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#1 2021-01-10 02:39:23

jfk
Member
Registered: 2017-12-11
Posts: 25

OpenVPN: port close while allowed in ufw

I'm trying to install OpenVPN on my Arch VPS. I used the default 1194 (udp) port which I allowed in ufw:

sudo ufw status
Status: active

To                         Action      From
--                         ------      ----
22                         ALLOW       Anywhere                  
1194/udp                   ALLOW       Anywhere                  
22 (v6)                    ALLOW       Anywhere (v6)             
1194/udp (v6)              ALLOW       Anywhere (v6)             

I also changed the DEFAULT_FORWARD_POLICY to "ACCEPT".

However, logs on the client side indicate the port is close, which is confirmed by nmap:

sudo nmap -sU localhost -p 1194

Starting Nmap 7.91 ( https://nmap.org ) at 2021-01-10 00:40 CET
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000071s latency).
Other addresses for localhost (not scanned): ::1
rDNS record for 127.0.0.1: localhost.localdomain

PORT     STATE  SERVICE
1194/udp closed openvpn

Nmap done: 1 IP address (1 host up) scanned in 0.19 seconds

My iptable:

sudo iptables -L
Chain INPUT (policy DROP)
target     prot opt source               destination         
ACCEPT     udp  --  anywhere             anywhere             udp dpt:openvpn
ACCEPT     all  --  anywhere             anywhere            
ufw-before-logging-input  all  --  anywhere             anywhere            
ufw-before-input  all  --  anywhere             anywhere            
ufw-after-input  all  --  anywhere             anywhere            
ufw-after-logging-input  all  --  anywhere             anywhere            
ufw-reject-input  all  --  anywhere             anywhere            
ufw-track-input  all  --  anywhere             anywhere            

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere            
ufw-before-logging-forward  all  --  anywhere             anywhere            
ufw-before-forward  all  --  anywhere             anywhere            
ufw-after-forward  all  --  anywhere             anywhere            
ufw-after-logging-forward  all  --  anywhere             anywhere            
ufw-reject-forward  all  --  anywhere             anywhere            
ufw-track-forward  all  --  anywhere             anywhere            

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
ufw-before-logging-output  all  --  anywhere             anywhere            
ufw-before-output  all  --  anywhere             anywhere            
ufw-after-output  all  --  anywhere             anywhere            
ufw-after-logging-output  all  --  anywhere             anywhere            
ufw-reject-output  all  --  anywhere             anywhere            
ufw-track-output  all  --  anywhere             anywhere            

Chain ufw-after-forward (1 references)
target     prot opt source               destination         

Chain ufw-after-input (1 references)
target     prot opt source               destination         
ufw-skip-to-policy-input  udp  --  anywhere             anywhere             udp dpt:netbios-ns
ufw-skip-to-policy-input  udp  --  anywhere             anywhere             udp dpt:netbios-dgm
ufw-skip-to-policy-input  tcp  --  anywhere             anywhere             tcp dpt:netbios-ssn
ufw-skip-to-policy-input  tcp  --  anywhere             anywhere             tcp dpt:microsoft-ds
ufw-skip-to-policy-input  udp  --  anywhere             anywhere             udp dpt:bootps
ufw-skip-to-policy-input  udp  --  anywhere             anywhere             udp dpt:bootpc
ufw-skip-to-policy-input  all  --  anywhere             anywhere             ADDRTYPE match dst-type BROADCAST

Chain ufw-after-logging-forward (1 references)
target     prot opt source               destination         

Chain ufw-after-logging-input (1 references)
target     prot opt source               destination         
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-after-logging-output (1 references)
target     prot opt source               destination         

Chain ufw-after-output (1 references)
target     prot opt source               destination         

Chain ufw-before-forward (1 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
ACCEPT     icmp --  anywhere             anywhere             icmp destination-unreachable
ACCEPT     icmp --  anywhere             anywhere             icmp time-exceeded
ACCEPT     icmp --  anywhere             anywhere             icmp parameter-problem
ACCEPT     icmp --  anywhere             anywhere             icmp echo-request
ufw-user-forward  all  --  anywhere             anywhere            

Chain ufw-before-input (1 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
ufw-logging-deny  all  --  anywhere             anywhere             ctstate INVALID
DROP       all  --  anywhere             anywhere             ctstate INVALID
ACCEPT     icmp --  anywhere             anywhere             icmp destination-unreachable
ACCEPT     icmp --  anywhere             anywhere             icmp time-exceeded
ACCEPT     icmp --  anywhere             anywhere             icmp parameter-problem
ACCEPT     icmp --  anywhere             anywhere             icmp echo-request
ACCEPT     udp  --  anywhere             anywhere             udp spt:bootps dpt:bootpc
ufw-not-local  all  --  anywhere             anywhere            
ACCEPT     udp  --  anywhere             224.0.0.251          udp dpt:mdns
ACCEPT     udp  --  anywhere             239.255.255.250      udp dpt:ssdp
ufw-user-input  all  --  anywhere             anywhere            

Chain ufw-before-logging-forward (1 references)
target     prot opt source               destination         

Chain ufw-before-logging-input (1 references)
target     prot opt source               destination         

Chain ufw-before-logging-output (1 references)
target     prot opt source               destination         

Chain ufw-before-output (1 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
ufw-user-output  all  --  anywhere             anywhere            

Chain ufw-logging-allow (0 references)
target     prot opt source               destination         
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW ALLOW] "

Chain ufw-logging-deny (2 references)
target     prot opt source               destination         
RETURN     all  --  anywhere             anywhere             ctstate INVALID limit: avg 3/min burst 10
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-not-local (1 references)
target     prot opt source               destination         
RETURN     all  --  anywhere             anywhere             ADDRTYPE match dst-type LOCAL
RETURN     all  --  anywhere             anywhere             ADDRTYPE match dst-type MULTICAST
RETURN     all  --  anywhere             anywhere             ADDRTYPE match dst-type BROADCAST
ufw-logging-deny  all  --  anywhere             anywhere             limit: avg 3/min burst 10
DROP       all  --  anywhere             anywhere            

Chain ufw-reject-forward (1 references)
target     prot opt source               destination         

Chain ufw-reject-input (1 references)
target     prot opt source               destination         

Chain ufw-reject-output (1 references)
target     prot opt source               destination         

Chain ufw-skip-to-policy-forward (0 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            

Chain ufw-skip-to-policy-input (7 references)
target     prot opt source               destination         
DROP       all  --  anywhere             anywhere            

Chain ufw-skip-to-policy-output (0 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            

Chain ufw-track-forward (1 references)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere             ctstate NEW
ACCEPT     udp  --  anywhere             anywhere             ctstate NEW

Chain ufw-track-input (1 references)
target     prot opt source               destination         

Chain ufw-track-output (1 references)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere             ctstate NEW
ACCEPT     udp  --  anywhere             anywhere             ctstate NEW

Chain ufw-user-forward (1 references)
target     prot opt source               destination         

Chain ufw-user-input (1 references)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh
ACCEPT     udp  --  anywhere             anywhere             udp dpt:ssh
ACCEPT     udp  --  anywhere             anywhere             udp dpt:openvpn

Chain ufw-user-limit (0 references)
target     prot opt source               destination         
LOG        all  --  anywhere             anywhere             limit: avg 3/min burst 5 LOG level warning prefix "[UFW LIMIT BLOCK] "
REJECT     all  --  anywhere             anywhere             reject-with icmp-port-unreachable

Chain ufw-user-limit-accept (0 references)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            

Chain ufw-user-logging-forward (0 references)
target     prot opt source               destination         

Chain ufw-user-logging-input (0 references)
target     prot opt source               destination         

Chain ufw-user-logging-output (0 references)
target     prot opt source               destination         

Chain ufw-user-output (1 references)
target     prot opt source               destination    

What am I missing?

Last edited by jfk (2021-01-10 02:59:23)

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#2 2021-01-10 07:36:06

frostschutz
Member
Registered: 2013-11-15
Posts: 1,031

Re: OpenVPN: port close while allowed in ufw

Is openvpn running at all? Does it show up in `ss -uln`?

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#3 2021-01-11 00:07:35

jfk
Member
Registered: 2017-12-11
Posts: 25

Re: OpenVPN: port close while allowed in ufw

Thank you, here is what happened. I tested the VPN server with that command:

sudo openvpn /etc/openvpn/server/server.conf

As it worked, I enabled the service (without starting it since I was to reboot). Here I tested the client and got this "port close" with nmap. And it appears, as you suggested, that there is an issue with systemd since

sudo systemctl start openvpn-server@server

gives me

Job for openvpn-server@server.service failed because the control process exited with error code.
See "systemctl status openvpn-server@server.service" and "journalctl -xe" for details.

More refined logs tell me that systemd cannot open the config file for lack of proper permissions.

Indeed, my /etc/openvpn/server/ files were all owned by root and openvpn systemd service definition require openvpn as user.

chown openvpn:network /etc/openvpn/server/*

did the trick.

Special thanks to Tootea: https://unix.stackexchange.com/question … md-on-arch

Last edited by jfk (2021-01-11 16:41:41)

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