Posts Tagged ‘system resources’

How to install Viber client on Debian GNU / Linux / Ubuntu / Mint in 2022 and enable Bulgarian language cyrillic phonetic keyboard

Tuesday, October 4th, 2022

How to install Viber client on Debian GNU / Linux / Ubuntu / Mint in 2022 and enable Bulgarian language cyrillic phonetic keyboard

how-to-install-and-use-viber-on-gnu-linux-desktop-viber-logo-tux-for-audio-video-communication-with-nonfree-world

So far I've always used Viber on my mobile phone earlier on my Blu H1 HD and now after my dear friend Nomen give me his old iPhone X, i have switched to the iOS version which i find still a bit strangely looking.
Using Viber on the phone and stretching for the Phone all day long is really annoying especially if you work in the field of Information technology like me as System Administrator programmer. Thus having a copy of Viber on your Linux desktop that is next to you is a must.
Viber is proprietary software on M$ Windows its installation is a piece of cake, you install confirm that you want to use it on a secondary device by scanning the QR and opening the URL with your phone and you're ready to Chat and Viber Call with your friends or colleagues

As often on Linux, it is a bit more complicated as the developers of Viber, perhaps did not put too much effort to port it to Linux or did not have much knowledge of how Linux is organized or they simply did not have the time to put for enough testing, and hence installing the Viber on Linux does not straight supported the Bulgarian traditional cyrillic. I've done some small experimentation and installed Viber on Linux both as inidividual package from their official Linux .deb package as well as of a custom build flatpak. In this small article, i'll put it down how i completed that as well as how managed to workaround the language layout problems with a simple setxkbmap cmd.

How to install Viber client on Debian GNU / Linux / Ubuntu / Mint in 2022 and enable Bulgarian language cyrillic phonetic

1.Install and use Viber as a standard Desktop user Linux application

Download latest Debian AMD64 .deb binary from official Viber website inside some dir with Opera / Chrome / Firefox browser and store it in:

hipo@jericho: ~$ cd /usr/local/src

Alternatively you can run the above wget command, but this is not the recommended way since you might end up with Viber Linux version that is older.

hipo@jericho: ~$ sudo wget http://download.cdn.viber.com/cdn/desktop/Linux/viber.deb
hipo@jericho: ~$ su – root

1.2. Resolve the required Viber .deb package dependecies

To resolve the required dependencies of viber.deb package, easiest way is to use gdebi-core # apt-cache show gdebi-core|grep Description-en -A4 Description-en: simple tool to install deb files  gdebi lets you install local deb packages resolving and installing  its dependencies. apt does the same, but only for remote (http, ftp)  located packages. # apt-get install gdebi-core … # apt-get install -f ./viber

1.3. Setting the default language for Viber to support non-latin languages like Cyrillic

I'm Bulgarian and I use the Phonetic Traidional BG keyboard that is UTF8 compatible but cyrillic and non latin. However Viber developers seems to not put much effort and resolve that the Bulgarian Phonetic Traditional keyboard added in my Mate Desktop Environment to work out of the box with Viber on Linux. So as usual in Linux you need a hack ! The hack consists of using setxkbmap to set supported keyboard layouts for Viber US,BG and Traditional Phonetic. This can be done with above command:

setxkbmap -layout 'us,bg' -variant ' ,phonetic' -option 'grp:lalt_lshift_toggle'

To run it everytime together with the Viber binary executable that is stored in location /opt/viber/Viber as prepared by the package developer by install and post-install scripts in the viber.deb, prepared also a 3 liner tine script:

# cat start_viber.sh
#!/bin/bash
cd /opt/viber; setxkbmap -layout 'us,bg' -variant ' ,phonetic' -option 'grp:lalt_lshift_toggle'
./Viber


viber-appearance-menu-screenshot-linux


2. Install Viber in separated isolated sandbox from wider system

Second way if you don't trust a priorietary third party binary of Viber (and don't want for Viber to be able to possibly read data of your login GNOME / KDE user, e.g. not be spied by KGB 🙂

For those curious why i'm saying that Viber is mostly used mainly in the ex Soviet Union and in the countries that used to be Soviet satellite ones for one or another reason and though being developed in Israel some of its development in the past was done in Belarus as far as I remember one of the main 3 members (Ukraine, Belarus and Russia) that took the decision to dissolve the USSR 🙂

Talking about privacy if you're really concerned about privacy the best practice is not to use neither WhatApp nor Viber at all on any OS, but this is hard as usually most people are already "educated" to use one of the two. 
For the enthusiasts however I do recommend just to use the Viber / WhatsApp free GPLed software alternative for Vital communication that you don't want to have been listened to by the China / USA / Russia etc. 
Such a good free software alternative is Jitsy and it has both a Web interface that can be used very easily straight inside a browser or you could install a desktop version for PC / iOS and Android and more.
An interesting and proud fact to mention about Jitsy is that its main development that led the project to the state it is now is being done by a buddy Bulgarian ! Good Job man ! 🙂

If you want to give jitsy a try in web with a friend just clik over my pc-freak home lab machine has installed usable version on meet.pc-freak.net

In the same way people in most countries with American and English free world use the WhatsApp which is a another free spy and self analysis software offered by America most likely collecting your chat data and info about you in the (US Central Intelligence Agency) CIA databases. But enough blant so to minimize a bit the security risks of having the binary run directly as a process you can use a containerization like docker to run it inside and isolate from the rest of your Linux desktop. flatpak is a tool developed exactly for that.

 

hipo@jeremiah:/opt/viber$ apt-cache show flatpak|grep -i Description-en -A 13

Description-en: Application deployment framework for desktop apps
 Flatpak installs, manages and runs sandboxed desktop application bundles.
 Application bundles run partially isolated from the wider system, using
 containerization techniques such as namespaces to prevent direct access
 to system resources. Resources from outside the sandbox can be accessed
 via "portal" services, which are responsible for access control; for
 example, the Documents portal displays an "Open" dialog outside the
 sandbox, then allows the application to access only the selected file.
 .
 Each application uses a specified "runtime", or set of libraries, which is
 available as /usr inside its sandbox. This can be used to run application
 bundles with multiple, potentially incompatible sets of dependencies within
 the same desktop environment.

Having Viber installed on Linux inside a container with flatpak is as simple as to adding, repository and installing the flatpak package
already bundled and stored inside flathub repository, e.g.:
 

2.1. Install flatpak 

# sudo apt install flatpak


flatpak-viber-installation-linux-screenshot
 

2.2. Add flathub install repository

flatpak is pretty much like dockerhub, it contains images of containered sandbox copies of software, the main advantage of flatpak is its portability, scalability and security.
Of course if you're a complete security freak you can prepare yourself an own set of Viber and add it to flathub and use instead of the original one 🙂
 

# sudo flatpak remote-add –if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

2.3. Install Flatpak-ed Viber 

#sudo flatpak install flathub com.viber.Viber

 

Reboot the PC and to test Viber will run containerized normally issue below flapak start command:

# /usr/bin/flatpak run –branch=stable –arch=x86_64 –command=viber com.viber.Viber

 

Viber-inside-flatpak-sandbox-on-debian-linux-screenshot-running

! NOTE !  The Linux version of Viber is missing Backups options, exclusively the Settings -> Account -> Viber backup menus is missing, but the good news is that if you're using the Viber client
as a secondary device message client, on first login you'll be offered to Synchronize your Viber data with your 1st Active device (usually your Smart Phone). Just click on it and allow the synchronization from your phone and in a while the Contacts and message history should be on the Linux Viber client.

That's it Enjoy your Viber Sound and Video on Linux ! 🙂

Secure Apache webserver against basic Denial of Service attacks with mod_evasive on Debian Linux

Wednesday, September 7th, 2011

Secure Apache against basic Denial of Service attacks with mod evasive, how webserver DDoS works

One good module that helps in mitigating, very basic Denial of Service attacks against Apache 1.3.x 2.0.x and 2.2.x webserver is mod_evasive

I’ve noticed however many Apache administrators out there does forget to install it on new Apache installations or even some of them haven’t heard about of it.
Therefore I wrote this small article to create some more awareness of the existence of the anti DoS module and hopefully thorugh it help some of my readers to strengthen their server security.

Here is a description on what exactly mod-evasive module does:

debian:~# apt-cache show libapache2-mod-evasive | grep -i description -A 7

Description: evasive module to minimize HTTP DoS or brute force attacks
mod_evasive is an evasive maneuvers module for Apache to provide some
protection in the event of an HTTP DoS or DDoS attack or brute force attack.
.
It is also designed to be a detection tool, and can be easily configured to
talk to ipchains, firewalls, routers, and etcetera.
.
This module only works on Apache 2.x servers

How does mod-evasive anti DoS module works?

Detection is performed by creating an internal dynamic hash table of IP Addresses and URIs, and denying any single IP address which matches the criterias:

  • Requesting the same page more than number of times per second
  • Making more than N (number) of concurrent requests on the same child per second
  • Making requests to Apache during the IP is temporarily blacklisted (in a blocking list – IP blacklist is removed after a time period))

These anti DDoS and DoS attack protection decreases the possibility that Apache gets DoSed by ana amateur DoS attack, however it still opens doors for attacks who has a large bot-nets of zoombie hosts (let’s say 10000) which will simultaneously request a page from the Apache server. The result in a scenario with a infected botnet running a DoS tool in most of the cases will be a quick exhaustion of system resources available (bandwidth, server memory and processor consumption).
Thus mod-evasive just grants a DoS and DDoS security only on a basic, level where someone tries to DoS a webserver with only possessing access to few hosts.
mod-evasive however in many cases mesaure to protect against DoS and does a great job if combined with Apache mod-security module discussed in one of my previous blog posts – Tightening PHP Security on Debian with Apache 2.2 with ModSecurity2
1. Install mod-evasive

Installing mod-evasive on Debian Lenny, Squeeze and even Wheezy is done in identical way straight using apt-get:

deiban:~# apt-get install libapache2-mod-evasive
...

2. Enable mod-evasive in Apache

debian:~# ln -sf /etc/apache2/mods-available/mod-evasive.load /etc/apache2/mods-enabled/mod-evasive.load

3. Configure the way mod-evasive deals with potential DoS attacks

Open /etc/apache2/apache2.conf, go down to the end of the file and paste inside, below three mod-evasive configuration directives:

<IfModule mod_evasive20.c>
DOSHashTableSize 3097DOS
PageCount 30
DOSSiteCount 40
DOSPageInterval 2
DOSSiteInterval 1
DOSBlockingPeriod 120
#DOSEmailNotify hipo@mymailserver.com
</IfModule>

In case of the above configuration criterias are matched, mod-evasive instructs Apache to return a 403 (Forbidden by default) error page which will conserve bandwidth and system resources in case of DoS attack attempt, especially if the DoS attack targets multiple requests to let’s say a large downloadable file or a PHP,Perl,Python script which does a lot of computation and thus consumes large portion of server CPU time.

The meaning of the above three mod-evasive config vars are as follows:

DOSHashTableSize 3097 – Increasing the DoSHashTableSize will increase performance of mod-evasive but will consume more server memory, on a busy webserver this value however should be increased
DOSPageCount 30 – Add IP in evasive temporary blacklist if a request for any IP that hits the same page 30 consequential times.
DOSSiteCount 40 – Add IP to be be blacklisted if 40 requests are made to a one and the same URL location in 1 second time
DOSBlockingPeriod 120 – Instructs the time in seconds for which an IP will get blacklisted (e.g. will get returned the 403 foribden page), this settings instructs mod-evasive to block every intruder which matches DOSPageCount 30 or DOSSiteCount 40 for 2 minutes time.
DOSPageInterval 2 – Interval of 2 seconds for which DOSPageCount can be reached.
DOSSiteInterval 1 – Interval of 1 second in which if DOSSiteCount of 40 is matched the matched IP will be blacklisted for configured period of time.

mod-evasive also supports IP whitelisting with its option DOSWhitelist , handy in cases if for example, you should allow access to a single webpage from office env consisting of hundred computers behind a NAT.
Another handy configuration option is the module capability to notify, if a DoS is originating from a number of IP addresses using the option DOSEmailNotify
Using the DOSSystemCommand in relation with iptables, could be configured to filter out any IP addresses which are found to be matching the configured mod-evasive rules.
The module also supports custom logging, if you want to keep track on IPs which are found to be trying a DoS attack against the server place in above shown configuration DOSLogDir “/var/log/apache2/evasive” and create the /var/log/apache2/evasive directory, with:
debian:~# mkdir /var/log/apache2/evasive

I decided not to log mod-evasive DoS IP matches as this will just add some extra load on the server, however in debugging some mistakenly blacklisted IPs logging is sure a must.

4. Restart Apache to load up mod-evasive debian:~# /etc/init.d/apache2 restart
...

Finally a very good reading which sheds more light on how exactly mod-evasive works and some extra module configuration options are located in the documentation bundled with the deb package to read it, issue:

debian:~# zless /usr/share/doc/libapache2-mod-evasive/README.gz

Speeding up Apache through apache2-mpm-worker and php5-cgi on Debian / How to improve Apache performance and decrease server memory consumption

Friday, March 18th, 2011

speeding up apache through apache2-mpm-worker and php5-cgi on Debian Linux / how to improve apache performance and decrease server responce time
By default most Apache running Linux servers on the Internet are configured to use with the mpm prefork apache module
Historically prefork apache module is the predecessor of the worker module therefore it's believed to be a way more tested and reliable, if you need a critical reliable webserver configuration.

However from my experience by so far with the Apache MPM Worker I can boldly say that many of the rumors concerning the unreliabity of apache2-mpm-worker are just myths.

The old way Apache handles connections e.g. the mod prefork is the well known way that high amount of the daemons on Linux and BSD are still realying on.
When prefork is a used by Apache, every new TCP/IP connection arriving at your Linux server on the Apache configured port let's say on port 80 is being served by Apache in a way that the Apache process (mother process) parent does fork a new Apache parent copy in order to serve the new request.
Thus by using the prefork Apache needs to fork new process (if it doesn't have already an empty forked one waiting for connections) and serve the HTTP request of the new client, after the request of the client is completed the newly forked Apache usually dies (even though it again depends on the way the Apache server is configured via the Apache configuration – apache2.conf / httpd.conf etc.).

Now you can imagine how slow and memory consuming it is that all the time the parent Apache process spawns new processes, kills old ones etc. in order to fulfill the client requests.

Now just to compare the Apace mpm prefork does not use the old forking way, but relies on a few Apache processes which handles all the requests without constantly being destroyed and recreated like with the prefork module.
This saves operations and system resources, threaded programming has already been proven to be more efficient way to handle tasks and is heavily adopted in GUI programming for instance in Microsoft Windows, Mac OS X, Linux Gnome, KDE etc.

There is plenty of information and statistical data which compares Apache running with prefork and respectively worker modules online.
As the goal of this article is not to went in depths with this kind of information I would not say more on it but let you explore online a bit more about them in case if you're interested.

The purpose of this article is to explain in short how to substitute the Apache2-MPM-Prefork and how your server performance could benefit out of the use of Apache2-MPM-Worker.
On Debian the default Apache process serving module in Apache 1.3x,Apache 2.0x and 2.2x is prefork thus the installation of apache2-mpm-worker is not "a standard way" to install Apache

Deciding to swith from the default Debian apache-mpm-prefork to apache-mpm-worker is quite a serious and responsible decision and in some cases might cause troubles, if you have decided to follow my article be sure to consider all the possible negative consequences of switching to the apache worker !

Now after having said a bunch of info which might be not necessary with the experienced system admin I'll continue on with the steps to install the apache2-mpm-worker.

1. Install the apache2-mpm-worker

debian:~# apt-get install apache2-mpm-worker php5-cgi
Reading state information... Done
The following packages were automatically installed and are no longer required:
The following packages will be REMOVED apache2-mpm-prefork libapache2-mod-php5
The following NEW packages will be installed apache2-mpm-worker
0 upgraded, 1 newly installed, 2 to remove and 46 not upgraded.
Need to get 0B/259kB of archives.After this operation, 6193kB disk space will be freed.

As you can notice in below's text confirmation which will appear you will have to remove the apache2-mpm-prefork and the apache2-mpm-worker modules before you can proceed to install the apache2-mpm-prefork.

You might ask yourself if I remove my installed libphp how would I be able to use my Apache with my PHP based websites? And why does the apt package manager requires the libapache2-mod-php5 to get removed.
The explanation is simple apache2-mpm-worker is not thread safe, in other words scripts which does use the php fork(); function would not work correctly with the Apache worker module and will probably be leading to PHP and Apache crashes.
Therefore in order to install the apache mod worker it's necessary that no libapache2-mod-php5 is existent on the system.
In order to have a PHP installed on the server again you will have to use the php5-cgi deb package, this is the reason in the above apt-get command I'm also requesting apt to install the php5-cgi package next to apache2-mpm-worker.

2. Enable the cgi and cgid apache modules

debian:~# a2enmod cgi
debian:~# a2enmod cgid

3. Activate the mod_actions apache modules

debian:~# cd /etc/apache2/mods-enabled
debian:~# ln -sf ../mods-available/actions.load
debian:~# ln -sf ../mods-available/actions.conf

4. Add configuration options in order to enable mod worker to use the newly installed php5-cgi

Edit /etc/apache2/mods-available/actions.conf vim, mcedit or nano (e.g. your editor of choice and add inside:

&ltIfModule mod_actions.c>
Action application/x-httpd-php /cgi-bin/php5
</IfModule>

After completing all the above instructions, you might also need to edit your /etc/apache2/apache2.conf to tune up, how your Apache mpm worker will serve client requests.
Configuring the <IfModule mpm_worker_module> in apache2.conf is necessary to optimize your newly installed mpm_worker module for performance.

5. Configure the mod_worker_module in apache2.conf One example configuration for the mod worker is:

<IfModule mpm_worker_module>
StartServers 2
MaxClients 150
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
MaxRequestsPerChild 0
</IfModule>

Consider the fact that this configuration is just a sample and it's in no means configured for serving Apache requests for high load Apache servers and you need to further play with the values to have a good results on your server.

6. Check that all is fine with your Apache configurations and no syntax errors are encountered

debian:~# /usr/sbin/apache2ctl -t
Syntax OK

If you get something different from Syntax OK track the error and fix it before you're ready to restart the Apache server.

7. Now restart the Apache server

debian:~# /etc/init.d/apache2 restart

All should run fine and hopefully your PHP scripts should be interpreted just fine through the php5-cgi instead of the libapache2-mod-php5.
Using the /usr/bin/php5-cgi will increase with some percentage your server CPU load but on other hand will drasticly decrease the Webserver memory consumption.
That's quite logical because the libapache2-mod-hp5 is loaded once during apache server whether a new instance of /usr/bin/php5-cgi is invoked during each of Apache requests via the mod worker.

There is one serious security flow coming with php5-cgi, DoS against a server processing scripts through php5-cgi is much easier to be achieved.
An example for a denial attack which could affect a website running with mod worker and php5-cgi, could be simulated from a simple user with a web browser which holds up the f5 or ctrl + r browser page refresh buttons.
In that case whenever php5-cgi is used the CPU load would rise drastic, one possible solution to this denial of service issues is by installing and using libapache2-mod-evasive like so:

8. Install libapache2-mod-evasive

debian:~# apt-get install libapache2-mod-evasive
The Apache mod evasive module is a nice apache module to minimize HTTP DoS and brute force attacks.
Now with mod worker through the php5-cgi, your apache should start serving requests more efficiently than before.
For some performance reasons some might even want to try out the fastcgi with the worker to boost the Apache performance but as I have never tried that I can't say how reliable a a mod worker with a fastcgi would be.

N.B. ! If you have some specific php configurations within /etc/php5/apache2/php.ini you will have to set them also in /etc/php5/cgi/php.ini before you proceed with the above instructions to install Apache otherwise your PHP scripts might not work as expected.

Mod worker is also capable to work with the standard mod php5 Apache module, but if you decide to go this route you will have to recompile your PHP lib manually from source as in Debian this option is not possible with the default php library.
This installation worked fine on Debian Lenny but suppose the same installation should work fine on Debian Squeeze as well as Debian testing/unstable.
Feedback on the afore-described mod worker installation is very welcome!