continue to be used and even extended to monitor the infrastructure using the managed Windows AD.

As you can see this is an extremely powerful capability and makes the service a good for almost every Windows AD scenario.  So that’s all well and good, but if you wanted marketing material you’d be reading the official documentation right?  You came here for the deep dive, so let’s get into it.

The first thing that popped into my mind was the question as to how Amazon would be providing this capability in a managed service model.  Creating a forest trust typically requires membership in privileged groups such as Enterprise Admins and Domain Admins, which obviously isn’t possible in a manged service.  I’m sure it’s possible to delegate the creation of Active Directory trusts and DNS conditional forwarders with modifications of directory permissions and possibly user rights, but there’s a better way.  What is this better way you may be asking yourself?  Perhaps serving it up via the Directory Services console in the same way schema modifications are served up?

Let’s walk through the process of setting up an Active Directory forest trust with a customer-managed traditional implementation of Windows Active Directory and an instance of AWS Managed Microsoft AD.  For this I’ll be leveraging my home Hyper-V lab.  I’m actually in the process of rebuilding it so there isn’t much there right now.  The home lab consists of two virtual machines, one named JOG-DC running Windows Server 2016 and functions as a domain controller (AD DS) and certificate authority (AD CS) for the journeyofthegeek.com Active Directory forest.  The other virtual machine is named named JOG-CLIENT, runs Windows 10, and is joined to the journeyofthegeek.com domain.  I’ve connected my VPC with my home lab using AWS’s Managed VPN to setup a site-to-site IPSec VPN connection with my local pfSense box.

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Prior to setting up the trusts there are a few preparatory steps that need to be completed.  The steps will be familiar to those of you who have established forests trusts across firewalled network segments.  At a high level, you’ll want to perform the following tasks:

  1. Ensure the appropriate ports are opened between the two forests.
  2. Ensure DNS resolution between the two forests is established

For the first step I played it lazy since this is is a temporary configuration (please don’t do this in production).   I allowed all traffic from the VPC address range to my lab environment by modifying the firewall rules on my pfSense box.  On the AWS side I needed to adjust the traffic rules for the security group SERVER01 is in as well as the security group for the managed domain controllers.

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To establish DNS resolution between the two forests I’ll be using conditional forwarders setup within each forest.  Setting the conditional forwarders up in the journeyofthegeek.com forest means I have to locate the IP addresses of the managed domain controllers in AWS.  There are a few ways you could do it, but I went to the AWS Directory Services Console and selected the geekintheweeds.com directory.

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On the Directory details section of the console the DNS addresses list the IP addresses the domain controllers are using.

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After creating the conditional forwarder in the DNS Management MMC in the journeyofthegeek.com forest, DNS resolution of a domain controller from geekintheweeds.com was successful.

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I next created the trust in the journeyofthegeek.com domain ensuring to select the option to create the trust in this domain only and recording the trust password using the Active Directory Domains and Trusts.  We can’t create the trusts in both domains since we don’t have an account with the appropriate privileges in the AWS managed domain.

Next up I bounced back over to the Directory Services console and selected the geekintheweeds.com directory.  From there I selected the Network & security tab to open the menu needed to create the trust.

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From here I clicked the Add trust relationship button which brings up the Add a trust relationship menu.  Here I filled in the name of the domain I want to establish the trust with, the trust password I setup in the journeyofthegeek.com domain, select a two-way trust, and add an IP that will be used within configuration of the conditional forwarder setup by the managed service.

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After clicking the Add button the status of the trust is updated to Creating.

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The process takes a few minutes after which the status reports as verified.

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Opening up the Active Directory Users and Computers (ADUC) MMC in the journeyofthegeek.com domain and selecting the geekintheweeds.com domain successfully displays the directory structure.  Trying the opposite in the geekintheweeds.com domain works correctly as well.  So our two-way trust has been created successfully.  We would now have the ability to setup any of the scenarios I talked about earlier in the post including a resource forest or leveraging the managed domain as a primary Windows AD service for on-premises infrastructure.

The second capability I want to briefly touch on is the ability to view the Security Event Log and DNS Server logs on the managed domain controllers.  Unlike Microsoft’s managed Windows AD service, Amazon provides ongoing access to the Security Event Log and DNS Server Log.  The logs can be viewed using the Event Log MMC from a domain-joined machine or programmatically with PowerShell.  The group policy assigned to the Domain Controllers OU enforces a maximum event log size of 256MB but Amazon also archives a year’s worth of logs which can be requested in the event of an incident.  The lack of this capability was a big sore spot for me when I looked at Azure Active Directory Domain Services.  It’s great to see Amazon has identified this critical use case.

Last but definitely not least, let’s quickly cover the scalability of the service.  Follow Microsoft best practices and you can take full advantage of scaling horizontally with the click of a single button.  Be aware that the service only scales horizontally and not vertically.  If you have applications that don’t follow best practices and point to specific domain controllers or perform extremely inefficient LDAP queries (yes I’m talking to you developers who perform searches using front and rear-facing wildcards and use LDAP_MATCHING_RULE_IN_CHAIN filters) horizontal scaling isn’t going to help you.

Well folks that rounds out this entry into the series.  As we saw in the post Amazon has added key capabilities that Microsoft’s managed service is missing right now.  This makes AWS Managed Microsoft AD the more versatile of the two services and more than likely a better fit in almost any scenario where there is a reliance on Windows AD.

In my final posts of the series I’ll provide a comparison chart showing the differing capabilities of both AWS and Microsoft’s services.

See you next post!