autodiscover flow in an exchange on-premises | non-active directory | part 3#3 | part 28#36

of 20 | Autodiscover flow in an Exchange on-Premises environment | non-Active

Directory environment| Part 3#3 | Part 28#36

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

Autodiscover flow in an Exchange on-

Premises environment | non-Active

Directory environment| Part 3#3 | Part

28#36

The current article is the continuation of the previous article, in which we review the

Autodiscover flow that is implemented in Autodiscover flow in an Exchange on-

Premises environment | non-Active Directory environment, by using the Microsoft

web-based tool, the Microsoft Remote Connectivity Analyzer (ExRCA).

Autodiscover flow in an Exchange on-Premises environment |

non-Active Directory environment | The article series

http://o365info.com/autodiscover-flow-in-an-exchange-on-premises-environment-non-active-directory-environment-part-3-of-3-part-28-of-36


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The current article is the third article in a series of three articles.

The additional articles in the series are:

Autodiscover flow in an Exchange on-Premises environment | non-Active


Autodiscover flow in an Exchange on-Premises environment | non-Active


To be able to review each of the steps and each of the parts that include a specific

Autodiscover step, we will use the powerful tool- the Microsoft remote connectivity

analyzer.

The Microsoft remote connectivity analyzer includes many tabs and options. In our

specific scenario, we want to test Exchange on-Premises infrastructure. To be able

to implement the required test, we will choose the Exchange server tab, Microsoft

Office Outlook Connectivity test and then, the option of – Outlook Autodiscover.












Note – in case that you need to get more details about the Microsoft remote

connectivity analyzer web tool you can read the article –Microsoft Remote

Connectivity Analyzer (ExRCA) | Autodiscover troubleshooting tools | Part 2#4 |

Part 22#36

Scenario description

To demonstrate the Autodiscover workflow that is implemented, in a “non-Active

Directory environment” when using an Exchange on-Premises infrastructure, let’s

use the following scenario:





http://o365info.com/microsoft-remote-connectivity-analyzer-exrca-autodiscover-troubleshooting-tools-part-2-of-4-part-22-of-36






John is an organization’s user who needs to access his mailbox that is hosted on the

Exchange on-Premise server.

John is physically located on a public network and, for this reason, he cannot use

the Autodiscover process that is implemented in an Active Directory environment.

The John E-mail address is – [email protected]

John task is- creating a new Outlook mail profile that will enable him to connect his

mailbox. The Outlook profile will be based on the Outlook Anywhere service.

Note that the company has a public website that is published using the host

named-o365info.com








Analyzing the Autodiscover process by using ExRCA

Before we will “dive in” into the details let’s start from a High-level view of the

Autodiscover test results.

In the following screenshot, we can see that the Autodiscover processes complete

successfully.

By looking at the Autodiscover results reports structure, we can see that the “first

part” failed (did not complete successfully) but the second part (B section) was

successfully completed.

Note – Autodiscover flow will “contain” a couple of “steps failure” 99% of times but,

still ended as a successful process.

The second part (B section) includes the “high level” description of each of the five

Autodiscover steps that were implemented and documented in the result report

(we will review in details each of these steps in the next section).








Analyzing the Autodiscover process | Steps described

in details








Step 1/9: Attempting to resolve the host name o365info.com in

DNS

By default, Autodiscover client will try to locate a “potential Autodiscover Endpoint”,

by using a host name that was “extracted” from the recipient E-mail address.

Autodiscover client will use the “right part” of the recipient E-mail address that

includes the SMTP domain name.

In our scenario, the recipient E-mail address is – [email protected]

Based on this specific E-mail address; the Autodiscover client will create a DNS

query looking for an IP address of a host named – o365info.com

The “answer” of the DNS server, depend on the specific organization public server’s

and services infrastructure.

For example, most of the organizations have a public website and, most of the time,

the public domain name is “mapped” to the public IP of the website.

In our scenario, the DNS reply with a public IP address of the requested host name.

The IP that was provided by the DNS server doesn’t “belong” to an Exchange server

(Autodiscover Endpoint) but instead, this public IP address is assigned to a standard

web server.

Step 1/9: Analyzing the data from the ExRCA connectiv ity test

In the ExRCA result page, we can see the following information:








The ExRCA tests results start with an error message that the connection attempt to

the host named – o365info.com failed.

Attempting to test potential Autodiscover URL

https://o365info.com:443/Autodiscover/Autodiscover.xml

testing of this potential Autodiscover URL failed.

(We will get more details about the reason for the failure in the next section).

Note that when we look at the details of the workflow that was performed by the

Autodiscover client, we can see that some of the steps to complete successfully.

For example, the resolution step in which the Autodiscover client asks for the DNS

server the IP address of the host o365info.com complete successfully.

Attempting to resolve the host name o365info.com in DNS. The host name resolved

successfully. IP addresses returned: 104.28.12.85, 104.28.13.85

Step 2/9: Testing TCP port 443 on host o365info.com to ensure

it’s listening and open.

The Autodiscover client addresses the potential Autodiscover Endpoint, using the IP

address that he got in the former step.

The Autodiscover client will try to verify if the potential Autodiscover Endpoint is

listing on port 443 (HTTPS).

In our scenario, the HTTPS communication test fails because the “destination host”

doesn’t support HTTPS communication.








Step 2/9: Analyzing the data from the ExRCA connectivity test

In the ExRCA result page, we can see the following information about the Testing

TCP port 443 on host o365info.com:

The specified port is either blocked, not listening, or not producing the expected

response. A network error occurred while communicating with the remote host.

Step 3/9: Attempting to resolve the host name

autodiscover.o365info.com in DNS

Because the communication attempt with the potential Autodiscover Endpoint

using the hostname o365info.com fails, Autodiscover client move to the next

method, in which Autodiscover client will look for a potential Autodiscover Endpoint

using the following naming scheme – autodiscover + <Recipient SMTP domain>








In our scenario, the recipient E-mail address is – [email protected]

Based on this specific E-mail address, the Autodiscover client will create a DNS

query looking for an IP address of a host named – autodiscover.o365info.com


In the ExRCA result page, we can see the following information about the

Attempting resolve the hostname o365info.com:

Attempting to resolve the host name autodiscover.o365info.com in DNS.

The host name resolved successfully. IP addresses returned: 212.25.80.239

Step 4/9: Testing TCP port 443 on host

autodiscover.o365info.com to ensure it’s listening and open.

The Autodiscover client, address the potential Autodiscover Endpoint using the IP

address that he got in the former step.

The Autodiscover client, will try to verify if the potential Autodiscover Endpoint is

listing on port 443 (HTTPS).








In our scenario, the HTTPS communication test succeeded, meaning that the

destination host (the Autodiscover Endpoint) supports HTTPS communication.


In the ExRCA result page, we can see the following information about the Testing

TCP port 443 on host autodiscover.o365info.com :

Testing TCP port 443 on host autodiscover.o365info.com to ensure it’s listening and

open. The port was opened successfully.

Step 5/9: Asking from the potential Autodiscover Endpoint to

provide a public server certificate

The Autodiscover client “assume” that the destination host is a “potential

Autodiscover Endpoint”, that can provide him the required Autodiscover

information.

Before the Autodiscover client will ask for the required information, he will have to

a successfully complete couple of steps.








The Autodiscover client need “to be sure” that the destination host is a reliable\trust

wordy.

To be able to trust the potential Autodiscover Endpoint, the Autodiscover client will

ask for the server to prove his identity by providing a valid public certificate.


In the ExRCA result page, we can see the following information about the step in

which the Autodiscover client asks for the potential Autodiscover Endpoint to

provide a public server certificate:

The Microsoft Connectivity Analyzer is attempting to obtain the SSL certificate from

remote server autodiscover.o365info.com on port 443.

The Microsoft Connectivity Analyzer successfully obtained the remote SSL

certificate.








Step 6/9: Testing the SSL certificate to make sure it’s valid

The certificate validation test which the Autodiscover client performs, includes

three different parts.

1. Validating the certificate name

The Autodiscover client addresses the potential Autodiscover Endpoint using the

host name –autodiscover.o365info.com

To be able to know that this is the “real host”, Autodiscover client will check if the

certificate includes the specified host name (autodiscover.o365info.com )

Note – this description is relevant to a scenario in which the server uses an SAN

certificate.

In case that the potential Autodiscover Endpoint uses a wildcard certificate, the

client will validate only the domain name (in our scenario, the domain name that

the client will validate is –o365info.com).

2. Validating the certificate trusts

The public certificate that the server provide was created by a CA (certificate

authority).

The Autodiscover client will need also to validate the CA certificate that provides the

server his certificate.

3. Verify that the certificate date is valid

The Autodiscover client will need to verify that the server certificate date is valid.

Note – In case that you want to read more detailed information about the subject of

Autodiscover, security mechanism and certificates, read the article – Autodiscover

process and Exchange security infrastructure | Part 20#36





http://o365info.com/autodiscover-process-and-exchange-security-infrastructure-part-20-of-36

http://o365info.com/autodiscover-process-and-exchange-security-infrastructure-part-20-of-36





1. Validating the certificate name

In the ExRCA result page, we can see the following information about the validation

test for the Autodiscover Endpoint name:

The certificate name was validated successfully.

Host name autodiscover.o365info.com was found in the Certificate Subject

Alternative Name entry.

2. Validating the certificate trust


test for the certificate trust:








Certificate trust is being validated. The certificate is trusted and all certificates are

present in the chain. The Microsoft Connectivity Analyzer is attempting to build

certificate chains for certificate CN=mail.o365info.com, OU=Domain Control

Validated, O=mail.o365info.com.

One or more certificate chains were constructed successfully.

3. Verify that the certificate date is valid


test for the certificate data:

Testing the certificate date to confirm the certificate is valid. Date validation passed.

The certificate hasn’t expired.

The certificate is valid. NotBefore = 1/26/2013 11:22:11 PM, NotAfter = 1/26/2015

11:22:11 PM

Step 7/9: Checking the IIS configuration for client certificate

authentication

The Autodiscover client checks if the destination host (the Autodiscover Endpoint)

needs a client certificate. A client certificate is a method in which the client can

prove his identity by providing a certificate.








The use of the client certificate is very rare and most of the time, the way that the

client use for “proof his identity” is by providing user credentials.


On the ExRCA result page, we can see the following information about the client

certificate authentication test:

Checking the IIS configuration for client certificate authentication. Client certificate

authentication wasn’t detected. Accept/Require Client Certificates isn’t configured.

Step 8/9: Providing user credentials

After the certificate validation test was successfully completed and, the

Autodiscover client can “trust” the destination host, the Autodiscover client will also

need to prove his identity.








The Autodiscover client will identify himself by providing user credentials”

(Username + password).

Note – the part of “providing user credentials “doesn’t appear in the ExRCA results.

Step 9/9: Attempting to send an Autodiscover POST request to

potential Autodiscover URLs

This is the final step in the Autodiscover journey.

After a successful compilation of all the steps, the Autodiscover client completes his

mission – getting the Autodiscover file.

The Autodiscover Endpoint, will generate the Autodiscover response that was

“customized” to the specific Autodiscover client that requires the information (John

in our scenario).









In the ExRCA result page, we can see the following information about the

Autodiscover response that was sent by the Exchange CAS server to the client:

Attempting to send an Autodiscover POST request to potential Autodiscover URLs.

The Microsoft Connectivity Analyzer successfully retrieved Autodiscover settings by

sending an Autodiscover POST.

The Microsoft Connectivity Analyzer is attempting to retrieve an XML Autodiscover

response from URL

https://autodiscover.o365info.com:443/Autodiscover/Autodiscover.xml for user

[email protected] . The Autodiscover XML response was successfully retrieved.

The Autodiscover response included tons of information.

We will not review each of the “sections” that include in the Autodiscover responds,








but just as an example, we can see a couple of details that include in the

Autodiscover respond file:

The Autodiscover Exchange provider

Exchange CAS server include a couple of Outlook providers.

The Autodiscover will include a dedicated section for each of this provider.

In our example, we took a screenshot from the part that include the information for

the EXCH provider – <Type>EXCH</Type>

Note – If you need more detailed information about the Exchange CAS server

Autodiscover provider read the article – The content of the Autodiscover server

response | Part 11#36

In the following screenshot, we can see that the Autodiscover response includes the

“private” or the “hidden name” of the Exchange CAS server that provide the

Autodiscover services –<Server>EX01.o365info.local</Server>

The Autodiscover response, includes a detailed information about each of the

available Exchange web services.

In the following example we can see the information about the available

services:<ASUrl>https://ex01.o365info.local/ews/exchange.asmx</ASUrl>

And about the Automatic reply (Out of office)

services:<OOFUrl>https://ex01.o365info.local/ews/exchange.asmx</OOFUrl>





http://o365info.com/the-content-of-the-autodiscover-server-response-part-11-of-36

http://o365info.com/the-content-of-the-autodiscover-server-response-part-11-of-36

autodiscover flow in an exchange on-premises | non-active directory | part 3#3 | part 28#36

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