Remove bin.lua unpacking from more scripts

scripts/broadcast-igmp-discovery.nse

@@ -1,7 +1,6 @@
 local nmap = require "nmap"
 local stdnse = require "stdnse"
 local table = require "table"
-local bin = require "bin"
 local packet = require "packet"
 local ipOps = require "ipOps"
 local target = require "target"
@@ -113,42 +112,30 @@ local igmpParse = function(data)
   local response = {}
   local group, source
   -- Report type (0x12 == v1, 0x16 == v2, 0x22 == v3)
-  index, response.type = bin.unpack(">C", data, index)
+  response.type, index = string.unpack(">B", data, index)
   if response.type == 0x12 or response.type == 0x16 then
-    -- Max response time
+    -- Max response time, Checksum, Multicast group
-    index, response.maxrt = bin.unpack(">C", data, index)
+    response.maxrt, response.checksum, response.group, index = string.unpack(">B I2 c4", data, index)
-    -- Checksum
+    response.group = ipOps.str_to_ip(response.group)
-    index, response.checksum = bin.unpack(">S", data, index)
-    -- Multicast group
-    index, response.group = bin.unpack(">I", data, index)
-    response.group = ipOps.fromdword(response.group)
     return response
   elseif response.type == 0x22 and #data >= 12 then
-    -- Skip reserved byte
+    -- Skip reserved byte, Checksum, Skip reserved bytes, Number of groups
-    index = index + 1
+    response.checksum, response.ngroups, index = string.unpack(">x I2 xx I2", data, index)
-    -- Checksum
-    index, response.checksum = bin.unpack(">S", data, index)
-    -- Skip reserved byte
-    index = index + 2
-    -- Number of groups
-    index, response.ngroups = bin.unpack(">S", data, index)
     response.groups = {}
     for i=1,response.ngroups do
       group = {}
       -- Mode is either INCLUDE or EXCLUDE
-      index, group.mode = bin.unpack(">C", data, index)
+      group.mode,
       -- Auxiliary data length in the group record (in 32bits units)
-      index, group.auxdlen = bin.unpack(">C", data, index)
+      group.auxdlen,
       -- Number of source addresses
-      index, group.nsrc = bin.unpack(">S", data, index)
+      group.nsrc,
-      index, group.address = bin.unpack(">I", data, index)
+      group.address, index = string.unpack(">BB I2 c4", data, index)
-      group.address = ipOps.fromdword(group.address)
+      group.address = ipOps.str_to_ip(group.address)
       group.src = {}
-      if group.nsrc > 0 then
       for i=1,group.nsrc do
-          index, source = bin.unpack(">I", data, index)
+        source, index = string.unpack(">c4", data, index)
-          table.insert(group.src, ipOps.fromdword(source))
+        table.insert(group.src, ipOps.str_to_ip(source))
-        end
       end
       -- Skip auxiliary data
       index = index + group.auxdlen
@@ -214,7 +201,7 @@ local igmpRaw = function(interface, version)
   end
 
   -- Let's craft an IGMP Membership Query
-  local igmp_raw = bin.pack(">CCSI",
+  local igmp_raw = string.pack(">BB I2 I4",
     0x11, -- Membership Query, same for all versions
     version == 1 and 0 or 0x16, -- Max response time: 10 Seconds, for version 2 and 3
     0, -- Checksum, calculated later
@@ -222,18 +209,18 @@ local igmpRaw = function(interface, version)
     )
 
   if version == 3 then
-    igmp_raw = bin.pack(">ACCSI", igmp_raw,
+    igmp_raw = igmp_raw .. string.pack(">BB I2",
       0, -- Reserved = 4 bits (Should be zeroed)
       -- Supress Flag = 1 bit
       -- QRV (Querier's Robustness Variable) = 3 bits
       -- all are set to 0
       0x10, -- QQIC (Querier's Query Interval Code) in seconds = Set to 0 to get insta replies.
-      0x0001, -- Number of sources (in the next arrays) = 1 ( Our IP only)
+      0x0001 -- Number of sources (in the next arrays) = 1 ( Our IP only)
-      ipOps.todword(interface.address) -- Source = Our IP address
       )
+      .. ipOps.ip_to_str(interface.address) -- Source = Our IP address
   end
 
-  igmp_raw = igmp_raw:sub(1,2) .. bin.pack(">S", packet.in_cksum(igmp_raw)) .. igmp_raw:sub(5)
+  igmp_raw = igmp_raw:sub(1,2) .. string.pack(">I2", packet.in_cksum(igmp_raw)) .. igmp_raw:sub(5)
 
   return igmp_raw
 end
@@ -267,7 +254,7 @@ igmpQuery = function(interface, version)
     sock:ethernet_open(interface.device)
 
     -- Ethernet IPv4 multicast, our ethernet address and type IP
-    local eth_hdr = bin.pack("HAH", "01 00 5e 00 00 01", interface.mac, "08 00")
+    local eth_hdr = "\x01\x00\x5e\x00\x00\x01" .. interface.mac .. "\x08\x00"
     sock:ethernet_send(eth_hdr .. igmp_packet.buf)
     sock:ethernet_close()
   end

scripts/broadcast-pim-discovery.nse

@@ -1,7 +1,6 @@
 local nmap = require "nmap"
 local packet = require "packet"
 local ipOps = require "ipOps"
-local bin = require "bin"
 local stdnse = require "stdnse"
 local target = require "target"
 local table = require "table"
@@ -55,18 +54,17 @@ end
 -- Generates a raw PIM Hello message.
 --@return hello Raw PIM Hello message
 local helloRaw = function()
-  local hello_raw = bin.pack(">CCSAAAA",
+  local hello_raw = string.pack(">BB I2",
     0x20, -- Version: 2, Type: Hello (0)
     0x00, -- Reserved
-    0x0000, -- Checksum: Calculated later
+    0x0000) -- Checksum: Calculated later
     -- Options (TLVs)
-    bin.pack(">SSS", 0x01, 0x02, 0x01), -- Hold time 1 second
+    .. string.pack(">I2I2 I2", 0x01, 0x02, 0x01) -- Hold time 1 second
-    bin.pack(">SSI", 0x14, 0x04, math.random(23456)), -- Generation ID: Random
+    .. string.pack(">I2I2 I4", 0x14, 0x04, math.random(23456)) -- Generation ID: Random
-    bin.pack(">SSI", 0x13, 0x04, 0x01), -- DR Priority: 1
+    .. string.pack(">I2I2 I4", 0x13, 0x04, 0x01) -- DR Priority: 1
-    bin.pack(">SSCCS", 0x15, 0x04, 0x01, 0x00, 0x00) -- State fresh capable: Version = 1, interval = 0, Reserved
+    .. string.pack(">I2I2 BBI2", 0x15, 0x04, 0x01, 0x00, 0x00) -- State fresh capable: Version = 1, interval = 0, Reserved
-    )
   -- Calculate checksum
-  hello_raw = hello_raw:sub(1,2) .. bin.pack(">S", packet.in_cksum(hello_raw)) .. hello_raw:sub(5)
+  hello_raw = hello_raw:sub(1,2) .. string.pack(">I2", packet.in_cksum(hello_raw)) .. hello_raw:sub(5)
 
   return hello_raw
 end
@@ -88,7 +86,7 @@ local helloQuery = function(interface, dstip)
   sock = nmap.new_dnet()
   sock:ethernet_open(interface.device)
   -- Ethernet multicast for PIM, our ethernet address and packet type IP
-  eth_hdr = bin.pack(">HAS", "01 00 5e 00 00 0d", interface.mac, 0x0800)
+  eth_hdr = "\x01\x00\x5e\x00\x00\x0d" .. interface.mac .. "\x08\x00"
   sock:ethernet_send(eth_hdr .. hello_packet.buf)
   sock:ethernet_close()
 end

scripts/broadcast-ripng-discover.nse

@@ -1,7 +1,7 @@
-local bin = require "bin"
 local ipOps = require "ipOps"
 local nmap = require "nmap"
 local stdnse = require "stdnse"
+local string = require "string"
 local tab = require "tab"
 local table = require "table"
 
@@ -69,9 +69,8 @@ RIPng = {
       local rte = RIPng.RTE:new()
       local pos, ip
 
-      pos, ip, rte.tag, rte.prefix_len, rte.metric = bin.unpack(">A16SCC", data)
+      ip, rte.tag, rte.prefix_len, rte.metric, pos = string.unpack(">c16 I2 BB", data)
-      ip = select(2, bin.unpack("B" .. #ip, ip))
+      rte.prefix = ipOps.str_to_ip(ip, 'inet6')
-      rte.prefix = ipOps.bin_to_ip(ip)
       return rte
     end,
 
@@ -80,7 +79,7 @@ RIPng = {
     __tostring = function(self)
       local ipstr = ipOps.ip_to_str(self.prefix)
       assert(16 == #ipstr, "Invalid IPv6 address encountered")
-      return bin.pack(">ASCC", ipstr, self.tag, self.prefix_len, self.metric)
+      return ipstr .. string.pack(">I2 BB", self.tag, self.prefix_len, self.metric)
     end,
 
 
@@ -107,7 +106,7 @@ RIPng = {
     -- Converts the whole request to a string
     __tostring = function(self)
       local RESERVED = 0
-      local str = {bin.pack(">CCS", self.command, self.version, RESERVED)}
+      local str = {string.pack(">BB I2", self.command, self.version, RESERVED)}
       for _, rte in ipairs(self.entries) do
         str[#str+1] = tostring(rte)
       end
@@ -134,7 +133,7 @@ RIPng = {
       local resp = RIPng.Response:new()
       local pos, _
 
-      pos, resp.command, resp.version, _ = bin.unpack(">CCS", data)
+      resp.command, resp.version, _, pos = string.unpack(">BB I2", data)
       resp.entries = {}
       while( pos < #data ) do
         local e = RIPng.RTE.parse(data:sub(pos))

scripts/broadcast-sybase-asa-discover.nse

@@ -1,7 +1,7 @@
-local bin = require "bin"
 local nmap = require "nmap"
 local os = require "os"
 local stdnse = require "stdnse"
+local string = require "string"
 local table = require "table"
 
 description = [[
@@ -44,8 +44,9 @@ Ping = {
 
     -- returns the ping request as a string
     __tostring = function(self)
-      return bin.pack("HAH", "1b00003d0000000012", "CONNECTIONLESS_TDS",
+      return stdnse.fromhex("1b00003d0000000012")
-      "000000010000040005000500000102000003010104080000000000000000070204b1")
+      .. "CONNECTIONLESS_TDS"
+      .. stdnse.fromhex("000000010000040005000500000102000003010104080000000000000000070204b1")
     end
   },
 
@@ -68,7 +69,7 @@ Ping = {
     -- <code>dbinstance.name</code> and <code>dbinstance.port</code> fields
     parse = function(self)
       -- do a very basic length check
-      local pos, len = bin.unpack(">I", self.data)
+      local len, pos = string.unpack(">I4", self.data)
       len = len & 0x0000FFFF
 
       if ( len ~= #self.data ) then
@@ -77,16 +78,16 @@ Ping = {
       end
 
       local connectionless_tds
-      pos, connectionless_tds = bin.unpack("p", self.data, 9)
+      connectionless_tds, pos = string.unpack("s1", self.data, 9)
       if ( connectionless_tds ~= "CONNECTIONLESS_TDS" ) then
         stdnse.debug2("Did not find the expected CONNECTIONLESS_TDS header")
         return
       end
 
       self.dbinstance = {}
-      pos, self.dbinstance.name = bin.unpack("p", self.data, 40)
+      self.dbinstance.name, pos = string.unpack("s1", self.data, 40)
       pos = pos + 2
-      pos, self.dbinstance.port = bin.unpack(">S", self.data, pos)
+      self.dbinstance.port, pos = string.unpack(">I2", self.data, pos)
     end,
   }
 

scripts/daap-get-library.nse

@@ -1,4 +1,3 @@
-local bin = require "bin"
 local http = require "http"
 local nmap = require "nmap"
 local shortport = require "shortport"
@@ -57,7 +56,7 @@ portrule = shortport.port_or_service(3689, "daap")
 -- @param port table containing number and protocol fields.
 -- @return string containing the name of the library
 function getLibraryName( host, port )
-  local _, libname, pos
+  local libname, pos
   local url = "daap://" .. host.ip .. "/server-info"
   local response = http.get( host, port, url, nil, nil, nil)
 
@@ -68,10 +67,8 @@ function getLibraryName( host, port )
   pos = string.find(response.body, "minm")
 
   if pos > 0 then
-    local len
     pos = pos + 4
-    pos, len = bin.unpack( ">I", response.body, pos )
+    libname, pos = string.unpack( ">s4", response.body, pos )
-    pos, libname = bin.unpack( "A" .. len, response.body, pos )
   end
 
   return libname
@@ -90,14 +87,14 @@ local function getAttributeAsInt( data, name )
   if pos and pos > 0 then
     pos = pos + 4
     local len
-    pos, len = bin.unpack( ">I", data, pos )
+    len, pos = string.unpack( ">I4", data, pos )
 
     if ( len ~= 4 ) then
       stdnse.debug1("Unexpected length returned: %d", len )
       return
     end
 
-    pos, attrib = bin.unpack( ">I", data, pos )
+    attrib, pos = string.unpack( ">I4", data, pos )
   end
 
   return attrib
@@ -111,7 +108,7 @@ end
 -- @return number containing the session identity received from the server
 function getSessionId( host, port )
 
-  local _, sessionid
+  local sessionid
   local response = http.get( host, port, "/login", nil, nil, nil )
 
   if response ~= nil then
@@ -129,7 +126,7 @@ end
 -- @return number containing the revision number for the library
 function getRevisionNumber( host, port, sessionid )
   local url = "/update?session-id=" .. sessionid .. "&revision-number=1"
-  local _, revision
+  local revision
   local response = http.get( host, port, url, nil, nil, nil )
 
   if response ~= nil then
@@ -164,14 +161,8 @@ end
 -- @return pos number containing new position after reading string
 -- @return value string containing the string item that was read
 local function getStringItem( data, pos )
-  local len
+  local item, pos = string.unpack(">s4", data, pos)
-
+  return pos, item
-  pos, len = bin.unpack(">I", data, pos)
-
-  if ( len > 0 ) then
-    return bin.unpack( "A"..len, data, pos )
-  end
-
 end
 
 local itemFetcher = {}
@@ -194,7 +185,7 @@ parseItem = function( data, len )
   local item = {}
 
   while( len - pos > 0 ) do
-    pos, name = bin.unpack( "A4", data, pos )
+    name, pos = string.unpack( "c4", data, pos )
 
     if itemFetcher[name] then
       pos, item[name] = itemFetcher[name](data, pos )
@@ -239,10 +230,10 @@ function getItems( host, port, sessionid, revid, dbid, limit )
     pos = string.find(response.body, "mlit", pos)
     pos = pos + 4
 
-    pos, len = bin.unpack( ">I", response.body, pos )
+    len, pos = string.unpack( ">I4", response.body, pos )
 
     if ( pos < response.body:len() and pos + len < response.body:len() ) then
-      pos, data = bin.unpack( "A" .. len, response.body, pos )
+      data, pos = string.unpack( "c" .. len, response.body, pos )
     else
       break
     end

scripts/db2-das-info.nse

@@ -1,4 +1,3 @@
-local bin = require "bin"
 local nmap = require "nmap"
 local shortport = require "shortport"
 local stdnse = require "stdnse"
@@ -134,8 +133,8 @@ function parse_db2_packet(packet)
     return
   end
 
-  local _, len = bin.unpack(">S", packet.data:sub(info_length_offset, info_length_offset + 1))
+  local len = string.unpack(">I2", packet.data, info_length_offset)
-  _, response.version = bin.unpack("z", packet.data:sub(version_offset) )
+  response.version = string.unpack("z", packet.data, version_offset)
   response.info_length = len - 4
   response.info = packet.data:sub(info_offset, info_offset + response.info_length - (info_offset-info_length_offset))
 
@@ -187,12 +186,12 @@ function read_db2_packet(socket)
 
     stdnse.debug1("Got DB2DAS packet")
 
-    local _, endian = bin.unpack( "A2", packet.header.raw, ENDIANESS_OFFSET )
+    local endian = string.unpack( "c2", packet.header.raw, ENDIANESS_OFFSET )
 
     if endian == "9z" then
-      _, packet.header.data_len = bin.unpack("<I", packet.header.raw, DATA_LENGTH_OFFSET )
+      packet.header.data_len = string.unpack("<I4", packet.header.raw, DATA_LENGTH_OFFSET )
     else
-      _, packet.header.data_len = bin.unpack(">I", packet.header.raw, DATA_LENGTH_OFFSET )
+      packet.header.data_len = string.unpack(">I4", packet.header.raw, DATA_LENGTH_OFFSET )
     end
 
     total_len = header_len + packet.header.data_len
@@ -269,8 +268,7 @@ function create_das_packet( magic, data )
   packet.header.raw = "\x00\x00\x00\x00\x44\x42\x32\x44\x41\x53\x20\x20\x20\x20\x20\x20"
   .. "\x01\x04\x00\x00\x00\x10\x39\x7a\x00\x05\x00\x00\x00\x00\x00\x00"
   .. "\x00\x00\x00\x00"
-  .. bin.pack("C", magic)
+  .. string.pack("<B I2", magic, data_len)
-  .. bin.pack("<S", data_len)
   .. "\x00\x00"
 
   packet.header.data_len = data_len

scripts/dns-zone-transfer.nse

@@ -1,4 +1,3 @@
-local bin = require "bin"
 local dns = require "dns"
 local ipOps = require "ipOps"
 local listop = require "listop"
@@ -249,10 +248,7 @@ local function parse_num_domain(data, offset)
 end
 
 local function parse_txt(data, offset)
-  local field, len
+  local field, offset = string.unpack("s1", data, offset)
-  len = string.byte(data, offset)
-  offset = offset + 1
-  offset, field = bin.unpack("A" .. len, data, offset)
   return offset, string.format('"%s"', field)
 end
 
@@ -337,7 +333,7 @@ local RD = {
   RT = parse_num_domain,
   NSAP = function(data, offset)
     local field
-    offset, field = bin.unpack("A" .. bto16(data, offset-2), data, offset)
+    field, offset = string.unpack(">s2", data, offset - 2)
     return offset, ("0x%s"):format(stdnse.tohex(field))
   end,
   ["NSAP-PTR"] = parse_domain,
@@ -373,7 +369,7 @@ local RD = {
     vp = string.byte(data, offset+3)
     vp = (vp >> 4) * 10 ^ (vp & 0x0f) / 100
     offset = offset + 4
-    offset, lat, lon, alt = bin.unpack(">III", data, offset)
+    lat, lon, alt, offset = string.unpack(">I4I4I4", data, offset)
     lat = (lat-2^31)/3600000 --degrees
     local latd = 'N'
     if lat < 0 then
@@ -393,7 +389,7 @@ local RD = {
   --EID NIMLOC --related to Nimrod DARPA project (Patton1995)
   SRV = function(data, offset)
     local priority, weight, port, info
-    offset, priority, weight, port = bin.unpack(">SSS", data, offset)
+    priority, weight, port, offset = string.unpack(">I2I2I2", data, offset)
     offset, info = parse_domain(data, offset)
     return offset, string.format("%d %d %d %s", priority, weight, port, info)
   end,
@@ -425,11 +421,11 @@ local RD = {
     return offset, string.format("%d %s %s", prefix, addr, name)
   end,
   DNAME = parse_domain,
-  SINK = function(data, offset) -- http://bgp.potaroo.net/ietf/all-ids/draft-eastlake-kitchen-sink-02.txt
+  SINK = function(data, offset) -- https://tools.ietf.org/html/draft-eastlake-kitchen-sink-02
     local coding, subcoding, field
     coding = string.byte(data, offset)
     subcoding = string.byte(data, offset+1)
-    offset, field = bin.unpack("A" .. (bto16(data, offset-2)-2), data, offset+2)
+    field, offset = string.unpack("c" .. (bto16(data, offset-2)-2), data, offset+2)
     return offset, string.format("%d %d %s", coding, subcoding, stdnse.tohex(field))
   end,
   --OPT APL DS
@@ -467,7 +463,7 @@ function get_rdata(data, offset, ttype)
     return RD[typetab[ttype]](data, offset)
   else
     local field
-    offset, field = bin.unpack("A" .. bto16(data, offset-2), data, offset)
+    field, offset = string.unpack(">s2", data, offset - 2)
     return offset, ("hex: %s"):format(stdnse.tohex(field))
   end
 end

scripts/enip-info.nse

@@ -1,4 +1,3 @@
-local bin = require "bin"
 local ipOps = require "ipOps"
 local nmap = require "nmap"
 local shortport = require "shortport"
@@ -1666,41 +1665,35 @@ action = function(host,port)
     return false, response
   end
   -- unpack the response command
-  local pos, command = bin.unpack("C", response, 1)
+  local command = string.byte(response, 1)
   -- unpack the response type id
-  local typeid
+  local typeid = string.byte(response, 27)
-  pos, typeid = bin.unpack("C", response, 27)
   -- if command is 0x63
   if ( command == 0x63) then
     -- if typeid == 0x0c (req ident)
     if( typeid == 0x0c) then
       -- vendor number
-      local vennum
+      local vennum = string.unpack("<I2", response, 49)
-      pos, vennum = bin.unpack("<S", response, 49)
       -- look up vendor number and store in output table
       output["Vendor"] = vendor_lookup(vennum) .. " (" .. vennum .. ")"
       -- unpack product name into output table
-      pos, output["Product Name"] = bin.unpack("p", response, 63)
+      output["Product Name"] = string.unpack("s1", response, 63)
       -- unpack the serial number
-      local serial
+      local serial = string.unpack("<I4", response, 59)
-      pos, serial = bin.unpack("<I", response, 59)
       -- print it out in hex format
       output["Serial Number"] = string.format("%#0.8x", serial)
       -- device type number
-      local devnum
+      local devnum = string.unpack("<I2", response, 51)
-      pos, devnum = bin.unpack("<S", response, 51)
       -- lookup device type based off number, return to output table
       output["Device Type"] = device_type_lookup(devnum) .. " (" .. devnum .. ")"
       -- unpack product code as a two byte int
-      pos, output["Product Code"] = bin.unpack("<S", response, 53)
+      output["Product Code"] = string.unpack("<I2", response, 53)
       -- Revision Nuumber
-      local char1, char2
+      local char1, char2 = string.unpack("BB", response, 55)
-      pos, char1, char2 = bin.unpack("CC", response, 55)
       output["Revision"] = char1 .. "." .. char2
       -- Device IP, this could be the same, as the IP scanning, or may be actual IP behind NAT
-      local dword
+      local ip = string.unpack("c4", response, 37)
-      pos, dword = bin.unpack(">I", response, 37)
+      output["Device IP"] = ipOps.str_to_ip(ip)
-      output["Device IP"] = ipOps.fromdword(dword)
       -- set Nmap output
       set_nmap(host, port)
       -- close socket

scripts/http-exif-spider.nse

@@ -30,7 +30,6 @@ local shortport = require 'shortport'
 local stdnse = require 'stdnse'
 local httpspider = require 'httpspider'
 local string = require 'string'
-local bin = require 'bin'
 local table = require 'table'
 
 -- These definitions are copied/pasted/reformatted from the jhead-2.96 sourcecode
@@ -338,7 +337,7 @@ portrule = shortport.http
 --@return the new position, and the value.
 local function unpack_rational(endian, data, pos)
   local v1, v2
-  pos, v1, v2 = bin.unpack(endian .. "II", data, pos)
+  v1, v2, pos = string.unpack(endian .. "I4I4", data, pos)
   return pos, v1 / v2
 end
 
@@ -347,7 +346,7 @@ local function process_gps(data, pos, endian, result)
   local latitude, latitude_ref, longitude, longitude_ref
 
   -- The first entry in the gps section is a 16-bit size
-  pos, num_entries = bin.unpack(endian .. "S", data, pos)
+  num_entries, pos = string.unpack(endian .. "I2", data, pos)
 
   -- Loop through the entries to find the fun stuff
   for i=1, num_entries do
@@ -403,8 +402,8 @@ local function parse_exif(exif_data)
   result = {}
 
   -- Read the verify the EXIF header
-  local pos, header1, header2, endian = bin.unpack(">ISS", exif_data, 1)
+  local header, endian, pos = string.unpack(">c6 I2", exif_data, 1)
-  if(header1 ~= 0x45786966 or header2 ~= 0x0000) then
+  if(header ~= "Exif\0\0") then
     return false, "Invalid EXIF header"
   end
 
@@ -419,7 +418,7 @@ local function parse_exif(exif_data)
   end
 
   -- Read the first tiff header and the offset to the first data entry (should be 8)
-  pos, tiff_header_1, first_offset = bin.unpack(endian .. "SI", exif_data, pos)
+  tiff_header_1, first_offset, pos = string.unpack(endian .. "I2 I4", exif_data, pos)
   if(tiff_header_1 ~= 0x002A or first_offset ~= 0x00000008) then
     return false, "Invalid tiff header"
   end
@@ -428,12 +427,12 @@ local function parse_exif(exif_data)
   pos = first_offset + 8 - 1
 
   -- The first 16-bit value is the number of entries
-  local pos, num_entries = bin.unpack(endian .. "S", exif_data, pos)
+  local num_entries, pos = string.unpack(endian .. "I2", exif_data, pos)
 
   -- Loop through the entries
   for i=1,num_entries do
     -- Read the entry's header
-    pos, tag, format, components, value = bin.unpack(endian .. "SSII", exif_data, pos)
+    tag, format, components, value, pos = string.unpack(endian .. "I2 I2 I4 I4", exif_data, pos)
 
     -- Look at the tags we care about
     if(tag == TAG_GPSINFO) then
@@ -442,17 +441,17 @@ local function parse_exif(exif_data)
       if(not(status)) then
         return false, result
       end
-    elseif(tag == TAG_MAKE) then
+    else
-      dummy, value = bin.unpack("z", exif_data, value + 8 - 1)
+      value = string.unpack("z", exif_data, value + 8 - 1)
+      if (tag == TAG_MAKE) then
         table.insert(result, string.format("Make: %s", value))
       elseif(tag == TAG_MODEL) then
-      dummy, value = bin.unpack("z", exif_data, value + 8 - 1)
         table.insert(result, string.format("Model: %s", value))
       elseif(tag == TAG_DATETIME) then
-      dummy, value = bin.unpack("z", exif_data, value + 8 - 1)
         table.insert(result, string.format("Date: %s", value))
       end
     end
+  end
 
   return true, result
 end
@@ -462,14 +461,14 @@ local function parse_jpeg(s)
   local pos, sig, marker, size, exif_data
 
   -- Parse the jpeg header, make sure it's valid (we expect 0xFFD8)
-  pos, sig = bin.unpack(">S", s, pos)
+  sig, pos = string.unpack(">I2", s, pos)
   if(sig ~= 0xFFD8) then
     return false, "Unexpected signature"
   end
 
   -- Parse the sections to find the exif marker (0xffe1)
   while(true) do
-    pos, marker, size = bin.unpack(">SS", s, pos)
+    marker, size, pos = string.unpack(">I2I2", s, pos)
 
     -- Check if we found the exif metadata section, break if we did
     if(marker == 0xffe1) then
@@ -483,7 +482,7 @@ local function parse_jpeg(s)
     pos = pos + size - 2
   end
 
-  pos, exif_data = bin.unpack(string.format(">A%d", size), s, pos)
+  exif_data, pos = string.unpack(string.format(">c%d", size), s, pos)
 
   return parse_exif(exif_data)
 end