The Idp that is used to authenticate visitors to our SharePoint application requires a custom query string parameter used to control content. I can append the parameter using an http module before it goes to SharePoint's STS but then it is dropped before getting to adfs. In Fiddler it looks like this:
Here is the last GET to the /_trust in SharePoint and the Query String parameter is there
GET /_trust/default.aspx?trust=ADFS01&ReturnUrl=/abc/_layouts/Authenticate.aspx?Source=%2Fabc&Source=/abc&whr=https%3A%2F%2Fwww.customidp.com%2FBrandedSTS%2F¶metercode=abc HTTP/1.1
trust ADFS01
ReturnUrl /abc/_layouts/Authenticate.aspx?Source=/abc
Source /abc
whr https://www.customidp.com/BrandedSTS/
parametercode abc
But the GET to ADFS ends up dropping it.
GET /adfs/ls/?wa=wsignin1.0&wtrealm=urn%3awww%3aportal%3acom&wctx=https%3a%2f%2fwww.portal.com%2fabc%2f_layouts%2fAuthenticate.aspx%3fSource%3d%2fabc&whr=https%3a%2f%2fwww.customidp.com%2fBrandedSTS%2f HTTP/1.1
wa wsignin1.0
wtrealm urn:www:portal:com
wctx https://www.portal.com/abc/_layouts/Authenticate.aspx?Source=/abc
whr https://www.customidp.com/BrandedSTS/
I'm wondering if anyone knows of a way to get SharePoint's STS to pass along any query string parameters or if an Http Module could be added to the STS to accomplish this.