SharePoint 2010 reverse-published through TMG - 403 Forbidden when switching user after successfully authenticating

Hi - hoping someone out there has seen this issue and can help.

We're in the process of migrating to TMG 2010 in a single-network adapter config to reverse-publish SharePoint 2010 sites. We're presently using ISA 2006 in a dual-NIC configuration (one NIC internal, one connected to Internet)

TMG is taking the request, offloading the SSL and sending it to port 80 (we've also tried using TMG as an SSL pass-through and having SSL terminate on the SharePoint web front-end).  We're using LDAP-AD validation for our HTTP Basic auth.

Clients can authenticate successfully and all SharePoint functionality is there, but when a user chooses Sign In As A Different User, instead of being presented with an auth prompt, a 403 Forbidden The server denied the specified Uniform Resource Locator (URL) results.

Here is the GET from a Fiddler trace of the page when the 403 is generated ---- I've changed the URLs, IP's and usernames to generic ones:

GET /_layouts/accessdenied.aspx?loginasanotheruser=true&Source=https%3A%2F%2Fsharepoint%2Esite%2Ecom%2FSitePages%2FHome%2Easpx HTTP/1.1

The referer:

Referer: https://sharepoint.site.com/_layouts/closeConnection.aspx?loginasanotheruser=true&Source=https%3A%2F%2Fsharepoint%2Esite%2Ecom%2FSitePages%2FHome%2Easpx

TMG logs show first a 12210 An Internet Server API (ISAPI) filter has finished handling the request

 

Failed Connection Attempt TMGSERVER 6/20/2013 8:20:54 AM 
Log type: Web Proxy (Reverse) 
Status: 12210 An Internet Server API (ISAPI) filter has finished handling the request. Contact your system administrator.  
Rule: sharepoint.site.com 
Source: Internal (ip coming from internet) 
Destination: Local Host (ip of sharepoint web server:80) 
Request: GET http://sharepoint.site.com/_layouts/blank.htm 
Filter information: Req ID: 0e5cbf7c; Compression: client=Yes, server=Yes, compress rate=0% decompress rate=0% 
Protocol: https 
User: (LDAP)xxxxx
 Additional information 
Client agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)
Object source: Internet (Source is the Internet. Object was added to the cache.)
Cache info: 0x4000008 (Request includes the AUTHORIZATION header. Response includes the WWW-AUTHENTICATE header.)
Processing time: 94 MIME type: 

Then further down the logs 

Denied Connection TMGSERVER 6/20/2013 8:31:43 AM 
Log type: Web Proxy (Reverse) 
Status: 12202 Forefront TMG denied the specified Uniform Resource Locator (URL).  
Rule: sharepoint.site.com 
Source: Internal (ip coming from internet) 
Destination: Local Host (ip of sharepoint web server:80) 
Request: GET http://sharepoint.site.com/_layouts/accessdenied.aspx?loginasanotheruser=true&Source=https%3A%2F%2Fsharepoint%2Esite%2Ecom%2FSitePages%2FHome%2Easpx 
Filter information: Req ID: 0e5cc098; Compression: client=Yes, server=Yes, compress rate=0% decompress rate=0% 
Protocol: https 
User: (LDAP) xxxxx
 Additional information  
Client agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)
Object source: Internet (Source is the Internet. Object was added to the cache.)
Cache info: 0x6020008 (Request includes the AUTHORIZATION header. Response includes the CACHE-CONTROL: PRIVATE header. Response includes the SET-COOKIE header. Response includes the WWW-AUTHENTICATE header.)
Processing time: 94 MIME type: 

I've tried re-publishing the rule, doing various link translations, the Path is set to /* to include everything after the host header.  Tried using different listeners/recreating listener.  We've even built TMG with a 2-NIC setup to match closely as possible the current ISA 2006 setup.  Always the same behavior.  ISA works fine, TMG behaves as outlined above.

I think I've run out of things to check, I've probably combed through every setting on each server and made sure they're identical.

Hopefully someone has seen/experienced this and has some things I can try.  Let me know if I need to supply more information about our environment/config.

Many thanks!

Tom

June 20th, 2013 4:52pm

Hi,

Thank you for the post.

Please install TMG BPA and run the wizard to check if there is any configuration errror with your settings.

Regards,

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June 26th, 2013 8:18am

Hi,

Try it http://support.microsoft.com/kb/920356

BTW, what is auth settings on the listener? Does the issue occur with Firefox/Chrome etc? Have you tried to publish SharePoint without offloading over HTTP?


June 26th, 2013 9:13pm

Thanks Nick, 

No errors in the BPA... currently have a ticket open with MS Premier support, so far they have been unable to solve as well.

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July 1st, 2013 6:51pm

Looks like that script/hotfix applies to ISA 2004...

Auth settings on listener are HTTP - Basic with LDAP (AD) credential validation

July 1st, 2013 6:54pm

some fixes can be applied to isa as well as tmg. anyway you have the option to remove it if something goes wrong afterwards.

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July 2nd, 2013 12:48pm

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