I am trying to access my api from java but I get the following error:

javax.net.ssl.SSLHandshakeException: Received fatal alert: certificate_required

I do not get this error when I test the code on my personal Windows computer. But this error does occur on my linux production server running Ubuntu with openjdk 11.

The server is hosted on that same ubuntu server, and proxied with Cloudflare SSL Full

HttpsURLConnection con = null;
    try {
        URL url = new URL("https://www.example.com/");
        con = (HttpsURLConnection) url.openConnection();
        con.addRequestProperty("XF-Api-Key", "key");
        con.addRequestProperty("XF-Api-User", "1");
        con.setConnectTimeout(5000);
        con.setReadTimeout(5000);
        con.addRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)");
        con.setRequestMethod("GET");
        con.setRequestProperty("Content-Type", "application/json");
        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String inputLine;
            StringBuffer content = new StringBuffer();
            while ((inputLine = in.readLine()) != null)
                content.append(inputLine);
            in.close();

            System.out.println(content.toString());
        } catch (Exception e) {
            e.printStackTrace();
            BufferedReader in = new BufferedReader(new InputStreamReader(con.getErrorStream()));
            String inputLine;
            StringBuffer content = new StringBuffer();
            while ((inputLine = in.readLine()) != null) {
                content.append(inputLine);
            }
            in.close();
            System.out.println(content.toString());
        }
    } catch (Exception exp) {
        System.out.println("Cant load data from API");
        exp.printStackTrace();
    } finally {
        if (con != null)
            con.disconnect();
    }

Is something not configured properly on my linux server?

 

hopefully youve found a solution for this by now. with SSL, are the root certificates up to date on the linux host? im not a linux person but this can sometimes cause issues on windows