If you went to the web page in a browser, there was a suggestion to use nmap. There was also an embedded video of Rick Astley.
Nmap is a tool I’ve used over and over in my career. I may have even had Nmap Ninja on my resume or LinkedIn at a time. I always get a kick out of seeing it used in movies, and it’s be used in a lot.
A basic, albeit thorough nmap command gives us:
Ok, so let’s start knocking on ports.
It’s not SSH. What about the other ports? When we telnet to port 8888 we get…
Use the tag #HuntressCTF on BakerStreetForensics.com to see all related posts and solutions for the 2023 Huntress CTF.
So we’ve got a url and a specific port. Firefox web browser yields…
So we need an Authorization header. 🤔
Time to look at the provided files. It looks to be the export of a Splunk application.
Time to download an eval copy of Splunk and… pause. There’s probably a simpler way to attack this.
The Silver Searcher is a command line tool I picked up during the CTF and I love it. It’s like Grep on PCP.
Once installed, the base command is ag, followed by what you’re searching for, and where. So let’s do a quick search for Authorization on all the contents of this directory.
That looks interesting. A clue? One of the PowerShell scripts has Authorization and what looks to be Base64 code.
We also see a comment about the $PORT being dynamic based on the Start button. Decoding the string in CyberChef…
At this point we have all the pieces, we just need to put them together. I started to look at different ways to pass an Authorization header to a web server. There’s proxy tools galore. And then there’s the basic’s like curl. After a bit of brushing up on my syntax I had:
Yay what looks like more Base64. Once more with our Chef’s hat and…
Traffic
rita was a tool I hadn’t used before but it was very easy to use. I installed it on my REMnux box and then ran it against the dataset.
I then used the command to generate an html report.
Looking through the DNS requests there’s something sketchy indeed.
Let’s go take a look at that.
Dumpster Fire
Let’s start with the_silver_searcher again and see if we have any luck with “Password”.
There’s a number of hits including references to an encryptedUsername and encryptedPassword in the logins.json file. So we’ve got some encrypted Firefox user passwords. If only there were a utility that could decrypt those. Enter firepwd.py, an open source tool to decrypt Mozilla protected passwords.
Run the script in Python and point it to the directory for the user profile (where the logins.json file is).
That’s a pretty LEET password 😉
Use the tag #HuntressCTF on BakerStreetForensics.com to see all related posts and solutions for the 2023 Huntress CTF.
The team at Huntress pulled off an amazing CTF that ran through the month of October with new challenges released daily. In this series, I’ll be providing my solutions to the challenges. WARNING Will Robinson, spoilers ahead! Use the tag #HuntressCTF to see all related posts.
Technical Support
There wasn’t really a solve to this one, but I’m including here for consistency. If you head to the Discord server for the event and went to the support channel, the flag was provided.
String Cheese
Taking this literally – we’ll run STRINGS on cheese:
If we scroll down through the output…
Notepad
Right click on the notepad file, open with VS Code or text editor of choice.
CaesarMirror
When you examined the text file you got
I copied the text over to CyberChef and started running some recipes on it. I found an algorithm that would work on it, well, one half at a time.
I took the original file and edited it into 2 versions, caesar_left.text and caesar_right.txt. I converted each side of the file, screenshotted the output, and then aligned them next to each other to read the complete output.
Book By Its Cover
Use the FILE command to get the properties of book.rar.
Hmm. A png file. Let’s open that with an image viewer.
BaseFFFF+1
Examining the file contents yielded…
Back to CyberChef. There’s Base64 and Base85 but neither of those work. Looking closer at the title…. BaseFFFF+1… FFFF is the Hexadecimal for 65535. Add one and you have 65536. I googled Base65536, and while it’s not in CyberChef it does exist.
Read the Rules
Head over to the Rules page. While you’re there, be sure to read up on what tools are not allowed. CTFs are usually not the situation where you bring a tank to a knife fight. Once you’ve read everything, visible, three or four times if you’re me, right, click on the webpage and choose view source.
Query Code
Once again the FILE command gives us our first clue.
It’s a png image so open with an image viewer and you have a QR code. Scan that with a QR reader and…
Dialtone
The provided wav file is a recording of different telephone buttons being pushed. The first thing to do is identify what buttons/numbers are being pushed. Using the site DialABC I uploaded the wav file and then transcribed the DTMF Tone outputs.
13040004482820197714705083053746380382743933853520408575731743622366387462228661894777288573. That is on heck of a phone number!
A hint on Discord led me to the next step. It referenced that this was a BigInteger value. After several trips with Alice down various rabbit holes I found a PowerShell syntax to convert BigInt to strings.
Hmm. Looks closer to what an encoded flag might look like, but still not there yet. Back over to CyberChef and sprinkle a little Magic dust… and we see that the next and last decoding step is to From_Hex.
Layered Security
The file command indicates that it’s a GIMP image file. I recall that GIMP is an open-source application that’s comparable to Adobe Photoshop. I’d used it previously but not in a long time. I also can’t help but think of Pulp Fiction and “Bring out the Gimp.”
After a morbid chuckle and a quick installation, I launch GIMP and open the file. In the bottom right we see there are a number of faces that are part of this picture.
As we peel down the layers we find the flag in one of the images.
Comprezz
We’ve been pretty successful starting with the file command, so let’s start there.
As the challenge suggests, no I have not heard of this file type. A quick google for compress’d data 16 bits takes me to several posts on how to uncompress theses files. After a brief trial and error (it may have taken me 2 times), I cat’d the file and then piped it to uncompress.
That’s it for the challenges in the Warm Up category. There were also challenges in Forensics, Malware and Miscellaneous.
Use the tag #HuntressCTF to see all related posts. Now that October is over, I’ll be releasing as many of these as I can.
Throughout October, as part of Cyber Security Awareness Month, the team over at Huntress put on a ~30 day Capture the Flag event with 58 unique challenges.
First and foremost, kudos to the organizers for pulling off an event of this size and duration. There were only minor technical difficulties noticed throughout the month, and on more than one occasion those were due to people not observing the rules and using brute force tools where they weren’t needed (or allowed.)
Overall, I found the event to be a great learning experience that challenged me, increased my confidence, and gave me an avenue to pursue skills I want to develop further.
The challenges covered a wide area of subjects with the majority being DFIR related. The categories included:
Warm Ups (14)
Forensics (10)
Malware (16)
M365 (4)
OSINT (3)
Steganography (1)
Miscellaneous (10)
Today the final challenge of the event, graced us with another lovely malware sample to analyze.
I was very pleased with myself at having solved nearly 80% of the challenges. There’s still another 20 or so hours to go, so we’ll see if that improves any further. The only categories I didn’t have 100% in were Miscellaneous and Malware. I think this is fair considering my skill levels. The Malware scenarios were appropriately challenging for someone newer to this area. This is an area that I’ve been developing my skills in more recently. I’m looking forward to seeing others’ write-ups on those challenges where I didn’t make it all the way through, and following along with my own data.
Tools used in the CTF
I added a number of new tools to my toolkit throughout the CTF, and got more experienced with some old friends as well. Depending on the challenge I switched between operating systems including MacOS, REMnux (Linux), and a customized Windows VM with a plethora of malware analysis utilities. By the end of the event the tools used included:
PowerShell
Strings
CyberChef
Gimp
Curl
Firepwd.py
rita
the_silver_searcher
nmap
dcode.fr
meld
Cutter
Ghidra
Python
ChatGPT
Google Chrome Developer Tools
iSteg
exiftool
Google Lens
Google Maps
detonaRE
Process Monitor (procmon)
Visual Studio Code
Site Sucker
7zip
Magnet AXIOM
olevba
x64dbg
AADInternals
Microsoft Excel
Event Viewer
chainsaw
PowerDecode
PowerShell ISE
rclone
Volatility3
hashcat
impacket
Write-Ups
Over the next few days I’ll be releasing the write-ups on how I solved each of the completed challenges. The organizers requested that no solutions be posted until 24 hours after the conclusion of the CTF.
Based on the amount of content, I’ll be breaking the write-ups down by week number (1-4) and challenge category.
Wednesday:
Thursday:
Friday:
Saturday:
You can follow along through the week, or come back on the weekend to read them all.
Once again, I want to extend my thanks to the Huntress team for a great event. I hope you’ll follow along with my solutions, and please comment with other ways to solve if you have them. It’s all about the learning.
Use the tag #HuntressCTF on BakerStreetForensics.com to see all related posts and solutions for the 2023 Huntress CTF.
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