Azure AD Connect Pass-Through Authentication

At Ignite 2017 it was announced that Pass Through Authentication (PTA) has reached General Availability (GA) so it is a fully supported scenario now.

But what is PTA? If Office 365 there are Cloud Identities, Synced Identities and Federated Identities. The first two are authenticated in Azure Active Directory, the last one is authenticated against on-premises Domain Controllers. For this to happen you need an ADFS infrastructure, consisting of multiple internal ADFS servers and multiple WAP (Windows Application Proxy) servers in the DMZ acting as ADFS proxies. Oh, and all servers need to be load balanced as well to provide redundancy and scalability.

PTA on the other hand is built on top of Azure AD Connect, and as such an interesting extension of the Synced Identities. PTA installs an agent on the Azure AD Connect server (AuthN agent) which accepts authentication requests from Azure AD and sends these to on-premises Domain Controllers. The advantage of authentication against on-premises Domain Controllers is that no passwords (or password hashes to be more precise) are stored in Azure Active Directory.

My first thought was how an authentication mechanism based on an asynchronous replication tool (Azure AD Connect synchronizes accounts every 30 minutes, and passwords within 2 minutes) ever be a reliable and safe solution. The last thing you want to happen is that you cannot authenticate to any service in the Microsoft cloud, because your Azure AD Connect server is busy doing other stuff (like automatically updating its engine for example ).

My second thought was how secure this could be. There’s no inbound connection to the Azure AD Connect server, there’s only an outbound connection on ports 80 (only used for SSL certificate revocation lists) and 443. And the communication itself should be secured as well, so…. But now that PTA is generally available more information becomes available, and things become clearer.

Authentication flow

For authentication to happen PTA uses a ‘service bus’ in Azure. The service bus is a standard Azure solution where application can store system messages in the service bus and where other applications can use these system messages. Using a service bus, you can create an asynchronous but reliable communication mechanism.

When logging to an Office 365 service the credentials are requested by Azure Active Directory, nothing new here. The credentials are encrypted and stored in the service bus. The AuthN agent on the Azure AD Connect server has a persistent connection to Azure AD and to the service bus, and retrieves the encrypted credentials from the service bus, decrypts them and presents them to the on-premises Domain Controller. The Domain Controller response (success, failure, password expired or user locked out) is returned to the AuthN agent and stored it on the service bus. Azure AD picks up this response and the user can continue working (or not of course, depending on the Domain Controller response).

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TrendMicro Hosted Email Security: SPF DKIM and DMARC Part III

In the previous two blogpost I discussed how to configure SPF, DKIM and DMARC for outbound messages using the TrendMicro Hosted Email Security solution, including Office 365 centralized mail transport. In this blog I’ll discuss SPF, DKIM and DMARC for inbound messages (i.e. the verification part) using the TrendMicro solution.

Inbound protection

For inbound protection there’s not too much configuration to do, the only thing when using an online service is enabling the services.

In HEC Console select Inbound Protection and select Domain-based Authentication. Here you’ll find the options for SPF, DKIM and DMARC:

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Select the Sender Policy Framework (SPF) option and in the SPF window check the enable SPF checkbox and when needed, check the Insert an X-header into email messages checkbox:

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Continue reading TrendMicro Hosted Email Security: SPF DKIM and DMARC Part III

TrendMicro Hosted Email Security: SPF DKIM and DMARC Part II

In my previous blog I showed you how I implemented Trend Micro Hosted Email Security (HES) in my Exchange 2010 environment. Interesting case, it’s an Exchange 2010 hybrid environment with mailboxes in on-premises Exchange 2010 as well as mailboxes in Exchange Online. Centralized mail transport is used, so mail to and from Office 365 always routes via HES and the on-premises Exchange 2010 servers to Exchange Online. In this blog I will focus on implementing SPF, DKIM and DMARC in Trend Micro Hosted Email Security.

SPF

SPF in itself is covered in more detail in a previous blog post “SenderID, SPF, DKIM and DMARC in Exchange 2016 – Part I” which can be found here: https://jaapwesselius.com/2016/08/19/senderid-spf-dkim-and-dmarc-in-exchange-2016-part-i/.

In this scenario, mail from the inframan.nl domain (including Office 365) is only routed via the Hosted Email Security environment so the SPF record is pretty simple:

v=spf1 include:spf.hes.trendmicro.com ~all

Set this TXT record in your public domain, start sending email and when checking the header information you’ll see your all good here:

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DKIM

DKIM is a little more work to configure and takes a bit more time. DKIM is covered more in detail in part II of a previous series “SenderID, SPF, DKIM and DMARC in Exchange 2016 – Part II” which can be found here: https://jaapwesselius.com/2016/08/22/senderid-spf-dkim-and-dmarc-in-exchange-2016-part-ii/

DKIM is about signing header information using a private key, and to decipher the signature you need a public key which is stored in public DNS, accessible for every mail server on the Internet. No need to worry about the configuration, HES will deliver all the details.

In the HES console select Outbound Protection and select DomainKeys Identified Mail (DKIM) Signing.

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Continue reading TrendMicro Hosted Email Security: SPF DKIM and DMARC Part II

TrendMicro Hosted Email Security: SPF DKIM and DMARC Part I

A couple of years ago I have been working with the TrendMicro Hosted Email Security (HES) solution and I was very satisfied with it. With the upcoming SPF, DKIM and DMARC awareness I was looking for online solutions that offer this kind of security measures and I found that HES now offers these solutions as well.

I have a hybrid Exchange environment with multi-role Exchange 2010 servers, Exchange 2010 Edge Transport servers and a hybrid configuration. There’s no dedicated Exchange 2016 server for this, the hybrid configuration just uses the existing Exchange 2010 servers. And this works well. There’s an additional namespace o365mail.inframan.nl, this is used solely for SMTP communication between Exchange Online and the on-premises Exchange 2010 servers (without the use of the Edge Transport servers). The configuration looks like this:

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This a hybrid configuration with a centralized mailflow. All email is sent and received through the on-premises Exchange environment, including email from and to Office 365. So, email sent to the internet by users in Office 365 are sent first to the Exchange 2010 servers, and then via the Edge Transport servers to the Internet. This way you have full control over your Internet mail flow.

The Edge Transport servers don’t do a great job when it comes to message hygiene. You can configure Realtime Block Lists (RBL) like Spamhaus, configure content filtering using word lists and attachment filtering, but still (a lot of) spam ends-up in the user’s mailboxes. Therefore 3rd party solutions like Cisco Email Security Appliance (ESA, formerly known as IronPort) are used in front of on-premises Exchange solutions

Continue reading TrendMicro Hosted Email Security: SPF DKIM and DMARC Part I

Your browser is currently set to block JavaScript

I hate this…. And most likely you too otherwise you didn’t end up here

When logged on to an Exchange server, ready for starting the Hybrid Configuration Wizard, you try to logon to Exchange Online you end up with a warning (or ‘error’) message:

We can’t sign you in

Your browser is currently set to block JavaScript. You need to allow JavaScript to use this service.

To learn how to allow JavaScript or to find out whether your browser supports JavaScript, check the online help in your web browser.

Like the screenshot below:

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To enable JavaScript on your computer you have to enable Active Scripting. To do so, go to Internet Options, select the Security tab and choose Custom Level.

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Now scroll all the way down (or press page down 12 times ) and enable Active Scripting:

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You will get a warning message “Are you sure you want to change the settings for this zone”, click Yes and click OK.

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Restart your Internet Explorer browser and you can login on Exchange Online and continue with the Hybrid Configuration Wizard (or whatever you were trying to achieve).