Get https certificate

Certificate:

 openssl s_client -connect <host>:<port> < /dev/null 2>/dev/null

Fingerprint of certificate:

openssl s_client -connect <host>:<port> < /dev/null 2>/dev/null | openssl x509 -fingerprint -noout -in /dev/stdin

Add custom CA to ubuntu

tested with ubuntu 18:04


1) sudo apt-get install ca-certificates



2) copy CA certificate to local:

      sudo cp CERTIFICATE.crt /usr/local/share/ca-certificates/

If your certificate in PEM format, need to convert to .crt using this command:

openssl x509 -outform der -in CERTIFICATE.pem -out CERTIFICATE.crt

3) update certificate

  sudo update-ca-certificates

ref:  

1) https://www.techrepublic.com/article/how-to-install-ca-certificates-in-ubuntu-server/

2) https://www.wikihow.com/Be-Your-Own-Certificate-Authority

become a CA, and force device to trust the CA

ref   https://deliciousbrains.com/ssl-certificate-authority-for-local-https-development/