SNI support for Dovecot and Postfix

If you are in position that you need multiple SSL certificates for different domains on single mail server, you can do it with SNI. Of corse, on very old versions this is not supported. Check documentation first, if its supported for your version of Dovecot and Postfix.

Dovecot:

In case of incoming mailserver Dovecot it’s easy as listed bellow. I made file ssl-sni.conf in which I add SNI configurations for my domains. Then I included ssl-sni.conf in main dovecot config.

Create ssl-sni.conf and add your SNI definitions in it:

local_name mail.domain1.com {
ssl_cert = </etc/ssl/certs/domain1/fullchain.pem
ssl_key = </etc/ssl/certs/domain1/privkey.pem
}

local_name pop3.domain2.com {
ssl_cert = </etc/ssl/certs/domain2/fullchain.pem
ssl_key = </etc/ssl/certs/domain2/privkey.pem
}
...

Then include this in main dovecot config (you can add those configurations directly in dovecot.conf or 00-ssl.conf also. I just prefer separate this):

# SNI include
!include ssl-sni.conf

Postfix:

As for Postfix, configuration is also simple:

Inside /etc/postfix/, create file domain_ssl.map and add ssl definitions in it:

mail.domain1.com /etc/ssl/certs/domain1/privkey.pem /etc/ssl/certs/domain1/fullchain.pem
smtp.domain2.net /etc/ssl/certs/domain2/privkey.pem /etc/ssl/certs/domain2/fullchain.pem

Run postmap and restart Postfix:

[root@mail postfix]# postmap -F domain_ssl.map which will create domain_ssl.map.db
[root@mail postfix]# systemctl restart postfix

If everything is OK, you should now have SNI supported mail server.

Limit number of email recipients with Roundcube

I had an issue with one of the mail servers on which one user’s account password was stolen and was sending spam. Spam was sent from Roundcube and there was a very large number of recipients in one email. Limit the number of recipients in Postfix was not an option. It had to be done on webmail. It is very simple with Roundcube. Just add variable bellow in your Roundcube configuration file – config.inc.php.

$config['max_recipients'] = 10;

This will allow only 10 recipients in one email message. Of course you can change the number according to your needs.

Build NGINX with GeoIP2 support from source

I used GeoIP library with Nginx for quite some time, but it came to EOL. GeoIP2 is now avalible. It is great tool for blocking unwanted traffic from your webserver. This was done on Centos 7. If you don’t want to pay for getpagespeed’s payed version, than you must build this module from source.

First, you’ll need to know your curent NGINX version


[root@myserver ~]# nginx -v
nginx version: nginx/1.16.1

Then, download exact same version of NGINX from this site and unpack it. In my case:


[root@myserver ~]# wget http://nginx.org/download/nginx-1.16.1.tar.gz
[root@myserver ~]# tar -xvzf nginx-1.16.1.tar.gz
[root@myserver ~]# cd nginx-1.16.1.tar.gz

Then you should download ngx_http_geoip2_module – geoip2 module for NGINX:


[root@myserver ~]# wget https://github.com/leev/ngx_http_geoip2_module/archive/master.zip
[root@myserver ~]# unzip master.zip

You should install GCC and Development Tools for dependencies.

[root@myserver ~]# yum groupinstall ‘Development Tools’
[root@myserver ~]# yum install gcc

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Disable OPcache for specific PHP script. Exclude from OPcache.

Sometimes accelerating with opcache can cause some problems with your application scripts. In those cases, when your script shouldn’t be accelerated, you can specify those scripts with opcache’s blacklist which will exclude this files from acceleration. Example bellow is done on CentOS 7.

First, find configuration file for your opcache php extension. You can do something like this:

[root@meow php.d]# php -i | grep opcache | grep ini
Additional .ini files parsed => /etc/php.d/10-opcache.ini,

Open 10-opcache.ini and you should see something like bellow. Path to opcache’s blacklist file.

; The location of the OPcache blacklist file (wildcards allowed).
; Each OPcache blacklist file is a text file that holds the names of files
; that should not be accelerated.
opcache.blacklist_filename=/etc/php.d/opcache*.blacklist

Close 10-opcache.ini and open file named opcache-default.blacklist which should be in same directory. If not, create one. This file will contain a list of php scripts which should be ignored by opcache. 

[root@meow php.d]# cat opcache-default.blacklist
; The blacklist file is a text file that holds the names of files
; that should not be accelerated. The file format is to add each filename
/path/to/ignored/script/ignoreThis.php
/path/to/another/ignored/script/ignoreThisToo.php
...

Multidomain webroot for Letsencrypt with NGINX

If you have web server on which there is a lot of virtual hosts, you may want to have one webroot directory for Letsencrypt SSL certificates only. So when Letsencrypt will make the requests for SSL registration or renewal, it will look in this directory. In this case I did this on CentOS 7 with NGINX web server.

First, let’s create directory what will be used for letsencrypt purposes. It must be writable by your web server user. You can define different path.

[root@machine ~]# mkdir -p /var/www/le-certs
[root@machine ~]# chown -R wwwuser:wwwgroup /var/www/le-certs

Letsencrypt will need access in “.well-known/acme-challenge”. For NGINX add something like this in your server block for desired virtual host.

location ~ /.well-known/acme-challenge/ {
             root /var/www/le-certs/;
             break;
}

You can also create new file named, for example le-config.conf and add block above in to it. Then you can simply include this line in your virtual hosts. 

server {
             listen :443 ssl http2;
             server_name mywebsite.com www.mywebsite.com;
             root /var/www/mywebsite/;

             include le-config.conf;
              ...
}

 

 

RoundCube: Could not save new password. Connection error. Recv failure: Connection reset by peer

If you’re having trouble when try to change your email password in Roundcube on your Directadmin installation, than error will be probably something like this:

Could not save new password. Connection error. Recv failure: Connection reset by peer

Solution is simple. Just open Roundcube configuration file (/var/www/html/roundcube/plugins/password/config.inc.php) and find:

$rcmail_config['password_directadmin_host'] = 'tls://localhost';

then, change it to:

$rcmail_config['password_directadmin_host'] = 'ssl://localhost';

It should work.

Limit xmlrpc.php to only specific web clients

Xmlrpc.php is very common target of attacks. In most cases you don’t need xmlrpc, but if you use third-party apps like WordPress for iPhone or android or other editors, then xmlrpc is the one who communicates between them and your WordPress installation. If you’ll be using it, it can be good idea to limit access to it only from “browsers” that you are using to access it. In case bellow, I’m using iPhone WordPress app.

When access to xmlrpc.php via iphone app, you’ll see that access log looks like this:

[11/Jun/2017:19:45:08 +0200] "POST /xmlrpc.php HTTP/2.0" 200 462 "-" "Mozilla/5.0 (iPhone; CPU iPhone OS 10_3_2 like Mac OS X) AppleWebKit/603.2.4 (KHTML, like Gecko) Mobile/14F89 wp-iphone/7.7"

From this you can see that wp-iphone/7.7 is named as client. So this will be our key for nginx configuration. We’ll make rule that will only accept requests to xmlrpc.php from clients containing string “wp-iphone”. Other clients will be denied. This is not bulletproof of as web client can be easily spoofed, but it should block majority of attacks.

location = /xmlrpc.php {
if ($http_user_agent !~* "wp-iphone")
{
return 403;
}
include fastcgi_params;
fastcgi_pass 127.0.0.1:<your_php_fpm_port>;
}

Bulk TTL change in Directadmin

You may want to change TTL values for all domains and their DNS records on your Directadmin server. This can be done very easily. Here is how.

  • Go to templates directory. 
    cd /usr/local/directadmin/data/templates
  • Directadmin’s default TTL value is 14400, so let’s say we want to change it to 300. You will have to edit template file named.db. 
    sed -ie 's/14400/300/g' named.db
  • Rewrite all configuration files for each user 
    echo "action=rewrite&value=named" >> /usr/local/directadmin/data/task.queue

Wait a minute or two, then check if user configs were rewrited with new values. Go to /etc/namedb and than open .db file of some domain. It should contain new TTL value.

cPanel – create directory alias on domain

Creating aliases on cpanel server is easy – for domains. But when you want to create directory alias for files outside of document root, there is no quick/click option in control panel. By directory alias I mean for example, http://mydomain.com/something. Where /something is directory that is outside of your document root – public_html of domain. Another example, you have domain mydomain.com and you want phpmyadmin to be accessible on http://mydomain.com/phpmyadmin, but phpmyadmin is installed outside of document root of  mydomain.com. You’ll need directory alias. Here is quick way to do it.

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Ultimate NGINX configuration for WordPress

Most of the sites that I created are based on WordPress. WordPress is great platform for your sites if you take a little care for it. different kind of abusive behavior on Wordpress systems is very common. Weak points are in most cases plugins, themes and outdated code in general. Many times people think, that security of their websites is all about hosting provider, firewalls… It’s true to some point. But one of the most fundamental steps to better WordPress security is up to the end-user. Take care of your site, update it regularly, use only good plugins and themes… It’s so important that you take care for regular updates and fixes. Also, try to use as least plugins as possible. If you are using only one theme, delete the ones that you don’t use. If you’ll  use theme downloaded from internet, only use themes from good providers.

NGINX in combination with good configuration and cache system can make your website lightning fast and super responsive. Memcached, Redis, Opcache are also great for optimizing your site. You definitely want to check into them too. W3 Total Cache plugin is great and easy to configure. More about this another time.

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