On 03/08/2016 10:59 AM, James Hogarth wrote: > On 8 March 2016 at 09:22, anax <anax at ayni.com> wrote: > >> >> >> On 03/08/2016 09:43 AM, James Hogarth wrote: >> >>> On 8 Mar 2016 07:36, "anax" <anax at ayni.com> wrote: >>> >>>> >>>> Hi >>>> strange behaviour of iptables on a centos 7.0 machine: >>>> The following rule is in the iptables of said machine: >>>> >>>> [root at myserver ~]# iptables -L -v -n --line-numbers |grep 175\. >>>> 9 9 456 DROP all -- * * 175.44.0.0/16 >>>> >>> 0.0.0.0/0 >>> >>>> [root at myserver ~]# >>>> >>>> The corresponding enty in /etc/sysconfig/iptables looks like: >>>> >>>> [root at myserver ~]# grep 175 /etc/sysconfig/iptables >>>> -A INPUT -s 175.44.0.0/16 -j DROP >>>> [root at myserver ~]# >>>> >>>> The rule must be there since ages, because it has number 9 out of 76 >>>> >>> similar rules. >>> >>>> >>>> Today, on the same machine (I rechecked it to make sure not to confound >>>> >>> machines), I see the following extract of the ftplog: >>> >>>> >>>> <snip> >>>> 175.44.4.127 2915 >>>> 175.44.26.128 2021 >>>> 175.44.26.138 1322 >>>> 175.44.6.186 1290 >>>> 175.44.24.88 1219 >>>> 175.44.4.199 1212 >>>> </snip> >>>> >>>> saying that from this IP addresse there have been this many connections >>>> >>> to the ftp server on that machine during the last two days, which means >>> that the iptables haven't dropped the connection to the machine. As far as >>> I know, the ftp server is behind the iptables. I also checked to see in >>> man >>> iptables, wheather the IP address is represented correctly. >>> >>>> >>>> What im I missing? >>>> >>>> >>> Please provide the full iptables listing as a snippet from one section is >>> not useful. >>> >>> Keep in mind iptables does not go by the most specific entry but rather >>> the >>> first matching rule hit. >>> >>> If there are any rules prior to this drop that would permit the traffic >>> then of course the traffic would be permitted. >>> >>> Also 7.0? Please get that system updated asap as you are missing many >>> important (and higher) issues being fixed. >>> _______________________________________________ >>> CentOS mailing list >>> CentOS at centos.org >>> https://lists.centos.org/mailman/listinfo/centos >>> >>> >> Hi James >> >> [root at myserver ~]# cat /etc/centos-release >> CentOS Linux release 7.2.1511 (Core) >> [root at myserver ~]# >> >> [root at myserver ~]# uname -a >> Linux myserver.mydomain.com 3.10.0-327.4.4.el7.x86_64 #1 SMP Tue Jan 5 >> 16:07:00 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux >> [root at myserver ~]# >> >> >> > A joyful thing to see ;) > > As for your issue itself - the rules seem sound to drop any packets > arriving at the server from that /16 network. > > Are you sure that the iptables rule was added before the transfer logs you > see? > > That it didn't happen that someone (or some process) saw abuse of ftp and > then inserted the DROP rule afterwards? > > Remember position isn't always useful to gauge age of the rule since you > can insert anywhere ... and only 9 packets have been matched by that rule > in the full output... > _______________________________________________ > CentOS mailing list > CentOS at centos.org > https://lists.centos.org/mailman/listinfo/centos > Hi james I am absolutely sure, that the rule in question has been insertet into iptables more than a year ago, because I am (hopefully) the only one with root access to this server. There is no fail2ban on the server, which could have introduced the rule into iptables automatically. I have written the ruby program to extract the snippet of the ftp-log yesterday and have taken notice of the iptables missbehaviour this morning. suomi