Tidbits on CUPS Integration with Exchange

Author
William Bell
Vice President, Solutions and Products

 Before laying out some of the gotchas, the basic integration requirements overview is provided here:

1. You need to have a user configured in AD for the CUPS server.  This is a service account for authenticating to AD and opening the Exchange calendar for the CUPS user.

2. This CUPS user needs to be configured in Exchange, have a valid mailbox, and part of the Exchange View Only Administrators group (that’s how it can open the user’s Exchange calendar).

3. The CUPS server actually uses WebDav to do its business.  Cisco is working on moving away from this API and using EWS, but this is not committed on the roadmap.  The move is a necessary one as Microsoft is pushing people away from WebDav.

4. CUPS uses OWA to connect to the Exchange services.  This should be running on the client access servers (CAS) in Exchange 2007 or the Exchange Front End servers in Exchange 2000/2003.

Important note: CUPS does not support forms based authentication (FBA) on Exchange 2007 (only version tested) (I will test 2003 in the lab later)

5. Since CUPS is using OWA, HTTPs is required, and CUPS has no way of dynamically accepting/storing certificates, IOW you have to upload the certificates to the CUPS server

So, some interesting tidbits:

CUPS 7.0 seems to only care about the root certificate for the Presence Engine trust.  At one of our customers I uploaded the root certificate and then the server/application certificate from the OWA server.  After refreshing services, the OWA server certificate disappears.

This behavior is different then loading the certificate for a local application service.  For instance, if you wanted to use a 3rd party certificate for the Tomcat service (web server) you must load the root certificate first and then load the application certificate.  Makes sense when you think about it.

Another interesting note is that when configuring the Presence gateway for the OWA server.  The gateway host should be the Fully Qualified Domain Name (FQDN).  Further, the FQDN must either be the CN of the certs Subject field or X.509 subject alternative name field of the OWA server certificate (the one you don’t need to install).

To determine the CN (or alternative name) use a web browser to open a SSL session to the OWA server.  Once connected to the server, use your browser to view the certificate properties.  This is also a good way to find the root authority if you don’t know it.

The final tidbit for today is related to DNS domain names and AD forst domains.  For CUPS, when you configure a user ID field in the Exchange presence gateway, it will attempt to authenticate with that user name as configured. So, cups is simply “cups”. However,  Exchange OWA wants some indication of the domain.  So, you have to specify the domain you are authenticating against in the logon request.  Further, CUPS won’t take the pre-2000 convention (e.g. netcraftsmencups). So, you have to use the format: cups@netcraftsmen.net (if you were one of those companies that configured your AD tree to use the SAME domain as your public DNS record, another can of worms). 

That is all for now.  There is plenty of info on Exchange and CUPS integration but that will be for another day.

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Nick Kelly

Cybersecurity Engineer, Cisco

Nick has over 20 years of experience in Security Operations and Security Sales. He is an avid student of cybersecurity and regularly engages with the Infosec community at events like BSides, RVASec, Derbycon and more. The son of an FBI forensics director, Nick holds a B.S. in Criminal Justice and is one of Cisco’s Fire Jumper Elite members. When he’s not working, he writes cyberpunk and punches aliens on his Playstation.

 

Virgilio “BONG” dela Cruz Jr.

CCDP, CCNA V, CCNP, Cisco IPS Express Security for AM/EE
Field Solutions Architect, Tech Data

Virgilio “Bong” has sixteen years of professional experience in IT industry from academe, technical and customer support, pre-sales, post sales, project management, training and enablement. He has worked in Cisco Technical Assistance Center (TAC) as a member of the WAN and LAN Switching team. Bong now works for Tech Data as the Field Solutions Architect with a focus on Cisco Security and holds a few Cisco certifications including Fire Jumper Elite.

 

John Cavanaugh

CCIE #1066, CCDE #20070002, CCAr
Chief Technology Officer, Practice Lead Security Services, NetCraftsmen

John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies. Previously he has held several positions including Executive Director/Chief Architect for Global Network Services at JPMorgan Chase. In that capacity, he led a team managing network architecture and services.  Prior to his role at JPMorgan Chase, John was a Distinguished Engineer at Cisco working across a number of verticals including Higher Education, Finance, Retail, Government, and Health Care.

He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes. John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.