Class: TDSSSLProxy

Inherits:
Object
  • Object
show all
Defined in:
lib/metasploit/framework/mssql/tdssslproxy.rb

Overview

TDSSSLProxy:

SQL Server uses the TDS protocol to transmit data between clients and servers. Of course this sits on top of TCP.

By default, the TDS payload is not encrypted. However, if “force encryption” is set under the SQL Server protocol properties, it will use SSL/TLS to encrypt the TDS data. Oddly, the entire TCP stream is not encrypted (as is say for HTTPS), but instead a TDS header is put on the front of the TLS packet. As a result, the full TLS/SSL setup is done within a series of TDS payloads.

This “proxy” basically creates a fake SSL endpoint (s2) from which it can add/remove the TDS header as required. This is implemented as a socket pair (think, a bidirectional pipe), where the other end is s1:

sslsock <-> s1 <-> s2 <-> tdssock <-> target SQL Server.

(tdssock is the reference to the “sock” from the scanner module)

TO DO:

This enables brute force of a SQL Server which requires encryption. However, future updates will permit any read/write using mssql_send_recv() to use crypto if required and transparently to other MSF developers.

Cheers, JH

Constant Summary collapse

TYPE_TDS7_LOGIN = 
16
TYPE_PRE_LOGIN_MESSAGE = 
18
STATUS_END_OF_MESSAGE = 
0x01

Instance Method Summary collapse

Constructor Details

#initialize(sock, sslkeylogfile: nil) ⇒ TDSSSLProxy

Returns a new instance of TDSSSLProxy.



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# File 'lib/metasploit/framework/mssql/tdssslproxy.rb', line 41

def initialize(sock, sslkeylogfile: nil)
  @tdssock = sock
  @sslkeylogfile = sslkeylogfile
  @s1, @s2 = Rex::Socket.tcp_socket_pair
end

Instance Method Details

#cleanup ⇒ Object 



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# File 'lib/metasploit/framework/mssql/tdssslproxy.rb', line 47

def cleanup
  @running = false
  @t1.join
end

#send_recv(pkt) ⇒ Object 



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# File 'lib/metasploit/framework/mssql/tdssslproxy.rb', line 78

def send_recv(pkt)
  @ssl_socket.write(pkt)
  done = false
  resp = ""

  while (not done)
    head = @ssl_socket.read(8)
    if !(head and head.length == 8)
      return false
    end

    # Is this the last buffer?
    if (head[1, 1] == "\x01" or not check_status)
      done = true
    end

    # Grab this block's length
    rlen = head[2, 2].unpack('n')[0] - 8

    while (rlen > 0)
      buff = @ssl_socket.read(rlen)
      return if not buff
      resp << buff
      rlen -= buff.length
    end

  end
  resp
end

#setup_ssl ⇒ Object 



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# File 'lib/metasploit/framework/mssql/tdssslproxy.rb', line 68

def setup_ssl
  @running = true
  @t1 = Thread.start { ssl_setup_thread }
  ctx = OpenSSL::SSL::SSLContext.new(:SSLv23)
  write_to_keylog_file(ctx, @sslkeylogfile)
  ctx.ciphers = "ALL:!ADH:!EXPORT:!SSLv2:!SSLv3:+HIGH:+MEDIUM"
  @ssl_socket = OpenSSL::SSL::SSLSocket.new(@s1, ctx)
  @ssl_socket.connect
end

#ssl_setup_thread ⇒ Object 



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# File 'lib/metasploit/framework/mssql/tdssslproxy.rb', line 108

def ssl_setup_thread
  while @running do
    res = select([@tdssock, @s2], nil, nil, 0.1)
    if res
      res[0].each do |r|
        # response from SQL Server for client
        if r == @tdssock
          resp = @tdssock.recv(4096)
          if @ssl_socket.state[0, 5] == "SSLOK"
            @s2.send(resp, 0)
          else
            @s2.send(resp[8..-1], 0)
          end
        end

        # request from client for SQL Server
        if r == @s2
          resp = @s2.recv(4096)
          # SSL negotiation completed - just send it on
          if @ssl_socket.state[0, 5] == "SSLOK"
            @tdssock.send(resp, 0)
            # Still doing SSL
          else
            tds_pkt_len = 8 + resp.length
            pkt_hdr = ''
            pkt_hdr << [TYPE_PRE_LOGIN_MESSAGE, STATUS_END_OF_MESSAGE, tds_pkt_len, 0x0000, 0x00, 0x00].pack('CCnnCC')
            pkt = pkt_hdr << resp
            @tdssock.send(pkt, 0)
          end
        end
      end
    end
  end
  @s1.close
  @s2.close
end

#write_to_keylog_file(ctx, sslkeylogfile) ⇒ Object 



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# File 'lib/metasploit/framework/mssql/tdssslproxy.rb', line 52

def write_to_keylog_file(ctx, sslkeylogfile)
  # writing to the sslkeylogfile is required, it adds support for network capture decryption which is useful to
  # decrypt TLS traffic in wireshark
  if sslkeylogfile
    unless ctx.respond_to?(:keylog_cb)
      raise 'Unable to create sslkeylogfile - Ruby 3.2 or above required for this functionality'
    end

    ctx.keylog_cb = proc do |_sock, line|
      File.open(sslkeylogfile, 'ab') do |file|
        file.write("#{line}\n")
      end
    end
  end
end