Script to download file from javascript Postback

PoSH_Postback.ps1

#URL that needs to be fetched
$url = "https://site.state.gov/default.aspx"

#get the server name in case the process jumps to another script
$serverName = $env:computername

#wrapped it into a try/catch for some type of error handling
TRY {
  #use invoke-webrequest to fetch a session from the site
  Invoke-WebRequest $url -SessionVariable session -UseBasicParsing

  #add a site using the session information from the above web request
  $addUserSite = Invoke-WebRequest $url -WebSession $session 
  $addUserForm = $addUserSite.Forms[0] #Invoke-WebRequest does a lot of auto processing. 

  #add form fields for the event target & argument that is needed to actually do the post back
  $addUserForm.Fields["__EVENTTARGET"] = "dnn`$abcd1234`$File`$ExcelFile" 
  $addUserForm.Fields["__EVENTARGUMENT"] = "" 

  #where are we saving the file & what is file name
  $filename = "C:\temp\Download_FIle_Name.txt"

  #invoke another web request using the same url, session information, and out put to the $filename variable
  Invoke-WebRequest -uri $url -method post -Body $addUserForm.Fields -WebSession $session  -UseBasicParsing -Outfile $fileName
}

# catch any errors from above and send an email to the right people
CATCH {
   Send-MailMessage -To "it@somecompany.com" -From "donotrely@somecompany.com" -Subject "Some important thing just happened" -SmtpServer "server.smtp.com" -Body "Check stuff out on $serverName"
}

Hi,

I am actually attempting to download a file from a site that uses javascript download button via Invoke-WebRequest.

Can you explain the parameters in event target which seem a bit random? The variables are not set in your code.

$addUserForm.Fields["__EVENTTARGET"] = "dnn$abcd1234$File$ExcelFile" `

The parameters are obtained by looking at the initial link that does the post back. That was written to handle the post back of the javascript and they have to be set in order for the powershell to work correctly.

The parameters are obtained by looking at the initial link that does the post back. That was written to handle the post back of the javascript and they have to be set in order for the powershell to work correctly.

How does one find the link that does the post back? I can't find any relevant information looking at the page in developer mode.

In my case, I was trying to do this post back where DNN was the provider. I was able to hover over the initial link to identify what the parameters had to be set to. I believe if you look at the HTML of the form/page itself there's a form the page that will identify the parameters as well.

I do not understand the same as @nicolaibaralmueller - I am attempting to get the excel file from this site: https://apps.dnr.wi.gov/pheasantstocking/Index.aspx

@jimbrig The event target would be "lnkExport" I believe. I have not tested it.

Yeah I eventually got it working - not an ideal scenario though especially because I wanted to allow it to be integrated into PowerQuery which is not possible without scripting.