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Firewall (UFW) #107

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samsapti merged 3 commits from :main into main 2022-11-22 20:05:01 +00:00
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1
roles/ubuntu_base/tasks/base.yml
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@ -9,6 +9,7 @@
- apparmor - apparmor
- haveged - haveged
- mosh - mosh
- ufw
- srvadmin-all # Dell OpenManage - srvadmin-all # Dell OpenManage
- name: Install necessary packages via pip - name: Install necessary packages via pip

20
roles/ubuntu_base/tasks/firewall.yml Normal file
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@ -0,0 +1,20 @@
---
- name: Setup firewall with UFW
community.general.ufw:
state: enabled
policy: deny
- name: Allow necessary ports
community.general.ufw:
rule: allow
port: "{{ item }}"
samsapti marked this conversation as resolved
reynir commented 2022-11-12 18:48:25 +00:00
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Udp? Tcp? Both?

Udp? Tcp? Both?
samsapti commented 2022-11-13 13:07:16 +00:00
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Do any of the services need UDP? Otherwise I can set them all to allow TCP only.

Do any of the services need UDP? Otherwise I can set them all to allow TCP only.
reynir commented 2022-11-13 15:57:40 +00:00
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I think we may need UDP to receive responses to DNS requests. Otherwise I don't think we use UDP. My question was also what protocol(s) this covers.

I think we may need UDP to receive responses to DNS requests. Otherwise I don't think we use UDP. My question was also what protocol(s) this covers.
samsapti commented 2022-11-13 16:50:58 +00:00
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Default is both.

Default is both.
samsapti commented 2022-11-13 17:02:46 +00:00
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I think we may need UDP to receive responses to DNS requests.

No, firewall is only for blocking incoming requests. Responses to outgoing requests are not affected.

> I think we may need UDP to receive responses to DNS requests. No, firewall is only for blocking incoming requests. Responses to outgoing requests are not affected.
reynir commented 2022-11-13 20:05:09 +00:00
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Yes, but you need to listen for the response :-)

Yes, but you need to listen for the response :-)
samsapti commented 2022-11-13 20:51:18 +00:00
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Still, DNS requests work even if UFW blocks UDP, since it only blocks incoming requests. A DNS response is not a request ;)

Still, DNS requests work even if UFW blocks UDP, since it only blocks incoming _requests_. A DNS response is not a request ;)
reynir commented 2022-11-14 09:24:07 +00:00
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Well, UDP is connectionless and doesn't know about requests and responses. The reply is sent to the sender on the sending port. It may be that the rule generated by ufw tracks the state and allows replies, but it is not immediately obvious from these invocations.

For other UDP uses it may not be desirable: for example, if the datagrams are metrics reports we don't expect a reply and it would be undesirable to allow incoming packets in that case.

Well, UDP is connectionless and doesn't know about requests and responses. The reply is sent to the sender on the sending port. It may be that the rule generated by ufw tracks the state and allows replies, but it is not immediately obvious from these invocations. For other UDP uses it may not be desirable: for example, if the datagrams are metrics reports we don't expect a reply and it would be undesirable to allow incoming packets in that case.
samsapti commented 2022-11-14 16:03:43 +00:00
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You're right, perhaps I wasn't clear enough. Yes, Iptables/Nftables (which is UFW's backend(s)) tracks the state, and thus allows replies. It will only block clients trying to connect to the denied port on the host, even if a service is listening on the port (but not in the case of Docker described below). Unless you deny outgoing traffic, DNS lookups will work fine.

Also, I've never had problems with UFW blocking DNS lookups with this configuration.

You're right, perhaps I wasn't clear enough. Yes, Iptables/Nftables (which is UFW's backend(s)) tracks the state, and thus allows replies. It will only block clients trying to connect to the denied port on the host, even if a service is listening on the port (but not in the case of Docker described below). Unless you deny outgoing traffic, DNS lookups will work fine. Also, I've never had problems with UFW blocking DNS lookups with this configuration.
samsapti commented 2022-11-15 19:42:54 +00:00
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I've changed it such that it only allows TCP on the specified ports.

I've changed it such that it only allows TCP on the specified ports.
loop:
- 22 # Gitea SSH
- 80 # HTTP
- 443 # HTTPS
- 389 # OpenLDAP
- 636 # OpenLDAP
- 25 # Email
- 465 # Email
- 587 # Email
- 993 # Email
- 19022 # SSH

2
roles/ubuntu_base/tasks/main.yml
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@ -7,4 +7,6 @@
tags: [install-base-packages] tags: [install-base-packages]
- import_tasks: users.yml - import_tasks: users.yml
tags: [setup-users] tags: [setup-users]
- import_tasks: firewall.yml
tags: [setup-firewall]