3 posts tagged with "firewall"

Anvil Secure recently published a post and whitepaper covering conntrack flaws that are common with many linux routers and linux "multihomed" devices. In this post we'll cover SPR, how our process mitigated the highest risk vulnerabilities, how we fixed the rest and other improvements we're making to be resilient against attacks like this in the future.

Overview​

Conntrack is part of Linux Netfilter and is an integral part of a stateful firewall for allowing Network Address Translation on a network. A router uses it to allow clients to establish connections through the uplink interfaces.

Anvil Secure published details on how devices often fail to lock down their firewalls correctly since Conntrack operates at layer 3. External attackers that are one hop away can abuse this to spoof IP addresses and send traffic to internal interfaces on devices and routers for an established connection managed with conntrack. For most of our users, this limits the attack to compromised or hostile ISP providers, which is an uncommon (but not unheard of attack vector). However, since the WiFi Pod can be used as a travel router, it's important to us that they are can withstand being attached to a hostile network.

The riskiest of the attacks happen to not affect SPR.

Here is an overview of how SPR helps defend users against attacks with multicast services. The capabilities let SPR users enjoy the benefits of multicast while also being able to constrain the attack surfaces to trusted devices only.

Overview​

1. Every WiFi device is placed on its own VLAN and has a unique Group Key blocking Direct Station to Station Multicast traffic
2. We employ a configurable multicast proxy to relay whitelisted multicast services. It support mDNS and SSDP by default for ease of use. The multicast proxy and mDNS & SSDP relaying can be completely turned off though.
3. We also support setting a tag for multicast services to limit relaying traffic to only devices with the same tag applied.

Envision a homelab scenario with a feature-rich router that's suitable as a container host with storage and memory. Locking down the router's container network policy is surprisingly difficult to set up and manage.

SPR makes it easy with secure by default network controls. Instead of worrying about IP ranges and interfaces, join the interfaces to the groups of devices they can communicate with and set internet access policy.