HTTPS to sites using LetsEncrypt certificates with MKR1000 fails

[kleag]

I cannot connect to my RESTful API (Django REST framework) using https on my mkr 1000.

It worked beforehand on my local network.

I updated the firmware and was able to connect to google.com, arduino.cc or amazon.com using the WifiSSLClient sketch.

When I import my domain root certificate, there is no error message but the sketch cannot connect to my site. I tried also to connect (after importing the certificate) to the letsencrypt.org site (which probably uses also a letsencrypt certificate) and it fails also.

There is no error message at all, just if (client.connect(server, 443)) { returns false.

I had a look to this question on the Arduino forum and tried to apply the change on the ciphers handling that was proposed, with no luck.

[kleag]

This problem is solved on my side by changing the nginx ssl configuration.
Is it a bug of this library anyway? Here are the settings I commented out to make it work:

#    ssl_buffer_size               8k;
#    ssl_protocols                 TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
#    ssl_ciphers                   TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256:TLS_AES_128_CCM_8_SHA256:TLS_AES_128_CCM_SHA256:ECDHE-ECDSA-AES128-GCM-SH A256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384;
#    ssl_prefer_server_ciphers     on;
#    ssl_stapling                  on;
#    ssl_stapling_verify           on;
#    ssl_ecdh_curve                secp384r1:X25519:prime256v1;

Feel free to close the issue if you think there is no problem with the library.