Open Radar

 
Summary:
In iOS WKWebView > 11.3
navigator.sendBeacon to HTTPS (TLS) fails with "Failed HTTP authentication" error in console. Network request is cancelled.

Technical hints:
1. The connection seems to break from the client side after a complete TLS handshake was performed. The server sends an "Encrypted Handshake Message" and the client responds with [FIN, ACK] and closes.
2. If the page provides a "preconnect" hint prior to the sendBeacon call (thus, preparing a valid TLS session beforehand) - the sendBeacon call succeeds!

example:
<link href='https://mytestserver.com/bug' rel='preconnect' crossorigin />

Steps to Reproduce:
1. Have a simple HTTPS CORS server that accepts POST to some url (/bug)
2. From an HTTPS simple HTML page, have inline javascript that POSTs to that url.
 2a. once with XHR (will succeed) like:
var xmlhttp = new XMLHttpRequest();   // new HttpRequest instance 
xmlhttp.open("POST", "https://mytestserver.com/bug");
xmlhttp.setRequestHeader("Content-Type", "application/json;charset=UTF-8");
xmlhttp.send(JSON.stringify({"a":"b"}));
 2b. with navigator.sendBeacon('https://mytestserver.com/bug', '');

Expected Results:
both 2a and 2b succeed.

Actual Results:
2a success, 2b fails.

Version/Build:
WKWebView iOS > 11.3 (tested on 11.4)