#!/bin/bash
# Copyright (C) 2016 Ian Kelling

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR

[[ $EUID == 0 ]] || exec sudo -E "$BASH_SOURCE" "$@"

usage() {
    cat <<EOF
usage: ${0##*/} VPN_SERVER_HOST

-b COMMON_NAME   By default, use CONFIG_NAME. If the cert already exists
                 on the server, with the CLIENT_NAME name, we use the
                 existing one. See comment below if we ever want to
                 check existing common names. They must be unique per
                 server, so you can use $(uuidgen) if needed. You used
                 to be able to create multiple with the same name, but
                 not connect at the same time, but now, the generator
                 keeps track, so you can't generate.
-c CLIENT_HOST   default is localhost. Else we ssh to root@CLIENT_HOST
-n CONFIG_NAME   default is client

Generate a client cert and config and install it on locally or on
CLIENT_HOST if given.  Uses default config options, and expects be able
to ssh to VPN_SERVER_HOST and CLIENT_HOST as root, or if CLIENT_HOST is
localhost, just to sudo this script as root.




Note: Uses GNU getopt options parsing style
EOF
    exit ${1:-0}
}

# to get the common name
# cn=$(s openssl x509 -noout -nameopt multiline -subject \
    #        -in /etc/openvpn/client/mail.crt | \
    #          sed -rn 's/^\s*commonName\s*=\s*(.*)/\1/p')


shell="bash -c"
name=client

temp=$(getopt -l help hb:c:n: "$@") || usage 1
eval set -- "$temp"
while true; do
    case $1 in
        -b) common_name="$2"; shift 2 ;;
        -c) shell="ssh root@$2"; shift 2 ;;
        -n) name="$2"; shift 2 ;;
        -h|--help) usage ;;
        --) shift; break ;;
        *) echo "$0: Internal error! unexpected args: $*" ; exit 1 ;;
    esac
done

if [[ ! $common_name ]]; then common_name=$name; fi

host=$1
[[ $host ]] || usage 1

# bash or else we get motd spam. note sleep 2, sleep 1 failed.
ssh root@$host bash <<EOF | $shell 'id -u | grep -xF 0 || s=sudo; $s tar xzv -C /etc/openvpn/client'
set -eE -o pipefail

exists=true
for x in /etc/openvpn/easy-rsa/keys/{$name.{crt,key},ca.crt}; do
  if [[ ! -e \$x ]]; then
     exists=false
     break
  fi
done

if ! \$exists; then
  cd /etc/openvpn/easy-rsa
  source vars >/dev/null

  { echo -e '\n\n\n\n\n'$common_name'\n\n\n\n\n'; sleep 2; echo -e 'y\ny\n'; } | ./build-key $name &>/dev/null
fi

d=\$(mktemp -d)
cp /etc/openvpn/easy-rsa/keys/ca.crt \$d/$name-ca.crt
cp /etc/openvpn/easy-rsa/keys/$name.{crt,key} \$d

tar cz -C \$d .
rm -rf \$d
EOF

f=/etc/openvpn/client/$name.crt
if [[ ! -s $f ]]; then
    echo "$0: error: $f is empty or otherwise bad. is this common name unique?"
    exit 1
fi

$shell "dd of=/etc/openvpn/client/$name.conf" <<EOF
# From example config, from debian stretch as of 1-2017
client
dev tun
proto udp
remote $host 1194
resolv-retry infinite
nobind
persist-key
persist-tun
ca $name-ca.crt
cert $name.crt
key $name.key
# disabled for better performance
#comp-lzo
verb 3

# This script will update local dns
# to what the server sends, if it sends dns.
script-security 2
up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf

# matching server config
cipher aes-256-cbc


# example config has the commented line, but this other thing looks stronger,
# and I've seen it in a vpn provider I trust
# ns-cert-type server
remote-cert-tls server

# more resilient when running as nonroot
persist-key

# see comments in server side configuration.
# the minimum of the 2 is used.
reneg-sec 2592000
EOF