function certchain() {
    # Usage: certchain
    # Display PKI chain-of-trust for a given domain
    # GistID: https://gist.github.com/joshenders/cda916797665de69ebcd
    if [[ "$#" -ne 1 ]]; then
        echo "Usage: ${FUNCNAME} <ip|domain[:port]>"
        return 1
    fi

    local host_port="$1"

    if [[ "$1" != *:* ]]; then
        local host_port="${1}:443"
    fi

    \openssl \
        s_client -connect "${host_port}" </dev/null 2>/dev/null \
        | \egrep \
            --color=never \
            --extended-regexp '\ (s|i):'
}