Script to verify ssl hosts and pem files.

verifyssl.rb

#!/usr/bin/env ruby

require 'net/https'
require 'open-uri'
require 'tmpdir'

unless ARGV[0]
  puts "Usage: #{File.basename(__FILE__)} hostname [pemfile]"
  puts "It will use http://curl.haxx.se/ca/cacert.pem if no pemfile is specified"
  exit false
end

if ARGV.size == 1
  ca_path = File.join(Dir.tmpdir, 'cacert.pem')
  if !File.exists? ca_path
    File.open(ca_path, 'w') do |f|
      f.write open("http://curl.haxx.se/ca/cacert.pem").read
    end
  end
else
  ca_path = ARGV[1]
end

http = Net::HTTP.new(ARGV[0], 443)
http.use_ssl = true
http.verify_mode = OpenSSL::SSL::VERIFY_PEER
http.ca_file = ca_path

success = nil
http.verify_callback = proc do |preverify_ok, ssl_context|
  if !preverify_ok
    issuer = ssl_context.current_cert.issuer.to_a.last[1]
    subject = ssl_context.current_cert.subject.to_a.last[1]
    puts "Verification failed: #{ssl_context.error_string} for issuer #{issuer} on #{subject}"
  end

  success = preverify_ok
end

http.get('/')

puts "Successful verificaton" if success

Consider also openssl s_client -CAfile cacert.pem -connect google.com:443 -verify -showcerts