prints server certificate

get_cert.sh

#!/bin/sh

exit_with_error () {
   rr=$1; shift
   >&2 echo "$@"
   exit $rr
}

is_installed () {
   cmd="$1"
   hash "${cmd}" 2> /dev/null || exit_with_error 1 "Missing ${cmd}"
}

parse_cert () {
  awk 'BEGIN { f = 0; }
       /^-----BEGIN CERTIFICATE-----/ || f == 1 { f = 1; print; }
       /^-----END CERTIFICATE-----/             { exit;}'
}

get_cert () {
  server="$1"

  if ct_data=$(openssl s_client -connect "${server}" </dev/null 2> /dev/null)
  then
     echo "${ct_data}" | parse_cert
  else
     exit_with_error $? "Failed to connect to ${server}"
  fi
}

has_right_tools () {
   is_installed awk && is_installed openssl
}

has_right_tools && get_cert $1