Re: [CentOS] hosts.deny, fail2ban etc.
On 07/27/2021 05:17 PM, Pete Biggs wrote: > On Tue, 2021-07-27 at 16:43 -0400, H wrote: >>> Running CentOS 7. I was under the impression - seemingly mistaken - >>> that by adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* >>> would ban all attempts from that network segment to connect to the >>> server, ie before fail2ban would (eventually) ban connection >>> attempts. >> This, however, does not seem correct and I could use a pointer to >> correct my misunderstanding. How is hosts.deny used and what have I >> missed? > hosts.deny is only used by specific programs that use TCP wrappers. It > is not a general "deny this host access". > > Also note that fail2ban operates on individual hosts, not subnets. > >> Is it necessary to run: >> >> iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP >> >> to drop incoming connection attempts from that subnet? >> > If you use iptables yes, probably. Firewalld has a specific drop zone > that you can use: > > firewall-cmd --zone=drop --add-source=aaa.bbb.ccc.0/24 > > (with suitable --permanent flag if you want it permanent). > > P. > > > ___ > CentOS mailing list > CentOS@centos.org > https://lists.centos.org/mailman/listinfo/centos Noted, I am using iptables. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On 07/28/2021 10:01 AM, Leon Fauster via CentOS wrote: > On 28.07.21 14:44, Jonathan Billings wrote: >> On Jul 27, 2021, at 16:43, H wrote: >>> >>> |Running CentOS 7. I was under the impression - seemingly mistaken - that >>> by adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* would ban >>> all attempts from that network segment to connect to the server, ie before >>> fail2ban would (eventually) ban connection attempts. >>> >>> This, however, does not seem correct and I could use a pointer to correct >>> my misunderstanding. How is hosts.deny used and what have I missed? >>> >>> Is it necessary to run: >>> >>> iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP >>> >>> to drop incoming connection attempts from that subnet? >> >> Upstream openssh dropped support for tcp wrappers (hosts.deny) a while ago >> but RHEL had patched support back in for a while, but I believe it isn’t >> supported anymore. >> >> For what it’s worth, if you use the fail2ban-firewalld package, it uses >> ipset rather than iptables, which is more efficient. >> >> > > TCP wrappers (hosts.allow/deny) are deprecated now. > > Its still supported in EL7 (sshd example) > > ldd /usr/sbin/sshd |grep wrap > libwrap.so.0 => /lib64/libwrap.so.0 (0x7fcc483ee000) > > but not in EL8 anymore. EL8 is based on F28/29 -> > https://fedoraproject.org/wiki/Changes/Deprecate_TCP_wrappers > > For the question above (for EL7): > only services that are compiled against libwrap uses hosts.deny > everything else will be reachable (if iptables does not drop it). > > For EL8, as depicted in the above URI: > systemd provide a similar functionality ... > > -- > Leon > > > > > ___ > CentOS mailing list > CentOS@centos.org > https://lists.centos.org/mailman/listinfo/centos Got it, will utilize iptables. I guess my previous experience was with C6. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On 07/28/2021 08:44 AM, Jonathan Billings wrote: > On Jul 27, 2021, at 16:43, H wrote: >> |Running CentOS 7. I was under the impression - seemingly mistaken - that >> by adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* would ban all >> attempts from that network segment to connect to the server, ie before >> fail2ban would (eventually) ban connection attempts. >> >> This, however, does not seem correct and I could use a pointer to correct my >> misunderstanding. How is hosts.deny used and what have I missed? >> >> Is it necessary to run: >> >> iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP >> >> to drop incoming connection attempts from that subnet? > Upstream openssh dropped support for tcp wrappers (hosts.deny) a while ago > but RHEL had patched support back in for a while, but I believe it isn’t > supported anymore. > > For what it’s worth, if you use the fail2ban-firewalld package, it uses ipset > rather than iptables, which is more efficient. > > -- > Jonathan Billings > ___ > CentOS mailing list > CentOS@centos.org > https://lists.centos.org/mailman/listinfo/centos Noted, thank you. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On 07/28/2021 05:12 AM, Stephen John Smoogen wrote: > On Tue, 27 Jul 2021 at 16:43, H wrote: >> |Running CentOS 7. I was under the impression - seemingly mistaken - that by >> adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* would ban all >> attempts from that network segment to connect to the server, ie before >> fail2ban would (eventually) ban connection attempts. >> >> This, however, does not seem correct and I could use a pointer to correct my >> misunderstanding. How is hosts.deny used and what have I missed? >> >> Is it necessary to run: >> >> iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP >> > yes. iptables is one of the first things which will see the packets > coming to the server as it is implemented in kernel space. hosts.deny > only comes in for specific services which are compiled to use it. > > [Internet] <-> [iptables] <-> [systemd if used] <-> [xinetd w/tcp-wrappers] > > In the above example, a packet coming from the internet gets > interpreted and dealt with multiple tools and hosts.deny is only used > in the last section where xinetd and similar programs compiled with > tcp-wrappers look at hosts.deny file. > > >> to drop incoming connection attempts from that subnet? >> >> Thank you! >> | >> ___ >> CentOS mailing list >> CentOS@centos.org >> https://lists.centos.org/mailman/listinfo/centos > > Thank you, I will utilize iptables (I am running C7). ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On 7/28/2021 1:57 PM, Scott Techlist wrote: Is that an improvement? I'm still running Centos7 so I'm not familiar with it. https://ungleich.ch/en-us/cms/blog/2018/08/18/iptables-vs-nftables/ ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
>> For what it’s worth, if you use the fail2ban-firewalld package, it uses >> ipset rather than iptables, which is more efficient. > >That’s in CentOS 7 though. >CentOS 8 firewalld uses nft instead of the older netfilter (iptables/ipset) >code. Is that an improvement? I'm still running Centos7 so I'm not familiar with it. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On 28.07.21 14:44, Jonathan Billings wrote: On Jul 27, 2021, at 16:43, H wrote: |Running CentOS 7. I was under the impression - seemingly mistaken - that by adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* would ban all attempts from that network segment to connect to the server, ie before fail2ban would (eventually) ban connection attempts. This, however, does not seem correct and I could use a pointer to correct my misunderstanding. How is hosts.deny used and what have I missed? Is it necessary to run: iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP to drop incoming connection attempts from that subnet? Upstream openssh dropped support for tcp wrappers (hosts.deny) a while ago but RHEL had patched support back in for a while, but I believe it isn’t supported anymore. For what it’s worth, if you use the fail2ban-firewalld package, it uses ipset rather than iptables, which is more efficient. TCP wrappers (hosts.allow/deny) are deprecated now. Its still supported in EL7 (sshd example) ldd /usr/sbin/sshd |grep wrap libwrap.so.0 => /lib64/libwrap.so.0 (0x7fcc483ee000) but not in EL8 anymore. EL8 is based on F28/29 -> https://fedoraproject.org/wiki/Changes/Deprecate_TCP_wrappers For the question above (for EL7): only services that are compiled against libwrap uses hosts.deny everything else will be reachable (if iptables does not drop it). For EL8, as depicted in the above URI: systemd provide a similar functionality ... -- Leon ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On Jul 28, 2021, at 08:44, Jonathan Billings wrote: > > For what it’s worth, if you use the fail2ban-firewalld package, it uses ipset > rather than iptables, which is more efficient. That’s in CentOS 7 though. CentOS 8 firewalld uses nft instead of the older netfilter (iptables/ipset) code. -- Jonathan Billings ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On Jul 27, 2021, at 16:43, H wrote: > > |Running CentOS 7. I was under the impression - seemingly mistaken - that by > adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* would ban all > attempts from that network segment to connect to the server, ie before > fail2ban would (eventually) ban connection attempts. > > This, however, does not seem correct and I could use a pointer to correct my > misunderstanding. How is hosts.deny used and what have I missed? > > Is it necessary to run: > > iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP > > to drop incoming connection attempts from that subnet? Upstream openssh dropped support for tcp wrappers (hosts.deny) a while ago but RHEL had patched support back in for a while, but I believe it isn’t supported anymore. For what it’s worth, if you use the fail2ban-firewalld package, it uses ipset rather than iptables, which is more efficient. -- Jonathan Billings ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On Tue, 27 Jul 2021 at 17:17, Pete Biggs wrote: > > On Tue, 2021-07-27 at 16:43 -0400, H wrote: > > > Running CentOS 7. I was under the impression - seemingly mistaken - > > > that by adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* > > > would ban all attempts from that network segment to connect to the > > > server, ie before fail2ban would (eventually) ban connection > > > attempts. > > > > This, however, does not seem correct and I could use a pointer to > > correct my misunderstanding. How is hosts.deny used and what have I > > missed? > > hosts.deny is only used by specific programs that use TCP wrappers. It > is not a general "deny this host access". > > Also note that fail2ban operates on individual hosts, not subnets. > [I should have waited and read all my email before responding. Peter covered parts I did not.] -- Stephen J Smoogen. I've seen things you people wouldn't believe. Flame wars in sci.astro.orion. I have seen SPAM filters overload because of Godwin's Law. All those moments will be lost in time... like posts on BBS... time to reboot. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On Tue, 27 Jul 2021 at 16:43, H wrote: > > |Running CentOS 7. I was under the impression - seemingly mistaken - that by > adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* would ban all > attempts from that network segment to connect to the server, ie before > fail2ban would (eventually) ban connection attempts. > > This, however, does not seem correct and I could use a pointer to correct my > misunderstanding. How is hosts.deny used and what have I missed? > > Is it necessary to run: > > iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP > yes. iptables is one of the first things which will see the packets coming to the server as it is implemented in kernel space. hosts.deny only comes in for specific services which are compiled to use it. [Internet] <-> [iptables] <-> [systemd if used] <-> [xinetd w/tcp-wrappers] In the above example, a packet coming from the internet gets interpreted and dealt with multiple tools and hosts.deny is only used in the last section where xinetd and similar programs compiled with tcp-wrappers look at hosts.deny file. > to drop incoming connection attempts from that subnet? > > Thank you! > | > ___ > CentOS mailing list > CentOS@centos.org > https://lists.centos.org/mailman/listinfo/centos -- Stephen J Smoogen. I've seen things you people wouldn't believe. Flame wars in sci.astro.orion. I have seen SPAM filters overload because of Godwin's Law. All those moments will be lost in time... like posts on BBS... time to reboot. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] hosts.deny, fail2ban etc.
On Tue, 2021-07-27 at 16:43 -0400, H wrote: > > Running CentOS 7. I was under the impression - seemingly mistaken - > > that by adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* > > would ban all attempts from that network segment to connect to the > > server, ie before fail2ban would (eventually) ban connection > > attempts. > > This, however, does not seem correct and I could use a pointer to > correct my misunderstanding. How is hosts.deny used and what have I > missed? hosts.deny is only used by specific programs that use TCP wrappers. It is not a general "deny this host access". Also note that fail2ban operates on individual hosts, not subnets. > > Is it necessary to run: > > iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP > > to drop incoming connection attempts from that subnet? > If you use iptables yes, probably. Firewalld has a specific drop zone that you can use: firewall-cmd --zone=drop --add-source=aaa.bbb.ccc.0/24 (with suitable --permanent flag if you want it permanent). P. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
[CentOS] hosts.deny, fail2ban etc.
|Running CentOS 7. I was under the impression - seemingly mistaken - that by adding a rule to /etc/hosts.deny such as ALL: aaa.bbb.ccc.* would ban all attempts from that network segment to connect to the server, ie before fail2ban would (eventually) ban connection attempts. This, however, does not seem correct and I could use a pointer to correct my misunderstanding. How is hosts.deny used and what have I missed? Is it necessary to run: iptables -I INPUT -s aaa.bbb.ccc.0/24 -j DROP to drop incoming connection attempts from that subnet? Thank you! | ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
