# Fetch a remote TLS certificate:
function tlscertget {
	local domain="${1}"
	shift
	openssl s_client \
		-connect "${domain}" \
		-servername "${domain}" \
		"$@" < /dev/null 2> /dev/null |\
		sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p'
}

# Show (in text form) a certificate passed through stdin; display
# full details (-text) if invoked without any argument. See man x509 for
# possible options.
function tlscertshow {
	if [ $# -eq 0 ]; then
		openssl x509 -noout -text
	else
		openssl x509 -noout "$@"
	fi
}

# Fetch a remote TLS certificate and display its subject, issuer and dates.
function tlscertcheck {
	local domain="${1}"
	shift
	tlscertget "${domain}" | tlscertshow -subject -issuer -dates "$@"
}