#!/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.

# usage: $0 SERVER_HOST [DEST_HOST]
# ssh to SERVER_HOST, create a cert & client config, put it on
# DEST_HOST, or localhost by default. Assumes server was setup
# by the other script in this dir.

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

-c CLIENT_HOST   default is localhost
-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.
EOF
    exit ${1:-0}
}

shell="bash -c"
name=client

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

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

# uuidgen because common name must be unique
{ echo -e '\n\n\n\n\n'\$(uuidgen)'\n\n\n\n\n'; sleep 2; echo -e 'y\ny\n'; } | ./build-key $name &>/dev/null

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

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

cat > /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
EOF