Proxmox VE Firewall provides an easy way to protect your IT infrastructure. You can 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 helps to make that task easier.
While all configuration is stored on the cluster file system, the iptables based firewall runs on each cluster node, and thus provides full isolation between virtual machines. The distributed nature of this system also provides much higher bandwidth than a central firewall solution.
The firewall has full support for IPv4 and IPv6. IPv6 support is fully transparent, and we filter traffic for both protocols by default. So there is no need to maintain a different set of rules for IPv6.
The Proxmox VE firewall groups the network into the following logical zones:
- 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.
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 changes.
You can configure anything using the GUI (i.e. Datacenter → Firewall, or on a Node → Firewall), or you can edit the configuration files directly using your preferred editor.
Firewall configuration files contains sections of key-value pairs. Lines beginning with a # and blank lines are considered comments. Sections starts with a header line containing the section name enclosed in [ and ].
The cluster wide firewall configuration is stored at:
/etc/pve/firewall/cluster.fw
The configuration can contain the following sections:
- [OPTIONS]
-
This is used to set cluster wide firewall options.
- [RULES]
-
This sections contains cluster wide firewall rules for all nodes.
- [IPSET <name>]
-
Cluster wide IP set definitions.
- [GROUP <name>]
-
Cluster wide security group definitions.
- [ALIASES]
-
Cluster wide Alias definitions.
The firewall is completely disabled by default, so you need to set the enable option here:
[OPTIONS] # enable firewall (cluster wide setting, default is disabled) enable: 1
|
Important
|
If you enable the firewall, traffic to all hosts is blocked by default. Only exceptions is WebGUI(8006) and ssh(22) from your local network. |
If you want to administrate your {pve} hosts from remote, you need to create rules to allow traffic from those remote IPs to the web GUI (port 8006). You may also want to allow ssh (port 22), and maybe SPICE (port 3128).
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Tip
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Please open a SSH connection to one of your {PVE} hosts before enabling the firewall. That way you still have access to the host if something goes wrong . |
To simplify that task, you can instead create an IPSet called management, and add all remote IPs there. This creates all required firewall rules to access the GUI from remote.
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. The configuration can contain the following sections:
- [OPTIONS]
-
This is used to set host related firewall options.
- [RULES]
-
This sections contains host specific firewall rules.
VM firewall configuration is read from:
/etc/pve/firewall/<VMID>.fw
and contains the following data:
- [OPTIONS]
-
This is used to set VM/Container related firewall options.
- [RULES]
-
This sections contains VM/Container firewall rules.
- [IPSET <name>]
-
IP set definitions.
- [ALIASES]
-
IP Alias definitions.
Each virtual network device has its own firewall enable flag. So you can selectively enable the firewall for each interface. This is required in addition to the general firewall enable option.
The firewall requires a special network device setup, so you need to restart the VM/container after enabling the firewall on a network interface.
Firewall rules consists of a direction (IN or OUT) and an
action (ACCEPT, DENY, REJECT). You can also specify a macro
name. Macros contain predifined sets of rules and options. Rules can be disabled by prefixing them with |.
[RULES] DIRECTION ACTION [OPTIONS] |DIRECTION ACTION [OPTIONS] # disabled rule DIRECTION MACRO(ACTION) [OPTIONS] # use predefined macro
The following options can be used to refine rule matches.
Here are some examples:
[RULES] 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 IN DROP # drop all incoming packages OUT ACCEPT # accept all outgoing packages
A security group is a collection of 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 the 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 to a VM’s firewall
# /etc/pve/firewall/<VMID>.fw [RULES] GROUP webserver
IP Aliases allow you to associate IP addresses of networks with a name. You can then refer to those names:
-
inside IP set definitions
-
in
sourceanddestproperties of firewall rules
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) using this alias.
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
# /etc/pve/firewall/cluster.fw [ALIASES] local_network 1.2.3.4 # use the single ip address
IP sets can be used to define groups of networks and hosts. You can
refer to them with +name in the firewall rules' source and dest
properties.
The following example allows HTTP traffic from the management IP
set.
IN HTTP(ACCEPT) -source +management
This IP set 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
Traffic from these ips is dropped by every host’s and VM’s firewall.
# /etc/pve/firewall/cluster.fw [IPSET blacklist] 77.240.159.182 213.87.123.0/24
These filters belong to a VM’s network interface and are mainly used to prevent IP spoofing. If such a set exists for an interface then any outgoing traffic with a source IP not matching its interface’s corresponding ipfilter set will be dropped.
For containers with configured IP addresses these sets, if they exist (or are
activated via the general IP Filter option in the VM’s firewall’s options
tab), implicitly contain the associated IP addresses.
For both virtual machines and containers they also implicitly contain the standard MAC-derived IPv6 link-local address in order to allow the neighbor discovery protocol to work.
/etc/pve/firewall/<VMID>.fw [IPSET ipfilter-net0] # only allow specified IPs on net0 192.168.2.10
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
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) .
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:
# apt-get install suricata # modprobe nfnetlink_queue
Don’t forget to add nfnetlink_queue to /etc/modules for next reboot.
Then, enable IPS for a specific VM with:
# /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
With IPv6 enabled by default every interface gets a MAC-derived link local address. However, most devices on a typical {pve} setup are connected to a bridge and so the bridge is the only interface which really needs one.
To disable a link local address on an interface you can set the interface’s
disable_ipv6 sysconf variable. Despite the name, this does not prevent IPv6
traffic from passing through the interface when routing or bridging, so the
only noticeable effect will be the removal of the link local address.
The easiest method of achieving this setting for all newly started VMs is to
set it for the default interface configuration and enabling it explicitly on
the interfaces which need it. This is also the case for other settings such as
forwarding, accept_ra or autoconf.
Here’s a possible setup:
# /etc/sysconf.d/90-ipv6.conf net.ipv6.conf.default.forwarding = 0 net.ipv6.conf.default.proxy_ndp = 0 net.ipv6.conf.default.autoconf = 0 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv6.conf.default.accept_ra = 0 net.ipv6.conf.lo.disable_ipv6 = 0
# /etc/network/interfaces
(...)
iface vmbr0 inet6 static
address fc00::31
netmask 16
gateway fc00::1
accept_ra 0
pre-up echo 0 > /proc/sys/net/ipv6/conf/$IFACE/disable_ipv6
(...)
The firewall contains a few IPv6 specific options. One thing to note is that IPv6 does not use the ARP protocol anymore, and instead uses NDP (Neighbor Discovery Protocol) which works on IP level and thus needs IP addresses to succeed. For this purpose link-local addresses derived from the interface’s MAC address are used. By default the NDP option is enabled on both host and VM level to allow neighbor discovery (NDP) packets to be sent and received.
Beside neighbor discovery NDP is also used for a couple of other things, like autoconfiguration and advertising routers.
By default VMs are allowed to send out router solicitation messages (to query
for a router), and to receive router advetisement packets. This allows them to
use stateless auto configuration. On the other hand VMs cannot advertise
themselves as routers unless the Allow Router Advertisement (radv: 1) option
is set.
As for the link local addresses required for NDP, there’s also an IP Filter
(ipfilter: 1) option which can be enabled which has the same effect as adding
an ipfilter-net* ipset for each of the VM’s network interfaces containing the
corresponding link local addresses. (See the
Standard IP set ipfilter-net* section for details.)