http cookie and form parsing updates

1. getattr now decodes html entities in attributes (useful for & in href
   attributes, for instance)
2. Cookie validation allows max-age, httponly, and secure attributes
3. Use table concatenation instead of repeated string concatenation to build
   cookie string.

nselib/http.lua

@@ -112,6 +112,7 @@ local coroutine = require "coroutine"
 local nmap = require "nmap"
 local os = require "os"
 local sasl = require "sasl"
+local slaxml = require "slaxml"
 local stdnse = require "stdnse"
 local string = require "string"
 local table = require "table"
@@ -305,7 +306,12 @@ local function validate_options(options)
                 stdnse.debug1("http: options.cookies[i].expires should be a string")
                 bad = true
               end
-            else
+            elseif(cookie_key == 'max-age') then
+              if(type(cookie_value) ~= 'string') then
+                stdnse.debug1("http: options.cookies[i].max-age should be a string")
+                bad = true
+              end
+            elseif not (cookie_key == 'httponly' or cookie_key == 'secure') then
               stdnse.debug1("http: Unknown field in cookie table: %s", cookie_key)
               bad = true
             end
@@ -871,8 +877,8 @@ end
 --  @param path If the argument exists, only cookies with this path are included to the request
 --  @return A string to be added to the mod_options table
 local function buildCookies(cookies, path)
-  local cookie = ""
   if type(cookies) == 'string' then return cookies end
+  local cookie = {}
   for _, ck in ipairs(cookies or {}) do
     local ckpath = ck["path"]
     if not path or not ckpath
@@ -880,10 +886,10 @@ local function buildCookies(cookies, path)
       or ckpath:sub(-1) == "/" and ckpath == path:sub(1, ckpath:len())
       or ckpath .. "/" == path:sub(1, ckpath:len()+1)
       then
-        cookie = cookie .. ck["name"] .. "=" .. ck["value"] .. "; "
+        cookie[#cookie+1] = ck["name"] .. "=" .. ck["value"]
       end
     end
-  return cookie:gsub("; $","")
+  return table.concat(cookie, "; ")
 end
 
 -- HTTP cache.
@@ -2073,7 +2079,7 @@ local function get_attr (html, name)
   if not value then
     value = html:match('^[^%s<>=\'"`]+', pos)
   end
-  return value
+  return slaxml.parser.unescape(value)
 end
 ---
 -- Parses a form, that is, finds its action and fields.