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SSL Offloading Question

Posted on 2014-07-29
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Last Modified: 2014-08-14
The security team and I are having a debate on how we want to setup the new Exchange system.  We will be using an F5 LB and they want traffic after the load balancer to be over port 80 instead of encrypted on 443.  The attached picture is how it would look.  

SSL Offloading
I would prefer to use SSL Bridging since it would be secure all the way through.

SSL Bridging
What are the security risks of doing SSL Offloading?

What would be the benefits of SSL Bridging vs SSL Offloading?

Thanks!
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Question by:Sedgwick_County
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by:Adam Farage
ID: 40227008
here are a few of the arguments I use for SSL bridging vs offloading:

- If you are doing SSL offloading, additional configurations need to be done at the IIS level for Exchange. During patches (for example, each CU in Exchange 2013 or SP in Exchange 2010 / 2007) these changes need to be backed up and reconfigured as IIS will be reset. This can cause additional downtime, along with complexity into the network. SSL bridging is mainly used for context routing (routing each request to the proper virtual directory) but re-encrypts the traffic, so configuration to the Exchange server is minimal.
- If you have a Rogue employee with a packet sniffer, all context of the Exchange packets (including passwords for some services) are sent via clear text. Someone on the internal network can figure out valuable PII and password data.

A big warning about SSL offloading, and that is proxy to a different site *will not work* for Exchange ActiveSync or OWA. So lets say you are having connections go into Site 1, but are going to proxy to a non-internet facing site (in this case, Exchange with the ExternalURL set to $NULL but the InternalURL set to something of value) then this wont work. The /proxy/ virtual directory will only accept connections over TCP 443, and not over TCP 80. Depending on your configuration, you might need to do SSL bridging only.
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by:Sedgwick_County
ID: 40227708
Thank you for the response that helps a lot!  You mentioned that some passwords are sent clear text for some services, do you know by chance what services those are?
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Adam Farage earned 500 total points
ID: 40227741
So any CAS related service that comes into the environment (or from the client machines themselves) over TCP 443 would then be decrypted by the load balancer, and then transmitted to the load balanced CAS over TCP 80.

This means the following services:

- Outlook Anywhere
- Outlook Web App / Exchange Control Panel
- PowerShell (if you are load balancing it through there)
- Exchange ActiveSync
- Exchange Web Services
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