Table of Contents

PPPoSSH client

This article relies on the following:

Introduction

Goals

  • Encrypt your internet connection to enforce security and privacy.
    • Prevent traffic leaks and spoofing on the client side.
  • Bypass regional restrictions using commercial providers.
    • Escape client side content filters and internet censorship.
  • Access your LAN services remotely without port forwarding.

Command-line instructions

1. Preparation

Install the required packages. Specify configuration parameters for VPN client. 

# Install packages
opkg update
opkg install pppossh
 
# Configuration parameters
VPN_IF="vpn"
VPN_PORT="22"
VPN_SERV="SERVER_ADDRESS"
VPN_ADDR="192.168.9.2 192.168.9.1"
VPN_USER="root"

2. Key management

Generate and exchange keys between server and client. Set up key-based authentication. 

# Client private key
VPN_KEY="/etc/dropbear/dropbear_ed25519_host_key"
 
# Generate client public key
dropbearkey -y -f ${VPN_KEY} \
| sed -n -e "/^ssh-\S*\s/p" > sshclient.pub
 
# Server public key
VPN_PUB="$(cat sshserver.pub)"
 
# Configure PKI
mkdir -p /root/.ssh
cat << EOF >> /root/.ssh/known_hosts
${VPN_SERV} ${VPN_PUB% *}
EOF
cat << EOF >> /etc/sysupgrade.conf
/root/.ssh
EOF

3. Firewall

Consider VPN network as public. Assign VPN interface to WAN zone to minimize firewall setup. 

# Configure firewall
uci rename firewall.@zone[0]="lan"
uci rename firewall.@zone[1]="wan"
uci del_list firewall.wan.network="${VPN_IF}"
uci add_list firewall.wan.network="${VPN_IF}"
uci commit firewall
service firewall restart

4. Network

Set up VPN interface. 

# Configure network
uci -q delete network.${VPN_IF}
uci set network.${VPN_IF}="interface"
uci set network.${VPN_IF}.proto="pppossh"
uci set network.${VPN_IF}.server="${VPN_SERV}"
uci set network.${VPN_IF}.port="${VPN_PORT}"
uci set network.${VPN_IF}.ipaddr="${VPN_ADDR% *}"
uci set network.${VPN_IF}.peeraddr="${VPN_ADDR#* }"
uci set network.${VPN_IF}.sshuser="${VPN_USER}"
uci add_list network.${VPN_IF}.identity="${VPN_KEY}"
uci set network.${VPN_IF}.ipv6="1"
uci commit network
service network restart

Configure dynamic connection if necessary.

Testing

Establish the VPN connection. Verify your routing with traceroute and traceroute6. 

traceroute openwrt.org
traceroute6 openwrt.org

Check your IP and DNS provider.

On router:

  • Go to LuCI > Status > Wireguard and look for peer device connected with an IPv4 or IPv6 address and with a recent handshake time
  • Go to LuCI > Network > Diagnostics and ipv4 ping client device IP eg. 10.0.0.10

On client device depending on wireguard software:

  • Check transfer traffic for tx & rx
  • Ping router internal lan IP
  • Check public IP address in a browser – https://whatsmyip.com – should see public IP address of ISP for the router

Troubleshooting

Collect and analyze the following information. 

# Restart services
service log restart; service network restart; sleep 10
 
# Log and status
logread -e netifd -e pppd
 
# Runtime configuration
pgrep -f -a ssh; pgrep -f -a pppd
ip address show; ip route show table all
ip rule show; ip -6 rule show; nft list ruleset
ssh -i ${VPN_KEY} -p ${VPN_PORT} \
${VPN_USER}@${VPN_SERV} ubus call system board
 
# Persistent configuration
uci show network; uci show firewall