UFW Allow ICMP (ping) Traffic

https://askubuntu.com/questions/6995/how-to-enable-ufw-firewall-to-allow-icmp-response

Open up the UFW before.rules config file

vi /etc/ufw/before.rules 

And make sure you have these rules in it

# ok icmp codes for INPUT
-A ufw-before-input -p icmp --icmp-type destination-unreachable -j ACCEPT
-A ufw-before-input -p icmp --icmp-type time-exceeded -j ACCEPT
-A ufw-before-input -p icmp --icmp-type parameter-problem -j ACCEPT
-A ufw-before-input -p icmp --icmp-type echo-request -j ACCEPT
# ok icmp code for FORWARD
-A ufw-before-forward -p icmp --icmp-type destination-unreachable -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type time-exceeded -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type parameter-problem -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type echo-request -j ACCEPT

Configure UFW Firewall on Ubuntu

Show status

sudo ufw status

Disable UFW Service

sudo systemctl stop ufw && sudo systemctl disable ufw

Stop UFW Service

sudo systemctl stop ufw

Start UFW service

sudo systemctl stop ufw

Enable UFW

sudo ufw enable

Allow SSH

sudo ufw allow 22/tcp

Show status

sudo ufw status numbered

Example output

sudo ufw status numbered
Status: active
To            Action   From 
--            ------   ----
[1] 3478/udp  ALLOW IN  Anywhere
[2] 5514/udp  ALLOW IN  Anywhere
[3] 8080/tcp  ALLOW IN  Anywhere
[4] 8443/tcp  ALLOW IN  Anywhere
[5] 8880/tcp  ALLOW IN  Anywhere
[6] 8843/tcp  ALLOW IN  Anywhere
[7] 6789/tcp  ALLOW IN  Anywhere
[8] 27117/tcp ALLOW IN  Anywhere
[9] 22/tcp    ALLOW IN  Anywhere

Delete rule

You need to know the number of the rule you want to delete. Replace number with the number of the rule from the status command

sudo ufw delete number

Reset rules

sudo ufw reset

WHM/cPanel Firewall

Had a weird issue where a certain address was unable to access the cpanel server, but it was intermittent with it working some times, but failing at other times.

Ended up being the firewall on the WHM server blocking that particular IP address due to failed log in attempts.

Check the status of LFD (Login Failure Daemon)

systemctl status lfd

How do I know which IP’s are being blocked?

Check the logs, dmesg or tail /var/log/messages

[1122639.674605] Firewall: UDP_IN Blocked IN=eth0 OUT= MAC=8e:23:f5:16:a6:b1:cc:51:54:6a:2e:ea:14:00 SRC=72.211.105.113 DST=192.168.1.12 LEN=64 TOS=0x00 PREC=0x00 TTL=246 ID=40014 PROTO=UDP SPT=9307 DPT=161 LEN=44
[1122646.728510] Firewall: TCP_IN Blocked IN=eth0 OUT= MAC=8e:23:f5:16:a6:b1:cc:51:54:6a:2e:ea:14:00 SRC=198.199.98.83 DST=192.168.1.12 LEN=40 TOS=0x00 PREC=0x00 TTL=244 ID=54321 PROTO=TCP SPT=57522 DPT=15672 WINDOW=65535 RES=0x00 SYN URGP=0

CSF keeps a file with addresses to deny in “/etc/csf/csf.deny” Also nice that if gives you a little bit of info on why it was blocked.

# grep -r "192.168.1.21" /etc/csf/csf.deny
192.168.1.21 # lfd: (pop3d) Failed POP3 login from 192.168.1.21 (US/United States/-): 10 in the last 3600 secs - Tue Jun 20 11:36:15 2020

You can also dump all of the rule in iptables with

iptables --list | egrep "192.168.1.21"

Change 192.168.1.21 with the IP you are looking for

Whitelist IP Addresses

Open up /etc/csf/csf.allow with a text editor and add the IP to the bottom of the file.

or add the IP address to the end of the file with the following command. Replace 192.168.1.21 with the IP address you want to whitelist.

echo "192.168.1.21" >> /etc/csf/csf.allow

You can also do all of this from the WHM web interface “Plugins -> ConfigServer Security & Firewall”

Further reading

https://documentation.cpanel.net/display/CKB/How+to+Configure+Your+Firewall+for+cPanel+Services

Mikrotik RouterOS – “drop all from WAN not DSTNATed”

The default DSTNATed firewall rule keeps traffic from the WAN accessing LAN side IP addresses.

More info here

Printing the rules on a router with the default config should show the following.

;;; defconf: drop all from WAN not DSTNATed
chain=forward action=drop connection-nat-state=!dstnat in-interface=ether1

If you are wanting to add the rule to a router, you can copy and past the following command. Replace in-interface=ether with your in interface.

/ip firewall add action=drop chain=forward comment=\ "defconf: drop all from WAN not DSTNATed" connection-nat-state=!dstnat in-interface=ether1

Check if Mikrotik is an Open DNS Resolver

https://www.openresolver.com

You can test if a router is acting as an open DNS resolver by running the following command from a Linux terminal. If you need to install dig, refer to here for Debian/Ubuntu and here for RPM/CentOS/Fedora Distros.

Replace 192.168.88.1 with the host you want to test against.

dig +short test.openresolver.com TXT @192.168.88.1

If you receive the following

"open-resolver-detected"

The router is acting as an open resolver.

If you get

;; connection timed out; no servers could be reached

Then you are unable to use that router to resolve DNS.

Example running the command against a Mikrotik router with Remote DNS turned on Then adding a firewall rule to block unwanted request.

bob@localhost:~$ dig +short test.openresolver.com TXT @192.168.88.1
"open-resolver-detected"
bob@localhost:~$ 
<<-- Put firewall rule on router -->>
bob@localhost:~$ dig +short test.openresolver.com TXT @192.168.88.1
;; connection timed out; no servers could be reached  
bob@localhost:~$ 

Extra notes

If you have firewall rules allowing your IP address to use the router for DNS, then the above command to test will show it as an Open Resolver. Ideally you would want a connection from the outside to test. Or you can use this link and test it from the website. https://www.openresolver.com

FreeBSD 7 Allow IP range to SSH to server – IPF

Edit IPF config

vi /etc/ipf.rules

Hit “i” to enter insert mode and add the following to allow SSH from the 192.168.0.0/24 ip range. Change range if needed.

pass    in     quick on bge0 proto tcp from 192.168.0.0/24 to any port = 22 flags S keep state

Save and exit the file by hitting “Esc” then typing “:wq” followed by enter.

And start IPF with new rules

ipf -Fa -f /etc/ipf.rules

cPanel unable to access locally hosted domains

Check and verify that DNS is not being blocked upstream by a firewall. Behavior is weird, the server can get out to the internet, access to the servers IP address is available, but can’t ping domains that are locally hosted. Are also unable to ping the domains from the internet in.

To resolve the issue either disable the DNS firewall rules, or better yet add some rules to allow access to the cPanel server.

semanage Allow and Delete ports in CentOS

The commands are for CentOS, but should work on Fedora and RedHat.

If semanage is not installed refer to here.

You would typically use this along with the systems firewall to allow a port through.  Guide for firewalld and iptables.  If you change it in the firewall and fail to add/edit it in semanage you can potentially get weird behavior like sshd not wanting to start after changing the port.

Add port

semanage port -a -t ssh_port_t -p tcp 2222

The above command allows the sshd service to start, using port 2222.

List allowed ports

semanage port -l

You can use grep to filter the results

Example:

[admin@localhost ~]# semanage port -l | grep ssh
ssh_port_t tcp 2222, 22
[admin@localhost ~]#

Delete port

semanage port -d -p tcp 2222

Other examples

Allow SNMP

semanage port -a -t snmp_port_t -p udp 161

 

Allow KDE Connect through firewall

Firewalld

sudo firewall-cmd --zone=public --permanent --add-port=1714-1764/tcp
sudo firewall-cmd --zone=public --permanent --add-port=1714-1764/udp
sudo systemctl restart firewalld.service

UFW firewall

sudo ufw allow 1714:1764/udp
sudo ufw allow 1714:1764/tcp
sudo ufw reload

More information https://community.kde.org/KDEConnect