In my DigitalOcean (DO) droplet I installed this image: Ubuntu Docker 17.12.0~ce on 16.04 (which is available on ** DO website > droplet> destroy> rebuild droplet**) , in ssh (after user configuration), I run
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw enable
sudo ufw status verbose
and get:
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), allow (routed)
New profiles: skip
To Action From
-- ------ ----
22 LIMIT IN Anywhere
2375/tcp ALLOW IN Anywhere
2376/tcp ALLOW IN Anywhere
22 (v6) LIMIT IN Anywhere (v6)
2375/tcp (v6) ALLOW IN Anywhere (v6)
2376/tcp (v6) ALLOW IN Anywhere (v6)
As you see, I don't allow any connections on port 80 (http). Ok to test that firewall really works I run following docker:
sudo docker run -d -p 80:80 -e ENABLE_IPV6=true -v /var/run/docker.sock:/tmp/docker.sock:ro jwilder/nginx-proxy:alpine
But when I go to chrome and type my droplet IP I see nginx response (!!!)
I try this also for Ubuntu 17 image (with docker installation by hand) but still get the same problem.
Conclusion: ufw firewall doesn't work at all in Ubuntu
Question: how to configure ufw/Ubuntu to fix this problem?
Docker and UFW don't work together too well as they both modify iptables but there's a way to fix this. You'll need to configure Docker to not use iptables. Add
DOCKER_OPTS="--iptables=false"
to /etc/default/docker and restart your host (or restart the Docker daemon and UFW).
These two links have a lot more information about the issue:
https://blog.viktorpetersson.com/2014/11/03/the-dangers-of-ufw-docker.html
https://www.techrepublic.com/article/how-to-fix-the-docker-and-ufw-security-flaw/
Doing this DOCKER_OPTS="--iptables=false" didn't work for me.
I suggest to add these lines at the end of /etc/ufw/after.rules
# BEGIN UFW AND DOCKER
*filter
:ufw-user-forward - [0:0]
:DOCKER-USER - [0:0]
-A DOCKER-USER -j RETURN -s 10.0.0.0/8
-A DOCKER-USER -j RETURN -s 172.16.0.0/12
-A DOCKER-USER -j RETURN -s 192.168.0.0/16
-A DOCKER-USER -p udp -m udp --sport 53 --dport 1024:65535 -j RETURN
-A DOCKER-USER -j ufw-user-forward
-A DOCKER-USER -j DROP -p tcp -m tcp --tcp-flags FIN,SYN,RST,ACK SYN -d 192.168.0.0/16
-A DOCKER-USER -j DROP -p tcp -m tcp --tcp-flags FIN,SYN,RST,ACK SYN -d 10.0.0.0/8
-A DOCKER-USER -j DROP -p tcp -m tcp --tcp-flags FIN,SYN,RST,ACK SYN -d 172.16.0.0/12
-A DOCKER-USER -j DROP -p udp -m udp --dport 0:32767 -d 192.168.0.0/16
-A DOCKER-USER -j DROP -p udp -m udp --dport 0:32767 -d 10.0.0.0/8
-A DOCKER-USER -j DROP -p udp -m udp --dport 0:32767 -d 172.16.0.0/12
-A DOCKER-USER -j RETURN
COMMIT
# END UFW AND DOCKER
This is the source https://github.com/chaifeng/ufw-docker
Alternative solution: Drop UFW and instead use Network Firewall available in digital ocean control panel (on website).
来源：https://stackoverflow.com/questions/49549834/ufw-firewall-is-not-working-on-ubuntu-in-digitalocean