TLSV1_ALERT_PROTOCOL_VERSION(tls_record.cc:587)) when using TLSv1.3 only.

[nfrelink]

Describe the bug When setting Lighttpd to using TLSv1.3 only, flutterhole reports an error and refuses to connect.

To Reproduce Steps to reproduce the behavior:

1. Use https://ssl-config.mozilla.org "modern" config in Lighttpd.
2. Set connection address in flutterhole to https://dns.1rs.eu port 443. [1]
3. Click validate.
4. See error in API log.

Expected behavior A secured, https connection without any problems.

Versions (please complete the following information):

• Pi-hole version: 5.1.2
• FlutterHole version: 5.2.3

Additional context

Alice - HTTP Inspector
App name:  flutterhole
Package: sterrenburg.github.flutterhole
Version: v5.2.3
Build number: 641
Generated: 2020-10-16T22:42:10.741171

===========================================
Id: 481116404
============================================
--------------------------------------------
General data
--------------------------------------------
Server: dns.1rs.eu 
Method: GET 
Endpoint: /admin/api.php 
Client: Dio 
Duration 118 ms
Secured connection: true
Completed: true 
--------------------------------------------
Request
--------------------------------------------
Request time: 2020-10-16 22:41:58.791531
Request content type: application/json; charset=utf-8
Request cookies: []
Request headers: {
  "user-agent": "flutterhole"
}
Request size: 0 B
Request body: Body is empty
--------------------------------------------
Response
--------------------------------------------
Response time: 2020-10-16 22:41:58.909874
Response status: -1
Response size: 0 B
Response headers: null
Response body: Body is empty
--------------------------------------------
Error
--------------------------------------------
Error: DioError [DioErrorType.DEFAULT]: HandshakeException: Handshake error in client (OS Error: 
    TLSV1_ALERT_PROTOCOL_VERSION(tls_record.cc:587))
--------------------------------------------
Curl
--------------------------------------------
curl -X GET -H 'user-agent: flutterhole' 'https://dns.1rs.eu/admin/api.php'
==============================================

[1]: I've updated my config to allow TLSv1.2 as well, all works fine that way.

[nfrelink]

Any updates on this?

[vinnyperella]

I'm having the same issue and enabling TLS 1.2 fixes it.