hi all, running centos 4.7 i686. I seem to have an o pen r elay sendmail server. How do I close it? I have the STRAIGHT centos install sendmail.mc file. Only thing I changed was: dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl so as to allow incoming email and not just localhost. however this seems to relay everyone. I looked at http://www.sendmail.org/tips/relaying but it just talks about (AFIKT) enabling specific relays to occur - not how to CLOSE the relaying. How do I close the relay? Jerry
Jerry Geis wrote:> I have the STRAIGHT centos install sendmail.mc file. > Only thing I changed was: > dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnlIt should be: DAEMON_OPTIONS(`Port=smtp, Name=MTA') M$-Internet Exploder est le cancer de l'Internet, voyez pourquoi ici : http://www.aful.org/ressources/documentations/msie-problemes-securite/ -- (?- Bernard Lheureux Gestionnaire des MailingLists ML, TechML, LinuxML //\ http://www.bbsoft4.org/Mailinglists.htm ** MailTo:root at bbsoft4.org v_/_ http://www.bbsoft4.org/ <<<<<< () >>>>> http://www.portalinux.org
On Wed, Nov 12, 2008 at 12:33 PM, Jerry Geis <geisj at pagestation.com> wrote:> hi all, running centos 4.7 i686. > > I seem to have an o pen r elay sendmail server. > How do I close it? > > I have the STRAIGHT centos install sendmail.mc file. > Only thing I changed was: > dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl > > so as to allow incoming email and not just localhost. however this seems to > relay everyone. > > I looked at http://www.sendmail.org/tips/relaying but it just talks about > (AFIKT) > enabling specific relays to occur - not how to CLOSE the relaying. > > How do I close the relay? >Google is your friend - look for "closing an open relay...." :-) mhr
> > It should be: > DAEMON_OPTIONS(`Port=smtp, Name=MTA') >I changed it to this and restarted sendmail, re-ran the test and still open. Jerry
lists-centos wrote:> You have to have changed more than just the sendmail.mc/cf to make a > default centos sendmail setup an open mail relay. > > Your /etc/mail/access file is where things are defined as to what > you relay for. The /etc/mail/local-host-names effects what you > accept mail for. > > Make certain that what you're using to test that's it's an open > relay is reporting things correctly. There's a difference between > sendmail being "open" (accepting mail from the outside) and an "open > relay". The former is expected from a mail server, the latter is a > problem. > > I use: > > <http://verify.abuse.net/cgi-bin/relaytest> > > which runs through a range of tests. I tried it against your > 24.123.23.170 mail server a few min. ago and all was fine. > > - Rick > > ------------ Original Message ------------ > >> Date: Wednesday, November 12, 2008 03:33:11 PM -0500 >> From: Jerry Geis <geisj at pagestation.com> >> To: CentOS ML <centos at centos.org> >> Subject: [CentOS] close open relay >> >> hi all, running centos 4.7 i686. >> >> I seem to have an o pen r elay sendmail server. >> How do I close it? >> >> I have the STRAIGHT centos install sendmail.mc file. >> Only thing I changed was: >> dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl >> >> so as to allow incoming email and not just localhost. however this >> seems to relay everyone. >> >> I looked at http://www.sendmail.org/tips/relaying but it just >> talks about (AFIKT) >> enabling specific relays to occur - not how to CLOSE the relaying. >> >> How do I close the relay? >> >> Jerry >> _______________________________________________ >> CentOS mailing list >> CentOS at centos.org >> http://lists.centos.org/mailman/listinfo/centos >> > > ------------ End Original Message ------------ > > > >When I run the following I get broken web page: http://verify.abuse.net/cgi-bin/relaytest I am getting investigating all this as I am getting return emails from sbcglobal that I am spam. Jerry
lists-centos wrote:> sorry, the start page is: > > <http://www.abuse.net/relay.html> > > > look at the headers of the original messages (probably included as > attachments) that sbcglobal is sending back. it's very possible that > a spammer has forged an address from your machine on their outbound > spam, and sbcglobal is bouncing that, (rather than rejecting, > because they haven't a clue), generating scatter-back spam. > > > - Rick > > ------------ Original Message ------------ > >> Date: Wednesday, November 12, 2008 04:44:02 PM -0500 >> From: Jerry Geis <geisj at pagestation.com> >> To: CentOS ML <centos at centos.org> >> Subject: Re: [CentOS] close open relay >> >> lists-centos wrote: >> >>> You have to have changed more than just the sendmail.mc/cf to >>> make a default centos sendmail setup an open mail relay. >>> >>> Your /etc/mail/access file is where things are defined as to what >>> you relay for. The /etc/mail/local-host-names effects what you >>> accept mail for. >>> >>> Make certain that what you're using to test that's it's an open >>> relay is reporting things correctly. There's a difference between >>> sendmail being "open" (accepting mail from the outside) and an >>> "open relay". The former is expected from a mail server, the >>> latter is a problem. >>> >>> I use: >>> >>> <http://verify.abuse.net/cgi-bin/relaytest> >>> >>> which runs through a range of tests. I tried it against your >>> 24.123.23.170 mail server a few min. ago and all was fine. >>> >>> - Rick >>> >>> ------------ Original Message ------------ >>> >>> >>>> Date: Wednesday, November 12, 2008 03:33:11 PM -0500 >>>> From: Jerry Geis <geisj at pagestation.com> >>>> To: CentOS ML <centos at centos.org> >>>> Subject: [CentOS] close open relay >>>> >>>> hi all, running centos 4.7 i686. >>>> >>>> I seem to have an o pen r elay sendmail server. >>>> How do I close it? >>>> >>>> I have the STRAIGHT centos install sendmail.mc file. >>>> Only thing I changed was: >>>> dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl >>>> >>>> so as to allow incoming email and not just localhost. however >>>> this seems to relay everyone. >>>> >>>> I looked at http://www.sendmail.org/tips/relaying but it just >>>> talks about (AFIKT) >>>> enabling specific relays to occur - not how to CLOSE the >>>> relaying. >>>> >>>> How do I close the relay? >>>> >>>> Jerry >>>> _______________________________________________ >>>> CentOS mailing list >>>> CentOS at centos.org >>>> http://lists.centos.org/mailman/listinfo/centos >>>> >>>> >>> ------------ End Original Message ------------ >>> >>> >>> >>> >>> >> When I run the following I get broken web page: >> >> http://verify.abuse.net/cgi-bin/relaytest >> >> >> I am getting investigating all this as I am getting return emails >> from sbcglobal that I am spam. >> >> Jerry >> >> >> >> _______________________________________________ >> CentOS mailing list >> CentOS at centos.org >> http://lists.centos.org/mailman/listinfo/centos >> > > ------------ End Original Message ------------ > > > >Sure enough I tried your test and that looks good... HOwever, when i run this test: HELO example.com MAIL From: TheBoss at example.com RCPT To: geisj at pagestation.com DATA Subject: Think we're insecure... I have a feeling our mail server is being abused... . QUIT and paste that into port 25 of my server (telnet I'm talking) I get the email and I should not ( I presume) as I am not example.com. Jerry
Jerry Geis <geisj at pagestation.com> wrote (with a few extraneous bits removed):> ------------ Original Message ------------ > >>> > >>> > >> >>>> Date: Wednesday, November 12, 2008 03:33:11 PM -0500 >> >>>> From: Jerry Geis <geisj at pagestation.com> >> >>>> To: CentOS ML <centos at centos.org> >> >>>> Subject: [CentOS] close open relay >> >>>> >> >>>> hi all, running centos 4.7 i686. >> >>>> >> >>>> I seem to have an o pen r elay sendmail server. >> >>>> How do I close it? >> >>>> >> >>>> I have the STRAIGHT centos install sendmail.mc file. >> >>>> Only thing I changed was: >> >>>> dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl >> >>>> >> >>>> so as to allow incoming email and not just localhost. however >> >>>> this seems to relay everyone. >> >>>> >> >>>> I looked at http://www.sendmail.org/tips/relaying but it just >> >>>> talks about (AFIKT) >> >>>> enabling specific relays to occur - not how to CLOSE the >> >>>> relaying. >> >>>> >> >>>> How do I close the relay? >> >>>> >> >>>> Jerry >> >>>> _______________________________________________ >> >>>> CentOS mailing list >> >>>> CentOS at centos.org >> >>>> http://lists.centos.org/mailman/listinfo/centos >> >>>> >> >>>> >> > >>> ------------ End Original Message ------------....> Sure enough I tried your test and that looks good... > > HOwever, when i run this test: > HELO example.com > MAIL From: TheBoss at example.com > RCPT To: geisj at pagestation.com > DATA > Subject: Think we're insecure... > I have a feeling our mail server is being abused... > .. > QUIT > > and paste that into port 25 of my server (telnet I'm talking) > I get the email and I should not ( I presume) as I am not example.com. > > JerryThe bottom of the file /etc/sendmail.mc should look like the following (change my domain, davenjudy.org, to whatever is appropriate for your domain). This won't get rid of any open relay problems but will at least fix the "example.com" issue: ... dnl # dnl # The following example makes mail from this host and any additional dnl # specified domains appear to be sent from mydomain.com dnl # MASQUERADE_AS(`davenjudy.org')dnl dnl # dnl # masquerade not just the headers, but the envelope as well dnl # dnl FEATURE(masquerade_envelope)dnl dnl # dnl # masquerade not just @mydomainalias.com, but @*.mydomainalias.com as well dnl # FEATURE(masquerade_entire_domain)dnl dnl # dnl MASQUERADE_DOMAIN(localhost)dnl dnl MASQUERADE_DOMAIN(localhost.localdomain)dnl MASQUERADE_DOMAIN(local.davenjudy.org)dnl MASQUERADE_DOMAIN(davenjudy.org)dnl As for possibly having an open relay, you also want to make sure that the following line is commented out (has dnl at the beginning): dnl # dnl FEATURE(`relay_based_on_MX')dnl dnl # Finally, you'll need a line like: FEATURE(`relay_entire_domain')dnl DO NOT uncomment any of the other lines in sendmail.mc regarding relay settings unless you know what you're doing. If you aren't sure what was changed from the default, remove the sendmail-cf rpm and reinstall it to get back to a clean, default sendmail.mc file. It's a good idea to explicitly run make in /etc/mail and then bounce sendmail rather than let the sendmail startup script decide something has changed since it's easier to catch syntax errors that way. Finally, get a free mail account at your provider of choice (Google, Hotmail, whoever) and use it for testing both sending and receiving mail. Cheers, Dave -- Politics, n. Strife of interests masquerading as a contest of principles. -- Ambrose Bierce