Category: Linux System

How i optimised my WordPress website ?

Some days back, I was brewing up some plans to optimise my website source codes, HTTP headers, latency and other security aspects. I had to carry out some analysis and research using some tools available on the internet. I should admit that, at first, it looked pretty simple, but it was not. For instance, I did not permit myself to directly modify the production environment. So, I had to migrate it on a pre-production environment. Page caching was yet another issue which could trick oneself after modifications.

Since my website is behind Cloudflare, which is already an advantage in terms of security, performance, reliability and insight, it does not mean that the website cannot be hacked. According to, websites using WordPress CMS are constantly being hacked. Of course, it depends on the mode of attack and the infection impact.

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Migrating to TLS

Migrating a CMS which already has several articles posted can be an issue as the URLs are already recorded in the database as well as in the source code itself. Also, there were links on the website which were not pointed on HTTPS. After moving to the HTTPS version, errors such as “Mixed content” could be noticed when accessing the website. One of the interesting free feature of Cloudflare is that everyone can have a free SSL certificate issued by Comodo. You will have to generate your certificate and your private key from Cloudflare and point it on your Virtual Host.

Some corrections on WordPress source code needed to be added in the wp-config file as follows:



On top of that, there seemed to be lots of URLs on the database itself that needed corrections using the following commands:

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update wp_options set option_value = replace(option_value, ‘’, ‘’) where option_name = ‘siteurl’;

update wp_posts set guid = replace(guid, '', '');

update wp_posts set post_content = replace(post_content, '', '');

However, there are some tricks to identify those non-HTTPS URLs by making a dump of the database and do a “Grep” in it, followed by a “Sed” to eliminate those unwanted parameters. Once the “Mixed Content” errors have been identified, I launched a scan on the Qualys SSL Labs website. The result was an “A+”. You can also use the Htbridge free SSL server test which is pretty fascinating especially to verify PCI DSS Compliance, HIPAA compliance, NIST guidelines and industry best practice in general. If all those criteria have been met, then you would score an “A+” rather than an “A” or worse a “F”.

Source code optimisation and Page speed verification

This can be verify using the GTmetrix tool available for free online. I noticed that my rank was a “C”. This was caused due to lack of minified HTML and CSS, and Image dimension. To handle the minify HTML errors, I enabled the plugin Minify HTML Markup on WordPress itself which corrected these errors. To tweak the Image dimension i downloaded the tool Optipng from Epel repository:

optipng.x86_64                  0.7.6-1.el6                        @epel        

For example, if you want to optimize a specific image, use the following command:

optipng -o2 Screen-Shot-2016-12-24-at-1.04.45-AM.png

Another verification was made on GTmetrix website and i noticed that the result was then an “A”


Tweaking the Web server HTTP headers

Htbridge will surely give you an overview of the web server security and will accompany you step by step to get a better result.

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Of course, since the website is behind cloudflare,  it is limited to certain security tweaks such as Public-key-pins.The Public Key Pinning Extension for HTTP (HPKP) is a security feature that tells a web client to associate a specific cryptographic public key with a certain web server to decrease the risk of Man-in-the-Middle (MITM) attacks with forged certificates. I found an interesting article on which explained how to activate the HPKP. 

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Once you are in possession of your certificate and Private key, you can create the public key and a token will be received to activate the HPKP extension. The following commands can be used to get the token and the public key.

# openssl x509 -noout -in certificate.pem -pubkey | openssl asn1parse -noout -inform pem -out public.key;

# openssl dgst -sha256 -binary public.key | openssl enc -base64

However, it looked that HPKP is not supported on Cloudflare. But, there are other issues such as HSTS. HTTP Strict Transport Security (HSTS, RFC 6797) is a web security policy technology designed to help secure HTTPS web servers against downgrade attacks. HSTS is a powerful technology which is not yet widely adopted. CloudFlare aims to change this. I enabled it as per recommendations by Cloudflare.

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A curl on the url now prompts the following headers :

No system is perfectly secure, but I believe that these modifications are worth to adventure around. I should say I was really impressed by free tools such as the Qualys SSL test, HTbridge free SSL and Web security test and Gtmetrix in terms of page speed.

 Hello Tunnelers, this is my first article for the year 2017, I seize this opportunity to wish my readers a Happy New Year 2017 and wish you all lots of prosperity. – TheTunnelix

Chef workstation and a basic cookbook

Since the main jobs of system administrator is to maintain systems, keep repeating ourselves which is kind boring as well as to dig into our memory of previous configurations that we have set up on a machine. No wonder, manual consistency configurations need to be checked on server configurations. It can be thousands of machines. Chef, is just another tool to get rid of these situations. It is a configuration management tool which is written in Ruby and Erlang for IT professional. Compared to Puppet which has only the Workstation and the Derver whilst Chef has three components that are the Chef Server, Chef workstation and Chef Node.

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The cookbooks are written on the Workstation, and its then uploaded to the Chef server (service) which will be executed on the nodes. Chef nodes can be physical, virtual or directly on the cloud. Normally, chef nodes cannot communicate directly to the workstation. Let’s not focus on the installation.

Let’s first get into the workstation.

1.On the workstation download and install the Chef client from the client download page. In my case, i am on a Centos7 virtual machine.

[[email protected] ~]# wget

2.After installation, you should notice the four utils already available: chef-apply chef-client chef-shell chef-solo

3. Now, we are going to create a cookbook. Since chef use the DSL – Domain specific language, the file created should end with the extension .rb Here is an example called file.rb. The first line means file resource which means a file is being created. The file resource will manage a file on the machine. The content of the file will be created with the line ‘Hello Tunnelix’

file 'file.txt' do
            content 'Hello Tunnelix'

4. The tool chef-apply can be used to run it as follows:

Screenshot from 2016-08-07 21-49-07

5. You will also noticed that the file.txt has been created in the current directory as the path has not been specified.

Screenshot from 2016-08-07 21-50-24


  • If the content of file.rb (refer to point 3) has not been modified and you fire a chef-apply again, you would notice a prompt that its already ‘up to date’ which means that it reduce the disk IO as well as the bandwidth. 
  • A string must be enclosed  in double quotes when using variables. You cannot use a single quote into another single quote. It won’t work!

Chef always check and refer to the resource and attributes in the cookbook to execute an order ; ie to cook a food. The thing is that Chef focus on the DSL with the aim to what the modifications need to be. Chef allows servers to be in a consistent state.

HTTPoxy – Is your nginx affected?

httpoxy is a set of vulnerabilities that affect application code running in CGI, or CGI-like environments. It comes down to a simple namespace conflict:

  • RFC 3875 (CGI) puts the HTTP Proxy header from a request into the environment variables as HTTP_PROXY
  • HTTP_PROXY is a popular environment variable used to configure an outgoing proxy

This leads to a remotely exploitable vulnerability. If you’re running PHP or CGI, you should block the Proxy header

httpoxy is a vulnerability for server-side web applications. If you’re not deploying code, you don’t need to worry. A number of CVEs have been assigned, covering specific languages and CGI implementations:

Screenshot from 2016-07-20 22-45-54

After receiving the updates from, I immediately started some heavy research. For Nginx users, to defeat the attack, modifications can be carried out in the fastcgi_params file.

1. Create a file called test.php containing the following codes in the source code.

[[email protected]]# cat test.php

 echo getenv ('HTTP_PROXY')

2. Launch a CURL as follows:

As you can see its “Affected”

[[email protected]]# curl -H 'Proxy: AFFECTED'

3. Add the following parameters in the /etc/nginx/fastcgi_params file

 fastcgi_param  HTTP_PROXY  "";

4. Stop and start the Nginx Service

5. Conduct the test again. You should be vulnerable by now.

Several links available already explaining this vulnerability :




Messing around PL/Tcl on PostgreSQL

Some days back, i was having an issue whilst activating the PL/Tcl extension/language on PostgreSQL. Luckily, it was possible with the help from Mauricio Cortes, a guy from the Facebook group PostgreSQL Server. Let’s first see what is TCL package. “PL/Tcl is a loadable procedural language for the PostgreSQL database system that enables the Tcl language to be used to write functions and trigger procedures.” – PostgreSQL This facilitates us to load the module and unload it if same is not being used. You can also activate it for a particular user.

Screenshot from 2016-03-30 19-04-12

Initially, after installing the package postgresql95-tcl, as per the documentation, i made a “create extension” but same was returning the error “ ERROR: could not open extension control file “/usr/pgsql-9.5/share/extension/pltcl.control : No such file or directory” I also noticed that the file pltcl.control is not present. The guy recommended me to try out a “create language” instead of “create extension” and it works!!.

How silly it may found that, on the official documentation, it was mentioned that the create language has been deprecated and now the create extension is being used. I immediately understand that i was using a bad repository. I would advice to use the official rpm file from the official website

Lets see how to activate it:

1.Simply fire a yum install postgresql95-tcl Make sure that you are using the right repo ( to be able to use the create extension

2.After login, you can verify same with the command \dx  to have a list of installed extensions or \dx+ to have more details about the object

Screenshot from 2016-07-04 20-56-56

3. Now, here is the catch, if you are using PostgreSQL having the version older than 9.5, this should be activated with a create language pltcl; otherwise if its version 9.5 or beta 9.6, you can use a create extension pltcl;.

After some more research i notice that the advantage of this feature is that when a create extension is performed for any plugin the dump of the database will also consist of the extension otherwise in older version the Tcl language would not be included in the dump.

Articles published on PostgreSQL:

Operation Prison Break by – Sandboxing and Firejail

This is yet another successful hackathon carried out under the umbrella of Branded by the theme “Operation PB – Prison Break”, members of shows skills of security innovations. We have also Rahul who is our proud newest member has created Sandboxing on  Strings

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Photo credits:
Photo credits:

Our task was to find out vulnerabilities in a linux application and create a Firejail environment. Firejailing is the art of using a SUID program that reduces the risk of security breaches by restricting the running environment of untrusted applications using Linux namespaces and seccomp-bpf. It allows a process and all its descendants to have their own private view of the globally shared kernel resources, such as the network stack, process table, mount tableFirejail can sandbox any type of processes: servers, graphical applications, and even user login sessions. The software includes security profiles for a large number of Linux programs: Mozilla Firefox, Chromium, VLC, Transmission etc. To start the sandbox, prefix your command with “firejail”.

I decided to chose the CPIO, a tool to copy files to and from archives which recently was find to be vulnerable to DOS attack. explained the CVE-2016-2037 vulnerability where the cpio_safer_name_suffix function in util.c in cpio 2.11 allows remote attackers to cause a denial of service (out-of-bounds write) via a crafted cpio file. In brief, when a user is going to decompress a file, a user will be able to pass out file for the purpose of the attack. This has been achieved by QuickFuzz.

To sandbox the CPIO tools when decompressing files, Firejail application was used to isolate the program by making use of the syscalls. Here is the firejail environment :

You need to watch this video to understand firejail before reading the Profile 🙂

include /usr/local/etc/firejail/server.profile
include /usr/local/etc/firejail/
include /usr/local/etc/firejail/
include /usr/local/etc/firejail/
caps.drop all
seccomp write,read,open,close,execve,access,brk,umask,munmap,fchmod,mprotect,mmap2,lstat64,fstat64,geteuid32,fchown32,set_thread_are,prctl,setresuid32,getgid32,setgroups32,setgid32,getuid32,setuid32,fcntl64,clone,rt_sigaction,nanosleep

Here are what participants in the hackathon are saying:

To prevent further vulnerabilities such as shown below from being used to target users, this firejail profile has been made. – Yash

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Decompressing .xz file within a sandboxing environment is just fascinating – Akhil

Many shell users, and certainly most of the people working in computer forensics or other fields of information security, have a habit of running /usr/bin/strings on binary files originating from the Internet. Their understanding is that the tool simply scans the file for runs of printable characters and dumps them to stdout – something that is very unlikely to put you at any risk. – Rahul

Previous hackathons carried out by cyberstorm Mauritius are as follows: