Ευάγγελος Μπαλάσκας - Network Namespaces - Part Three » Evaggelos Balaskas

May

2020

Network Namespaces - Part Three

Posted by ebal at 21:05:31 in blog, planet_ellak, planet_Sysadmin, planet_fsfe

Previously on … Network Namespaces - Part Two we provided internet access to the namespace, enabled a different DNS than our system and run a graphical application (xterm/firefox) from within.

The scope of this article is to run vpn service from this namespace. We will run a vpn-client and try to enable firewall rules inside.

ip-netns07

dsvpn

My VPN choice of preference is dsvpn and you can read in the below blog post, how to setup it.

How to setup dsvpn

dsvpn is a TCP, point-to-point VPN, using a symmetric key.

The instructions in this article will give you an understanding how to run a different vpn service.

Find your external IP

Before running the vpn client, let’s see what is our current external IP address

ip netns exec ebal curl ifconfig.co

62.103.103.103

The above IP is an example.

IP address and route of the namespace

ip netns exec ebal ip address show v-ebal

375: v-ebal@if376: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether c2:f3:a4:8a:41:47 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.10.10.20/24 scope global v-ebal
       valid_lft forever preferred_lft forever
    inet6 fe80::c0f3:a4ff:fe8a:4147/64 scope link
       valid_lft forever preferred_lft forever

ip netns exec ebal ip route show

default via 10.10.10.10 dev v-ebal
10.10.10.0/24 dev v-ebal proto kernel scope link src 10.10.10.20

Firefox

Open firefox (see part-two) and visit ifconfig.co we noticed see that the location of our IP is based in Athens, Greece.

ip netns exec ebal bash -c "XAUTHORITY=/root/.Xauthority firefox"

Run VPN client

We have the symmetric key dsvpn.key and we know the VPN server’s IP.

ip netns exec ebal dsvpn client dsvpn.key 93.184.216.34 443

Interface: [tun0]
Trying to reconnect
Connecting to 93.184.216.34:443...
net.ipv4.tcp_congestion_control = bbr
Connected

Host

We can not see this tunnel vpn interface from our host machine

# ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 94:de:80:6a:de:0e brd ff:ff:ff:ff:ff:ff

376: v-eth0@if375: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 1a:f7:c2:fb:60:ea brd ff:ff:ff:ff:ff:ff link-netns ebal

netns

but it exists inside the namespace, we can see tun0 interface here

ip netns exec ebal ip link

1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

3: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 9000 qdisc fq_codel state UNKNOWN mode DEFAULT group default qlen 500
    link/none

375: v-ebal@if376: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether c2:f3:a4:8a:41:47 brd ff:ff:ff:ff:ff:ff link-netnsid 0

Find your external IP again

Checking your external internet IP from within the namespace

ip netns exec ebal curl ifconfig.co

93.184.216.34

Firefox netns

running again firefox, we will noticed that our the location of our IP is based in Helsinki (vpn server’s location).

ip netns exec ebal bash -c "XAUTHORITY=/root/.Xauthority firefox"

systemd

We can wrap the dsvpn client under a systemcd service

[Unit]
Description=Dead Simple VPN - Client

[Service]
ExecStart=ip netns exec ebal /usr/local/bin/dsvpn client /root/dsvpn.key 93.184.216.34 443
Restart=always
RestartSec=20

[Install]
WantedBy=network.target

Start systemd service

systemctl start dsvpn.service

Verify

ip -n ebal a

1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

4: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 9000 qdisc fq_codel state UNKNOWN group default qlen 500
    link/none
    inet 192.168.192.1 peer 192.168.192.254/32 scope global tun0
       valid_lft forever preferred_lft forever
    inet6 64:ff9b::c0a8:c001 peer 64:ff9b::c0a8:c0fe/96 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::ee69:bdd8:3554:d81/64 scope link stable-privacy
       valid_lft forever preferred_lft forever

375: v-ebal@if376: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether c2:f3:a4:8a:41:47 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.10.10.20/24 scope global v-ebal
       valid_lft forever preferred_lft forever
    inet6 fe80::c0f3:a4ff:fe8a:4147/64 scope link
       valid_lft forever preferred_lft forever

ip -n ebal route

default via 10.10.10.10 dev v-ebal
10.10.10.0/24 dev v-ebal proto kernel scope link src 10.10.10.20
192.168.192.254 dev tun0 proto kernel scope link src 192.168.192.1

Firewall

We can also have different firewall policies for each namespace

outside

# iptables -nvL | wc -l
127

inside

ip netns exec ebal iptables -nvL

Chain INPUT (policy ACCEPT 9 packets, 2547 bytes)
 pkts bytes target     prot opt in     out     source        destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source        destination

Chain OUTPUT (policy ACCEPT 2 packets, 216 bytes)
 pkts bytes target     prot opt in     out     source        destination

So for the VPN service running inside the namespace, we can REJECT every network traffic, except the traffic towards our VPN server and of course the veth interface (point-to-point) to our host machine.

iptable rules

Enter the namespace

inside

ip netns exec ebal bash

Before

verify that iptables rules are clear

iptables -nvL

Chain INPUT (policy ACCEPT 25 packets, 7373 bytes)
 pkts bytes target     prot opt in     out     source        destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source        destination

Chain OUTPUT (policy ACCEPT 4 packets, 376 bytes)
 pkts bytes target     prot opt in     out     source        destination

Enable firewall

./iptables.netns.ebal.sh

The content of this file

## iptable rules

iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -m conntrack --ctstate INVALID -j DROP
iptables -A INPUT -p icmp --icmp-type 8 -m conntrack --ctstate NEW -j ACCEPT

## netns - incoming
iptables -A INPUT -i v-ebal -s 10.0.0.0/8 -j ACCEPT

## Reject incoming traffic
iptables -A INPUT -j REJECT

## DSVPN
iptables -A OUTPUT -p tcp -m tcp -o v-ebal -d 93.184.216.34 --dport 443 -j ACCEPT

## net-ns outgoing
iptables -A OUTPUT -o v-ebal -d 10.0.0.0/8 -j ACCEPT

## Allow tun
iptables -A OUTPUT -o tun+ -j ACCEPT

## Reject outgoing traffic
iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset
iptables -A OUTPUT -p udp -j REJECT --reject-with icmp-port-unreachable

After

iptables -nvL

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source        destination
    0     0 ACCEPT     all  --  lo     *       0.0.0.0/0     0.0.0.0/0
    0     0 ACCEPT     all  --  *      *       0.0.0.0/0     0.0.0.0/0     ctstate RELATED,ESTABLISHED
    0     0 DROP       all  --  *      *       0.0.0.0/0     0.0.0.0/0     ctstate INVALID
    0     0 ACCEPT     icmp --  *      *       0.0.0.0/0     0.0.0.0/0     icmptype 8 ctstate NEW
    1   349 ACCEPT     all  --  v-ebal *       10.0.0.0/8    0.0.0.0/0
    0     0 REJECT     all  --  *      *       0.0.0.0/0     0.0.0.0/0     reject-with icmp-port-unreachable
    0     0 ACCEPT     all  --  lo     *       0.0.0.0/0     0.0.0.0/0
    0     0 ACCEPT     all  --  *      *       0.0.0.0/0     0.0.0.0/0     ctstate RELATED,ESTABLISHED
    0     0 DROP       all  --  *      *       0.0.0.0/0     0.0.0.0/0     ctstate INVALID
    0     0 ACCEPT     icmp --  *      *       0.0.0.0/0     0.0.0.0/0     icmptype 8 ctstate NEW
    0     0 ACCEPT     all  --  v-ebal *       10.0.0.0/8    0.0.0.0/0
    0     0 REJECT     all  --  *      *       0.0.0.0/0     0.0.0.0/0     reject-with icmp-port-unreachable

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source        destination

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source        destination
    0     0 ACCEPT     tcp  --  *      v-ebal  0.0.0.0/0     95.216.215.96 tcp dpt:8443
    0     0 ACCEPT     all  --  *      v-ebal  0.0.0.0/0     10.0.0.0/8
    0     0 ACCEPT     all  --  *      tun+    0.0.0.0/0     0.0.0.0/0
    0     0 REJECT     tcp  --  *      *       0.0.0.0/0     0.0.0.0/0     reject-with tcp-reset
    0     0 REJECT     udp  --  *      *       0.0.0.0/0     0.0.0.0/0     reject-with icmp-port-unreachable
    0     0 ACCEPT     tcp  --  *      v-ebal  0.0.0.0/0     95.216.215.96 tcp dpt:8443
    0     0 ACCEPT     all  --  *      v-ebal  0.0.0.0/0     10.0.0.0/8
    0     0 ACCEPT     all  --  *      tun+    0.0.0.0/0     0.0.0.0/0
    0     0 REJECT     tcp  --  *      *       0.0.0.0/0     0.0.0.0/0     reject-with tcp-reset
    0     0 REJECT     udp  --  *      *       0.0.0.0/0     0.0.0.0/0     reject-with icmp-port-unreachable

PS: We reject tcp/udp traffic (last 2 linew), but allow icmp (ping).

ip-netns08

End of part three.

Tag(s): linux, namespaces, network, ip-netns, veth, iproute2

Evaggelos Balaskas - System Engineer

dsvpn

Find your external IP

IP address and route of the namespace

Firefox

Run VPN client

Host

netns

Find your external IP again

Firefox netns

systemd

Start systemd service

Verify

Firewall

iptable rules

Before

Enable firewall

After

Admin area

Categories

Archives

Evaggelos Balaskas - System Engineer

dsvpn

Find your external IP

IP address and route of the namespace

Firefox

Run VPN client

Host

netns

Find your external IP again

Firefox netns

systemd

Start systemd service

Verify

Firewall

iptable rules

Before

Enable firewall

After

Search

Admin area

Categories

Archives