Enforcing a match between FROM address and sasl username

-

Issue

If a user's password is compromised, the Server default setup allows the user to relay emails using a different email address than the one uses to authenticate with smtp.

A message header from that user looks like this: 

zimbra1 postfix/smtpd[29431]: B28914D5978: client=xxxxx.server.com[w.x.y.z], sasl_method=LOGIN, sasl_username=

Where the sender's user name and the from address are indicated in bold. This article explains how to ensure that the from address matches the sender's username. 


How-to

Zimbra Collaboration 8.8.x, 8.7.x, 8.6

Note:

Optional, use an exception DB

If you want an exceptions DB to allow people to send as alternate addresses 

 cd /opt/zimbra/conf
 edit slm-exceptions-db

Add the alternate ID addresses and the real userid, for example for the user joe who has joe@gmail.com 

 joe@gmail.com joe

Then run postmap slm-exceptions-db to generate the database 

postmap slm-exceptions-db

Update zimbraMtaSmtpdRejectUnlistedRecipient & zimbraMtaSmtpdRejectUnlistedSender

zmprov mcf zimbraMtaSmtpdRejectUnlistedRecipient yes
zmprov mcf zimbraMtaSmtpdRejectUnlistedSender yes
zmmtactl restart
zmconfigdctl restart

Set the zimbraMtaSmtpdSenderLoginMaps portion

If the exception db is used
zmprov mcf zimbraMtaSmtpdSenderLoginMaps 'lmdb:/opt/zimbra/conf/slm-exceptions-db, proxy:ldap:/opt/zimbra/conf/ldap-slm.cf' +zimbraMtaSmtpdSenderRestrictions reject_authenticated_sender_login_mismatch
If the exception db is not used
zmprov mcf zimbraMtaSmtpdSenderLoginMaps  proxy:ldap:/opt/zimbra/conf/ldap-slm.cf +zimbraMtaSmtpdSenderRestrictions reject_authenticated_sender_login_mismatch
Edit the file smtpd_sender_restrictions

You need to edit the file 

vi /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf

Should look like this: 

permit_mynetworks, reject_sender_login_mismatch

After a minute, zmconfigd will update the postfix configuration automatically and apply the new rules. Now if an account is hacked, and this is in place, they will not be able to send out emails with different "from" addresses. 


Ref:

https://wiki.zimbra.com/wiki/Enforcing_a_match_between_FROM_address_and_sasl_username_8.5

Comments

Post a Comment

Popular posts from this blog

Cambium cnPilot E400/E410/E500 Configuration Tutorial

-
Image
Basic Connectivity:   Router (Broadband/mikrotik |dhcp enabled) >>> E400/E410/E500 + LAPTOP Cambium (Powered ON) [POE port] >>>> LAPTOP [LAN port] Step 1: Open Cambium controller in the browser. Step 2: After entering in to the site click on the Onboard Device option from Home Tab of Left Panel. Step 3: In the Onboard Option, we will get Claim Device option to adopt a Cambium AP. Step 4: Now we will move to the Cambium AP configuration Part. Below are credentials of default login access of cnpilot E400/E410/E500/E410/E500. IP:192.168.0.1 Command Line Access: Username: admin Telnet: Disabled by default Password: admin SSH: Enabled by default (on standard port: 22) ***We can also use dhcp IP to login to the cnpilot E400/E410/E500. We will get login page. Step 5: We can see several TAB on left panel. On the DashBoard Tab, we will get some overall information. Some are useful for the configuration; some are useful for troubleshoo...
Read more

Disabling Zimbra's AntiSpam, Amavis and AntiVirus filtering

-
 Check whether antispam and antivirus service is enabled currently on server using the given command zmprov -l gs <mail.example.com> | egrep -i 'serviceen|servicein'  The above command will list all the services which are currently installed and enabled on the server. Disable the antivirus and antispam services using the given commands zmprov -l ms <mail.example.com> -zimbraServiceEnabled antispam  zmprov -l ms <mail.example.com> -zimbraServiceEnabled amavis zmprov -l ms <mail.example.com> -zimbraServiceEnabled antivirus  Comment the following line in the file /opt/zimbra/postfix/conf/main.cf content_filter = smtp-amavis:[127.0.0.1]:10024  Restart services on server zmcontrol restart  Confirm that the antispam and antivirus services are disabled with the given command zmprov -l gs <mail.example.com> | egrep -i 'serviceen|servicein'  zmcontrol status 
Read more

Error "Unable to retrive Zimbra GPG key for package validation"

-
From the installation log we see: Executing: /tmp/tmp.mSlzRMclVa/gpg.1.sh --keyserver keyserver.ubuntu.com --recv-keys 9BE6ED79 gpg: requesting key 9BE6ED79 from hkp server keyserver.ubuntu.com gpg: keyserver timed out gpg: keyserver receive failed: keyserver error 1. Open port 11371 11371 tcp,udp hkp OpenPGP HTTP Keyserver 2. Force it to use port 80: gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 9BE6ED79 Ref: https://wiki.zimbra.com/wiki/Error_%22Unable_to_retrive_Zimbra_GPG_key_for_package_validation%22
Read more