Swift HTTP Request Issue (Not sending HOST Header)

Question

I have a simple rest endpoint built on PHP that works on postman and browsers.

https://someserver.com/api/endpoint.php?name=hello

But the code fails to execute when invoked from Swift. Upon Investigation, I found out that Postman and Browser sends the Host Header whereas the Swift URLRequest doesn't. When you don't send the HOST Header, the php server refuses to accept the incoming request and I believe the request is rejected at the web server level. I tried using the

request.addValue("127.0.0.1", "Host")

but it still didn't work. Any help is appreciated.

Full Code (Swift 4)

let url = urlInput.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)!
        print("URL is: " + url)
        var request = URLRequest(url: URL(string: url)!)
        request.httpMethod = "GET"
            request.addValue(<#T##value: String##String#>, forHTTPHeaderField: <#T##String#>)
        let session = URLSession.shared
        let task = session.dataTask(with: request, completionHandler: { data, response, error -> Void in
            if let httpResponse = response as? HTTPURLResponse {
                
                let respStr = String(data: data!, encoding: String.Encoding.utf8) as String?
                print ("Response is \(respStr ?? "")")
                print("statusCode: \(httpResponse.statusCode)")
                
                let data: Data? = respStr?.data(using: .utf8)
}
})

These answers will help https://stackoverflow.com/q/25702354/9333764 — Jake, Aug 23 '21 at 18:54
"the Swift URLRequest doesn't" It's your job to set the http header. — El Tomato, Aug 23 '21 at 20:17
In HTTP 1.1, the Host request header is mandatory. URLSession will setup a valid request message including the Host header from your URLRequest, which usually does not contain a host header. — CouchDeveloper, Aug 24 '21 at 07:44
@Jake - the servers are not on the same domain. Swift is able to make calls to servers that are not in php. — touchydeer36, Aug 24 '21 at 13:15
@ElTomato - HOST is a reserved header and we cannot set the header. — touchydeer36, Aug 24 '21 at 13:15

score 0 · Answer 1 · answered Aug 23 '21 at 17:25

Swift is ignoring the fact that you set the header, as it typically should. See the docs about Swift headers and why it's ignoring your Host header.

The URL Loading System handles various aspects of the HTTP protocol 
for you (HTTP 1.1 persistent connections, proxies, authentication, 
and so on). As part of this support, the URL Loading System takes 
responsibility for certain HTTP headers:

Content-Length

Authorization

Connection

Host

Proxy-Authenticate

Proxy-Authorization

WWW-Authenticate

If you set a value for one of these reserved headers, the system may 
ignore the value you set, or overwrite it with its own value, or 
simply not send it. Moreover, the exact behavior may change over 
time. To avoid confusing problems like this, do not set these headers 
directly.

The documentation is here:

https://developer.apple.com/documentation/foundation/nsurlrequest#1776617

I have seen this before with Java - there is a workaround in Java depending on the library you are using, but I don't know about Swift.

score 0 · Answer 2 · answered Sep 16 '21 at 20:23

I figured out that the issue happens only when you hit a php server. The php web server looks for some header and cant find it when the call is made from Swift. I even copied the working code from Postman and results were the same.

The solution I went with was to create a proxy server using firebase cloud function. Swift code would hit a firebase cloud function which talks to php and sends the response to swift.

Swift HTTP Request Issue (Not sending HOST Header)

2 Answers2