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\newcommand{\titleOfProject}{Software for self-testing of the Telecommunication network of University of Freiburg}



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\title{Team project \\ ``\titleOfProject''}   % type title between braces
\date{\today}    % type date between braces
\author{Arda Akcay\\ Tri Atmoko\\ Refik Had\v{z}iali\'{c} }         % type author(s) between braces
\department{\vspace{1\baselineskip} \large Albert-Ludwigs-Universit\"{a}t Freiburg \\
Lehrstuhl f\"{u}r  Komunikationsysteme\\
Prof. Dr. Gerhard Schneider\\ \vspace{1\baselineskip} Supervisors: \\ Konrad Meier \\ Denis Wehrle \\ \vspace{1\baselineskip} Sommersemester 2011}

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% first chapter
\section{Introduction and Motivation}             % chapter 1
\large In the following report, the authors will try to give you a brief insight into our team project. The goal of our project was to develop a mechanism for automatic testing of our University Telecommunication network. The Telecommunication network of University of Freiburg consists of: our own internal GSM and telephone network systems; GSM redirecting device (if one initiates a call to one of the four external GSM networks, it redirects the calls to: T-mobile, 02, Vodaphone or E-Plus); a SIP gateway for landline calls inside of Germany (sipgate.de) and international calls. Since we did not have access to internal servers, our strategy was to exploit the existing systems and infer the results out of our findings.
Before we had started working on our project, we had to analyze the overall network to come up with test cases that contain the highest information content. The next step in our procedure was to implement our ideas into a working piece of software. 
Gradually we implemented a bit-by-bit of the final software. Every single step was accompanied by testing and validation procedures. At the end we connected all the ``black-boxes'' into one big piece of software. We have fulfilled our requests and goals and made a fully working and operable test software. Despite developing a working software, all the way along we thought about the simplicity of the usage of the software. In the following chapters we will describe in more detail our approach and how each subsystem works.
\newpage
\section{Requirements}           % chapter 2
\newpage
\section{Database design}
How we designed our database and why, explain in this section!
\newpage
\section{Software design}     % section 2.1
\subsection{Database access}         % subsection 2.1.1
\subsection{Controlling the cell phones}
Our first version of the developed program code for controlling the cell phones used predefined timed values
to send commands instead of using a state controlled approach to confirm that every command was successfuly received and executed by the cell phone. 
It meant we had to make an enormous number of assumptions. In comparison to our second approach, to build a state controlled cell phone control class,
our first approach was inferior and slower. The state controlled method connected two cell phones, on the same base station, up to 15 times faster than timed approach. 
\subsection{subsection}
\newpage
\section{Hardware design}
In our team project we had the option to choose all the required hardware ourself beside the two BeagleBoards, which we were supplied by Konrad and Dennis. 
Since one of the project goals was to reduce the costs as much as it was possible, we had tried to use some of the leftovers found in our lab.

\subsection{BeagleBoard}
``The BeagleBoard is an OMAP3530 platform designed specifically to address the Open 
Source Community.
\begin{figure}[ht!]
  \centering
  \includegraphics[width=130mm]{bb.jpg}
  \caption[]{BeagleBoard, a linux-on-chip board where our controller software runs the GSM device }
\end{figure}
It has been equipped with a minimum set of features to allow the 
user to experience the power of the OMAP3530 and is not intended as a full development 
platform as many of the features and interfaces supplied by the OMAP3530 are not 
accessible from the BeagleBoard'' \cite{beagleDataSheet}.
We run on it a special precompiled version of Ubuntu for the ARM processor type.
The board has an USB hub and network port attached to it. In our project it is connected to our
internal university LAN network and to a cell phone. We positioned the two BeagleBoards in rooms where
we had LAN access and GSM signal coverage of our two local base stations.

\subsection{Cell phones}
Our first attempt was to control a Nokia cell phone 3310 with the supplied USB connection cable. 
The protocols used by old versions of Nokia cell phones, as the 3310, use the F-Bus protocol. It was not easy to work with. 
After performing various experiments we succeeded to send and to read SMS messages. Later on we found out that it was not possible to 
send commands for receiving and making the calls. In the meantime we found two Siemens phones, one M45 and S55. 
The first one, Siemens M45, had a cable supplied with it and it was not difficult to control it with the standard set of AT modem commands. 
At the start we did not have a cable supplied for the Siemens S55 phone. We controlled it over the Bluetooth port.

\subsection{Cables for the cell phones}

\clearpage

\section{Communication protocol}
\subsection{Hanlder side}
\begin{figure}[ht!]
  \centering
  \includegraphics[width=130mm]{protocolCommunicationHandler.png}
  \caption[]{Flowchart of the protocol, on the handler side}
\end{figure}

\begin{figure}[ht!]
  \centering
  \includegraphics[width=130mm]{protocolCommunicationcControllerReceiver.png}
  \caption[]{Flowchart of the protocol, on the controller side for the caller}
\end{figure}

\begin{figure}[ht!]
  \centering
  \includegraphics[width=130mm]{protocolCommunicationcControllerCaller.png}
  \caption[]{Flowchart of the protocol, on the controller side for the receiver}
\end{figure}

\subsection{Verification of the protocol}
The verification results are listed here:
\begin{lstlisting}
(Spin Version 6.1.0 -- 2 May 2011)
    + Partial Order Reduction
Full statespace search for:
    never claim             - (none specified)
    assertion violations    +
    cycle checks           - (disabled by -DSAFETY)
    invalid end states    +
State-vector 44 byte, depth reached 65, errors: 0 
       40 states, stored
        3 states, matched
       43 transitions (= stored+matched)
       90 atomic steps
hash conflicts:         0 (resolved)
    2.195    memory usage (Mbyte)
unreached in proctype Server1
    (0 of 36 states)
unreached in proctype Server2
    (0 of 36 states)
unreached in proctype Client
    (0 of 67 states)
pan: elapsed time 0 seconds
\end{lstlisting}


\clearpage
\newpage


\section{Security and safety of the system}
\large Safety and security of the software plays a major role in our project. 
It is of vital importance that only as few as possible people have access to our test system since the resulting data could be exploited to plan an attack 
(e.g. assume the University alarm system uses the SIP gateway to connect to the outside world and to alarm the police, if one knows that the SIP gateway is not working properly, a burglar could plan to rob the University building just at that moment.) Therefore the choice to go Open Source is justified due to the fact that one should know how every single detail of the system works.
All the time, while we were working on the project, we were made aware of this issue by Denis and Konrad.  
We decided to use asymmetric key cryptography, where each side has two keys (private and public.) In the next sections we will explain in more details how we applied the methods.
\subsection{Encryption of the communication channels}
At first we thoought to encrypt the data before sending them but since none of us was an expert on encryption standards the idea was rejected. Alongside the fact that none of us had been an expert in the field of cryptography, we were neither experts in the field of internet programming. One could find maybe a way to disable our server software with various hacking methods (e.g. 
trying to open the port until the system runs out of memory and in our case the system which we used on the handler side was a BeagleBoard with ARM architecture running on a single chip TI OMAP processor, refer to the picture in figure 1.) 
We had to eliminate even the slightest possible threat in return for spending more time for debugging the test software system. Despite we were aware of all these facts, we had to choose one of the plenty implemented encryption standards on Linux.
Denis and Konrad suggested using the SSH Tunneling method. 

\begin{figure}[ht!]
  \centering
  \includegraphics[width=120mm]{sshTunnel.png}
  \caption[]{SSH Tunnel, all the communication inside the tunnel is encrypted }
\end{figure}

Using the SSH Tunnel port forwading method we could hide the real port we had used for our socket connection. On the other hand we could force the socket to accept only local connections (i.e. from the machine where the handler software was running.) 
The SSH Tunnel port forwarind method creates an encrypted tunnel between the two computers and then it creates two ports, one on the local and remote computer. All the data sent through the port on the local machine appear on the port at the remote machine. \newline The first problem we faced was that SSH required the username and password everytime we tried to make an SSH connection. We could avoid this problem by copying the public key from our server (where our test software runs) to the BeagleBoard \cite{sshTunnel}. 
This can be performed by executing the following commands in the terminal shell.
One has to create first the private and public keys on the local machine(i.e. server computer, where the test software runs):

\begin{lstlisting}
jsmith@local-host$ [Note: You are on local-host here]

jsmith@local-host$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/jsmith/.ssh/id_rsa):[Enter key]
Enter passphrase (empty for no passphrase): [Press enter key]
Enter same passphrase again: [Pess enter key]
Your identification has been saved in /home/jsmith/.ssh/id_rsa.
Your public key has been saved in /home/jsmith/.ssh/id_rsa.pub.
The key fingerprint is:
33:b3:fe:af:95:95:18:11:31:d5:de:96:2f:f2:35:f9 jsmith@local-host
\end{lstlisting}

Then one needs to copy the public key to the remote machine (BeagleBoard) using ssh-copy-id:

\begin{lstlisting}
jsmith@local-host$ ssh-copy-id -i ~/.ssh/id_rsa.pub remote-host
jsmith@remote-host's password:
Now try logging into the machine, with "ssh 'remote-host'", and check in:

.ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting. 
\end{lstlisting}

After we have created the public and private keys, and coppied the public key on the machine to which we want to connect, we can test if we can make an SSH connection to the remote machine:

\begin{lstlisting}
jsmith@local-host$ ssh remote-host
Last login: Sun Nov 16 17:22:33 2008 from 192.168.1.2
[Note: SSH did not ask for password.]

jsmith@remote-host$ [Note: You are on remote-host here]
\end{lstlisting}
The test was successful. We tested it with our SSH Tunnel port forwarding class and it worked perfectly. 
\subsection{Security on the web site}
Securing the communication channels without making certain the web site is safe would be worthless. 
We decided to use the \emph{https} protocol instead of the \emph{http} since a person in the middle 
could sniff our data (e.g. a person is connected with his/her smart-phone over an unprotected wireless network) \cite{https}.
At the same time the web site should be accessible only by the authorized personel. Our first approach to this 
problem was to build an PHP page with \emph{MD5} hashed passwords, however we got a suggestion by Konrad and Denis to 
use a safer encryption method implemented in the Apache web server software, \emph{.htaccess}. By using 
these two techniques we protected the web site of some vulnerabilities known to us. If the web site 
will be only accessed from our local university network, we can additionally add an IP filter mask as well.
In the following paragraph we will explain our procedure how to generate the keys and to enable the https protocol. 
\par First we want to generate a server key by typing the following command:
\begin{lstlisting}
openssl genrsa -des3 -out server.key 4096
\end{lstlisting}
\par This will generate a 4096 bit long private server key, one is asked to enter two times a password for the \emph{server.key}.
Using the generated private server key, we will create a certificate signing request, \emph{server.csr}. We were prompted with a series of questions 
like country, state, organization name and etc which we had to enter to resume.
\begin{lstlisting}
openssl req -new -key server.key -out server.csr 
\end{lstlisting}
\par In the next step we had to sign the certificate signing request and enter the amount of days for how long it should be valid. 
In our case we entered the duration of one year, one can make it for longer periods as well (i.e. the amount of 365 has to be changed.)
\begin{lstlisting}
openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt
\end{lstlisting}
\par We were asked to enter the password again for \emph{server.key}. After we have completed this step we had to make
a version of the \emph{server.key} which did not require a password, \emph{server.key.insecure} and we will rename the files appropriately. 
\begin{lstlisting}
openssl rsa -in server.key -out server.key.insecure
mv server.key server.key.secure
mv server.key.insecure server.key
\end{lstlisting}
\par The generated files are very sensitive, since they are our keys. After these steps were completed, we had generated 4 files (\emph{server.crt}, \emph{server.csr}, \emph{server.key} and \emph{server.key.secure}). Now we need to enable the SSL engine on the Apache web server. 
We coppied \emph{server.key} and \emph{server.crt} into \emph{/etc/appache2/ssl}. 
\begin{lstlisting}
refik@ubuntu:/etc/apache2$ sudo mkdir ssl
cp server.key /etc/apache2/ssl
cp server.crt /etc/apache2/ssl
\end{lstlisting}
\par Then we enabled SSL by typing in \emph{a2enmod ssl}, ``it is simply a general purpose utility to establish a symlink between a module in \emph{/etc/apache2/mods-available} to \emph{/etc/apache2/mods-enabled} (or give a message to the effect that a given module does not exist or that it is already symlinked for loading)'' \cite{https}.
\begin{lstlisting}
refik@ubuntu:/etc/apache2/ssl$ sudo a2enmod ssl
Enabling module ssl.
See /usr/share/doc/apache2.2-common/README.Debian.gz on how to configure SSL and create self-signed certificates.
Run '/etc/init.d/apache2 restart' to activate new configuration!
\end{lstlisting}
\par In the next procedure we had to establish a symlink from the 'available' default-ssl file to the 'enabled' file \cite{https}. Then we created a folder where our secured PHP files will be located (e.g. https://some-domain-name.com/test-software).
\begin{lstlisting}
refik@ubuntu:/etc/apache2/ssl$ sudo ln -s /etc/apache2/sites-available/default-ssl /etc/apache2/sites-enabled/000-default-ssl 
refik@ubuntu:/etc/apache2/ssl$ cd /var/
refik@ubuntu:/var$ sudo mkdir www-ssl
\end{lstlisting}
\par We had backed up our old configuration files for the virtual hosts, for the case that the damage the Apache configuration files. Then we edited the \emph{default-ssl} file.
\begin{lstlisting}
refik@ubuntu:/var$ cd /etc/apache2/sites-available
refik@ubuntu:/etc/apache2/sites-available$ sudo cp default default_original
refik@ubuntu:/etc/apache2/sites-available$ sudo cp default-ssl default-ssl_original
refik@ubuntu:/etc/apache2/sites-available$ sudo vim default-ssl
\end{lstlisting}
\par Only the begining of the file is listed here and we have modified the line starting with \emph{DocumentRoot}
from \emph{DocumentRoot /var/www} to \emph{DocumentRoot /var/www-ssl} (i.e. we had to redefine the location of our SSL directory.)
\begin{lstlisting}
<IfModule mod_ssl.c>
<VirtualHost _default_:443>
        ServerAdmin webmaster@localhost

        DocumentRoot /var/www-ssl
        <Directory />
                Options FollowSymLinks
                AllowOverride None
        </Directory>
\end{lstlisting}
\par One should keep in mind that the port 443 should be free for Apache to use it. In the proceeding step we had to ensure that Apache listens on the given port for a \emph{https} connection. 
One could test that by going into the \emph{/etc/apache2/ports.conf}. 
\begin{lstlisting}
<IfModule mod_ssl.c>
    # If you add NameVirtualHost *:443 here, you will also have to change
    # the VirtualHost statement in /etc/apache2/sites-available/default-ssl
    # to <VirtualHost *:443>
    # Server Name Indication for SSL named virtual hosts is currently not
    # supported by MSIE on Windows XP.
    Listen 443
</IfModule>
\end{lstlisting}
\par In our case it was set up correctly, since the command: \emph{Listen 443} was present. 
In our last configuration step we had to edit \emph{default-ssl} file to define the correct locations of our keys and to ensure the SSL engine was turned on.
\begin{lstlisting}
refik@ubuntu:/etc/apache2/sites-available$ sudo vim default-ssl
\end{lstlisting}
\newpage
\par The following part of the file had to be found and modified according to our locations:
\begin{lstlisting}
SSLEngine on

       #   A self-signed (snakeoil) certificate can be created by installing
       #   the ssl-cert package. See
       #   /usr/share/doc/apache2.2-common/README.Debian.gz for more info.
       #   If both key and certificate are stored in the same file, only the
       #   SSLCertificateFile directive is needed.
       SSLCertificateFile    /etc/apache2/ssl/server.crt
       SSLCertificateKeyFile /etc/apache2/ssl/server.key

       #   Server Certificate Chain:
       #   Point SSLCertificateChainFile at a file containing the
\end{lstlisting}
\par Finally we had configured our server and can proceed with the restart of the apache web server. We created a test web site \emph{/var/www-ssl/index.php} and navigated our browser to \emph{https://localhost}. The test was successful! 
\begin{lstlisting}
refik@ubuntu:/etc/apache2/sites-available$ sudo /etc/init.d/apache2 restart
 * Restarting web server apache2                                                                                                                                        [Sat Oct 08 21:52:51 2011] [warn] _default_ VirtualHost overlap on port 443, the first has precedence
 ... waiting [Sat Oct 08 21:52:52 2011] [warn] _default_ VirtualHost overlap on port 443, the first has precedence [ OK ]
refik@ubuntu:/etc/apache2/sites-available$  
\end{lstlisting}




  
\newpage
\section{Web page}
\large One of the requests of our team project was to build a test system that could be started from the web site.
Since we used the Open Source platform to base our project on, it was certain we will use it for the web site as well. 
The dynamic parts of the web site were programmed using PHP and JavaScript. The GUI was done using CSS. 
The web site opens TCP/IP sessions between itself and the Python test software. Due reasons explained in the section above, 
a test user needs first to enter his username and password to acccess the web site. Then a test user can manually select what type of tests he wants to perform or he can select already defined test, 
like the simple, smart or full test. (Describe here these three type of tests.) 
Data about the performing tests are inserted into the database only in the case if the mutex lock for the web site can be obtained\footnote{The mutex lock will be explained in the next subsection.}. 
This way we can avoid inserting data about the test in case there is already a test user on the website performing some tests on the system.
\subsection{Communication between the web page and the test software}
Our first idea was that the PHP file starts the test software. 
However, parts of our test software open new terminal windows and 
since PHP has restrictions for starting GUI applications our approach was condemned for a failure at the start. 
We had to deal with this problem and our solution to it was to write a little Python script that will run in background and start our
test software when required. Once a person starts the test over the web site, it automatically connects to the Python script over an TCP/IP socket. 
Before being able to start the test software one needs first to obtain the mutex lock on the web site and to check if there is a mutex lock for the test software running. 
Using this approach we can ensure that only one user at the time can be on the web site and run only one instance of the test software.
In the next step we send the Python script a message to start the test software. The test software obtains a mutex lock as well. 
When the test software is started the web page checks if a software lock is obtained. 
Once it is obtained we can proceed with creating a new socket connection between the web site and the test software. 
Our TCP/IP communication between the web site and the test software is not encrypted since both the web page and the test software run on the same server computer. 
The mutex locks are freed after the tests are performed. Our test software has a timeout timer in case that the web site hangs or somehow the socket connection breaks
where it automatically shuts down.  
\subsection{Results on the web page}
All the performed test results are displayed on the web site. The results are displayed in real time after each selected test case is performed. 
After all the test cases have been performed a topological picture is generated which represents the current state of the system, this can bee seen in the following figure. 
Afterwards, when the result picture is generated, the test user can easily see what is wrong in the system. Various icons represent different subsystems.
Reading the test results is simple as looking at the icons and identifying if they have: a green plus signs (i.e. working properly), a red minus sign (i.e. not working properly) and a yellow exclamation mark (i.e. it was not tested).

\begin{itemize}
\item Triangles represent BTS stations
\item Cellphones represent the external networks (E-Plus, Vodaphone, T-Mobile and O2)
\item Telephone represents the landline and a telephone with a mortarboard the University telephone network
\item Servers represent the OpenBSC and LsfKs-Asterisk
\item Two monitors represent the SIP system
\end{itemize} 

\par The inference mechanism works as following: if a test case works, we can conclude that the subsystems connected inbetween the two ends are working properly as well.
We use the pChart library\footnote{It is under the GNU GPLv3 license and our project is nonprofit!} to generate the topological picture of our telecommunication system \cite{pChart}. 
\begin{figure}[ht!]
  \centering
  \includegraphics[width=120mm]{resultsImage.png}
  \caption[]{Result image showing working, defected and not tested subsystems}
\end{figure}
\par On the right side of the result picture the test user can immediatelly identify the network operability in percentage\footnote{The test user has to take into account that this percantage is only valid if a full test is performed.}. Bellow the network operability statistics are the ping results statistics located. 
If one of the fields is red it means the subsystem is not online or cannot be seen by our server computer where the test software is located.
\newpage
\section{Conclusion}
\newpage

%bibliography start
\begin{thebibliography}{9}

\bibitem{site1} H. Simpson, \emph{Proof of the Riemann
Hypothesis},  preprint (2003), available at 
\url{http://www.math.drofnats.edu/riemann.ps}.
 
\bibitem{sshTunnel} R. Natarajan, \emph{3 Steps to perform SSH login without password using ssh-keygen \& ssh-copy-id},  accessed on 18.08.2011, available at 
\url{http://goo.gl/fX68N}.

\bibitem{https} P. Bramscher, \emph{Creating Certificate Authorities and self-signed SSL certificates},  accessed on 05.09.2011, available at 
\url{http://www.tc.umn.edu/~brams006/selfsign.html}.

\bibitem{pChart} \emph{pChart},  accessed on 15.08.2011, available at 
\url{http://http://www.pchart.net/}.

\bibitem{beagleDataSheet} \emph{BeagleBoard System Reference Manual},  accessed on 20.06.2011, available at 
\url{http://beagleboard.org/static/BBSRM_latest.pdf}.

%bibliography end
\end{thebibliography}

%end of the document
\end{document}