Install and configure Milter Manager

Install to CentOS 7

Install to CentOS 7 — How to install milter manager to CentOS 7

About this document

This document describes how to install milter manager to CentOS 7. See Install for general install information.

In this document, CentOS 7.6 is used. Sudo is used to run a command with root privilege. If you don’t use sudo, use su instead.

Install packages

Postfix is used as MTA because it’s installed by default.

Spamass-milter, clamav-milter and milter-greylist are used as milters. Milter packages registered in EPEL are used.

Register EPEL like the following:

% sudo yum install -y epel-release

Now, you install milters:

% sudo yum install -y spamass-milter-postfix clamav-scanner-systemd clamav-update clamav-milter clamav-milter-systemd milter-greylist

And you install RRDtool for generating graphs:

% sudo yum install -y rrdtool

Build and Install

milter manager can be installed by yum.

Register milter manager yum repository like the following:

% curl -s https://packagecloud.io/install/repositories/milter-manager/repos/script.rpm.sh | sudo bash

See also: <URL:https://packagecloud.io/milter-manager/repos/install>

Now, you install milter manager:

% sudo yum install -y milter-manager

Configuration

Here is a basic configuration policy.

milter-greylist should be applied only if S25R condition is matched to reduce needless delivery delay. But the configuration is automatically done by milter manager. You need to do nothing for it.

It’s difficult that milter manager runs on SELinux. Disable SELinux policy module for Postfix and Milter.

% sudo semodule -d postfix
% sudo semodule -d milter

Configure spamass-milter

At first, you configure spamd.

spamd adds “[SPAM]” to spam mail’s subject by default. If you don’t like the behavior, edit /etc/mail/spamassassin/local.cf.

Before:

rewrite_header Subject [SPAM]

After:

# rewrite_header Subject [SPAM]

Add the following configuration to /etc/mail/spamassassin/local.cf. This configuration is for adding headers only if spam detected.

remove_header ham Status
remove_header ham Level

Start spamd on startup:

% sudo systemctl enable spamassassin

Start spamd:

% sudo systemctl start spamassassin

Here are spamass-milter’s configuration items:

  • Disable needless body change feature.
  • Reject if score is larger than or equal to 15.

Change /etc/sysconfig/spamass-milter:

Before:

#EXTRA_FLAGS="-m -r 15"

After:

EXTRA_FLAGS="-m -r 15"

Start spamass-milter on startup:

% sudo systemctl enable spamass-milter

Start spamass-milter:

% sudo systemctl start spamass-milter

Configure clamav-milter

Update ClamAV virus database and start clamd.

Edit /etc/freshclam.conf like the following. It comments out “Example”, changes “NotifyClamd” value and uncomments other items.

Before:

Example
#LogFacility LOG_MAIL
#NotifyClamd /path/to/clamd.conf

After:

#Example
LogFacility LOG_MAIL
NotifyClamd /etc/clamd.d/scan.conf

Run freshclam by hand at the first time:

% sudo freshclam

Configure clamd.

Edit /etc/clamd.d/scan.conf like the following. It comments out “Example” and uncomments other items:

Before:

Example
#LogFacility LOG_MAIL
#LocalSocket /run/clamd.scan/clamd.sock

After:

#Example
LogFacility LOG_MAIL
LocalSocket /run/clamd.scan/clamd.sock

Start clamd on startup:

% sudo systemctl enable [email protected]

Start clamd:

% sudo systemctl start [email protected]

Configure clamav-milter.

Edit /etc/mail/clamav-milter.conf like the following. It comments out “Example”, change “ClamdSocket” value and uncomments other items:

Before:

Example
#MilterSocket /run/clamav-milter/clamav-milter.socket
#MilterSocketMode 660
#ClamdSocket tcp:scanner.mydomain:7357
#LogFacility LOG_MAIL

After:

#Example
MilterSocket /run/clamav-milter/clamav-milter.socket
MilterSocketMode 660
ClamdSocket unix:/run/clamd.scan/clamd.sock
LogFacility LOG_MAIL

Add “clamilt” user to “clamscan” group to access clamd’s socket:

% sudo usermod -G clamscan -a clamilt

Start clamav-milter on startup:

% sudo systemctl enable clamav-milter

Start clamav-milter:

% sudo systemctl start clamav-milter

Configure milter-greylist

Change /etc/mail/greylist.conf for the following configurations:

  • use the leading 24bits for IP address match to avoid Greylist adverse effect for sender uses some MTA case.
  • decrease retransmit check time to 10 minutes from 30 minutes (default value) to avoid Greylist adverse effect.
  • increase auto whitelist period to a week from 1 day (default value) to avoid Greylist adverse effect.
  • don’t use Greylist when trusted domain passes SPF. (Trusted domains are configured in milter manager)
  • use Greylist by default.

The configuration relaxes Greylist check to avoid Greylist adverse effect. It increases received spam mails but you should give priority to avoid false positive rather than false negative. You should not consider that you blocks all spam mails by Greylist. You can blocks spam mails that isn’t blocked by Greylist by other anti-spam technique such as SpamAssassin. milter manager helps constructing mail system that combines some anti-spam techniques.

Before:

socket "/run/milter-greylist/milter-greylist.sock"
# ...
racl whitelist default

After:

socket "/run/milter-greylist/milter-greylist.sock" 660
# ...
subnetmatch /24
greylist 10m
autowhite 1w
sm_macro "trusted_domain" "{trusted_domain}" "yes"
racl whitelist sm_macro "trusted_domain" spf pass
racl greylist sm_macro "trusted_domain" not spf pass
racl greylist default

Start milter-greylist on startup:

% sudo systemctl enable milter-greylist

Start milter-greylist:

% sudo systemctl start milter-greylist

Configure milter manager

Add “milter-manager” user to “clamilt” group to access clamav-milter’s socket:

% sudo usermod -G clamilt -a milter-manager

Add “milter-manager” user to “mail” group and “grmilter” group to access milter-greylist’s socket:

% sudo usermod -G mail -a milter-manager
% sudo usermod -G grmilter -a milter-manager

Add “milter-manager” user to “postfix”” group to access spamass-milter’s socket:

% sudo usermod -G postfix -a milter-manager

milter manager detects milters that installed in system. You can confirm spamass-milter, clamav-milter and milter-greylist are detected:

% sudo /usr/sbin/milter-manager -u milter-manager -g milter-manager --show-config

The following output shows milters are detected:

...
define_milter("milter-greylist") do |milter|
  milter.connection_spec = "unix:/run/milter-greylist/milter-greylist.sock"
  ...
  milter.enabled = true
  ...
end
...
define_milter("clamav-milter") do |milter|
  milter.connection_spec = "unix:/var/run/clamav-milter/clamav-milter.socket"
  ...
  milter.enabled = true
  ...
end
...
define_milter("spamass-milter") do |milter|
  milter.connection_spec = "unix:/run/spamass-milter/postfix/sock"
  ...
  milter.enabled = true
  ...
end
...

You should confirm that milter’s name, socket path and “enabled = true”. If the values are unexpected, you need to change /etc/milter-manager/milter-manager.local.conf. See Configuration for details of milter-manager.local.conf.

But if we can, we want to use milter manager without editing miter-manager.local.conf. If you report your environment to the milter manager project, the milter manager project may improve detect method.

milter manager’s configuration is finished.

Start to milter manager on startup:

% sudo systemctl enable milter-manager

Start to milter manager:

% sudo systemctl start milter-manager

milter-test-server is usuful to confirm milter manager was ran:

% sudo -u milter-manager milter-test-server -s unix:/var/run/milter-manager/milter-manager.sock

Here is a sample success output:

status: accept
elapsed-time: 0.128 seconds

If milter manager fails to run, the following message will be shown:

Failed to connect to unix:/var/run/milter-manager/milter-manager.sock

In this case, you can use log to solve the problem. milter manager is verbosily if –verbose option is specified. milter manager outputs logs to standard output if milter manager isn’t daemon process.

You can add the following configuration to /etc/sysconfig/milter-manager to output verbose log to standard output:

OPTION_ARGS="--verbose --no-daemon"

Restart milter manager:

% sudo systemctl restart milter-manager

Some logs are output if there is a problem. Running milter manager can be exitted by Ctrl+c.

OPTION_ARGS configuration in /etc/sysconfig/milter-manager should be commented out after the problem is solved to run milter manager as daemon process. And you should restart milter manager.


Configure Postfix

Enables Postfix:

% sudo systemctl enable postfix
% sudo systemctl start postfix

Configure Postfix for milters. Append following lines to /etc/postfix/main.cf:

milter_protocol = 6
milter_default_action = accept
milter_mail_macros = {auth_author} {auth_type} {auth_authen}

For details for each lines.

milter_protocol = 6Use milter protocol version 6.
milter_default_action = acceptMTA receives mails when MTA cannot access milter. Although there are problems between MTA and milter, MTA can deliver mails to clients. But until you recover milter, perhaps MTA receives spam mails and virus mails.

If you can recover the system quickly, you can specify ‘tempfail’ instead of ‘accept’. Default value is ‘tempfail’.

milter_mail_macros = {auth_author} {auth_type} {auth_authen}MTA gives information related SMTP Auth to milters. milter-greylist etc. uses it.

Register milter manager to Postfix. It’s important that spamass-milter, clamav-milter and milter-greylist aren’t needed to be registered because they are used via milter manager.

Append following lines to /etc/postfix/main.cf:

smtpd_milters = unix:/var/run/milter-manager/milter-manager.sock

Reload Postfix’s configuration.

% sudo systemctl reload postfix

milter manager logs to syslog. If milter manager works well, some logs can be shown in /var/log/maillog. You need to send a test mail for confirming.

Conclusion

There are many configurations to work milter and Postfix together. They can be reduced by introducing milter manager.

Without milter manager, you need to specify sockets of spamass-milter, clamav-milter and milter-greylist to /etc/postfix/main.cf. With milter manager, you don’t need to specify sockets of them, just specify a socket of milter manager. They are detected automatically. You don’t need to take care some small mistakes like typo.

milter manager also detects which ‘/sbin/chkconfig -add’ is done or not. If you disable a milter, you use the following steps:

% sudo systemctl stop milter-greylist
% sudo systemctl disable milter-greylist

You need to reload milter manager after you disable a milter.

% sudo systemctl reload milter-manager

milter manager detects a milter is disabled and doesn’t use it. You don’t need to change /etc/postfix/main.cf.

You can reduce maintainance cost by introducing milter manager if you use some milters on CentOS.

milter manager also provides tools to help operation. Installing them is optional but you can reduce operation cost too. If you also install them, you will go to Install to CentOS (optional) .

Yum warning

After a yum update I receive this worning :

warning: /etc/fail2ban/jail.conf created as /etc/fail2ban/jail.conf.rpmnew

Those warnings are expected if you have made changes to your configuration files. yum is kind enough to not overwrite your existing modified configuration, but instead writes the new default configuration file to a .rpmnew file, which you can then review and perhaps incorporate the new defaults etc to your own configuration. This is OK. The kernel module warnings are also of no concern.

 

How to Use Virtual Environments

Useful command for python system environment or custom environment.
When any environment is not activated you are using the system environment.
pip list
pip3 list
create new environment :
python3 -m venv env_name
create a directory env_name
activate the env_name :
source env_name/bin/activate
show which python :
which python
deactivate environment :
deactivate
create an environment with the same packages of the system environment :
python3 -m venv env_name –system-site-packages
how to show the only packages installed in the env_name environment
pip list –local

Yum clean package and fix duplicate packages

From time to time, the yum package manager may encounter issues with duplicate packages that are erroneously installed on a system. This manifests in a yum update going awry, telling us something along the lines of this:

You may at times install all other packages via yum update –skip-broken, but it will still leave some trouble on the system. Best to take care of it.

Here’s how I’ve managed to do it on many occasions:

Installing yum-utils

The utility that will help us fix these issues is called package-cleanup, and it’s part of the yum-utils package. Let’s install that first before we continue:

Next, let’s see what’s wrong with our system. package-cleanup –dupes will show us duplicate packages on the system:

The list could go on. Here we see that several packages are seemingly installed more than once. The –cleandupes parameter will take care of this, erasing such superfluous packages:

The process will look very similar to a yum update, with yum verifying and erasing the duplicates. It doesn’t hurt to make a note of the erased packages and check if the latest version is still installed. Should this not be the case, you can bring those packages back with “yum reinstall packagename”.

Finishing Up

At this point, let’s try to update the system again with a standard yum update command. This should take care of any missing dependencies that may have been removed in the previous process, and of course it’ll update the rest of your system too, hopefully taking care of the initial problem.

Finally, to see if there’s any remaining trouble with the yum database, we can issue the following and are – hopefully – greeted with the same message: