How to login to a site using POST request? (Swift,iOS) - ios

Question

I want to create an iOS Application that logs into a website and parses the data from several pages of that site, while maintaining the login session.This is what I have done so far. I send a GET request to retrieve the EVENTVALIDATON and VIEWSTATE parameters required for the POST request. (I looked at the POST by using 'Firebug'). When I run the following code, it gives back the same login page. But it should be giving me this page.
var parameter: Parameters = [:]
var viewstate: String = ""
var eventvalidation: String =
#IBAction func postRequest(_ sender: Any) {
Alamofire.request("https://ecampus.psgtech.ac.in/studzone/AttWfLoginPage.aspx").responseString { response in
print("\(response.result.isSuccess)")
if let html = response.result.value {
if let doc = Kanna.HTML(html: html, encoding: String.Encoding.utf8) {
// Search for nodes by CSS selector
for show in doc.css("input[id='__VIEWSTATE']") {
self.viewstate=show["value"]!
//print(show["value"] as Any)
}
for show in doc.css("input[id='__EVENTVALIDATION']") {
self.eventvalidation=show["value"]!
//print(show["value"] as Any)
}
}
}
//creating dictionary for parameters
self.parameter = ["__EVENTTARGET":"",
"__EVENTARGUMENT":"",
"__LASTFOCUS":"",
"__VIEWSTATE":self.viewstate,
"__EVENTVALIDATION":self.eventvalidation,
"rdolst":"S",
"Txtstudid":"<myrollno>",
"TxtPasswd":"<mypassword>",
"btnlogin":"Login"
]
}
Alamofire.request ("https://ecampus.psgtech.ac.in/studzone/AttWfLoginPage.aspx",method: .post, parameters: self.parameter, headers: headers).responseString { response in
print("\(response.result.isSuccess)")
print(response)
}
To be honest, I'm very new to requests and parsing data(I have finished the parsing part separately though). I did some more research and read about headers and cookies.So after checking the headers, the initial GET request by the browser has a response header of
Cache-Control : private
Content-Encoding : gzip
Content-Length : 4992
Content-Type : text/html; charset=utf-8
Date : Sun, 18 Jun 2017 14:25:50 GMT
Server : Microsoft-IIS/8.0
Set-Cookie : .ASPXAUTH=; expires=Mon, 11-Oct-1999 18:30:00 GMT; path=/; HttpOnly
Vary : Accept-Encoding
X-AspNet-Version : 4.0.30319
X-Powered-By : ASP.NET
and Request Header of
Accept : text/html,application/xhtml+xml,application/xml;q=0.9;q=0.8
Accept-Encoding : gzip, deflate, br
Accept-Language : en-US,en;q=0.5
Connection : keep-alive
Cookie : ASP.NET_SessionId=urzugt0zliwkmz3ab1fxx1ja
Host : ecampus.psgtech.ac.in
Upgrade-Insecure-Requests : 1
User-Agent : Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:54.0) Gecko/20100101 Firefox/54.0`
The problem is I don't understand how a initial GET request can have a token with it. If request happens first, response should be the one containing the token? I don't know what I am doing wrong and how to get this working. I don't know if I am missing something altogether. I came here only after trying everything I could think of. Any help would be appreciated. Thank you.

Answer 1

EVENTVALIDATON and VIEWSTATE parameters required for the POST <--
But in your code the POST request is executed immediately after the GET request, at this point the self.parameter is empty
Alamofire has asynchronous completionHandler
Wait for the GET request to complete, and then send the POST request:
var parameter: Parameters = [:]
var viewstate: String = ""
var eventvalidation: String =
#IBAction func postRequest(_ sender: Any) {
Alamofire.request("https://ecampus.psgtech.ac.in/studzone/AttWfLoginPage.aspx").responseString { response in
print("\(response.result.isSuccess)")
if let html = response.result.value {
if let doc = Kanna.HTML(html: html, encoding: String.Encoding.utf8) {
// Search for nodes by CSS selector
for show in doc.css("input[id='__VIEWSTATE']") {
self.viewstate=show["value"]!
//print(show["value"] as Any)
}
for show in doc.css("input[id='__EVENTVALIDATION']") {
self.eventvalidation=show["value"]!
//print(show["value"] as Any)
}
}
}
//creating dictionary for parameters
self.parameter = ["__EVENTTARGET":"",
"__EVENTARGUMENT":"",
"__LASTFOCUS":"",
"__VIEWSTATE":self.viewstate,
"__EVENTVALIDATION":self.eventvalidation,
"rdolst":"S",
"Txtstudid":"15i231",
"TxtPasswd":"OpenSesame",
"btnlogin":"Login"
]
//Wait for the GET request to complete, and then send the POST request: <<==
Alamofire.request ("https://ecampus.psgtech.ac.in/studzone/AttWfLoginPage.aspx",method: .post, parameters: self.parameter, headers: headers).responseString { response in
print("\(response.result.isSuccess)")
print(response)
}
}