Proxmox VE Firewall

Introduction

Proxmox VE Firewall provides an easy way to protect your IT infrastructure. You can easily setup firewall rules for all hosts inside a cluster, or define rules for virtual machines and containers. Features like firewall macros, security groups, IP sets and aliases help making that task easier.

All firewall related configuration is stored on the Proxmox cluster file system so those files are automatically distributed to all cluster nodes, and the 'pve-firewall' service updates the underlying iptables rules automatically on any change. Full isolation is thereby provided between virtual machines. The distributed nature of this system also delivers much higher bandwidth than a central firewall solution.

WARNING! Do NOT attempt to activate the firewall without reading the configuration warning below!

Zones

The Proxmox VE firewall groups the network into the following logical zones (shown in the top left corner of the main windows when using the WebUI):

• Datacenter: all traffic from/to all hosts
• Host: traffic from/to a cluster node
• VM: traffic from/to a specific VM

For each zone, you can define firewall rules for incoming and/or outgoing traffic.

Ports used by Proxmox VE

See further information here

IPv6

To enable filtering of IPv6 traffic, first ensure the host has a working IPv6 address configured on vmbr0 (or whichever WAN facing interface you are using) and that it has an IPv6 loopback interface ('iface lo inet6 loopback'). You can then enable the IPv6 macros as needed, which will ensure that any IPv4 rules will also be applied to IPv6.

WebUI Configuration

To enable the firewall service, go to the Firewall tab at the Datacenter (top) level and select the Options tab below it, i.e. Datacenter -> Firewall -> Options tab (tabs at the bottom of the page). Ensure the input policy is set to ACCEPT first, then set the firewall to "on".

WARNING: Failure to set the default input policy to ACCEPT (or explicitly adding tcp ACCEPT rules for port 22 and 8006) BEFORE activating the firewall at the Datacenter level will result in you being locked out of the system!

When the firewall is enabled, you can then configure it to control traffic at either the node or the individual VM level by enabling the firewall (using the Firewall -> Options tab) at either or both levels.

Command line configuration

Firewall configuration can be done using the GUI, so the following configuration file snippets are just for completeness:

Cluster wide configuration is stored at:

/etc/pve/firewall/cluster.fw

The firewall is completely disabled by default, so you need to set the enable option here (SEE ALSO WARNING ABOVE)

[OPTIONS]
# enable firewall (cluster wide setting, default is disabled)
enable: 1

The cluster wide configuration can contain the following data:

• IP set definitions
• alias definitions
• security group definitions
• cluster wide firewall rules for all nodes

VM firewall configuration is read from:

/etc/pve/firewall/<VMID>.fw

and contains the following data:

• IP set definitions
• alias definitions
• firewall rules for this VM
• VM specific options

And finally, any host related configuration is read from:

 /etc/pve/nodes/<nodename>/host.fw

This is useful if you want to overwrite rules from cluster.fw config. You can also increase log verbosity, and set netfilter related options.

Enabling firewall for qemu guest and openvz veth

For qemu guests, linux containers and openvz veth interfaces, you need to enable the firewall on the virtual network interface configuration.

Firewall Rules

Any firewall rule consists of a direction ('IN' or 'OUT') and an action (ACCEPT, DENY, REJECT). Additional options can be used to refine rule matches. Here are some examples:

[RULES]

#TYPE ACTION [OPTIONS]
#TYPE MACRO(ACTION) [OPTIONS]

# -i      <INTERFACE>
# -source <SOURCE>
# -dest   <DEST>
# -p      <PROTOCOL>
# -dport  <DESTINATION_PORT>
# -sport  <SOURCE_PORT>

IN SSH(ACCEPT) -i net0
IN SSH(ACCEPT) -i net0 # a comment
IN SSH(ACCEPT) -i net0 -source 192.168.2.192  # only allow SSH from 192.168.2.192
IN SSH(ACCEPT) -i net0 -source 10.0.0.1-10.0.0.10 # accept SSH for ip range
IN SSH(ACCEPT) -i net0 -source 10.0.0.1,10.0.0.2,10.0.0.3 #accept ssh for ip list
IN SSH(ACCEPT) -i net0 -source +mynetgroup   # accept ssh for ipset mynetgroup
IN SSH(ACCEPT) -i net0 -source myserveralias   #accept ssh for alias myserveralias

|IN SSH(ACCEPT) -i net0 # disabled rule

Security Groups

A security group is a group a rules, defined at cluster level, which can be used in all VMs' rules.

For example you can define a group named "webserver" with rules to open http and https ports.

/etc/pve/firewall/cluster.fw

[group webserver]
IN  ACCEPT -p tcp -dport 80
IN  ACCEPT -p tcp -dport 443

Then, you can add this group in a vm firewall

/etc/pve/firewall/<VMID>.fw

[RULES]
GROUP webserver

IP Aliases

IP Aliases allows you to associate IP addresses of Networks with a name. You can refer to those names:

• inside IP set definitions
• in 'source' and 'dest' properties of firewall rules

Standard IP alias 'local_network'

This alias is automatically defined. Please use the following command to see assigned values:

# pve-firewall localnet
local hostname: example
local IP address: 192.168.2.100
network auto detect: 192.168.0.0/20
using detected local_network: 192.168.0.0/20

The firewall automatically sets up rules to allow everything needed for cluster communication (corosync, API, SSH).

The user can overwrite these values in the cluster.fw alias section. If you use a single host on a public network, it is better to explicitly assign the local IP address

# --- example: /etc/pve/firewall/cluster.fw ---
[ALIASES]
local_network 1.2.3.4 # use the single ip address

IP Sets

IP sets can be used to define groups of networks and hosts. You can refer to them with '+name' in firewall rules' 'source' and 'dest' properties.

The following example allows HTTP traffic from the 'management' IP set.

IN HTTP(ACCEPT) -source +management

Standard IP set 'management'

This IPSET applies only to host firewalls (not VM firewalls). Those ips are allowed to do normal management tasks (PVE GUI, VNC, SPICE, SSH).

The local cluster network is automatically added to this IP set (alias 'cluster_network'), to enable inter-host cluster communication. (multicast,ssh,...)

/etc/pve/firewall/cluster.fw

[IPSET management] 
192.168.2.10
192.168.2.10/24

Standard IP set 'blacklist'

Traffic from those ips is dropped in all hosts' and VMs' firewalls.

/etc/pve/firewall/cluster.fw

[IPSET blacklist] 
77.240.159.182
213.87.123.0/24

Standard IP set 'ipfilter'

This ipset is used to prevent ip spoofing

/etc/pve/firewall/<VMID>.fw

qemu interface

[IPSET ipfilter-net0] # only allow specified IPs on net0
192.168.2.10

openvz veth interface

[IPSET ipfilter-eth0] # only allow specified IPs on veth eth0
192.168.2.10

Services and Commands

The firewall runs two service daemons on each node:

• pvefw-logger: NFLOG daemon (ulogd replacement).
• pve-firewall: updates iptables rules

There is also a CLI command named 'pve-firewall', which can be used to start and stop the firewall service:

# pve-firewall start
# pve-firewall stop

To get the status use:

# pve-firewall status

The above command reads and compiles all firewall rules, so you will see warnings if your firewall configuration contains any errors.

If you want to see the generated iptables rules you can use:

# iptables-save

Tips and Tricks

How to allow FTP

FTP is an old style protocol which uses port 21 and several other dynamic ports. So you need a rule to accept port 21. In addition, you need to load the 'ip_conntrack_ftp' module. So please run:

modprobe ip_conntrack_ftp

and add ip_conntrack_ftp to /etc/modules (so that it works after a reboot) .

Suricata IPS integration

If you want to use the Suricata IPS (intrusion prevention system), it's possible.

Packets will be forwarded to the IPS only after the firewall ACCEPTed them.

Rejected/Dropped firewall packets don't go to the IPS.

Install suricata on proxmox host:

1. apt-get install suricata
2. modprobe nfnetlink_queue

don't forget to add nfnetlink_queue to /etc/modules for next reboot

Then, enable IPS for a specific vm

/etc/pve/firewall/<VMID>.fw

[OPTIONS]
ips: 1
ips_queues: 0

ips_queues will bind a specific cpu queue for this vm.

Available queues are defined in

/etc/default/suricata
NFQUEUE=0

Video Tutorials

• tbd.