Allow .local domain suffix to be resolved

On many chances you may need to configure some domains using .local suffix. Unfortunately this is covered by RFC 6762 (multicast DNS). On specific Linux distributions you will not be able to resolv such domains using DNS server you set either in the machine or in the cloud settings (for instance Azure).

How to you know that the DNS query is not reaching your desired DNS server? In case you use named, then first enable query logging by the following comman:

rndc querylog on

Now DNS queries from the clients who set that particular DNS server as its resolved will be visible in system logger file, like /var/log/messages. Then try to make a ping or curl to the desired domain address with .local suffix and check if it appears in the DNS server log. You can also force DNS query to reach that DNS server by using dig command:

dig yourdomain.local @yourdnsserver

If it’s present in DNS server log file then you’re confident that if you reconfigure your client machine it will work properly. To do this on Ubuntu 20 few things are required. First one is to have IP configuration fixed (some yaml file in /etc/netplan/ directory):

network:
    ethernets:
        eth0:
            dhcp4: no
            addresses:
            - 10.99.99.10/24
            gateway4: 10.99.99.1
            nameservers:
              addresses: [10.99.99.20]
            dhcp4-overrides:
                route-metric: 100
            dhcp6: false
            match:
                driver: hv_netvsc
                macaddress: 60:45:bd:94:4a:85
            set-name: eth0
    version: 2

And also as suggested in the netplan configuration file, to disable cloud init feature create file in /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following content:

network: {config: disabled}

Then reapply network configuration:

sudo netplan try

For me, personally, it is sometimes overcomplicated as comparing to CentOS distribution. Now with the fixed settings that should not be overwritten by some other processes you can proceed with disabling local DNS stub listener:

cd /etc/
sudo ln -sf ../run/systemd/resolve/resolv.conf
cd /etc/systemd/
sudo sed -i -e 's/#DNSStubListener=yes/DNSStubListener=no/' resolved.conf
sudo systemctl restart systemd-resolved

You can put your own desired DNS server in the /etc/systemd/resolved.conf file. After all of these operations try ping, curl or wget with your .local domain and check if this query appears in the DNS server log file.

Disabling uncategorized internal Suricata rules in pfSense

I want to enable only particular rules categories. Do not want to have all these internal Suricate rules as they cover too broad variaty of cases including loads of false-positive. If one would like to go for deep traffic analysis then they would be fine, but in case you see “STUN Binding Request On Non-Standard High Port” and know that is your P2P camera in the LAN then it’s worth disabling all of that things at once. To disable them it is a little bit tricky on pfSense installation.

Go to Interfaces and selected desired one. Be sure to uncheck all snort or ET rules before. Then go to WAN Rules and select Active Rules in category dropdown box. Click Disable All. Now you are running without all default rules and can enable only those which you are interested most to have. For example you can try with the following:

  • attach_response
  • botcc
  • 3coresec
  • ciarmy
  • compromised
  • deleted
  • dos
  • exploit / exploit_kit
  • hunting
  • malware
  • phishing
  • scan
  • shellcode
  • sql
  • threatview_CS_c2
  • tor
  • user_agent
  • web_client
  • web_server
  • web_specific_apps
  • worm

Multiple ZFS pools on single drive

Image a hypothetical scenario having two 512 GB drives and want to use a Proxmox ZFS VM replication onto a second server with one 1 TB drive. Solution is quite simple. By using fdisk, create two primary partitions on the bigger drive and then go to Disks.ZFS.CreateZFS and you will be able to select a partition for the particular pool. One downside of such a setup is that ZFS liks to have whole drive for it’s own, please keep in mind that the performance may vary.

disk/partition ‘/dev/sdX’ has a holder (500)

Having LVM on the disk causes system to automatically active such volumes. I installed used drive with Ubuntu on it to my Proxmox server. Using Proxmox’s UI you will not be able to wipe this drive, because volume group has been already auto-activated. You need to log into shell and then:

vgs # pick VG on your interest
vgchange -a n vgname # pass your VG to deactivate it

After this, you are ready to wipe drive from the UI.

Package is in a very bad inconsistent state

Aborting Ubuntu packages update via Ansible gave me some weird state of libatk-wrapper-java-jni package. My playbook installs default-jre and it was painfully slow so I thought that there is some lockup, but there was not. My VM performed poorly at that moment, probably due to the fact that it came from a HDD with badblocks which got migrated to another one. It just works, but I’m not 100% sure if it is healhty. So… in case you have some broken package installation try:

sudo apt-get install --reinstall libatk-wrapper-java-jni

And now you are good to go with autoclean, update and possibly upgrade to check whether really there is no problem still dangling on your system. On mine, it is fine now.

UnsupportedClassVersionError

Changing Java language level to run compiled code on older runtimes

I’m working on some Java project. I use IntelliJ IDEA and deciced to go with Oracle’s OpenJDK-18. But… this runtime is available by default only during compilation in the IDE. In the system I have OpenJDK-11. Trying to run code compiled by JDK-18 on JDK-11 gives me the following message:

java.lang.UnsupportedClassVersionError: Main has been compiled by a more recent version of the Java Runtime (class file version 62.0), this version of the Java Runtime only recognizes class file versions up to 55.

To overcome this go to module settings (or Project Structure) and change Language Level to lower value. In case you compile with 18 then it will have version 18 set. Switch to version 11 (local variables syntax for lambda parameters) and compile once again. Now you will be able to launch your application even with older JDK.