This repository provides the janeczku/redwall image.

RedWall (Redis Firewall) is slim Alpine Linux based image acting as a firewall agent for managing iptables rules on a single server or whole clusters. The port- or IP-based rules are centrally stored in a Redis database and updates are dynamically applied to all hosts running the RedWall image.

Filter logic

In order to co-exist with the firewall rules created by the Docker daemon, RedWall inserts a jump rule at the top of the INPUT and FORWARD chains. Traffic arriving on the public interface is processed in the redwall-main user chain. Traffic not matching any of the port- or IP-based rules is dropped.

1. Setup a Redis instance accessible by the hosts that will run the RedWall Docker image
2. Enable Redis keyspace events notifications by including notify-keyspace-events Ks in redis.conf or by typing CONFIG SET notify-keyspace-events Ks in redis-cli.
3. Disable any existing firewall daemon on the hosts (e.g. UFW)

RedWall is designed to only filter traffic arriving on the specified public interface. This would normally be eth0. The public interface can be configured by either passing an environmental variable to the RedWall Docker container or by storing it in the Redis database in the key firewall:<security-group>:interface.

Configure the interface name in the database:

redis-cli SET firewall:<security-group>:interface eth0

Configure the interface name locally for a server:

docker run --env PUBLIC_IFACE=eth1 (...)

Port-based rules are stored in the database as members of the set firewall:<security-group>:services formatted as label:protocol:port.

Example Allow public access to a Nginx instance running on port 80/443:

redis-cli SADD firewall:<security-group>:services http:tcp:80
redis-cli SADD firewall:<security-group>:services https:tcp:443

Traffic matching an IPv4 address or network entry in the firewall:<security-group>:whitelist set will be allowed open access to all ports on the server. Values can be plain IPv4 addresses or networks (with /mask).

Example Allow access to all ports for IP address 208.208.208.208:

redis-cli SADD firewall:<security-group>:whitelist 208.208.208.208

Example Allow access to all ports for network 208.208.208.1/24:

redis-cli SADD firewall:<security-group>:whitelist 208.208.208.1/24

docker run -d --name redwall \
--cap-add=NET_ADMIN --net=host \
--env REDIS_HOST=*REPLACE_WITH_REDIS_IP:PORT* \
--env PUBLIC_IFACE=eth0 \
--restart on-failure janeczku/redwall

Alternatively, if your version of Docker doesn't support the --cap-add switch:

docker run -d --name redwall \
--privileged --net=host \
--env REDIS_HOST=*REPLACE_WITH_REDIS_IP:PORT*
--env PUBLIC_IFACE=eth0 \
--restart on-failure janeczku/redwall

REDIS_HOST
Default: REDIS_HOST=
The address of the Redis instance as ip:port.

PUBLIC_IFACE
Default: PUBLIC_IFACE=
The name of the public interface on the server. This is the interface that will be firewalled.

SECURITY_GROUP
Default: SECURITY_GROUP=default
The name of the firewall security group from which rules are applied

REDIS_PASS
Default: REDIS_PASS=
The password for a password-protected Redis instance. Leave empty to disable password-authentication.

FILTER_DOCKER
Default: FILTER_DOCKER=TRUE
Set to FALSE to disable filtering docker container network (FORWARD chain)

ALLOW_SSH
Default: ALLOW_SSH=TRUE
Allow public access to SSH (port 22). Set to FALSE only if you know what you are doing.

LIMIT_SSH_ATTACKS
Default: LIMIT_SSH_ATTACKS=FALSE
Detect and rate-limit SSH brute-force attacks. Set to TRUE to enable.

REDWALL_DEBUG
Default: REDWALL_DEBUG=FALSE
Set to TRUE to enable debug log (run docker logs redwall to inspect the log)