ssl-expiry: displays the expiry date of SSL certificates associated with any domains passed on the command line

ssl-expiry.rb

#!/usr/bin/env ruby
#
# ssl-expiry
#
# Author: Rob Miller <rob@bigfish.co.uk>
#
# For a given domain or domains, checks to see if an SSL certificate is
# present; if one is, outputs the date of its expiry.
#
# Usage:
#
#   % ssl-expiry example.com
#   example.com	2017-01-01 00:00:00+0000
#
#   % ssl-expiry example.com | cut -f2
#   2017-01-01 00:00:00+0000
#
#   $ ssl-expiry example.com example.org
#   example.com	2017-01-01 00:00:00+0000
#   example.org	2017-03-08 09:36:00+0000

require "net/http"
require "openssl"

domains = ARGV.to_a

unless domains.length > 0
  abort "Usage: #$0 DOMAIN [DOMAIN...]"
end

domains.each do |domain|
  uri = URI.parse("https://" + domain)

  http = Net::HTTP.new(uri.host, uri.port)
  http.use_ssl = true
  http.verify_mode = OpenSSL::SSL::VERIFY_NONE

  cert = nil
  begin
    http.start do |h|
      cert = h.peer_cert
    end
  rescue Exception => e
    $stderr.puts "#{domain}\tCouldn't connect to site (#{e.message})"
    next
  end

  unless cert
    $stderr.puts "#{domain}\tCouldn't find SSL certificate"
    next
  end

  expiry = cert.not_after
  puts "#{domain}\t#{expiry.strftime("%F %T%z")}"
end