Fix human-readable sizes in ls.lua

First, enforce significant digits when converting, e.g. 1.1K to bytes.
Next, use the server-returned human-readable format instead of
converting to bytes by default. The conversion to bytes is still done to
get total byte count.

Also changed how boolean options work to better match existing
convention: --script-args ls.human or --script-args ls.human=1 now work.
You must explicitly say "false", "no", or "0" to make a boolean flag
false (or just leave it out).

nselib/ls.lua

@@ -23,7 +23,9 @@
 -- @args ls.empty    (boolean) Report empty volumes (with no information
 --                   or error)
 -- @args ls.human    (boolean) Show file sizes in human-readable format with K,
---                   M, G, T, P suffixes.
+--                   M, G, T, P suffixes. Some services return human-readable
+--                   sizes natively; in these cases, the size is reported as
+--                   given.
 --
 -- @author Pierre Lalet <pierre@droids-corp.org>
 -- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
@@ -31,6 +33,7 @@
 
 local LIBRARY_NAME = "ls"
 
+local math = require "math"
 local stdnse = require "stdnse"
 local string = require "string"
 local tab = require "tab"
@@ -52,10 +55,10 @@ local function convert_arg(argval, argtype)
   if argtype == "number" then
     return tonumber(argval)
   elseif argtype == "boolean" then
-    if argval == "true" or argval == "yes" then
-      return true
-    else
+    if argval == "false" or argval == "no" or argval == "0" then
       return false
+    else
+      return true
     end
   end
   return argval
@@ -180,13 +183,21 @@ local units = {
 
 --- Get a size as an integer from a (possibly) human readable input.
 local function get_size(size)
-  local bsize
-  bsize = tonumber(size)
+  local bsize = tonumber(size)
   if bsize == nil then
     local unit = string.lower(string.sub(size, -1, -1))
     bsize = tonumber(string.sub(size, 0, -2))
     if units[unit] ~= nil and bsize ~= nil then
       bsize = bsize * units[unit]
+      local sigfigs = #(string.match(size, "[0-9.]+"))
+      if string.find(size, "%.") then
+        sigfigs = sigfigs - 1
+      end
+      local d = math.ceil(math.log(bsize, 10))
+      local power = sigfigs - d
+      local magnitude = 10^power
+      local shifted = math.floor(bsize * magnitude)
+      bsize = math.floor(shifted / magnitude)
     else
       bsize = nil
     end
@@ -202,20 +213,13 @@ end
 function add_file(output, file)
   local curvol = output.curvol
   local files = curvol["files"]
-  local isize = 1
-  if curvol["hasperms"] then
-    isize = 4
-  end
   for i, info in ipairs(file) do
-    if i == isize then
-      local size = get_size(info)
-      if size then
-        curvol["bytes"] = curvol["bytes"] + size
-        info = tostring(size)
-      end
-    end
     tab.add(files, i, info)
   end
+  local size = get_size(file[curvol.hasperms and 4 or 1])
+  if size then
+    curvol["bytes"] = curvol["bytes"] + size
+  end
   tab.nextrow(files)
   curvol["count"] = curvol["count"] + 1
   return (config("maxfiles") == 0 or config("maxfiles") == nil
@@ -286,9 +290,10 @@ local function files_to_readable(files)
     end
     if config("human") then
       local size = tonumber(outfile[isize])
+      -- If tonumber didn't work, it's already in human-readable format
       if size ~= nil then
         local iunit = 0
-        while size > 1024 and units[iunit] do
+        while size > 1024 and units[iunit+1] do
           size = size / 1024
           iunit = iunit + 1
         end