Move service fingerprint unwrapping code from scripts to lpeg-utility

scripts/http-server-header.nse

@@ -4,7 +4,6 @@ local table = require "table"
 local shortport = require "shortport"
 local nmap = require "nmap"
 local stdnse = require "stdnse"
-local lpeg = require "lpeg"
 local U = require "lpeg-utility"
 
 description = [[
@@ -37,43 +36,15 @@ portrule = function(host, port)
   return (shortport.http(host,port) and nmap.version_intensity() >= 7)
 end
 
--- Cache the returned pattern
-local getquote = U.escaped_quote()
-
--- Substitution pattern to unescape a string
-local unescape = lpeg.P {
-  -- Substitute captures
-  lpeg.Cs((lpeg.V "simple_char" + lpeg.V "unesc")^0),
-  -- Escape char is '\'
-  esc = lpeg.P "\\",
-  -- Simple char is anything but escape char
-  simple_char = lpeg.P(1) - lpeg.V "esc",
-  -- If we hit an escape, process specials or hex code, otherwise remove the escape
-  unesc = (lpeg.V "esc" * lpeg.Cs( lpeg.V "specials" + lpeg.V "code" + lpeg.P(1) ))/"%1",
-  -- single-char escapes. These are the only ones service_scan uses
-  specials = lpeg.S "trn0" / {t="\t", r="\r", n="\n", ["0"]="\0"},
-  -- hex escape: convert to char
-  code = (lpeg.P "x" * lpeg.C(lpeg.S "0123456789abcdefABCDEF"^-2))/function(c)
-  return string.char(tonumber(c,16)) end,
-}
-
--- Turn the service fingerprint reply to a probe into a binary blob
-local function get_response (fp, probe)
-  local i, e = string.find(fp, string.format("%s,%%x+,", probe))
-  if i == nil then return nil end
-  return unescape:match(getquote:match(fp, e+1))
-end
-
 action = function(host, port)
   local responses = {}
   -- Did the service engine already do the hard work?
   if port.version and port.version.service_fp then
-    -- Probes sent, replies received, but no match. Unwrap the fingerprint:
-    local fp = string.gsub(port.version.service_fp, "\nSF:", "")
+    -- Probes sent, replies received, but no match.
     -- Loop through the probes most likely to receive HTTP responses
     for _, p in ipairs({"GetRequest", "GenericLines", "HTTPOptions",
       "FourOhFourRequest", "NULL", "RTSPRequest", "Help", "SIPOptions"}) do
-      responses[#responses+1] = get_response(fp, p)
+      responses[#responses+1] = U.get_response(port.version.service_fp, p)
     end
   end
   if #responses == 0 then