Monday, July 6, 2009

Publishing Exchange 2007 OWA via ISA 2006 Reverse Proxy

The best way to publish OWA is to publish via ISA reverse proxy deployment. In this blog i will discuss the process for publishing OWA via ISA reverse proxy. The process will be like this;

1. Generate CSR for Exchange 2007 CAS server(s).

I have discussed CSR generation in my previous blogs (http://khurramullah.wordpress.com/2009/07/01/exchange-2007-certificate-request-generator/ and http://khurramullah.wordpress.com/2009/07/01/command-for-generating-csr-for-exchange-servers/) if you have more than one CAS servers then you have to repeat the steps for all of them.

Make sure you have included all Subject Alternative  Names (SANs) in your certificate requests such as for webmail, auto discover services etc.

2. Submit this request to online Certificate Authorities such as VeriSign, Thwate or Entrust for purchasing UCC (Unified communication certificate). (Exchange 2007 only supports UCC type certificates, UCC=multiple SANs).

3. Now we have to import these certificates to Exchange CAS servers.( I have discussed these steps in my previous blog http://khurramullah.wordpress.com/2009/07/01/importing-certificates-to-exchange-servers/)

4. Now we have to deploy this certificate to ISA servers. In order to do this you have to first Export certificate from CAS server in .PFX format and then imports it to the ISA servers. Following is the process for doing this;

  1. Open Certificate MMC Snap in on the CAS server for local computer.
  2. Go to personal container and locate the certificate which you want to Deploy on ISA Server.
  3. Export this certificate with private key in .PFX format.
  4. Copy this certificate on ISA Server.
  5. Open Certificate MMC Snap in on the ISA server for local computer.
  6. Import the copied certificate.
  7. Repeat steps 4 to 7 if you have more than one ISA Servers.

5. Forms-based authentication can be configured on the Client Access server when not using ISA Server to publish Exchange Web client access. When ISA Server is being used to publish Exchange Web client access, forms-based authentication should only be configured on the ISA Server computer following are the steps for validating this;

  1. Start the Exchange Management Console.
  2. In the Exchange Management Console, expand Server Configuration, and then click Client Access.
  3. Select a Client Access server and then select owa (Default Web Site) on the Outlook Web Access page.OWA5
  4. In the action pane, click Properties under owa (Default Web Site).
  5. Select the Authentication page, and confirm that the following are selected: Use one or more of the following standard authentication methods and Integrated + Basic authentication (password is sent in clear text).clip_image001
  6. Click OK.
  7. Review the Microsoft Exchange Warning dialog box and click OK. clip_image001[6]
  8. Restart IIS by running following command: "iisreset /noforce".
  9. Perform this procedure for every Exchange Client Access server.

6. On the CAS server please make sure that “Forms based authentication” is not configured on the Exchange Client Access Activesync folder. By default it is configured for basic authentication.This folder is configured to Basic authentication by default.

7. On the enabling page for Outlook Anywhere, we will use Basic authentication (default).

OWA1

Note: The external host name used here should match the common name or FQDN used in the server certificate installed on the ISA Server computer

8. Now we need to publish a Rule for OWA on ISA but before doing this we need to configure web Listener for OWA which will be responsible for  listening OWA requests, following are the steps for configuring web listener for OWA

  1. In the console tree of ISA Server Management, click Firewall Policy:
  2. For ISA Server 2006 Standard Edition, expand Microsoft Internet Security and Acceleration Server 2006, expand Server_Name, and then click Firewall Policy.
  3. For ISA Server 2006 Enterprise Edition, expand Microsoft Internet Security and Acceleration Server 2006, expand Arrays, expand Array_Name, and then click Firewall Policy.
  4. On the Toolbox tab, click Network Objects, click New, and then select Web Listener. Use the wizard to create the Web listener as outlined in the following table

Page

Field or property

Setting

Welcome

Web listener name

Type a name for the Web listener. For example, type Exchange Web Listener.

Client Connection Security

Select what type of connections this Web listener will establish with clients

Select Require SSL secured connections with clients.

Web Listener IP Addresses

Listen for incoming Web requests on these networks

ISA Server will compress content

Select the External and Internal networks.

Check box should be selected (default).

Click Select IP Addresses

External Network Listener IP Selection

Listen for requests on

Available IP Addresses

Select Specified IP addresses on the ISA Server computer in the selected network.

Select the correct IP address and click Add.

clip_image001

clip_image002  Notes

For ISA Server Enterprise Edition with an NLB-enabled array, you should select a virtual IP address.

Listener SSL Certificates

Select a certificate for each IP address, or specify a single certificate for this Web listener

Select Assign a certificate for each IP address.

Select the IP address you just selected and click Select Certificate.

Choose the certificate corresponding to the url mapped to this IP in the public DNS/NAT configuration

Example:

External 192.168.1.101 for abcmail; .102 for xyzmail and .103 for autodiscover

Internal: 192.168.12.101 for abcmail; .102 for xyzmail (autodiscover is resolved differently in intranet)

clip_image003

Authentication Settings

Select how clients will provide credentials to ISA Server

Select how ISA Server will validate client credentials

Select HTML Form Authentication for forms-based authentication and select the appropriate method that ISA Server will use to validate the client's credentials.

clip_image004

Single Sign On Settings

Enable SSO for Web sites published with this Web listener

SSO domain name

Leave the default setting to enable SSO.

To enable SSO between two published sites, such as abcmail.Contoso.com and autodiscover.Constoso.com, type .Contoso.com (with the dot)

clip_image005[1]

Completing the New Web Listener Wizard

Completing the New Web Listener Wizard

Review the selected settings and click Back to make changes or Finish to complete the wizard.

 

9.  Now after creating web Listener we need to publish a rule for OWA, following are the steps for this process;

  1. In the console tree of ISA Server Management, click Firewall Policy:
  2. For ISA Server 2006 Enterprise Edition, expand Microsoft Internet Security and Acceleration Server 2006, expand Arrays, expand Array_Name, and then click Firewall Policy.
  3. On the Tasks tab, click Exchange Web Client Access Publishing rule.image
  4. Use the wizard to create the rule as outlined in the following tables. For a single Web server, use the table in New Exchange Publishing Rule wizard for a single Web site. If you are using a server farm, use the table in New Exchange Publishing Rule wizard for a server farm.

    Page

    Field or property

    Setting

    Welcome

    Exchange Publishing rule name

    Type a name for the rule. For example Constoso OWA Publishing Rule

    Select Services

    Exchange version

    Web client mail services

    Select Exchange Server 2007.

    Select the desired access method – begin with OWA, then Outlook Anywhere (Select to publish additional folders) and finally choose ActiveSync

    clip_image001[8]

    Publishing Type

    Select if this rule will publish a single Web site or external load balancer, a Web server farm, or multiple Web sites

    Select Publish a single Web site or load balancer.

    clip_image002[11]

    Server Connection Security

    Choose the type of connections ISA Server will establish with the published Web server or server farm

    Select Use SSL to connect to the published Web server or server farm.

    clip_image003[1]  Note

    A server certificate must be installed on the published Exchange Client Access server, and the root CA certificate of the CA that issued the server certificate on the Exchange Client Access server must be installed on the ISA Server computer.

    Internal Publishing Details

    Internal site name

    Type abc.contoso.com or whatever you like

    clip_image004  Important

    The internal site name must match the name of the server certificate that is installed on the internal Exchange Client Access server.

    Public Name Details

    Accept requests for

    Public name

    This domain name (type below)

    Type the domain name that you want ISA Server to accept the connection for. For example, type abc.contoso.com. This must match the FQDN of the certificate selected when creating the Web listener.

    clip_image005[3]

    Select Web Listener

    Web listener

    Select the Web listener you created previously, Exchange Web Listener

    Authentication Delegation

    Select the method used by ISA Server to authenticate to the published Web server

    For Outlook Web Access, select Basic Authentication.

    For Exchange ActiveSync, select Basic Authentication

    For Outlook Anywhere, select Basic Authentication

    clip_image006[6]

    User Sets

    This rule applies to requests from the following user sets

    Select the user set approved to access this rule. Replace the default All Authenticated users with All Users

    clip_image007[5]

    Pass the warning

    clip_image008[4]

    Completing the New Exchange Publishing Rule Wizard

    Completing the New Exchange Publishing Wizard.

    Review the selected settings, click Back to make changes or Finish to complete the wizard.

    Note: When publishing Outlook Web Access, after you click Finish, review the Remaining Exchange Publishing Tasks dialog box, and then click OK.

  5. In the path tab (properties of the OWA rule), add the path “/” in order to be able to access OWA without typing /owa at the end of the url

 

2 comments:

BlogMonkey said...

Usually (like ours) the ISA server is in a DMZ with limited acces to the CAS server. Can you talk about which ports need to be open between ISA and CAS and the DC's for publishing to work?
Thanks!

sachinraj said...

Hi Deepak



I have gone through your blog this morning and found you are good in ISA .I am having one doubt on ISA 2006 Ent edition .I have already posted it as a comment in your blog .Can you please answer this question







My network is having more than one VLAN so I am using ISA as my Proxy server with only one Network card. I wish to have a load balancing and failover setup for this by using NLB concept.



Keeping these issues in mind, I know that

ISA will not work with more than 1 Gateway

ISA will not support Routing

ISA will not understand VLANs





I am having ISA 2006 Ent license and wish to configure ISA as a proxy with NLB, so that if one ISA is down users can browse internet using the other .

I hope we need to keep ISA with 1 LAN card to configure it as a Proxy because to listen different VLANS, ISA should have gateway in the network configuration .If I am using more than 1 LAN card, ISA will work as a gateway, and its internal LAN card will not have any Gateway, so only the home VLAN can contact this ISA