Webrequest from website that needs login

Question

I'm trying to login to a website using webrequest and POST.

I've used Chrome's Inspect Element to see what data is being posted:
at login on POST the request header contains this information:

ret=%2Fro%2Findex.php&sha1=2254****79a19&summon=8b5df8dc0c10323669f43105848ad40b8953fc8e&username=gabriel.zanc&password=&login=Conectare

I can't login with webrequest because the 'summon' value is hardcoded into html from the webpage like this:

<input type=hidden name=summon value='4974d2b410da0ed9abf7079f461eac22d02fb3c9'>

and changes at every session.

The sha1 field is a SHA1 encoding from password & summon.

Any help, or pointing in the right direction would be greatly appreciated.

Thanks SO.

Later:
I tried this:

 Dim username As String = "accName"
    Dim password As String = "pass"
    Dim summon As String = ""

    ' Connect to WebSite
    Dim wbReq As Net.HttpWebRequest = DirectCast(Net.WebRequest.Create("http://www2.gpstracking.ro/ro/login.php?ret=%2Fro%2Findex.php"), Net.HttpWebRequest)
    Dim wbResp As Net.HttpWebResponse = DirectCast(wbReq.GetResponse(), Net.HttpWebResponse)
    Dim wbHCol As Net.WebHeaderCollection = wbResp.Headers
    Dim wbCookieJar As New CookieContainer
    wbReq.CookieContainer = wbCookieJar
    Dim myStream As IO.Stream = wbResp.GetResponseStream()
    Dim myreader As New IO.StreamReader(myStream)
    Me.TextBox2.Text = myreader.ReadToEnd
    Dim doc As New HtmlAgilityPack.HtmlDocument
    doc.LoadHtml(Me.TextBox2.Text)
    ' get summon value
    For Each input As HtmlNode In doc.DocumentNode.SelectNodes("//input")
        If input.Attributes("name").Value = "summon" Then
            summon = input.Attributes("value").Value
        End If
    Next
    'login
    Dim sha1Obj As New System.Security.Cryptography.SHA1CryptoServiceProvider
    Dim bytesToHash() As Byte = System.Text.Encoding.ASCII.GetBytes(password + summon)
    bytesToHash = sha1Obj.ComputeHash(bytesToHash)
    Dim sha1 As String = ""
    For Each b As Byte In bytesToHash
        sha1 += b.ToString("x2")
    Next
    Dim postdata = System.Text.Encoding.Default.GetBytes("ret=%2Fro%2Findex.php&sha1=" + sha1 + "&summon=" + summon + "&username=" + username + "&password=&login=Conectare")

    Dim postReq As HttpWebRequest = DirectCast(WebRequest.Create("http://www2.gpstracking.ro/ro/login.php"), HttpWebRequest)
    postReq.Method = "POST"
    postReq.KeepAlive = True
    postReq.CookieContainer = wbCookieJar
    postReq.ContentType = "application/x-www-form-urlencoded"
    postReq.Referer = "http://www2.gpstracking.ro/ro/login.php?ret=%2Fro%2Findex.php"
    postReq.UserAgent = "Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Firefox/24.0"
    postReq.ContentLength = postdata.Length

    Dim postreqstream As Stream = postReq.GetRequestStream()
    postreqstream.Write(postdata, 0, postdata.Length)
    postreqstream.Close()
    Dim postresponse As HttpWebResponse

    postresponse = DirectCast(postReq.GetResponse(), HttpWebResponse)
    wbCookieJar.Add(postresponse.Cookies)
    Dim logincookie = wbCookieJar
    Dim postreqreader As New StreamReader(postresponse.GetResponseStream())

    Me.TextBox1.Text += postreqreader.ReadToEnd

but it's not loggin in.

Answer 1

Basically you're talking about a screen scrape, first use a web request to get the page that contains the hidden summon field, then you could use something like the HtmlAgilityPack to parse the html and get the value to include on your post.

Also remember when working with an authenticated website that uses cookies your HttpWebRequest will need to be attached to a cookie container for each request to ensure the cookies returned by the authentication request flow with each subsequent request.