Write-up on RootBSD's forensics challenge

Saturday, RootBSD (@r00tbsd #hackbbs) organized a small forensics challenge (french). About 30 people played the challenge, and we had fun. Fellow Nibbles member sh4ka quickly took the first place in just 2 hours and therefore won a shirt of his choice at getdigital.de. I played with two friends - 0vercl0k and thaw - and we took second place a few minutes after sh4ka. Below is my write-up for all the flags, but other players have also posted their write-ups: m_101 and tryks.

CVE-2010-2529 ping infinite loop

On friday, Ovidiu Mara reported a vulnerability in ping utility from iputils package. It was announced as MDVSA-2010:138 by Mandriva Security on Full Disclosure mailing list, and CVE-2010-2529 has been reserved for it. Be assured it is not a critical bug. In fact if you ping a malicious host which replies a malicious packet, ping goes in an infinite loop. Just kill it and you're done.

However, I like networking and found the vulnerability funny (reminds me a bit the ping of death), so I investigated, found the vulnerability and developed an exploit.

smpCTF challenge #11 write-up, phplist 0day

Challenge #11 of smpCTF was interesting: we were given an URL to a phplist version 2.10.12 installation - with default admin/phplist administrator account - and instructed to find a 0day.

smpCTF challenge #2 write-up

Challenge #2 was similar to defcon trivial 200: you had to escape from a VIM editor, but this time it was not evil - you can see the screen.

We were given the following instructions:

ssh -l luser gordo.smpctf.com -p 2282 Password: smpctf
Help find waldo..

smpCTF challenge #1 write-up

smpCTF challenge #1 was a simple web + programming challenge.

We were given the following instructions:

Set S = 1
Set P = 1
Set previous answer = 1

answer = S * P + previous answer + R
R = 39

After this => S + 1 and P + 1 ('answer' becomes 'previous answer') + 39
then repeat this till you have S = 11065.

The final key will be the value of 'answer' when S = 11065.

Example:
So if R = 15..

17 = 1 * 1 + 1 + 15
36 = 2 * 2 + 17 + 15
60 = 3 * 3 + 36 + 15

Submit the correct answer and you will recieve a flag. Have fun ;D

smpCTF challenge #5 write-up - Forensic

smpCTF challenge #5 was forensics: we were given the file forensic1-image and instructed to find a flag.

As usual, we start our analysis with file command:

$ file forensic1-image
forensic1-image: rzip compressed data - version 2.1 (15185973 bytes)

smpCTF challenge #3 write-up

This week-end was smpCTF, again I played with Nibbles and we ended 1st!

Challenge #3 was just horrible, right? ;) Worse than defcon packet100! But we finally got it, after PPP.

We were given the following instructions and hints:

• Generate a file which has a SHA-1 hash of: 008ce55c7d1b602dc4c4c3ad52a5d064e6d1ef12
• Hint: DRM-0, Linux-1
• _DO NOT BRUTE FORCE_ it's not required...
• Hidden hint (HTML comment): t3=(*((unsigned int *)(key+2)))^(*((unsigned int *)(sec+0x56)));

From file tampering to local root

Ubuntu Security Notice USN-959-1 (CVE-2010-0832) reports that Denis Excoffier discovered a serious flaw in PAM MOTD module in Ubuntu: it does not correctly handle path permissions when creating user file stamps. For more details, just have a look at the diff.

The exploit made by Kristian Erik Hermansen allows tampering any file. From that, we can get root for example by adding a user with uid 0. We don't want an empty password because the SSH server sshd has default PermitEmptyPasswords to no. Also, we don't want to prompt the user for his password at SSH connection, so we could create a temporary SSH key and add it to authorized_keys. Also, we want to be sure we backup any file we modify. Finally, we want to remove the rogue user and restore files we modified.

UnrealIRCd 3.2.8.1 backdoored, investigation

UnrealIRCd is a great IRC server software (daemon) and very popular among mid-sized networks because of its highly advanced features and the fact that it is cross-platform (at least Windows/Linux fully supported).

Yesterday, bad news: some versions of Unreal3.2.8.1.tar.gz contain a backdoor because download mirrors have been compromised.. since november 2009! Read the official security advisory for more information. Other websites are reporting the issue, someone even provided a small shell script to fix the flaw: it basically reverts the changes with diff+patch, make clean & make again, so you just have to restart your IRCd. If you're running an UnrealIRCd you should double check your installation because some exploits are already widespread, as well as an NSE (Nmap Scripting Engine) script (seen on nmap-dev mailing list) to scan & kill IRC servers infected by the backdoor.

Oh and funny thing on Yahoo news and techworld (who seems to have copy/pasted yahoo news..):

The good news [...] is that the Trojan is in a game download so it should
have no bearing on Linux in a business setting.
Unreal is a popular first-person shooter game--similar to Doom or Quake.

No, Unreal is not UnrealIRCd. :)

As a curious person I wanted to know more about this backdoor, so let's investigate.

Updated links, XMLStarlet

Just a small message to let you know that I have updated my links list. Big thanks to these good sites/blogs that I read regularly via their RSS/Atom feeds.

To create this list, I exported my subscriptions from Google Reader and used XMLStarlet to easily parse the XML.

F=google-reader-subscriptions.xml
for N in $(xmlstarlet sel -t -m '/opml/body/outline' -v "@title" -n $F); do
  echo "# $N"
  xmlstarlet sel -t -m "/opml/body/outline[@title='$N']/outline" -v "@title" -o '|' -v '@htmlUrl' -n $F
done > subscriptions
# manual edit to remove some things
grep -v '^#' subscriptions |sort |awk 'BEGIN{FS="|"} {if ($0!="") print "<a href=\""$2"\">"$1"</a><br />"}' > feeds.html

Some resources about XMLStarlet.

Update 2011: too many feeds to fit nicely on the blog so I removed it. If you are looking for feeds, check out infond's or eikonal's.