foren-no-time-to-register (CSAW-CTF-2021) writeup

writeup for no-time-to-register challange in CSAW CTF 2021 finals

Posted by 0xMohammed on November 14, 2021 · 6 mins read

Description

James Bonderman has retrieved some files from an enemy agent’s system. As one of R Branch’s support engineers, Bonderman is trusting you to find any information relevant to his investigation. R has sent you a checklist of what he wants you to find. That should be easy for an agent such as yourself.

nc misc.chal.csaw.io 5015

Author: Regulus915ap

Challenge Files: https://drive.google.com/file/d/1Xyy__6d_bV3E5mRvF719i2nHJ0PHh7RZ/view?usp=sharing

Tools

  1. RegistryExplorer
  2. RegRipper
  3. USB Forensic Tracker
  4. Windows Registry analysis cheat sheet
  5. DCode™ – Timestamp Decoder
  6. USBDeview
  7. WinProdKeyFinder

Walkthrough

We were given a server to connect to, asking for data to extract from the registry hives (SAM, SYSTEM, SOFTWARE). We will start our analysis by running regrip to scan the registry hives then load them to registry explorer.
sourcecode 1.Hostname of the machine
a. Registry Explorer: Check Tcpip in the bookmarks menu or browse to SYSTEM:ControlSet001\Services\Tcpip\Parameters.
b. RegRipper: Search for ‘Hostname’ in the system hive report.txt generated by RegRipper.
Answer: 5P3C7r3-1MP3r1UM
sourcecode 2.Region the machine belong to
a. Registry Explorer: Registry Explorer: check Timezoneinformation in the bookmarks menu or browse to SYSTEM:ControlSet001\Control\TimeZoneInformation.
b. RegRipper: Search for ‘timezone’ in the system hive report.txt generated by RegRipper.
Answer: Singapore
sourcecode 3.User registered on the machine
a. Registry Explorer: check Users in the bookmarks menu or browse to SAM:SAM\Domains\Account\Users.
b. RegRipper: Check registered users in the sam hive report.txt generated by RegRipper.
Answer: Spectre
sourcecode 4.GUID of the user from 3
a. Registry Explorer: browse to SOFTWARE:Microsoft\Windows NT\CurrentVersion\ProfileList. Check the keys listed under ProfileList.
b. RegRipper: Search for ‘spectre’ in the software hive report.txt generated by RegRipper.
Answer: S-1-5-21-4228526091-1870561526-3973218081-1001
sourcecode 5.Last login time of user from 3 using the timezone found in 2. (Use format HH:MM:SS MM/DD/YYYY)
a. Registry Explorer: check Users in the bookmarks menu or browse to SAM:SAM\Domains\Account\Users.
b. RegRipper: Check spectre in the sam hive report.txt generated by RegRipper.
Answer: 2021-11-01 09:01:28Z
sourcecode 6.Other accounts enabled on the machine
a. Registry Explorer: check Users in the bookmarks menu or browse to SAM:SAM\Domains\Account\Users. Check accounts which has last login date.
b. RegRipper: Check users in the sam hive report.txt generated by RegRipper.
Answer: Administrator
sourcecode For USB artifacts, we will analyze registry hives with USB FORENSICS TRACKER and USBDeview.
USB FORENSICS TRACKER: Click on the windows icon in the toolbar and select the folder which contains registry hives.
sourcecode USBDeview: Load the system hive from Options menu => Advanced Options
sourcecode 7.Name of USB attached to the machine
Answer: 3v1L_Dr1v3
sourcecode 8.Letter assigned to USB attached to the machine
Answer: E
sourcecode 9.Serial number of USB attached to the machine
Answer: 04016cd7fe9bdb2e12fdc62886a111831a8be58c0143f781b2179f053e968
sourcecode 10.Timestamp of first connection of USB to the machine. (Use format HH:MM:SS MM/DD/YYYY)
Answer: First install time = 10/30/2021 10:36:59 PM
11.Timestamp of last connection of USB to the machine. (Use format HH:MM:SS MM/DD/YYYY)
Answer: Connect time = 11/1/2021 9:49:01 AM
12.Timestamp of last write to USB attached to the machine. (Use format HH:MM:SS MM/DD/YYYY)
Answer: Disconnect time = 11/1/2021 9:49:13 AM
sourcecode 13.GUID of USB attached to the machine
Answer: d53e38d0-36db-11ec-ae51-080027ec0de9
sourcecode 14.Windows Activation Key
For this question, load SYSTEM hive in Registry explorer and browse to SOFTWARE:Microsoft\Windows NT\CurrentVersion. Export CurrentVersion key to reg format.
sourcecode Open the reg file in Notepad and copy the digitalproductid. Use WinProdKeyFinder to decode the digitalproductid and get the activation key.
Answer: VK7JG-NPHTM-C97JM-9MPGT-3V66T
sourcecode 15.Windows Edition
a. Registry Explorer: check CurrentVersion (Windows NT) in the bookmarks menu or browse to SOFTWARE:Microsoft\Windows NT\CurrentVersion. Check ProductName.
b. RegRipper: search ProductName in the software hive report.txt generated by RegRipper.
Answer: Windows 10 pro
sourcecode 16.Windows Version
a. Registry Explorer: check CurrentVersion (Windows NT) in bookmarks menu or browse to SOFTWARE:Microsoft\Windows NT\CurrentVersion. Check DisplayVersion.
Answer: 21H1
sourcecode 17.Windows Registered Owner
a. Registry Explorer: check CurrentVersion (Windows NT) in bookmarks menu or browse to SOFTWARE:Microsoft\Windows NT\CurrentVersion. Check RegisteredOwner.
b. RegRipper: search RegisteredOwner in the software hive report.txt generated by RegRipper.
Answer: Spectre
sourcecode 18.Windows Install Date. (Use format HH:MM:SS MM/DD/YYYY)
a. Registry Explorer: check CurrentVersion (Windows NT) in bookmarks menu or browse to SOFTWARE:Microsoft\Windows NT\CurrentVersion. Check Install time. Use Dcode to decode windows time.
sourcecode b. RegRipper: search InstallDate in the software hive report.txt generated by RegRipper.
Answer: 2021-10-26 08:02:09Z
sourcecode