2016. április 11., hétfő

A Mikrotik guest network can be more difficult than you may think

In recent RouterOS is a single click to set up a guest wifi AP. Saying guest I mean such a network that is fully or partly allowed to reach public internet but denied to reach the internal private network. Here is a simple howto about adding a second wifi AP/ slave interface. The only problem with that is it's unsecure. :( A most common way is using the QuickSet method. Everyone knows what to do seeing this window:
So if you I build a second AP like this:

it's going to use the same DHCP server as the internal WIFI. Obviously, because it's on the same bridge (switch) interface. I always wondered how they are still separeted by the RouterOS? The answer is Mikrotik's genius Layer2 firewall called Bridge filtering.

But you discover an embarassing problem if you have more IP subnets (e.g. VPN networks over pub net) and also want to accept the guest wifi filtering to them. One simply can't utilize Layer2 filtering over Layer3 routing and, of course, there is no work vice versa.

Soution: forget the built-in bridge and create a new bridge only for your guest wifi.
/interface bridge add name=bridge-guestwifi
Add a new security profile for guest if you happen to still doesn't have any:  
/interface wireless security-profiles add authentication-types=wpa2-psk mode=dynamic-keys name=guestwifi wpa2-pre-shared-key=topsecretpassword
Add your new slave interface:
 /interface wireless
add disabled=no mac-address=D6:CA:6E:4F:54:28 master-interface=wlan1 name=wlan2 security-profile=guest ssid="For Guests" wds-default-bridge=bridge-guestwifi
and link these 2 to each other.
/interface bridge port add bridge=bridge-guestwifi interface=wlan2

So far so good. Layer2 filtering is done now. But now the guests are totally separeted from your DHCP server so you need to create a new, dedicated DHCP pool for them. It requires a new address and subnet.
/ip address add address= interface=bridge-guest network=
/ip pool add name=guest ranges=
/ip dhcp-server add address-pool=guest disabled=no interface=bridge-guest name=guest
/ip dhcp-server network add address= dns-server= gateway=

Lets suppose that you have such a source nating rule that nats anything that is going out to the internet:
In that case we have good news. You don't have to set up any more nat rule because the guest network will hit the above rule. But it's not secured yet. The following Layer3 high priority firewall rule will take care of them:
/ip firewall filter
add action=drop chain=forward in-interface=bridge-guestwifi out-interface=!ether1-gateway
So from now on, guests are denied to go anywhere but the public internet.

2016. április 7., csütörtök

Ban / reject users with freeradius based on MAC addresses

Freeradius is a common tool if someone wants to set up an enterprise WiFi authentication. But if it's in a public institude, e.g. a school, sooner or later your WiFi users' passwords will leak out and after password changes your logs get full of incorrect logins from the mischievous studends. Solution: build a script that scan the logfile for incorrect logins and ban the MAC addresses of those devices. Here is a little help on how to start thinking:
add the following to your /etc/freeradius/modules/files

files rejectmac {
                key = "%{Calling-Station-ID}"
                usersfile = ${confdir}/rejectmacaddress.txt
                compat = no

add the following to authorize{} section of your /etc/freeradius/sites/sites-enabled/default

        if (ok) {

create a new file /etc/freeradius/rejectmac.conf and add 
passwd rejectmac {
  filename = /etc/freeradius/rejectmacaddress.txt
      delimiter = ,
      format = "*Calling-Station-Id"

create a new file /etc/freeradius/rejectmacaddress.txt and fill it with the kiddies MACs like this

add this to the beginning of your radiusd.conf
$INCLUDE rejectmac.conf

restart your freeradius daemon and get ready to go home.

2016. április 6., szerda

Debian Wheezy Mail Server – Postfix Dovecot Sasl MySQL PostfixAdmin and RoundCube

Shamefully I didn't want to find my own way so the whole tutorial I followed is here.
For my personal further usage, I attached the working nginx, dovecot, postfix and php5 config to this post. There are two minor differences from the original tutorial: I don't use spam filtering because at me it's done by a 3rd party provider. Second, I use an outgoing TLS smarthost via mail submission 587 port, detailed in the postfix/main.cnf.
Note that sensitive infos are all removed and in the tgz there is a missing sock, obviously, because sockets can't be packed. (tar example/php5/fpm/socks/ssl_example.com.sock: socket ignored.)
Follow the original howto first.

Versions for my pack are:
Linux box 3.2.0-4-amd64 #1 SMP Debian 3.2.73-2+deb7u3 x86_64 GNU/Linux
ii  nginx                              1.2.1-2.2+wheezy4                 all          small, powerful, scalable web/proxy server
ii  nginx-common                       1.2.1-2.2+wheezy4                 all          small, powerful, scalable web/proxy server - common files
ii  nginx-full                         1.2.1-2.2+wheezy4                 amd64        nginx web/proxy server (standard version)
ii  dovecot-common                     1:2.1.7-7+deb7u1                  all          Transitional package for dovecot
ii  dovecot-core                       1:2.1.7-7+deb7u1                  amd64        secure mail server that supports mbox, maildir, dbox and mdbox mailboxes
ii  dovecot-gssapi                     1:2.1.7-7+deb7u1                  amd64        GSSAPI authentication support for Dovecot
ii  dovecot-imapd                      1:2.1.7-7+deb7u1                  amd64        secure IMAP server that supports mbox, maildir, dbox and mdbox mailboxes
ii  dovecot-ldap                       1:2.1.7-7+deb7u1                  amd64        LDAP support for Dovecot
ii  dovecot-lmtpd                      1:2.1.7-7+deb7u1                  amd64        secure LMTP server for Dovecot
ii  dovecot-mysql                      1:2.1.7-7+deb7u1                  amd64        MySQL support for Dovecot
ii  dovecot-pgsql                      1:2.1.7-7+deb7u1                  amd64        PostgreSQL support for Dovecot
ii  dovecot-pop3d                      1:2.1.7-7+deb7u1                  amd64        secure POP3 server that supports mbox, maildir, dbox and mdbox mailboxes
ii  dovecot-sieve                      1:2.1.7-7+deb7u1                  amd64        sieve filters support for Dovecot
ii  dovecot-sqlite                     1:2.1.7-7+deb7u1                  amd64        SQLite support for Dovecot
ii  postfix                            2.9.6-2                           amd64        High-performance mail transport agent
ii  postfix-mysql                      2.9.6-2                           amd64        MySQL map support for Postfix
ii  php5-common                        5.5.33-1~dotdeb+7.1               amd64        Common files for packages built from the php5 source
ii  php5-fpm                           5.5.33-1~dotdeb+7.1               amd64        server-side, HTML-embedded scripting language (FPM-CGI binary)
ii  php5-imap                          5.5.33-1~dotdeb+7.1               amd64        IMAP module for php5
ii  php5-intl                          5.5.33-1~dotdeb+7.1               amd64        internationalisation module for php5
ii  php5-mcrypt                        5.5.33-1~dotdeb+7.1               amd64        MCrypt module for php5
ii  p
hp5-mysql                         5.5.33-1~dotdeb+7.1               amd64        MySQL module for php5