Thursday, October 14, 2010

Making OWA canary's sing using cookies in your OWA scripts

In Exchange 2007 SP3 Microsoft implemented canaries in OWA to help prevent man in the middle/cross scripting attacks in OWA gives a good explanation around why you would want to use a canary and what it is. But put basically a canary is a secret between the client and server in OWA this gets stored in cookie collection of your browser and then it gets submitted with the various requests that your browser sends. If your request doesn't have the canary then the server pretty much says "no OWA for you!". Because in the scripting world it can be useful as a workaround to instrument OWA to automate particular things such as enabling the extended junk-Email rule in OWA and Outlook in the past I've posted scripts that use OWA automation that have now pretty much been broken by the canary's.

So to fix this you need to add some code that will deal with the canary my favorite object to use for these type of scripts is the MSXML2.ServerXMLHTTP object because this handles all the FBA cookies in OWA without the need to add lines of code. To Get the canary from the cookie collection once you have logged on it needs another request to the mailbox your going to access which if things go well means your cookie collection should now be populated and you can just parse the cookie with a few lines of script eg

req.Open "GET", "https://" & snServername & "/owa/" & Targetmailbox & "", False
req.SetOption 2, 13056
req.setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
req.setRequestHeader "Content-Length", Len(xmlstr)
req.send szXml
reqhedrarry = split(req.GetAllResponseHeaders(), vbCrLf,-1,1)
for each ent in reqhedrarry
wscript.echo ent
cookie = req.getResponseHeader("Set-Cookie")
if instr(cookie,"=") then
slen = instr(cookie,"=")+1
elen = instr(slen,cookie,"&")
canary = mid(cookie,slen,elen-slen)
wscript.echo "parsed canary : " & canary
end if

Once you have the canary you need to make sure you include it in your request for the junkemail script you need to modify the XML sent to look like

"<params><canary>" & canary & "</canary><fEnbl>1</fEnbl></params>"

And if everything is good your canary should sing to OWA to and achieve what it is your asking it to do. I've put a updated version of the junkemail script here

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