Setting up IPS/inline for Linux ================================ Setting up IPS with Netfilter ----------------------------- In this guide, we'll discuss how to work with Suricata in layer3 `inline mode` using ``iptables``. First, start by compiling Suricata with NFQ support. For instructions see `Ubuntu Installation `_. For more information about NFQ and ``iptables``, see :ref:`suricata-yaml-nfq`. To check if you have NFQ enabled in your Suricata build, enter the following command: :: suricata --build-info and make sure that NFQ is listed in the output. To run Suricata with the NFQ mode, you have to make use of the ``-q`` option. This option tells Suricata which queue numbers it should use. :: sudo suricata -c /etc/suricata/suricata.yaml -q 0 Iptables configuration ~~~~~~~~~~~~~~~~~~~~~~ First of all, it is important to know which traffic you would like to send to Suricata. There are two choices: 1. Traffic that passes your computer 2. Traffic that is generated by your computer. .. image:: setting-up-ipsinline-for-linux/IPtables.png .. image:: setting-up-ipsinline-for-linux/iptables1.png If Suricata is running on a gateway and is meant to protect the computers behind that gateway you are dealing with the first scenario: *forward_ing* . If Suricata has to protect the computer it is running on, you are dealing with the second scenario: *host* (see drawing 2). These two ways of using Suricata can also be combined. The easiest rule in case of the gateway-scenario to send traffic to Suricata is: :: sudo iptables -I FORWARD -j NFQUEUE In this case, all forwarded traffic goes to Suricata. In case of the host situation, these are the two most simple ``iptables`` rules; :: sudo iptables -I INPUT -j NFQUEUE sudo iptables -I OUTPUT -j NFQUEUE It is possible to set a queue number. If you do not, the queue number will be 0 by default. Imagine you want Suricata to check for example just TCP traffic, or all incoming traffic on port 80, or all traffic on destination-port 80, you can do so like this: :: sudo iptables -I INPUT -p tcp -j NFQUEUE sudo iptables -I OUTPUT -p tcp -j NFQUEUE In this case, Suricata checks just TCP traffic. :: sudo iptables -I INPUT -p tcp --sport 80 -j NFQUEUE sudo iptables -I OUTPUT -p tcp --dport 80 -j NFQUEUE In this example, Suricata checks all packets for outgoing connections to port 80. .. image:: setting-up-ipsinline-for-linux/iptables2.png .. image:: setting-up-ipsinline-for-linux/IPtables3.png To see if you have set your ``iptables`` rules correct make sure Suricata is running and enter: :: sudo iptables -vnL In the example you can see if packets are being logged. .. image:: setting-up-ipsinline-for-linux/iptables_vnL.png This description of the use of ``iptables`` is the way to use it with IPv4. To use it with IPv6 all previous mentioned commands have to start with ``ip6tables``. It is also possible to let Suricata check both kinds of traffic. There is also a way to use ``iptables`` with multiple networks (and interface cards). Example: .. image:: setting-up-ipsinline-for-linux/iptables4.png :: sudo iptables -I FORWARD -i eth0 -o eth1 -j NFQUEUE sudo iptables -I FORWARD -i eth1 -o eth0 -j NFQUEUE The options ``-i`` (input) ``-o`` (output) can be combined with all previous mentioned options. If you would stop Suricata and use internet, the traffic will not come through. To make internet work correctly, first delete all ``iptables`` rules. To erase all ``iptables`` rules, enter: :: sudo iptables -F NFtables configuration ~~~~~~~~~~~~~~~~~~~~~~ The NFtables configuration is straight forward and allows mixing firewall rules with IPS. The concept is to create a dedicated chain for the IPS that will be evaluated after the firewalling rule. If your main table is named `filter` it can be created like so:: nft> add chain filter IPS { type filter hook forward priority 10;} To send all forwarded packets to Suricata one can use :: nft> add rule filter IPS queue To only do it for packets exchanged between eth0 and eth1 :: nft> add rule filter IPS iif eth0 oif eth1 queue nft> add rule filter IPS iif eth1 oif eth0 queue NFQUEUE advanced options ~~~~~~~~~~~~~~~~~~~~~~~~ The NFQUEUE mechanism supports some interesting options. The ``nftables`` configuration will be shown there but the features are also available in ``iptables``. The full syntax of the queuing mechanism is as follows:: nft add rule filter IPS queue num 3-5 options fanout,bypass This rule sends matching packets to 3 load-balanced queues starting at 3 and ending at 5. To get the packets in Suricata with this setup, you need to specify multiple queues on command line: :: suricata -q 3 -q 4 -q 5 `fanout` and `bypass` are the two available options: - `fanout`: When used together with load balancing, this will use the CPU ID instead of connection hash as an index to map packets to the queues. The idea is that you can improve performance if there’s one queue per CPU. This requires total with a number of queues superior to 1 to be specified. - `bypass`: By default, if no userspace program is listening on an Netfilter queue, then all packets that are to be queued are dropped. When this option is used, the queue rule behaves like ACCEPT if there is no program listening, and the packet will move on to the next table. The `bypass` option can be used to avoid downtime of link when Suricata is not running but this also means that the blocking feature will not be present. Setting up IPS at Layer 2 ------------------------- .. _afp-ips-l2-mode: AF_PACKET IPS mode ~~~~~~~~~~~~~~~~~~ AF_PACKET capture method is supporting a IPS/Tap mode. In this mode, you just need the interfaces to be up. Suricata will take care of copying the packets from one interface to the other. No ``iptables`` or ``nftables`` configuration is necessary. You need to dedicate two network interfaces for this mode. The configuration is made via configuration variable available in the description of an AF_PACKET interface. For example, the following configuration will create a Suricata acting as IPS between interface ``eth0`` and ``eth1``: :: af-packet: - interface: eth0 threads: 1 defrag: no cluster-type: cluster_flow cluster-id: 98 copy-mode: ips copy-iface: eth1 buffer-size: 64535 use-mmap: yes - interface: eth1 threads: 1 cluster-id: 97 defrag: no cluster-type: cluster_flow copy-mode: ips copy-iface: eth0 buffer-size: 64535 use-mmap: yes This is a basic af-packet configuration using two interfaces. Interface ``eth0`` will copy all received packets to ``eth1`` because of the `copy-*` configuration variable :: copy-mode: ips copy-iface: eth1 The configuration on ``eth1`` is symmetric :: copy-mode: ips copy-iface: eth0 There are some important points to consider when setting up this mode: - The implementation of this mode is dependent of the zero copy mode of AF_PACKET. Thus you need to set `use-mmap` to `yes` on both interface. - MTU on both interfaces have to be equal: the copy from one interface to the other is direct and packets bigger then the MTU will be dropped by kernel. - Set different values of `cluster-id` on both interfaces to avoid conflict. - Any network card offloading creating bigger then physical layer datagram (like GRO, LRO, TSO) will result in dropped packets as the transmit path can not handle them. - Set `stream.inline` to `auto` or `yes` so Suricata switches to blocking mode. The `copy-mode` variable can take the following values: - `ips`: the drop keyword is honored and matching packets are dropped. - `tap`: no drop occurs, Suricata acts as a bridge Some specific care must be taken to scale the capture method on multiple threads. As we can't use defrag that will generate too big frames, the in kernel load balancing will not be correct: the IP-only fragment will not reach the same thread as the full featured packet of the same flow because the port information will not be present. A solution is to use eBPF load balancing to get an IP pair load balancing without fragmentation. The AF_PACKET IPS Configuration using multiple threads and eBPF load balancing looks like the following: :: af-packet: - interface: eth0 threads: 16 defrag: no cluster-type: cluster_ebpf ebpf-lb-file: /usr/libexec/suricata/ebpf/lb.bpf cluster-id: 98 copy-mode: ips copy-iface: eth1 buffer-size: 64535 use-mmap: yes - interface: eth1 threads: 16 cluster-id: 97 defrag: no cluster-type: cluster_ebpf ebpf-lb-file: /usr/libexec/suricata/ebpf/lb.bpf copy-mode: ips copy-iface: eth0 buffer-size: 64535 use-mmap: yes The eBPF file ``/usr/libexec/suricata/ebpf/lb.bpf`` may not be present on disk. See :ref:`ebpf-xdp` for more information. DPDK IPS mode ~~~~~~~~~~~~~ In the same way as you would configure AF_PACKET IPS mode, you can configure the DPDK capture module. Prior to starting with IPS (inline) setup, it is recommended to go over :ref:`dpdk-capture-module` manual page to understand the setup essentials. DPDK IPS mode, similarly to AF-Packet, uses two interfaces. Packets received on the first network interface (``0000:3b:00.1``) are transmitted by the second network interface (``0000:3b:00.0``) and similarly, packets received on the second interface (``0000:3b:00.0``) are transmitted by the first interface (``0000:3b:00.1``). Packets are not altered in any way in this mode. The following configuration snippet configures Suricata DPDK IPS mode between two NICs: :: dpdk: eal-params: proc-type: primary interfaces: - interface: 0000:3b:00.1 threads: 4 promisc: true multicast: true checksum-checks: true checksum-checks-offload: true mempool-size: 262143 mempool-cache-size: 511 rx-descriptors: 4096 tx-descriptors: 4096 copy-mode: ips copy-iface: 0000:3b:00.0 mtu: 3000 - interface: 0000:3b:00.0 threads: 4 promisc: true multicast: true checksum-checks: true checksum-checks-offload: true mempool-size: 262143 mempool-cache-size: 511 rx-descriptors: 4096 tx-descriptors: 4096 copy-mode: ips copy-iface: 0000:3b:00.1 mtu: 3000 The previous DPDK configuration snippet outlines several things to consider: - ``copy-mode`` - see Section :ref:`afp-ips-l2-mode` for more details. - ``copy-iface`` - see Section :ref:`afp-ips-l2-mode` for more details. - ``threads`` - all interface entries must have their thread count configured and paired/connected interfaces must be configured with the same amount of threads. - ``mtu`` - MTU must be the same on both paired interfaces. DPDK capture module also requires having CPU affinity set in the configuration file. For the best performance, every Suricata worker should be pinned to a separate CPU core that is not shared with any other Suricata thread (e.g. management threads). The following snippet shows a possible :ref:`suricata-yaml-threading` configuration set-up for DPDK IPS mode. :: threading: set-cpu-affinity: yes cpu-affinity: - management-cpu-set: cpu: [ 0 ] - worker-cpu-set: cpu: [ 2,4,6,8,10,12,14,16 ] Netmap IPS mode ~~~~~~~~~~~~~~~ Using Netmap to support IPS requires setting up pairs of interfaces; packets are received on one interface within the pair, inspected by Suricata, and transmitted on the other paired interface. You can use native or host stack mode; host stack mode is used when the interface name contains the ``^`` character, e.g, ``enp6s0f0^``. host stack mode does not require multiple physical network interfaces. Netmap Host Stack Mode ^^^^^^^^^^^^^^^^^^^^^^ Netmap's host stack mode allows packets that flow through Suricata to be used with other host OS applications, e.g., a firewall or similar. Additionally, host stack mode allows traffic to be received and transmitted on one network interface card. With host stack mode, Netmap establishes a pair of host stack mode rings (one each for RX and TX). Packets pass through the host operating system network protocol stack. Ingress network packets flow from the network interface card to the network protocol stack and then into the host stack mode rings. Outbound packets flow from the host stack mode rings to the network protocol stack and finally, to the network interface card. Suricata receives packets from the host stack mode rings and, in IPS mode, places packets to be transmitted into the host stack mode rings. Packets transmitted by Suricata into the host stack mode rings are available for other host OS applications. Paired network interfaces are specified in the ``netmap`` configuration section. For example, the following configuration will create a Suricata acting as IPS between interface ``enp6s0f0`` and ``enp6s0f1`` :: netmap: - interface: enp6s0f0 threads: auto copy-mode: ips copy-iface: enp6s0f1 - interface: enp6s0f1 threads: auto copy-mode: ips copy-iface: enp6s0f0 You can specify the ``threads`` value; the default value of ``auto`` will create a thread for each queue supported by the NIC; restrict the thread count by specifying a value, e.g., ``threads: 1`` This is a basic netmap configuration using two interfaces. Suricata will copy packets between interfaces ``enp6s0f0`` and ``en60sf1`` because of the `copy-*` configuration variable in interface's ``enp6s0f0`` configuration :: copy-mode: ips copy-iface: enp6s0f1 The configuration on ``enp6s0f1`` is symmetric :: copy-mode: ips copy-iface: enp6s0f0 The host stack mode feature of Netmap can be used. host stack mode doesn't require a second network interface. This example demonstrates host stack mode with a single physical network interface ``enp6s0f01`` :: - interface: enp60s0f0 copy-mode: ips copy-iface: enp6s0f0^ The configuration on ``enp6s0f0^`` is symmetric :: - interface: enp60s0f0^ copy-mode: ips copy-iface: enp6s0f0 Suricata will use zero-copy mode when the runmode is ``workers``. There are some important points to consider when setting up this mode: - Any network card offloading creating bigger then physical layer datagram (like GRO, LRO, TSO) will result in dropped packets as the transmit path can not handle them. - Set `stream.inline` to `auto` or `yes` so Suricata switches to blocking mode. The default value is `auto`. The `copy-mode` variable can take the following values: - `ips`: the drop keyword is honored and matching packets are dropped. - `tap`: no drop occurs, Suricata acts as a bridge