Category Archives: Ubuntu

Secure download of Ubuntu ISO installation images

Please follow the instructions on this page:
https://help.ubuntu.com/community/VerifyIsoHowto

There is another website, but it doesn't use SSL / HTTPS:
http://www.ubuntu.com/download/how-to-verify

The procedure is the same as I have already described for CentOS or Debian in my previous posts:

  1. Import the GPG-key and verify its fingerprint.
  2. Download the checksum file and verify its signature with the GPG-key.
  3. Check the iso file with the checksum file.

Again the fingerprint of the GPG-key is on a SSL encrypted website where you have to check the website certificate and its root CA.

Firefox ships with its own set of root CAs ("Builtin Object Token" as the Security Device in advanced preference settings). Here is a list of all root CAs included in Firefox along with their fingerprints:
https://mozillacaprogram.secure.force.com/CA/IncludedCACertificateReport

Builtin root CAs are hardcoded in /usr/lib/firefox/libnssckbi.so

CAs marked as "Software Security Device" are usually intermediate certificates that are downloaded from websites and stored locally. These CAs that are not builtin are either stored on a PKCS#11 compatible smartcard attached to your PC/laptop or saved to your home directory:
certutil -d ~/.mozilla/firefox/xxx.default -L

Chromium / Google Chrome does not ship with its own CA list but uses the CAs from the underlying operating system:
https://www.chromium.org/Home/chromium-security/root-ca-policy

On Ubuntu 16.04 these CAs are hardcoded in /usr/lib/x86_64-linux-gnu/nss/libnssckbi.so which is part of the package "libnss3".

Important things to note:

  • Verification of ISO images is based on GPG-keys which have to be checked by its fingerprints. You can get that fingerprint from a SSL secured website.
  • The security of a website depends on the root CA which is used to sign the website certificate. These CAs are stored locally in different locations based on the browser you are using.
  • Neither Firefox nor Chromium / Google Chrome are using CAs from the package "ca-certificates".
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Farmville 2 on Ubuntu Linux (Flash)

If you have trouble running Farmville 2 on you Linux installation in your browser, you should consider upgrading to the latest Ubuntu 16.04 version. I was experiencing some strange problems with an older Ubuntu 14.04 installation and from one day to the next could not run Farmville 2 any longer:

  • Farmville 2 was showing the initial loading screen with the progress bar right in the center, but the progress bar was not moving at all. There was no sound, no error message. Other flash applications were working fine.
  • I tried different browsers with no success: Chromium, Google Chrome, Firefox
  • I tried different Flash versions with no success: adobe flash, pepperflash

Upgrading to Ubuntu 16.04 (see one of my previous posts) solved the problem. I am using the following versions:

  • Chromium (chromium-browser 50.0.2661.102)
  • Flash (pepperflashplugin-nonfree 1.8.2, flash version 21.0.0.242)

Make sure your browser is using the right flash plugin by typing "about:plugins" in the address bar of your Chromium browser (UPDATE: this page is not working anymore, s. https://bugs.chromium.org/p/chromium/issues/detail?id=615738). It might be that you have several flash versions installed on your computer and Chromium is using an old one. Check your flash version on the official Adobe website: http://www.adobe.com/software/flash/about

Chromium is storing flash plugin information in the folder /etc/chromium-browser/customizations. For every installed flash plugin, there is a flash configuration file:

  • 10-flash (adobe-flashplugin / flashplugin-installer)
  • pepperflashplugin-nonfree (pepperflashplugin-nonfree)

Move the file of the flash package you are not using to a backup location and restart Chromium. The flash configuration file also sets the file location of the flash plugin that gets loaded into your browser. Make sure the plugin file path is pointing to the official flash plugin shared object (/usr/lib/pepperflashplugin-nonfree/libpepflashplayer.so).

With that configuration I am now able to run Farmville 2 on Facebook and use all of its features (which were not all working before either):

  • Full screen mode
  • Sound on/off toggle
  • Screenshot

WARNING:

  • Flash is known to have frequent security issues. If you do not absolutely need Flash, you should remove it from your computer.
  • If you choose to install it, at least make sure to only run Flash applications after you have confirmed them manually. Both Firefox and Chrome/Chromium allow you to configure this option.
  • You might also want to install a second browser without Flash for regular internet surfing, and only use your Flash enabled browser for Farmville 2.
  • Make sure to regularly update your Flash package as soon as there is a new version available.
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Upgrade from Ubuntu Desktop 14.04 LTS to 16.04 LTS (KDE desktop)

I just upgraded from Ubuntu Desktop 14.04 LTS to 16.04 LTS. It worked without major problems and didn't take a long time. I am not using the Kubuntu distribution, only the native Ubuntu Desktop version. You can still use KDE as the standard desktop. Here are some notes:

- "do-release-upgrade" didn't work for some reason. It just showed "No new release found". I had to use "do-release-upgrade -p".

- Versions:

  • Kernel 4.4.0-21
  • KDE Framework 5.18.0
  • libvirt 1.3.1
  • virt-manager 1.3.2
  • MySQL 5.7.12
  • Apache 2.4.18
  • ClamAV 0.99
  • OpenSSL 1.0.2g-fips
  • OpenSSH 7.2p2
  • Bacula 7.0.5

- No problems upgrading LVM root partition on LUKS encrypted disk partition.

- Virtual Machine Manager now supports snapshots and cache modes "directsync" and "unsafe" for disk devices. Some options are missing though, like cpu pinning.

- KDE did not work after upgrading and rebooting. I had to install the meta package "kubuntu-desktop" manually, which pulls in all necessary dependencies to run KDE as the standard desktop manager. The display manager "kdm" is now replaced by "sddm", which works great. So the "kdm" package is missing now and no longer part of the default repositories.

You can change the default display manager by editing /etc/X11/default-display-manager or by running "dpkg-reconfigure sddm".

- KDE desktop theme Breeze looks very nice. Take a look here:
http://kde-look.org/content/show.php/Elegant+Breeze?content=166630

- Upstart has been replaced by systemd. Make sure to know some basics about the command line interface "systemctl" before upgrading in case there are problems during the upgrade process.

Typing "systemctl<tab><tab> gives you a list of command line options. Just typing "systemctl" lists all services. The column "SUB" shows you if the service is running or not.

With the switch to systemd, consolekit is no longer required. kubuntu-desktop depends on either systemd or consolekit. As systemd is installed now, you can safely delete all consolekit packages, especially if the package is no longer supported by Ubuntu anyway (e.g. consolekit, libck-connector0). 

- ZFS is part of the standard repositories. You do not have to add any 3rd party repository to try it out.

- Bacula client (bacula-fd 7.0.5) is not compatible with previous version of Bacula server (bacula-director/bacula-sd 5.2.6) on Ubuntu 14.04. Checking the status of the client works in bacula director, but running a job on bacula-fd in debug mode (bacula-fd -c /etc/bacula/bacula-fd.conf -f -d 100) shows the following output:

bacula-fd: job.c:1855-0 StorageCmd: storage address=x.x.x.x port=9103 ssl=0
bacula-fd: bsock.c:208-0 Current x.x.x.x:9103 All x.x.x.x:9103
bacula-fd: bsock.c:137-0 who=Storage daemon host=x.x.x.x port=9103
bacula-fd: bsock.c:310-0 OK connected to server Storage daemon x.x.x.x:9103.
bacula-fd: authenticate.c:237-0 Send to SD: Hello Bacula SD: Start Job bacula-data.2016-05-29_07.53.26_05 5
bacula-fd: authenticate.c:240-0 ==== respond to SD challenge
bacula-fd: cram-md5.c:119-0 cram-get received: authenticate.c:79 Bad Hello command from Director at client: Hello Bacula SD: Start Job bacula-data.2016-05-29_07.53.26_05 5
bacula-fd: cram-md5.c:124-0 Cannot scan received response to challenge: authenticate.c:79 Bad Hello command from Director at client: Hello Bacula SD: Start Job bacula-data.2016-05-29_07.53.26_05 5
bacula-fd: authenticate.c:247-0 cram_respond failed for SD: Storage daemon

It is however quite simple to download and compile the latest 5.2.x version of bacula (5.2.13):

  • systemctl stop bacula-fd
  • Install packages required for building bacula client from source:
    apt-get install build-essentials libssl-dev
  • Download bacula-5.2.13.tar.gz and bacula-5.2.13.tar.gz.sig from https://sourceforge.net/projects/bacula/files/bacula/5.2.13/
  • Import Bacula Distribution Verification Key and check key fingerprint (fingerprint for my downloaded Bacula key is 2CA9 F510 CA5C CAF6 1AB5  29F5 9E98 BF32 10A7 92AD):
    gpg --recv-keys 10A792AD
    gpg --fingerprint -k 10A792AD
  • Check signature of downloaded files:
    gpg --verify bacula-5.2.13.tar.gz.sig 
  • tar -xzvf bacula-5.2.13.tar.gz
  • cd bacula-5.2.13
  • ./configure --prefix=/usr/local --enable-client-only --disable-build-dird --disable-build-stored --with-openssl --with-pid-dir=/var/run/bacula
  • check output of previous configure command
  • make && make install
  • check output of previous command for any errors
  • create new file /etc/ld.so.conf.d/local.conf:
    /usr/local/lib
  • ldconfig
  • edit file /etc/init.d/bacula-fd and change variable DAEMON:
    DAEMON=/usr/local/sbin/bacula-fd
  • systemctl daemon-reload
  • systemctl start bacula-fd

- I experienced a problem with the ntp service. "systemctl start ntp" did not show any error messages, but the ntp service was not running afterwards. There were no suspicious entries in the log files. I had to remove / purge the "upstart" package and then reinstall the package "ntp" to make it work again. ntp does still use the old init-script under "/etc/init.d". Starting the service with the init-script did work, but using "service ntp start" or "systemctl start ntp" did not start the ntp process. It did not even try to run the init-script in "/etc/init.d". Not sure what the real cause for the problem was, but as I said removing upstart and reinstalling ntp fixed the problem.

- Changes in configuration files or software features:

  • New default for /etc/ssh/sshd_config / permit_root_login: "yes" -> "prohibit-password"
    With this default setting, root is no longer able to login to SSH with username/password.
  • chkrootkit is trying to run "ssh -G" which is not working without a hostname (false positive, ignore): 
    "Searching for Linux/Ebury - Operation Windigo ssh...        Possible Linux/Ebury - Operation Windigo installetd"
  • "dpkg-log-summary" shows a history of recent package installations (install, update, remove) 

 - Post-installation task: Remove all packages that you don't need or which are no longer supported by Ubuntu: 

ubuntu-support-status --show-unsupported
  • upstart packages (upstart, libupstart1)
  • unity
  • ubuntu-desktop
  • lightdm
  • anacron (if running Ubuntu on a 24x7 installation)
  • bluez, bluedevil (if you don't need bluetooth)
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