certshow

#!/bin/bash

show_validity=0

function showHelp() {
  cat << EOF
Show a certificate from a remote service.

Usage:

  certshow [-d] TARGET[:PORT]

  -d Show validity information only.
EOF
}

while getopts "h?d" opt; do
  case "${opt}" in
  h|\?)
    showHelp
    exit 0
    ;;
  d)
    show_validity=1
    ;;
  esac
done

shift $((OPTIND-1))
TARGET="${1}"
if [[ "${TARGET}" != *:* ]]; then
  TARGET="${TARGET}:443"
fi
if [[ ${show_validity} == "1" ]]; then
  echo "Q" | openssl s_client -connect "${TARGET}" | openssl x509 -text -noout | grep -A3 "^[[:space:]]*Validity"
  exit 0
fi
echo "Q" | openssl s_client -connect "${TARGET}" | openssl x509 -text -noout