How to implement SSL validation of a domain certificate?

Question

ruby

Greetings, how can you, having domains, find out information about their certificates, and, accordingly, check whether other SSL errors have expired or not. Verification should be carried out without third-party api and services. You can use openSSL. Can you "poke" where to draw resources?

Answer 1

To start
openssl s_client -connect qna.habr.com:443
and start learning/parsing the relevant parts

Answer 2

require 'net/http'
require 'openssl'

domain_name = 'qna.habr.com'

uri = URI::HTTPS.build host: domain_name
response = Net::HTTP.start uri.host, uri.port, use_ssl: true
cert = response.peer_cert

# @return [Time] 
cert.not_after