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DDoS attacks OpenVPN on Pfsense

Scheduled Pinned Locked Moved Firewalling
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  • J
    johnpoz LAYER 8 Global Moderator @leungda
    last edited by johnpoz Sep 10, 2018, 3:05 PM Sep 10, 2018, 3:04 PM

    @leungda said in DDoS attacks OpenVPN on Pfsense:

    I can see the IP but I have no idea how to block it.

    So its just 1 IP? 10, 100, 10,000 different IPs? If you don't want specific IPs to be able to attempt a connection to your openvpn server port. This can be blocked by a simple rule above the wan rule that allows access to your openvpn port.

    You can use whole network blocks if coming from large number of IPs in a whole block.. You could use pfblocker to easy assign blocks to whole ranges of IPs used from a specific country, etc.

    Can you post some example of IPs that you would like to block.. Them filling up your number of openvpn connections you allow for is a quite different than a volumetric attack filling up your pipe..

    You sure its not just a configured client of yours trying to connect and failing, so it just continues to try and try and try?

    An intelligent man is sometimes forced to be drunk to spend time with his fools
    If you get confused: Listen to the Music Play
    Please don't Chat/PM me for help, unless mod related
    SG-4860 24.11 | Lab VMs 2.8, 24.11

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    • L
      leungda
      last edited by Sep 10, 2018, 5:28 PM

      It is an IPv4 address and yes, it is what I am doing is limited all known IPs to access OpenVPN.

      I will try to unblock the IP. After I see the IP address, I will post a screenshot.

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      • N
        netblues
        last edited by Sep 10, 2018, 6:35 PM

        Are you using a static tls key?
        Quoting from pfsense configuration screen

        A TLS key enhances security of an OpenVPN connection by requiring both parties >to have a common key before a peer can perform a TLS handshake. This layer of HMAC authentication allows control channel packets without the proper key to be dropped, protecting the peers from attack or unauthorized connections.The TLS Key does not have any effect on tunnel data.

        Puts much less strain on the box and you don't have to administer ip's anymore
        Just an idea.

        D 1 Reply Last reply Sep 10, 2018, 6:56 PM Reply Quote 0
        • K
          KOM
          last edited by Sep 10, 2018, 6:48 PM

          I don't understand. I've been running OpenVPN for years now, and I've never had any ghost connections tying everything up. I'm being scanned and probed just as much as everyone else. Nothing ever connects to it except for valid users. Does this happen to anyone else? In all my years here, I've never heard of a similar complaint. Is this actually a real problem?

          L G 2 Replies Last reply Sep 10, 2018, 6:53 PM Reply Quote 0
          • J
            johnpoz LAYER 8 Global Moderator
            last edited by Sep 10, 2018, 6:50 PM

            I have never see bogus hits on openvpn tie up a connection no..

            An intelligent man is sometimes forced to be drunk to spend time with his fools
            If you get confused: Listen to the Music Play
            Please don't Chat/PM me for help, unless mod related
            SG-4860 24.11 | Lab VMs 2.8, 24.11

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            • L
              leungda @KOM
              last edited by Sep 10, 2018, 6:53 PM

              @kom

              I can say you are lucky

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              • D
                Derelict LAYER 8 Netgate @netblues
                last edited by Sep 10, 2018, 6:56 PM

                @netblues said in DDoS attacks OpenVPN on Pfsense:

                Are you using a static tls key?

                Are you using a static TLS key? How is your server configured?

                Chattanooga, Tennessee, USA
                A comprehensive network diagram is worth 10,000 words and 15 conference calls.
                DO NOT set a source address/port in a port forward or firewall rule unless you KNOW you need it!
                Do Not Chat For Help! NO_WAN_EGRESS(TM)

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                • G
                  Gertjan @KOM
                  last edited by Sep 10, 2018, 7:19 PM

                  @kom said in DDoS attacks OpenVPN on Pfsense:

                  Does this happen to anyone else?

                  #Metoo.
                  Having a static IPv4 your years now, but never saw something like that.
                  TLS Keys : of course, I use these.

                  No "help me" PM's please. Use the forum, the community will thank you.
                  Edit : and where are the logs ??

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                  • L
                    leungda
                    last edited by leungda Sep 10, 2018, 7:23 PM Sep 10, 2018, 7:22 PM

                    two different sites got attacked. They are different client and network. They got attacked with the same IP address.

                    How can i extract OpenVPN log from pfsense

                    1 Reply Last reply Reply Quote 0
                    • N
                      NogBadTheBad @leungda
                      last edited by Sep 10, 2018, 7:44 PM

                      @leungda

                      Whats the IP address, it's not comming from shodan or shadowserver is it ?

                      I get these almost every day poking my IPsec VPN, create a blacklist in snort if it is.

                      shadowserver:-
                      
                      216.218.206.0/24
                      
                      shodan:-
                      
                      198.20.69.72/29		# census1.shodan.io
                      198.20.69.96/29		# census2.shodan.io
                      198.20.70.112/29	# census3.shodan.io
                      198.20.99.128/29	# census4.shodan.io
                      93.120.27.62		# census5.shodan.io
                      66.240.236.119		# census6.shodan.io
                      71.6.135.131		# census7.shodan.io
                      66.240.192.138		# census8.shodan.io
                      71.6.167.142		# census9.shodan.io
                      82.221.105.6		# census10.shodan.io
                      82.221.105.7		# census11.shodan.io
                      71.6.165.200		# census12.shodan.io
                      188.138.9.50		# atlantic.census.shodan.io
                      85.25.103.50		# pacific.census.shodan.io
                      85.25.43.94			# rim.census.shodan.io
                      71.6.146.185		# pirate.census.shodan.io
                      71.6.146.186		# inspire.census.shodan.io
                      71.6.158.166		# ninja.census.shodan.io
                      198.20.87.96/29		# border.census.shodan.io
                      66.240.219.146		# burger.census.shodan.io
                      209.126.110.38		# atlantic.dns.shodan.io
                      104.236.198.48		# blog.shodan.io
                      104.131.0.69		# hello.data.shodan.io
                      162.159.244.38		# www.shodan.io
                      159.203.176.62		# ny.private.shodan.io
                      188.138.1.119		# atlantic249.serverprofi24.com
                      80.82.77.33		# sky.census.shodan.io
                      80.82.77.139		# dojo.census.shodan.io
                      71.6.146.130		# ubtuntu16146130.aspadmin.com
                      66.240.205.34		# shodan.io
                      216.117.2.180		# malware-hunter.census.shodan.io
                      93.174.95.106		# battery.census.shodan.io
                      89.248.172.16		# house.census.shodan.io
                      185.163.109.66		# goldfish.census.shodan.io
                      93.174.95.106		# battery.census.shodan.io
                      89.248.167.131		# mason.census.shodan.io
                      94.102.49.190		# flower.census.shodan.io
                      94.102.49.193		# cloud.census.shodan.io
                      185.181.102.18		# turtle.census.shodan.io
                      

                      Andy

                      1 x Netgate SG-4860 - 3 x Linksys LGS308P - 1 x Aruba InstantOn AP22

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                      • L
                        leungda
                        last edited by Sep 10, 2018, 7:59 PM

                        Could you tell me how to create a blacklist in snort?

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                        • N
                          NogBadTheBad
                          last edited by Sep 10, 2018, 8:04 PM

                          Create the blacklist file:-

                          0_1536609734495_Untitled.jpeg

                          Apply it to the interface:-

                          0_1536609743860_Untitled 2.jpeg

                          You then should see (spp_reputation) packets blacklisted in the blocked list:-

                          0_1536609872518_Untitled 3.jpeg

                          Andy

                          1 x Netgate SG-4860 - 3 x Linksys LGS308P - 1 x Aruba InstantOn AP22

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                          • L
                            leungda
                            last edited by Sep 10, 2018, 8:23 PM

                            Love it. Thanks for your help

                            1 Reply Last reply Reply Quote 0
                            • K
                              KOM
                              last edited by Sep 10, 2018, 8:23 PM

                              @netblues said in DDoS attacks OpenVPN on Pfsense:

                              Are you using a static tls key?

                              You have been asked this twice now. It's hard to help you when you don't answer questions.

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                              • J
                                johnpoz LAYER 8 Global Moderator
                                last edited by Sep 10, 2018, 8:27 PM

                                You have ZERO need of snort to stop traffic from hitting your wan IP on your openvpn port - ZERO!!!

                                Im with kom - you going to answer the simple TLS key question??

                                An intelligent man is sometimes forced to be drunk to spend time with his fools
                                If you get confused: Listen to the Music Play
                                Please don't Chat/PM me for help, unless mod related
                                SG-4860 24.11 | Lab VMs 2.8, 24.11

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                                • L
                                  leungda
                                  last edited by leungda Sep 10, 2018, 8:31 PM Sep 10, 2018, 8:29 PM

                                  I checked. I didn't use TLS key on OpenVPN setting. Might be you can help me to set this up for extra layer.

                                  My OpenVPN set up look like this

                                  SSL/TLS + user auth -> DUO -> AD for people to sign in. I am not using local database for user auth

                                  Do you sugguest any online guide that I can read of TLS?

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                                  • K
                                    KOM
                                    last edited by Sep 10, 2018, 8:42 PM

                                    I think you just have to check the Use a TLS key box and then generate new user config that has the TLS key embedded in the .ovpn file, for instance.

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                                    • N
                                      netblues
                                      last edited by Sep 10, 2018, 8:51 PM

                                      The guide on openvpn hardening has lots of info
                                      https://community.openvpn.net/openvpn/wiki/Hardening
                                      tls key is described in section Use of --tls-auth
                                      As for pfsense, its rather straight forward to implement what it suggests.
                                      It also means that you need to send the tls.key to all your clients somehow.
                                      Now if you are running clients by the thousands, this is definitely an issue on its own.
                                      Imagine this as an initial passphrase. If the client connecting knows it, thserver will deal with him further, spending computing resources to do all the needed security handshakes
                                      Obviously it won;t help if you are experiencing a network level attack, ie ping flood saturating your line.

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                                      • L
                                        leungda
                                        last edited by leungda Sep 10, 2018, 9:54 PM Sep 10, 2018, 9:53 PM

                                        I got the TLS in place at one site. I will keep my eyes on it for the next few days. Also, set up a blocklist on Snort is also a good idea.

                                        This guide is quite useful too. Thanks
                                        https://community.openvpn.net/openvpn/wiki/Hardening

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