Configuring Squid as an accelerator/SSL offload for Outlook Web Access
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Squid can be easily used to provide SSL acceleration services for Outlook Web Access. It can also speak SSL to the backend Exchange server. Later versions of Squid-2.6 support all the methods used by WebDAV by default. Please consider upgrading to at least the latest Squid-2.6 STABLE release before attempting this.
The example situation involves a single Outlook Web Access server and a single Squid server. The following information is required:
- The IP of the Squid server (ip_of_squid)
- The 'public' domain used for Outlook Web Access (owa_domain_name)
- The IP of the Outlook Web Access server (ip_of_owa_server)
This configuration MUST appear at the top of squid.conf above any other forward-proxy configuration (http_access etc). Otherwise the standard proxy access rules block some people viewing the accelerated site.
https_port ip_of_squid:443 accel cert=/path/to/certificate/ defaultsite=owa_domain_name cache_peer ip_of_owa_server parent 80 0 no-query originserver login=PASS front-end-https=on name=owaServer acl OWA dstdomain owa_domain_name cache_peer_access owaServer allow OWA never_direct allow OWA # lock down access to only query the OWA server! http_access allow OWA http_access deny all miss_access allow OWA miss_access deny all
If the connection to the OWA server requires SSL then the cache_peer line should be changed appropriately:
cache_peer ip_of_owa_server parent 443 0 no-query originserver login=PASS ssl sslcert=/path/to/client-certificate name=owaServer
an apparent bug in Squid-3.1 means that https_port may also need to use the connection-auth=off option for now.
OWA works but ActiveSync fails
Windows Phone says "Connection error. Try again later." and current status shows "Unable to connect. Retrying."
The device sending Expect: 100-continue HTTP/1.1 headers, but being unable to retry correctly when presented with the 417 response.
Squid-3.2 supports the HTTP/1.1 feature these clients depend on. This problem will not occur there.
http://support.microsoft.com/?scid=kb%3Ben-us%3B327800&x=17&y=16 - "How to configure SSL Offloading for Outlook Web Access in Exchange 2000 Server and in Exchange Server 2003"
Thanks to Tuukka Laurikainen <firstname.lastname@example.org> for providing the background information for this article.