I'm back, somehow.
Been busy, hard disk crashed, bad things happened, etc.
Restarting things from scratch, somehow.
Tuesday, December 6, 2016
Tadaima
Tuesday, May 13, 2014
ASIS CTF Quals 2014
A great CTF with a lot of interesting steganos has ended. Too bad the event took place on workdays, so our team didn't have much time for it (probably many other teams shared the same problem). We ended up at #10, which wasn't too bad :P Below you can find write-ups for a few challs I solved.
Trivia 50: Image
The file was actually an amazing image of the once popular NES game Battle City, and as a fan of Nintendo I had the emulator ready to play it :P Just complete the first stage and you'll get the flag: 8BIT_RULEZ (although it is a bit different from what is written and caused a lot of confusions for everyone :P)
Web 75: Hidden flag
A web challenge with barely any description, however the title suggests that the flag should be hidden somewhere. It didn't take us much time to notice the HTTP header named x-flag with the value ASIS_b6b?244608c2?c2e869cb56?67b64?b1. Now obviously the task was to find the full hash. My first thought was using a dictionary attack to find a string that generates a hash with the same pattern, but because of work I didn't really have any time to try it :P
At one point, some members in our team noticed that when a wrong solution was submitted, the response was almost instant. This suggested that there should be a javascript check somewhere. From here it didn't take much time for us to find the sha256 hash and recover the full flag: ASIS_b6be244608c27c2e869cb56167b649b1
Stego 100: Spy Paper
The image was quite big and it was quite easy for me to overlook every detail :P Fortunately redoc found anomalies in the blue channels and these dots reminded me of punched tape, which was very close to the final solution. We were able to quickly figure out the parity bits and decrypt the second part, however we could not find anything meaningful from the first part:
After a lot of time spending on it, we came to realize that this could be printer steganography, and the first part could be date and time. With that we were able to fully decrypt the flag: 9/6/19 13:22:44 E4sy_0n3.
Crypto 150: Random Image
This isn't a hard chall, the code seems to randomly create a new image based on the flag but in fact there is quite a big correlation between the "random" result and the original one. Specifically, if the value of the pixel is less than 250, the resulting pixel is the result of some operation on the coordinates xored with a random value which is the same for all pixels. We do not know the random value however we know the result of the operation on the coordinates and by xoring the encrypted image with this value all pixels with values less than 250 should stand out. Here is the final result of the decryption:
Stego 175: White noise
This is an easy prey for my powerful Steganabara, and that was the reason why our team quickly became the first solver. A quick histogram analysis shows that the values in the green and blue channels are evenly distributed, and the reason behind this is that they were made to be used as coordinates to rearrange the pixels.
However, the red channel only has 1 value: 128, so it is pointless if you rearrange the whole image, you'll get just a red square. This got me stumped for a little while, until I realized that the order of arrangement could be important too. With this I only used the first 30 lines of the image for rearrangement, and got the flag:
Wednesday, April 30, 2014
0x3004 CTF
Another great CTF just ended and we were the champion! 0x3004 CTF was a 5-day event to celebrate the Liberation Day 30/04/1975 that ended all the miseries and brought about happiness to everyone. It was a pleasure having solved so many challenges of such great qualities thanks to the administrators.
Below you can find a quick write-up of some challs. Because there are so many of them, I'm only writing out the key points, the rest is up to you :P
Crypto 50: Phú Yên :: No Encryption Here
The cipher text:
TSwnQFMsI2BUPlchTDk2JVM5NV1TPTYpTTo3MT89JkFJPFVdUzoiJVQ3ViVOOSVdRzk3MT8+Nl1V PEVdUic5Nz1BPEYxUz8wYGA=
The = signature at the end makes it fairly easy to identify it as base64 encoded. The decoded text is M,'@S,#`T>W!L96%S95]S=6)M:71?...
This text is still encrypted and because it consists of only printable characters it can be guessed that encryption method is uuencode. It can be decrypted using this online decryption tool but you have to break it into 2 parts to fully decrypt the flag: 0x3004{please_submit_this_sh!t_and_get_your_rewards}
The encryption is done in the cookie. Trying with different inputs should bring you to a conclusion that the username and the timestamp are combined, xored with a binary key and then base64 encoded.
The string encrypted in the cookie is something like "username=admin;time=2014-04-27T16:27:24.644158", to solve the challenge you have to append ";admin=true" to it and get the flag: 0x3004{you_control_the_world}
Someone else in our team solved it, basically the session is managed by the serialized data in the cookie and you can exploit the deserialization to do SQL injection and get the flag.
The flag is hidden somewhere in the source code of the challenge page: 0x3004{_haha_you_found_it_:D}
Misc 50: Đà Nẵng :: Áo Dài
This is a BMP stegano. Analysis with my Steganabara's Bit Mask Filter (or Caesum's Stegsolve) will reveal that there is data hidden in the LSB of the pixels:
In fact the authors herd you like BMP so they put a BMP in your BMP so you can extract while you extract :P xp45g did this with a "murderous unreadable 1-liner", and here's the final result:
This is similar to the famous HeartBleed bug in OpenSSL. It is even easier because you can input the length directly into the URL. If you input a bigger length than the actual string the rest of the memory will be printed out. We used a length of -1 to dump out everything and after some tries we were able to get the flag: 0x3004{He4rtBle3d_works_this_way}
The encryption can be broken using differential attack. In each loop the ciphertext is xored with a hash created from a character in the input and a character in the flag so you can use 2 inputs with the same length as the flag (31) but with different characters at the end, xor the results (which is also the xored result of 2 hashes in the last loop) and from there work out the last character in the flag. Continuing backwards and you can recover the flag: 0x3004{p_to_the_h_to_the_p_yo!}
10:54:36: $ phpsessid="$(tr -cd a-zA-Z0-9 < /dev/urandom | head -c 32)" ; curl -s http://challenges.wargame.vn/100-Injection2_00cda8c5d1f13e0e2cb2825c0e9e6618/ -H "Cookie: PHPSESSID=$phpsessid;login=$(./ser.php "wtf',''),(null,(select flag from web100_flag), '$phpsessid') #")" | html2text
10:54:38: Welcome you back. This time, we made it more secure!
10:54:40: Your action has been logged to our DB.
10:54:42: You are logged in as guest.
10:54:44: Your action has been logged to our DB.
10:54:46: Your last logged in time: 0x3004{php_0bj3ct_m4k35_1t_3a5y}.
10:54:48: win \o/
This was quite an annoying chall. At first we found the blind SQL injection with double quotes and substring function and used it to get the admin password YOUWONTBEABLETOGUESSTHISPASS__@#!@(#*!@(#*!@(#*)(!@*# but that wasn't enough to get the flag.
We were having troubles identifying the DBMS because of so many abnormalities and in the end it turned out the challenge was about XPATH injection, something similar to SQL injection in theory but not as popular in practice. The flag was 0x3004{XXXpath}
Our team had some troubles with this chall because of misinterpreting the code but it was basically just hash collision. Just generate 2 strings with the same MD5 hashes and the chall is solved.
The method to solve this chall is similar to the one described in the RSA page: you factorize n, calculate phi(n), then calculate modulus multiplication inverse and decrypt the message. The result is: 6396138900968155672706619512005662088160241943837385041483898733707420105484519573719621312884.
This was an easy chall. At first glance we thought the traffic was encrypted using SSL but in the end the flag was transferred in just plain text and you can see it by searching for 0x3004 in a text editor: 0x3004{I_l0v3_wir35h4rk_S0_MUCH!}
Our analysis was like this: f(12)/f(11) ~= 2.8, f(11)/f(10) ~= 3.1, (12/11)^12 = 2.84094437661548, (11/10)^12 = 3.138428376721 so the function should be a polynomial with the degree of 12. With this the problem becomes solving a system of 13 equations and even though I only had to modify my old program a little I was still a lot slower than xp45g's z3. The flag was 0x3004{M4thz1g}
This is basically a stegano, the flag was hidden insite the KingthingsTrypewriter2 font file. Opening it using a font editor like ttfedit and you'll get the flag: 0x3004{H4Ppy_huNt1Ng} - it was changed later but someone else in our team solved it and I'm too lazy to solve it again :P
If you use the default login suggested by the page you'll get a cookie that decrypts to something like ["guest","guest",1234]. Using a python mysql bug you can use ["guest",0,1234] and the session is still valid. Changing the username to admin and brute-forcing the pin you can get the flag: 0x3004{goooo_home_homie}
Crypto 200: An Giang :: Super RSA
Your job is to break an RSA encryption knowing just the public key. However with the source code available you can see that there is a weakness in the encryption: the private key is small (only 1024 bits) while the public key is big (6144 bits). Now the encryption can be broken using Wiener's attack.
In this chall you need to bypass the hash check to do SQL injection. This can be done using hash length extension attack. At first we were getting no result because of assuming the secret length of 6 but in the end we wrote a program to brute-force the length (which turned out to be more than 20) and got the flag: 0x3004{www_mix_crypto_ftw}
The nerd term for this type of challenge is "golfing". Below is the result of our python experts' teamwork. Don't ask me for the code explaination :P In fact after the CTF ended they managed to golf it down even more :P
For more information and solutions for other challs, you can visit stypr's write-up page :P
Monday, March 10, 2014
RuCTF Quals 2014
Another great CTF with many challenges in all categories just ended. Our team was #7. Nana. Not too bad, but it was so annoying that without a network specialist we could not solve admin 200 task "Troubleshooting" which 97 other teams solved with ease.
Below are some write-ups. Hopefully they can give new players an introduction to steganalysis.
stegano 100: Cat's eye
This is an easy GIF stegano, but it took me quite a while analysing the image until I noticed it contained 8 similar frames which wasn't easy to notice in GIMP by default (note to myself: next time check the frames first). It is common sense to combine them and find the differences. The positions of the different pixels are as marked below:
It isn't very straightforward, but the flag is hidden here in binary representation. Using black pixels as 0s and green pixels as 1s give you the flag: RUCTF_e4dd9f5cee307b322c3a27abe66e3df9
stegano 300: Nyan-task
This is a very famous image. By finding and comparing it with the original image it can be concluded that there is no information hidden visually. Analysis with Caesum's StegSolve brought me to the conclusion that the only place to hide the flag is inside the palette. It is also suspicious to see only 14 colors used for the image while the palette contains 256 colors with a lot of repetition.
After extracting the palette I found out that this is actually a DataMatrix barcode (thanks stypr). The rest is easy. The hidden text is u.to/P4JUBg, which is a link to the flag: RUCTF_ca8250c2b4b50581afc9ffd1f403f3f2
crypto 200: Mary Queen
The task is to decipher a message written in Chinese characters. The title suggests that this is similar to the cipher used by Mary Queen of Scots, which is a cryptosystem in which simple substitution is used. This cipher is so weak that many tools have been created to solve it automatically, SCBSolvr is one of them. The decrypted text is chapter I of Alice's Adventures in Wonderlands by Lewis Carroll. The name of the book is also the flag.
Sunday, February 9, 2014
Olympic CTF Sochi 2014
The CTF just ended. And by breathtakingly solving a chall at the last minutes we won the silver medals. Banzai!
Update: With this achievement our team qualified for DEFCON 22 CTF. So awesome, but Las Vegas is so far away :(
Monday, January 27, 2014
PHDays CTF Quals 2014
The qualification round just ended today. Our team finished at rank #9. Chinese new year is coming soon so I only managed to catch up with the guys for just a little more than one hour. During that short period of time our team impressed even ourselves by solving 3 challenges and jumped back to top 10. I was involved in 1 of the challs: a ucucuga challenge titled "mp3 me".
The challenge is basically an mp3 stegano. After examining the file we came to a conclusion that there was no where else to hide the flag other than in the id3 part of the file.
Now this is the part where losers are separated from winners. The RGB tags and the presentation of values in triplets make most people try to find a way to get an image, but they are actually just red herrings. The real clue here is the occurrence of NULL. It suggests the end of a message. After trying some conversion, I found out that "78-9c" (hex values of 120-156) was the signature of zlib compressed data, and with that dloser was able to quickly recover the precious flag.
<dloser> >>> zlib.decompress('789ccb8ccf482c498d2f4d06c2f444002a9f05b7'.decode('hex'))
<dloser> 'i_hate_ucucuga'
Solving challenges is fun, and it's even more thrilling when there is a time limit. Oh, it is also good to be able to let everyone know how you solved them, not just limited to the solvers as on normal challenge sites.
Monday, January 20, 2014
Ghost in the Shellcode 2014
Recently, I have been invited to join team penthackon, a team full of veterans, to participate in CTF events.
As someone who only plays for fun, I find the recent Ghost in the Shellcode 2014 CTF quite an enjoyable experience. It's really amazing to see the creators spending a lot of efforts to put up an MMORPG named "Choose Your Pwn Adventure 2", just to be hacked by the players :P
As an uber cheater, I was involved in 2 of the quests: A Boaring Quest and Unbearable. The first quest requires killing over 9000 boars, something not easily done and most cheaters don't want to do it the normal way. jjk was the one who solved it for our team, but his method involved capturing and replaying the kill packet, and it was hard for everyone else to follow the same method.
Because the logic of the game was implemented in .NET, using .NET Reflector with Reflexil plugin I was able to patch the game to send 1001 kills to the server. So only 10 kills were needed to finish the quest (Actually it was possible to send 10000 kills in 1 go but we did it this way to be "nice" to the server :P)
The second quest was a little bit trickier: the treasure chest was protected by a shitload of bears, and after opening it you had to survive for 5 minutes before getting the flag. To make it even more impossible, the bears were armed with guns and they would all shoot you to death. This was actually a fun experience, everyone tried to avoid being hit, killing bears with uber weapons, changing the bear's AI... with no success. In the end, the solution was quite simple and logical. There was this holy item called wine that gave you 10-20% damage protection, however that protection can be patched from the client. I patched it to 100% to become invincible (also because each wine only last for 1 minute, I needed to drink 6 of them :P)
Below is the screenshot of my character after winning both flags
Sunday, January 12, 2014
Ubuntu 14.04 Trusty Tahr
My box was running Ubuntu 12.10 Quantal Quetzal for quite a long time because I was too lazy to upgrade it so recently I had to go through hella lot of upgrades to catch up with the latest technologies :P
The upgrade to 13.04 Raring Ringtail was quite smooth but while I was upgrading to 13.10 Saucy Salamander my laptop was overheating and shut down without a warning (they seriously should give us like 10 seconds to do something first). And that marked the beginning of hell :P
After powering on, Ubuntu couldn't start because of broken packages, but luckily there was no problem with the kernel and it only took me a bit to play around with the recovery menu to get the packages rebuilt.
However because the installation was incomplete there were many features missing and since there was no easy way to get them installed I decided to go a bit further to upgrade to the development version 14.04 Trusty Tahr.
Unsurprisingly, I was caught up in a serious sendmail bug - the installation went into an infinite loop. The bug was said to have been fixed a few months ago, but I don't know for which reason the fix hasn't made it to the Ubuntu repository yet. There was a workaround mentioned in the bug report, but the whole thing was a mess, and someone even suggested something as complicated as modifying the installation package. After some time reading all the available solutions, I got it done in a simple way. Just look for update_db in /usr/share/sendmail/ and replace the following lines:
str=$(echo "$line" | cut -d "
" -f 1);
line=$(echo "$line" | cut -d "
" -f 2-);
with
str=$(echo "$line" | head -n 1);
line=$(echo "$line" | tail -n +2);
and after that do a
sudo dpkg --configure -a
to reconfigure the packages :P
The Ubuntu team name their releases after the letters of the alphabet, and they already reached T. I wonder what will happen in a few years when all are used up :P
Sunday, October 27, 2013
Back.. and a new chall!
Maybe some of you haven't noticed it, but I've defeated some of my laziness and now officially back and kicking :P
Recently I've solved many challs on WeChall and Rankk, and got some of my ranks back (although horst35 is a real monster :P)
Maybe there is a connection between the chall and my crazy version of minesweeper, but probably knowing it will not help much :P
Sunday, September 15, 2013
JMine
I tried to defeat my crazy version of minesweeper.. and failed :D
Wish I had more time now to create more crazy stuff and change the world in the process :P
PS. There's a bug with the timer but I'm too lazy to fix it :D
Saturday, February 11, 2012
One blog to rule them all
So apparently I have been creating too many blogs while having no time to keep them updated and today I have decided to merge some of them together. As a result, you can see how my penguin taming business is going on here from now on.
Recently, I have successfully managed to install BackTract 5 R1 to my hard disk without having to burn the installer to DVD or USB (somehow my Lenovo laptop couldn't boot from USB even though I enabled all the relevant BIOS settings). Since BT is based on Ubuntu, I followed this guide with some necessary changes and boom! mission accomplished!
Here's a screenshot:
I even planned to install Solaris 11 on my comp, but in the end couldn't because there was some conflict with Linux swap partition which required changes to the entire partition table.
Monday, September 26, 2011
FreeRice updated
Do you still remember the FreeRice bot I wrote years ago?
I'm not sure if the bot is still working but recently I received an email from the United Nations World Food Programme saying that it "has been highly damaging to Freerice and has serious repercussions for the people we help". Below are the three reasons given:
- You overload our servers and crash the site, so that real people cannot play and learn. This means less people want to play, and we raise less rice.
- You damage our reputation and discourage sponsors from supporting Freerice, making it impossible for us to pay for the rice you raise. This means we cannot provide rice to those who need it most
- At times, the bots raise more rice than we can pay for!
Apparently, there have been many bots created since then and I wonder if my bot alone can damage the site that much but for now I have removed the bot from the downloads. If you are a bot author, maybe you should consider doing the same.
Statistically, about 40% of the visitors to my site are for the bot. Well, that gotta change now!
Saturday, December 4, 2010
Chess
Just a quick update. I haven't been very active in challenge solving during the past few months. However, I just developed some interest in chess. I am doing pretty well on chess.com with a rating closing 1700.
This is one of my favourite games: http://www.chess.com/echess/game.html?id=42014101
You know what, I found some of the geeks there too. Caesum the alien is playing more than 100 games at the same time, while TheHiveMind with his super chess bot has already reached a rating of 2200+.
I'm having a duel with Caesum atm, and the game is a bit on my side. Wish me luck!
Wednesday, July 28, 2010
Thursday, July 15, 2010
Hacker skills in action
Have you ever needed to use your 1337 hacker skills in real life as a non-security professional?
I was once given the task of writing a Windows library to connect to a Juniper VPN system. All I was given was just the web interface of the system. A task that cannot be completed without reverse-engineering skills.
Some experiments with the system showed me that the VPN system wasn't too complicated. After the user authorizes himself via the login page, an ActiveX or Java applet will be launched, which will subsequently download and run a Windows application that is responsible for the VPN connection.
Authenticating via the login page programmatically to retrieve the cookie for the session was a trivial task. For downloading and running the Windows VPN application, with my 1337 Java skills, I decided that reverse-engineering the Java applet was the way to go. After decompiling the applet with Jad, all I needed to do was modifying the code to make it run in a "simulated" applet environment, and everything went on smoothly.
Saturday, May 22, 2010
Year 2038 problem - not very far away
Maybe some of you have already heard about the year 2038 problem, caused by software and systems storing system time as a signed 32-bit integer. I thought it would be quite a while until I'd have to care about it, but it seems that isn't the case.
A little while ago, my yahoo mailbox was hit by a lot of spammers sending from the future date of 18th Jan 2038. Back then, I thought it was funny. Spammers always want their spam mails to appear on top by setting the date to the farthest in the future. But this is as far as they can go ;)
However, recently, I have discovered the bug lying in an authentication server by a well-known security company I'm testing. It appears all certificates signed by the server cannot have an expiry date of later than 19th Jan 2038. If not discovered early, this could cost us a lot of maintenance fee when the time comes close.
Sunday, May 9, 2010
Mandriva 2010
Although Mandriva 2010 was released a long time ago, I haven't had the time to upgrade until now.
Just like the last time, I received the message that "the system could not be safely upgraded to Mandriva Linux 2009" (yes, it did say 2009, probably someone overlooked that trivial bit). Nevertheless, as a professional penguin tamer, I decided to take the risk and continued. This time the estimated upgrade time was 5 hours. But in the end it only took about 1 hour and a half.
Brilliantly, the new system booted smoothly without any problems. Time to see what this great new system has to offer ;)
Wednesday, May 5, 2010
Ubuntu 10.04 LTS
Ubuntu 10.04 LTS was finally released last week, and I just managed to upgrade it today. Unlike Mandriva, to upgrade Ubuntu, I needed to use the alternate CD image instead of the normal one.
The upgrade took about an hour, which was actually quite long for such a newly installed system. However, on the bright side, it could be done while the system was running.
The Ubuntu guys boasted about the 10 second startup time. And in fact, my new system booted really fast. I doubt if it's as fast as 10 seconds though :P
There's a very annoying problem with the new Gnome button layout: the minimize, maximize, and close button are moved to the top left of the windows, whichever theme you use. A guide to fixing that problem is available here: http://www.howtogeek.com/howto/13535/move-window-buttons-back-to-the-right-in-ubuntu-10.04/
Monday, March 15, 2010
Ubuntu
So I got a new laptop, and of course I installed another Linux distro on it. Ubuntu seems to be a very popular one now, so I decided to give it a try.
Gnome seems to have improved a lot since the last time I tried it on Fedora. After some modding it looks quite awesome now ;)
Another thing I like about Ubuntu is the free 2GB Ubuntu One space I can use to synchronize and share my data.
Is cloud computing really the way to go?
Saturday, September 19, 2009
Some updates
So I updated my kernel to 2.6.29.1, however the computer failed to boot. Probably there were some changes in the system structure. I guess I'll stick with 2.6.27 for a little more.
On the bright side, I have finally managed to find a way to connect to vpn from my Linux box. At first I went through the trouble of installing the Cisco VPN client for Linux, but no matter how hard I tried it couldn't connect to the gateway. Next I tried OpenVPN, but it didn't seem to be compatible either. In the end I tried vpnc. It was impossible to get it to work using certificate authentication, however group authentication worked fine ;)
Now probably there'll be no big changes until Mandriva Linux 2010 comes out!
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