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# -*- coding: binary -*-
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require 'openssl'
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#
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# TDSSSLProxy:
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#
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# SQL Server uses the TDS protocol to transmit data between clients and
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# servers. Of course this sits on top of TCP.
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#
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# By default, the TDS payload is not encrypted. However, if "force
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# encryption" is set under the SQL Server protocol properties, it will
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# use SSL/TLS to encrypt the TDS data. Oddly, the entire TCP stream is
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# not encrypted (as is say for HTTPS), but instead a TDS header is
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# put on the front of the TLS packet. As a result, the full TLS/SSL
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# setup is done within a series of TDS payloads.
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#
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# This "proxy" basically creates a fake SSL endpoint (s2) from which it
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# can add/remove the TDS header as required. This is implemented as a
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# socket pair (think, a bidirectional pipe), where the other end is s1:
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#
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# sslsock <-> s1 <-> s2 <-> tdssock <-> target SQL Server.
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#
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# (tdssock is the reference to the "sock" from the scanner module)
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#
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# TO DO:
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#
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# This enables brute force of a SQL Server which requires encryption.
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# However, future updates will permit any read/write using
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# mssql_send_recv() to use crypto if required and transparently to
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# other MSF developers.
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#
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# Cheers, JH
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class TDSSSLProxy
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  TYPE_TDS7_LOGIN = 16
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  TYPE_PRE_LOGIN_MESSAGE = 18
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  STATUS_END_OF_MESSAGE = 0x01
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  def initialize(sock)
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    @tdssock = sock
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    @s1, @s2 = Rex::Socket.tcp_socket_pair
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  end
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  def cleanup
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    @running = false
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    @t1.join
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  end
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  def setup_ssl
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    @running = true
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    @t1 = Thread.start { ssl_setup_thread }
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    ctx = OpenSSL::SSL::SSLContext.new(:SSLv23)
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    ctx.ciphers = "ALL:!ADH:!EXPORT:!SSLv2:!SSLv3:+HIGH:+MEDIUM"
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    @ssl_socket = OpenSSL::SSL::SSLSocket.new(@s1, ctx)
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    @ssl_socket.connect
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  end
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  def send_recv(pkt)
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    @ssl_socket.write(pkt)
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    done = false
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    resp = ""
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    while (not done)
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      head = @ssl_socket.read(8)
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      if !(head and head.length == 8)
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        return false
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      end
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      # Is this the last buffer?
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      if (head[1, 1] == "\x01" or not check_status)
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        done = true
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      end
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      # Grab this block's length
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      rlen = head[2, 2].unpack('n')[0] - 8
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      while (rlen > 0)
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        buff = @ssl_socket.read(rlen)
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        return if not buff
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        resp << buff
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        rlen -= buff.length
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      end
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    end
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    resp
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  end
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  def ssl_setup_thread
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    while @running do
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      res = select([@tdssock, @s2], nil, nil, 0.1)
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      if res
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        res[0].each do |r|
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          # response from SQL Server for client
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          if r == @tdssock
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            resp = @tdssock.recv(4096)
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            if @ssl_socket.state[0, 5] == "SSLOK"
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              @s2.send(resp, 0)
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            else
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              @s2.send(resp[8..-1], 0)
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            end
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          end
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          # request from client for SQL Server
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          if r == @s2
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            resp = @s2.recv(4096)
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            # SSL negotiation completed - just send it on
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            if @ssl_socket.state[0, 5] == "SSLOK"
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              @tdssock.send(resp, 0)
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              # Still doing SSL
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            else
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              tds_pkt_len = 8 + resp.length
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              pkt_hdr = ''
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              pkt_hdr << [TYPE_PRE_LOGIN_MESSAGE, STATUS_END_OF_MESSAGE, tds_pkt_len, 0x0000, 0x00, 0x00].pack('CCnnCC')
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              pkt = pkt_hdr << resp
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              @tdssock.send(pkt, 0)
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            end
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          end
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        end
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      end
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    end
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    @s1.close
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    @s2.close
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  end
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end
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