Refactor some code from sslv2.nse into sslv2.lua

scripts/sslv2.nse

@@ -7,6 +7,7 @@ local bin = require "bin"
 local bit = require "bit"
 local stdnse = require "stdnse"
 local sslcert = require "sslcert"
+local sslv2 = require "sslv2"
 
 description = [[
 Determines whether the server supports obsolete and less secure SSLv2, and discovers which ciphers it
@@ -49,91 +50,6 @@ portrule = function(host, port)
   return shortport.ssl(host, port) or sslcert.getPrepareTLSWithoutReconnect(port)
 end
 
-local ssl_ciphers = {
-  -- (cut down) table of codes with their corresponding ciphers.
-  -- inspired by Wireshark's 'epan/dissectors/packet-ssl-utils.h'
-  ["\x00\x00\x00"] = "SSL2_NULL_WITH_MD5",
-  ["\x01\x00\x80"] = "SSL2_RC4_128_WITH_MD5",
-  ["\x02\x00\x80"] = "SSL2_RC4_128_EXPORT40_WITH_MD5",
-  ["\x03\x00\x80"] = "SSL2_RC2_128_CBC_WITH_MD5",
-  ["\x04\x00\x80"] = "SSL2_RC2_128_CBC_EXPORT40_WITH_MD5",
-  ["\x05\x00\x80"] = "SSL2_IDEA_128_CBC_WITH_MD5",
-  ["\x06\x00\x40"] = "SSL2_DES_64_CBC_WITH_MD5",
-  ["\x07\x00\xc0"] = "SSL2_DES_192_EDE3_CBC_WITH_MD5",
-  ["\x08\x00\x80"] = "SSL2_RC4_64_WITH_MD5",
-}
-
---Invert a one-to-one mapping
-local function invert(t)
-  local out = {}
-  for k, v in pairs(t) do
-    out[v] = k
-  end
-  return out
-end
-
-local cipher_codes = invert(ssl_ciphers)
-
-local ciphers = function(cipher_list)
-
-  -- returns names of ciphers supported by the server
-
-  local seen = {}
-  local available_ciphers = {}
-
-  for idx = 1, #cipher_list, 3 do
-    local _, cipher = bin.unpack("A3", cipher_list, idx)
-    local cipher_name = ssl_ciphers[cipher] or ("0x" .. stdnse.tohex(cipher))
-
-    -- Check for duplicate ciphers
-    if not seen[cipher] then
-      table.insert(available_ciphers, cipher_name)
-      seen[cipher] = true
-    end
-  end
-
-  return available_ciphers
-end
-
-local function parse_record_header_1_2(header_1_2)
-  local _, b0, b1 = bin.unpack(">CC", header_1_2)
-  local msb = bit.band(b0, 0x80) == 0x80
-  local header_length
-  local record_length
-  if msb then
-    header_length = 2
-    record_length = bit.bor(bit.lshift(bit.band(b0, 0x7f), 8), b1)
-  else
-    header_length = 3
-    record_length = bit.bor(bit.lshift(bit.band(b0, 0x3f), 8), b1)
-  end
-  return header_length, record_length
-end
-
-local function read_ssl_record(sock)
-  local status, header_1_2 = sock:receive_buf(match.numbytes(2), true)
-  if not status then
-    return status
-  end
-
-  local header_length, record_length = parse_record_header_1_2(header_1_2)
-  local padding_length
-  if header_length == 2 then
-    padding_length = 0
-  else
-    local status, header_3 = sock:receive_buf(match.numbytes(1), true)
-    if not status then
-      return status
-    end
-    local _
-    _, padding_length = bin.unpack(">C", header_3)
-  end
-
-  local status, payload = sock:receive_buf(match.numbytes(record_length), true)
-
-  return status, payload, padding_length
-end
-
 action = function(host, port)
   local timeout = stdnse.get_timeout(host, 10000, 5000)
 
@@ -158,67 +74,35 @@ action = function(host, port)
 
   socket:set_timeout(timeout)
 
-  -- build client hello packet (contents inspired by
-  -- http://mail.nessus.org/pipermail/plugins-writers/2004-October/msg00041.html )
-  local cipher_list = (
-    cipher_codes.SSL2_DES_192_EDE3_CBC_WITH_MD5 ..
-    cipher_codes.SSL2_IDEA_128_CBC_WITH_MD5 ..
-    cipher_codes.SSL2_RC2_128_CBC_WITH_MD5 ..
-    cipher_codes.SSL2_RC4_128_WITH_MD5 ..
-    cipher_codes.SSL2_RC4_64_WITH_MD5 ..
-    cipher_codes.SSL2_DES_64_CBC_WITH_MD5 ..
-    cipher_codes.SSL2_RC2_128_CBC_EXPORT40_WITH_MD5 ..
-    cipher_codes.SSL2_RC4_128_EXPORT40_WITH_MD5 ..
-    cipher_codes.SSL2_NULL_WITH_MD5
-    )
-  -- Random
-  local challenge = "\xe4\xbd\x00\x00\xa4\x41\xb6\x74\x71\x2b\x27\x95\x44\xc0\x3d\xc0"
-  local ssl_v2_hello = bin.pack(">CSSSSAA",
-    1, -- MSG-CLIENT-HELLO
-    2, -- version: SSL 2.0
-    #cipher_list, -- cipher spec length
-    0, -- session ID length
-    #challenge, -- challenge length
-    cipher_list,
-    challenge
-    )
-  -- Prepend length plus MSB
-  ssl_v2_hello = bin.pack(">SA", #ssl_v2_hello + 0x8000, ssl_v2_hello)
+  local ssl_v2_hello = sslv2.client_hello(stdnse.keys(sslv2.SSL_CIPHER_CODES))
 
   socket:send(ssl_v2_hello)
 
-  local status, server_hello = read_ssl_record(socket)
+  local status, record = sslv2.record_buffer(socket)
   socket:close();
   if not status then
     return nil
   end
 
-  -- split up server hello into components
-  local idx, message_type, SID_hit, certificate_type, ssl_version, certificate_len, ciphers_len, connection_ID_len = bin.unpack(">CCCSSSS", server_hello)
+  local _, message = sslv2.record_read(record)
+
   -- some sanity checks:
   -- is it SSLv2?
-  if (ssl_version ~= 2) then
+  if not message or not message.body then
     return
   end
   -- is response a server hello?
-  if (message_type ~= 4) then
+  if (message.message_type ~= sslv2.SSL_MESSAGE_TYPES.SERVER_HELLO) then
     return
   end
-  -- is certificate in X.509 format?
-  if (certificate_type ~= 1) then
-    return
-  end
-
-  local idx, certificate = bin.unpack("A" .. certificate_len, server_hello, idx)
-  local idx, cipher_list = bin.unpack("A" .. ciphers_len, server_hello, idx)
-  local idx, connection_ID = bin.unpack("A" .. connection_ID_len, server_hello, idx)
-
-  -- get a list of ciphers offered
-  local available_ciphers = ciphers_len > 0 and ciphers(cipher_list) or "none"
+  ---- is certificate in X.509 format?
+  --if (message.body.cert_type ~= 1) then
+  --  return
+  --end
 
   return {
     "SSLv2 supported",
-    ciphers = available_ciphers
+    ciphers = #message.body.ciphers > 0 and message.body.ciphers or "none"
   }
 
 end