diff --git a/nselib/bin.lua b/nselib/bin.lua
index 41320beb5..ac8290610 100644
--- a/nselib/bin.lua
+++ b/nselib/bin.lua
@@ -78,6 +78,10 @@ local function clamp (args, i, j, mask)
     end
 end
 
+local function _fromhex (s)
+  return char(tonumber(s, 16))
+end
+
 --- Returns a binary packed string.
 --
 -- The format string describes how the parameters (<code>p1</code>,
@@ -107,7 +111,7 @@ function _ENV.pack (format, ...)
             assert(n > 0, "n cannot be 0") -- original bin library allowed this, it doesn't make sense
             local new = "=" -- !! in original bin library, hex strings are always native
             for j = i, i+n-1 do
-                args[j] = tostring(args[j]):gsub("%s*(%S%S?)%s*", function (s) return char(tonumber(s, 16)) end)
+                args[j] = tostring(args[j]):gsub("%s*(%S%S?)%s*", _fromhex)
                 new = new .. ("c%d"):format(#args[j])
             end
             new = new .. endianness -- restore old endianness
@@ -208,15 +212,24 @@ do
     assert(_ENV.pack("<C2SIL", 0x123, 0xfff1, 0x1ffff, 0x112345678, 0x1234567812345678) == "\x23\xf1\xff\xff\x78\x56\x34\x12\x78\x56\x34\x12\x78\x56\x34\x12")
 end
 
+local function _fmt_hex (c)
+  return ("%02X"):format(c:byte())
+end
+
+local function _fmt_bin (c)
+  local n = tobinary(c:byte())
+  return ("0"):rep(8-#n)..n
+end
+
 local function unpacker (fixer, status, ...)
     if not status then return 1 end
     -- Lua's unpack gives the stop index last:
     local list = pack(...)
     for i, v in ipairs(fixer) do
         if v.what == "H" then
-            list[v.which] = list[v.which]:gsub(".", function (c) return ("%02X"):format(c:byte()) end)
+            list[v.which] = list[v.which]:gsub(".", _fmt_hex)
         elseif v.what == "B" then
-            list[v.which] = list[v.which]:gsub(".", function (c) local n = tobinary(c:byte()); return ("0"):rep(8-#n)..n end)
+            list[v.which] = list[v.which]:gsub(".", _fmt_bin)
         else
             assert(false)
         end
diff --git a/nselib/ipOps.lua b/nselib/ipOps.lua
index 0feef1a58..aa45dac7d 100644
--- a/nselib/ipOps.lua
+++ b/nselib/ipOps.lua
@@ -680,9 +680,28 @@ end
 
 
 local bin_lookup = {
-  [0]="0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111",
-      "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111",
+  ["0"]="0000",
+  ["1"]="0001",
+  ["2"]="0010",
+  ["3"]="0011",
+  ["4"]="0100",
+  ["5"]="0101",
+  ["6"]="0110",
+  ["7"]="0111",
+  ["8"]="1000",
+  ["9"]="1001",
+  ["a"]="1010",
+  ["b"]="1011",
+  ["c"]="1100",
+  ["d"]="1101",
+  ["e"]="1110",
+  ["f"]="1111",
 }
+setmetatable(bin_lookup, {
+    __index = function()
+      error("Error in ipOps.hex_to_bin: Expected string representing a hexadecimal number.")
+    end
+  })
 ---
 -- Converts a string of hexadecimal digits into the corresponding string of
 -- binary digits.
@@ -699,14 +718,7 @@ hex_to_bin = function( hex )
     return nil, "Error in ipOps.hex_to_bin: Expected string"
   end
 
-  local status, result = pcall( string.gsub, hex, ".", function(nibble)
-      local n = bin_lookup[tonumber(nibble, 16)]
-      if n then
-        return n
-      else
-        error("Error in ipOps.hex_to_bin: Expected string representing a hexadecimal number.")
-      end
-    end)
+  local status, result = pcall( string.gsub, string.lower(hex), ".", bin_lookup)
   if status then
     return result
   end
@@ -820,7 +832,7 @@ end
 do
   for _, h in ipairs({
       {"a", "1010"},
-      {"aa", "10101010"},
+      {"aA", "10101010"},
       {"12", "00010010"},
       {"54321", "01010100001100100001"},
       {"123error", false},
diff --git a/nselib/packet.lua b/nselib/packet.lua
index a868c089d..b09dcc967 100644
--- a/nselib/packet.lua
+++ b/nselib/packet.lua
@@ -445,6 +445,9 @@ end
 -- Helpers
 
 
+local function _hex_str (x)
+  return string.char(tonumber(x, 16))
+end
 --- Convert a MAC address string (like <code>"00:23:ae:5d:3b:10"</code>) to
 -- a raw six-byte long.
 -- @param str MAC address string.
@@ -453,9 +456,7 @@ function mactobin(str)
   if not str then
     return nil, "MAC was not specified."
   end
-  return (str:gsub("(%x%x)[^%x]?", function (x)
-        return string.char(tonumber(x, 16))
-    end))
+  return (str:gsub("(%x%x)[^%x]?", _hex_str))
 end
 
 --- Generate the link-local IPv6 address from the MAC address.
diff --git a/nselib/stringaux.lua b/nselib/stringaux.lua
index 797473f14..96417b19c 100644
--- a/nselib/stringaux.lua
+++ b/nselib/stringaux.lua
@@ -70,6 +70,9 @@ end
 -- This pattern must match the percent sign '%' since it is used in
 -- escaping.
 local FILESYSTEM_UNSAFE = "[^a-zA-Z0-9._-]"
+local function _escape_helper (c)
+  return format("%%%02x", byte(c))
+end
 ---
 -- Escape a string to remove bytes and strings that may have meaning to
 -- a filesystem, such as slashes.
@@ -97,9 +100,7 @@ function filename_escape(s)
   elseif s == ".." then
     return "%2e%2e"
   else
-    return (gsub(s, FILESYSTEM_UNSAFE, function (c)
-      return format("%%%02x", byte(c))
-    end))
+    return (gsub(s, FILESYSTEM_UNSAFE, _escape_helper))
   end
 end
 
diff --git a/nselib/url.lua b/nselib/url.lua
index 241753842..737a1ea29 100644
--- a/nselib/url.lua
+++ b/nselib/url.lua
@@ -57,12 +57,17 @@ local function make_set(t)
   return s
 end
 
+local function hex_esc (c)
+  return string.format("%%%02x", string.byte(c))
+end
+
 -- these are allowed within a path segment, along with alphanum
 -- other characters must be escaped
 local segment_set = make_set {
   "-", "_", ".", "!", "~", "*", "'", "(",
   ")", ":", "@", "&", "=", "+", "$", ",",
 }
+setmetatable(segment_set, { __index = hex_esc })
 
 ---
 -- Protects a path segment, to prevent it from interfering with the
@@ -70,10 +75,7 @@ local segment_set = make_set {
 -- @param s Binary string to be encoded.
 -- @return Escaped representation of string.
 local function protect_segment(s)
-  return string.gsub(s, "([^A-Za-z0-9_.~-])", function (c)
-    if segment_set[c] then return c
-    else return string.format("%%%02x", string.byte(c)) end
-  end)
+  return string.gsub(s, "([^A-Za-z0-9_.~-])", segment_set)
 end
 
 ---
@@ -115,25 +117,26 @@ end
 -- @return Escaped representation of string.
 -----------------------------------------------------------------------------
 function escape(s)
-  local ret = string.gsub(s, "([^A-Za-z0-9_.~-])", function(c)
-    return string.format("%%%02x", string.byte(c))
-  end)
-  return ret
+  return (string.gsub(s, "([^A-Za-z0-9_.~-])", hex_esc))
 end
 
 
+local function hex_unesc (hex)
+    return string.char(base.tonumber(hex, 16))
+end
+
 ---
 -- Decodes an escaped hexadecimal string.
 -- @param s Hexadecimal-encoded string.
 -- @return Decoded string.
 -----------------------------------------------------------------------------
 function unescape(s)
-  local ret = string.gsub(s, "%%(%x%x)", function(hex)
-    return string.char(base.tonumber(hex, 16))
-  end)
-  return ret
+  return (string.gsub(s, "%%(%x%x)", hex_unesc))
 end
 
+local function normalize_escape (s)
+  return escape(unescape(s))
+end
 
 ---
 -- Parses a URL and returns a table with all its parts according to RFC 3986.
@@ -171,14 +174,7 @@ function parse(url, default)
   -- remove whitespace
   -- url = string.gsub(url, "%s", "")
   -- Decode unreserved characters
-  url = string.gsub(url, "%%(%x%x)", function(hex)
-      local char = string.char(base.tonumber(hex, 16))
-      if string.match(char, "[a-zA-Z0-9._~-]") then
-        return char
-      end
-      -- Hex encodings that are not unreserved must be preserved.
-      return nil
-    end)
+  url = string.gsub(url, "%%%x%x", normalize_escape)
   -- get fragment
   url = string.gsub(url, "#(.*)$", function(f)
     parsed.fragment = f
@@ -353,6 +349,11 @@ function build_path(parsed, unsafe)
   return table.concat(path)
 end
 
+local entities = {
+  ["amp"] = "&",
+  ["lt"] = "<",
+  ["gt"] = ">"
+}
 ---
 -- Breaks a query string into name/value pairs.
 --
@@ -369,9 +370,7 @@ function parse_query(query)
   local parsed = {}
   local pos = 1
 
-  query = string.gsub(query, "&amp;", "&")
-  query = string.gsub(query, "&lt;", "<")
-  query = string.gsub(query, "&gt;", ">")
+  query = string.gsub(query, "&([ampltg]+);", entities)
 
   local function ginsert(qstr)
     local pos = qstr:find("=", 1, true)