Forgrd "From" mail in maillog Forgrd "From" mail in maillog brk1221 (MIS) (OP) 9 Jun 08 15:58 Hi we're running Fedora Core5 with Sendmail 8.13. I notice a ton of email leaving the server with unknown "from" addreses. Shouldn't mail from our local domain only be allowed to send out?ThanksTim RE: Forgrd "From" mail in maillog RhythmAce (TechnicalUser) 9 Jun 08 18:58 You may have an open relay. For example, if you have sendmail configured to relay mail if the return address is from one of the domains you host. Any time you relay based on a local return address, you invite mischief such as address spoofing. The best way is to not use the access or Relay Domains (CR) files and use smtpauth instead. By default, smtp mail is handled first then pop3 mail is processed. The pop3 server requires authentication but it's too late for the outgoing mail at this point. An original work-around was to use a method called "pop before smtp" but this has given way to smtpauth which is what it shounds like. It requires your smtp server to require authentication. It is very easy to setup. I've explained it a few times here on this forum so you may be able to do a seach for "smtpauth". If you don't get anywhere with that, I or anyone here will be glad to help you. RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 9 Jun 08 20:46 Thanks I'll give a look RE: Forgrd "From" mail in maillog elgrandeperro (TechnicalUser) 9 Jun 08 20:46 Are you running the smtp server as inbound, outbound, or both? There are several web sites that can verify a open relay. RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 10 Jun 08 08:30 I'm not sure, how the smtp server is running. How would I check? I've ran some of the online open relay scans and they all come back "not" an open relay, smtpauth sounds like something I will try.ThanksTim RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 10 Jun 08 09:27 Also, I do have entries in the /etc/mail/access file that need to be there. They are other servers that are configured to send mail. Would that be a problem getting smtpauth to work correctly?ThanksTim RE: Forgrd "From" mail in maillog elgrandeperro (TechnicalUser) 10 Jun 08 12:03 Yes, I believe you cannot use smtpauth in this case if the other servers can't authenticate. You can restrict the ips you allow to connect to your server.When you tested open relay, did it say it could connect to port 25? If not, then you aren't a direct inbound mail gateway.Are both the To and From not in your domain? You need to analyze some of the headers to see the origins of the email.I would check some of the letters to see that possibly that your other servers are acting as an relay (which passes through you). Even web apps can be fooled into sending forged email. RE: Forgrd "From" mail in maillog RhythmAce (TechnicalUser) 10 Jun 08 17:49 Anything in "access" is ignored by the smtpauth process and therefor can be exploited by someone wanting to spoof (forge)those domains. The only thing you really need in the are localhost, localhost.localdomain and 127.0.0.1. If you don't mind posting your sendmail.mc file, we can take a look at it and see if anything jumps out that shouldn't be there. RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 11 Jun 08 08:33 Than how would I relay mail from a unix box through the fedora box?Here's the sendmail.mcdivert(-1)dnldnl #dnl # This is the sendmail macro config file for m4. If you make changes todnl # /etc/mail/sendmail.mc, you will need to regenerate thednl # /etc/mail/sendmail.cf file by confirming that the sendmail-cf package isdnl # installed and then performing adnl #dnl # make -C /etc/maildnl #include(`/usr/share/sendmail-cf/m4/cf.m4')dnlVERSIONID(`setup for linux')dnlOSTYPE(`linux')dnldnl #dnl # default logging level is 9, you might want to set it higher todnl # debug the configurationdnl #dnl define(`confLOG_LEVEL', `9')dnldnl #dnl # Uncomment and edit the following line if your outgoing mail needs todnl # be sent out through an external mail server:dnl #dnl define(`SMART_HOST',`smtp.your.provider')dnldnl #define(`confDEF_USER_ID',``8:12'')dnldnl define(`confAUTO_REBUILD')dnldefine(`confTO_CONNECT', `1m')dnldefine(`confTRY_NULL_MX_LIST',true)dnldefine(`confDONT_PROBE_INTERFACES',true)dnldefine(`PROCMAIL_MAILER_PATH',`/usr/bin/procmail')dnldefine(`ALIAS_FILE', `/etc/aliases')dnldefine(`STATUS_FILE', `/var/log/mail/statistics')dnldefine(`UUCP_MAILER_MAX', `2000000')dnldefine(`confUSERDB_SPEC', `/etc/mail/userdb.db')dnldefine(`confPRIVACY_FLAGS', `authwarnings,novrfy,noexpn,restrictqrun')dnldefine(`confAUTH_OPTIONS', `A')dnldnl #dnl # The following allows relaying if the user authenticates, and disallowsdnl # plaintext authentication (PLAIN/LOGIN) on non-TLS linksdnl #dnl define(`confAUTH_OPTIONS', `A p')dnldnl #dnl # PLAIN is the preferred plaintext authentication method and used bydnl # Mozilla Mail and Evolution, though Outlook Express and other MUAs dodnl # use LOGIN. Other mechanisms should be used if the connection is notdnl # guaranteed secure.dnl # Please remember that saslauthd needs to be running for AUTH.dnl #dnl TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnldnl define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnldnl #dnl # Rudimentary information on creating certificates for sendmail TLS:dnl # cd /usr/share/ssl/certs; make sendmail.pemdnl # Complete usage:dnl # make -C /usr/share/ssl/certs usagednl #dnl define(`confCACERT_PATH',`/etc/pki/tls/certs')dnldnl define(`confCACERT',`/etc/pki/tls/certs/ca-bundle.crt')dnldnl define(`confSERVER_CERT',`/etc/pki/tls/certs/sendmail.pem')dnldnl define(`confSERVER_KEY',`/etc/pki/tls/certs/sendmail.pem')dnldnl #dnl # This allows sendmail to use a keyfile that is shared with OpenLDAP'sdnl # slapd, which requires the file to be readble by group ldapdnl #dnl define(`confDONT_BLAME_SENDMAIL',`groupreadablekeyfile')dnldnl #dnl define(`confTO_QUEUEWARN', `4h')dnldnl define(`confTO_QUEUERETURN', `5d')dnldnl define(`confQUEUE_LA', `12')dnldnl define(`confREFUSE_LA', `18')dnldefine(`confTO_IDENT', `0')dnldnl FEATURE(delay_checks)dnlFEATURE(`no_default_msa',`dnl')dnlFEATURE(`smrsh',`/usr/sbin/smrsh')dnlFEATURE(`mailertable',`hash -o /etc/mail/mailertable.db')dnlFEATURE(`virtusertable',`hash -o /etc/mail/virtusertable.db')dnlFEATURE(redirect)dnlFEATURE(always_add_domain)dnlFEATURE(use_cw_file)dnlFEATURE(use_ct_file)dnldnl #dnl # The following limits the number of processes sendmail can fork to acceptdnl # incoming messages or process its message queues to 12.) sendmail refusesdnl # to accept connections once it has reached its quota of child processes.dnl #dnl define(`confMAX_DAEMON_CHILDREN', 12)dnldnl #dnl # Limits the number of new connections per second. This caps the overheaddnl # incurred due to forking new sendmail processes. May be useful againstdnl # DoS attacks or barrages of spam. (As mentioned below, a per-IP addressdnl # limit would be useful but is not available as an option at this writing.)dnl #dnl define(`confCONNECTION_RATE_THROTTLE', 3)dnldnl #dnl # The -t option will retry delivery if e.g. the user runs over his quota.dnl #FEATURE(local_procmail,`',`procmail -t -Y -a $h -d $u')dnlFEATURE(`access_db',`hash -T<TMPF> -o /etc/mail/access.db')dnlFEATURE(`blacklist_recipients')dnlEXPOSED_USER(`root')dnldnl #dnl # For using Cyrus-IMAPd as POP3/IMAP server through LMTP delivery uncommentdnl # the following 2 definitions and activate below in the MAILER section thednl # cyrusv2 mailer.dnl #dnl define(`confLOCAL_MAILER', `cyrusv2')dnldnl define(`CYRUSV2_MAILER_ARGS', `FILE /var/lib/imap/socket/lmtp')dnldnl #dnl # The following causes sendmail to only listen on the IPv4 loopback addressdnl # 127.0.0.1 and not on any other network devices. Remove the loopbackdnl # address restriction to accept email from the internet or intranet.dnl #dnl #DAEMON_OPTIONS(`Port=smtp,Addr=172.17.1.5, Name=MTA')dnlDAEMON_OPTIONS(`Port=smtp, Name=MTA')dnldnl #dnl # The following causes sendmail to additionally listen to port 587 fordnl # mail from MUAs that authenticate. Roaming users who can't reach theirdnl # preferred sendmail daemon due to port 25 being blocked or redirected finddnl # this useful.dnl #dnl DAEMON_OPTIONS(`Port=submission, Name=MSA, M=Ea')dnldnl #dnl # The following causes sendmail to additionally listen to port 465, butdnl # starting immediately in TLS mode upon connecting. Port 25 or 587 followeddnl # by STARTTLS is preferred, but roaming clients using Outlook Express can'tdnl # do STARTTLS on ports other than 25. Mozilla Mail can ONLY use STARTTLSdnl # and doesn't support the deprecated smtps; Evolution <1.1.1 uses smtpsdnl # when SSL is enabled-- STARTTLS support is available in version 1.1.1.dnl #dnl # For this to work your OpenSSL certificates must be configured.dnl #dnl DAEMON_OPTIONS(`Port=smtps, Name=TLSMTA, M=s')dnldnl #dnl # The following causes sendmail to additionally listen on the IPv6 loopbackdnl # device. Remove the loopback address restriction listen to the network.dnl #dnl DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6')dnldnl #dnl # enable both ipv6 and ipv4 in sendmail:dnl #dnl DAEMON_OPTIONS(`Name=MTA-v4, Family=inet, Name=MTA-v6, Family=inet6')dnl #dnl # We strongly recommend not accepting unresolvable domains if you want todnl # protect yourself from spam. However, the laptop and users on computersdnl # that do not have 24x7 DNS do need this.dnl #FEATURE(`accept_unresolvable_domains')dnldnl #dnl FEATURE(`relay_based_on_MX')dnldnl #dnl # Also accept email sent to "localhost.localdomain" as local email.dnl #LOCAL_DOMAIN(`netmax.jonesmotor.com')dnldnl #dnl # The following example makes mail from this host and any additionaldnl # specified domains appear to be sent from mydomain.comdnl #dnl MASQUERADE_AS(`jonesmotor.com')dnldnl #dnl # masquerade not just the headers, but the envelope as welldnl #dnl FEATURE(masquerade_envelope)dnldnl #dnl # masquerade not just @mydomainalias.com, but @*.mydomainalias.com as welldnl #dnl FEATURE(masquerade_entire_domain)dnldnl #dnl MASQUERADE_DOMAIN(localhost)dnldnl MASQUERADE_DOMAIN(localhost.localdomain)dnldnl MASQUERADE_DOMAIN(mydomainalias.com)dnldnl MASQUERADE_DOMAIN(mydomain.lan)dnlMAILER(smtp)dnlMAILER(procmail)dnldnl MAILER(cyrusv2)dnlINPUT_MAIL_FILTER(`clamav', `S=local:/var/run/clamav/clmilter.sock, F=, T=S:4m;R:4m')dnl RE: Forgrd "From" mail in maillog elgrandeperro (TechnicalUser) 11 Jun 08 13:12 Did you build/rebuild access database? Can you post (in generic terms) what is in /etc/mail/access? RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 11 Jun 08 14:40 The current access file# Check the /usr/share/doc/sendmail/README.cf file for a description# of the format of this file. (search for access_db in that file)# The /usr/share/doc/sendmail/README.cf is part of the sendmail-doc# package.## by default we allow relaying from localhost...Connect:localhost.localdomain RELAYConnect:localhost RELAYConnect:172.17.1.5 RELAYConnect:127.0.0.1 RELAYConnect:18.104.22.168 RELAYConnect:172.17.2 RELAYConnect:172.17.3 RELAY#Phone systemConnect:172.18.1.3 RELAYConnect:172.18.1.13 RELAY#Don SheehyConnect:22.214.171.124 RELAYConnect:126.96.36.199 RELAY#Avalon NJConnect:188.8.131.52 RELAY#Scan StationsConnect:172.17.1.102 RELAYConnect:172.17.1.103 RELAYConnect:172.17.1.104 RELAYsbowen@veneziainc.com REJECTsharicecloe@yahoo.com REJECT RE: Forgrd "From" mail in maillog elgrandeperro (TechnicalUser) 11 Jun 08 15:54 And the obvious question, you do know how to rebuild it? (I have to ask)... RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 11 Jun 08 16:12 Yes I do. It's starts with a makemap command RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 11 Jun 08 16:53 So does it look like I can setup smtpauth?Also if every test I run says I'm not an open relay, why are there hundreds of unknown emails leaving my mail server.Can anyone explain how the originator of these email gained access?Thanks Tim RE: Forgrd "From" mail in maillog elgrandeperro (TechnicalUser) 11 Jun 08 19:06 I think that is the point. You first need to trace back some of those messages through the log to figure out how they are getting to your system. If they were relayed from one of your other hosts, or originated from your box. By "relay" you are "trusting" those hosts. SMTPauth is mostly used by email clients (eudora, outlook, etc.) not intended for server to server operations.The times I was compromised:A web application that was allowing crafting of mail.A PC that was compromised.A unix box that was hosting an illegal mailing list.A unix box that someone was using as a mass mailer.None of these were on my relay itself but were in my trusted network... RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 12 Jun 08 08:23 Here is an example of one of the foreign emails leaving my server:Jun 12 08:22:00 netmax sendmail: m5CCLrKl013852: from=<email@example.com>, size=2376, class=0, nrcpts=1, msgid=<01c8cc9f$cd857100$ef1a645c@eicndmule>, proto=SMTP, daemon=MTA, relay=ppp92-100-26-239.pppoe.avangarddsl.ru [184.108.40.206]How I could trace this back to anything in my trusted network?Tim RE: Forgrd "From" mail in maillog elgrandeperro (TechnicalUser) 12 Jun 08 16:32 There should be a matching to: line, in this case it should be marked as m5CCLrKl013852. I assume 220.127.116.11 isn't your network...if this is outbound gateway only, you don't need port 25 open inbound. RE: Forgrd "From" mail in maillog brk1221 (MIS) (OP) 23 Jun 08 10:49 How can I trace the origin of outgoing email from my lan? The /var/log/maillog does not show the computer that sent the email. Are there any other logs I can view? Are there any utilities that can be installed?ThanksTim RE: Forgrd "From" mail in maillog elgrandeperro (TechnicalUser) 23 Jun 08 12:43 Going by the example, the answer is right there.The origin IP is 18.104.22.168, and if that isn't your IP range AND the TO is not to you AND you don't deny it or reject it, then you have a relay problem.If the TO is to you, then you this is most likely spam and you need to install some antispam package.