Pure lua MD5 Implementation

gistfile1.lua

--[[---------------
LuaBit v0.4
-------------------
a bitwise operation lib for lua.

http://luaforge.net/projects/bit/

How to use:
-------------------
 bit.bnot(n) -- bitwise not (~n)
 bit.band(m, n) -- bitwise and (m & n)
 bit.bor(m, n) -- bitwise or (m | n)
 bit.bxor(m, n) -- bitwise xor (m ^ n)
 bit.brshift(n, bits) -- right shift (n >> bits)
 bit.blshift(n, bits) -- left shift (n << bits)
 bit.blogic_rshift(n, bits) -- logic right shift(zero fill >>>)
 
Please note that bit.brshift and bit.blshift only support number within
32 bits.

2 utility functions are provided too:
 bit.tobits(n) -- convert n into a bit table(which is a 1/0 sequence)
               -- high bits first
 bit.tonumb(bit_tbl) -- convert a bit table into a number 
-------------------

Under the MIT license.

copyright(c) 2006~2007 hanzhao (abrash_han@hotmail.com)
--]]---------------

--do

------------------------
-- bit lib implementions

local function check_int(n)
 -- checking not float
 if(n - math.floor(n) > 0) then
  error("trying to use bitwise operation on non-integer!")
 end
end

local function tbl_to_number(tbl)
 local n = #tbl

 local rslt = 0
 local power = 1
 for i = 1, n do
  rslt = rslt + tbl[i]*power
  power = power*2
 end
 
 return rslt
end

local function expand(tbl_m, tbl_n)
 local big = {}
 local small = {}
 if(#tbl_m > #tbl_n) then
  big = tbl_m
  small = tbl_n
 else
  big = tbl_n
  small = tbl_m
 end
 -- expand small
 for i = #small + 1, #big do
  small[i] = 0
 end

end

local to_bits = function () end

local function bit_not(n)
 local tbl = to_bits(n)
 local size = math.max(#tbl, 32)
 for i = 1, size do
  if(tbl[i] == 1) then
   tbl[i] = 0
  else
   tbl[i] = 1
  end
 end
 return tbl_to_number(tbl)
end


to_bits = function (n)
 check_int(n)
 if(n < 0) then
  -- negative
  return to_bits(bit_not(math.abs(n)) + 1)
 end
 -- to bits table
 local tbl = {}
 local cnt = 1
 while (n > 0) do
  local last = math.mod(n,2)
  if(last == 1) then
   tbl[cnt] = 1
  else
   tbl[cnt] = 0
  end
  n = (n-last)/2
  cnt = cnt + 1
 end

 return tbl
end


local function bit_or(m, n)
 local tbl_m = to_bits(m)
 local tbl_n = to_bits(n)
 expand(tbl_m, tbl_n)

 local tbl = {}
 local rslt = math.max(#tbl_m, #tbl_n)
 for i = 1, rslt do
  if(tbl_m[i]== 0 and tbl_n[i] == 0) then
   tbl[i] = 0
  else
   tbl[i] = 1
  end
 end
 
 return tbl_to_number(tbl)
end

local function bit_and(m, n)
 local tbl_m = to_bits(m)
 local tbl_n = to_bits(n)
 expand(tbl_m, tbl_n) 

 local tbl = {}
 local rslt = math.max(#tbl_m, #tbl_n)
 for i = 1, rslt do
  if(tbl_m[i]== 0 or tbl_n[i] == 0) then
   tbl[i] = 0
  else
   tbl[i] = 1
  end
 end

 return tbl_to_number(tbl)
end

local function bit_xor(m, n)
 local tbl_m = to_bits(m)
 local tbl_n = to_bits(n)
 expand(tbl_m, tbl_n) 

 local tbl = {}
 local rslt = math.max(#tbl_m, #tbl_n)
 for i = 1, rslt do
  if(tbl_m[i] ~= tbl_n[i]) then
   tbl[i] = 1
  else
   tbl[i] = 0
  end
 end
 
 --table.foreach(tbl, print)

 return tbl_to_number(tbl)
end

local function bit_rshift(n, bits)
 check_int(n)
 
 local high_bit = 0
 if(n < 0) then
  -- negative
  n = bit_not(math.abs(n)) + 1
  high_bit = 2147483648 -- 0x80000000
 end

 for i=1, bits do
  n = n/2
  n = bit_or(math.floor(n), high_bit)
 end
 return math.floor(n)
end

-- logic rightshift assures zero filling shift
local function bit_logic_rshift(n, bits)
 check_int(n)
 if(n < 0) then
  -- negative
  n = bit_not(math.abs(n)) + 1
 end
 for i=1, bits do
  n = n/2
 end
 return math.floor(n)
end

local function bit_lshift(n, bits)
 check_int(n)
 
 if(n < 0) then
  -- negative
  n = bit_not(math.abs(n)) + 1
 end

 for i=1, bits do
  n = n*2
 end
 return bit_and(n, 4294967295) -- 0xFFFFFFFF
end

local function bit_xor2(m, n)
 local rhs = bit_or(bit_not(m), bit_not(n))
 local lhs = bit_or(m, n)
 local rslt = bit_and(lhs, rhs)
 return rslt
end

-- An MD5 mplementation in Lua, requires bitlib (hacked to use LuaBit from above, ugh)
-- 10/02/2001 jcw@equi4.com

local md5={ff=tonumber('ffffffff',16),consts={}}

string.gsub([[ d76aa478 e8c7b756 242070db c1bdceee
    f57c0faf 4787c62a a8304613 fd469501
    698098d8 8b44f7af ffff5bb1 895cd7be
    6b901122 fd987193 a679438e 49b40821
    f61e2562 c040b340 265e5a51 e9b6c7aa
    d62f105d 02441453 d8a1e681 e7d3fbc8
    21e1cde6 c33707d6 f4d50d87 455a14ed
    a9e3e905 fcefa3f8 676f02d9 8d2a4c8a
    fffa3942 8771f681 6d9d6122 fde5380c
    a4beea44 4bdecfa9 f6bb4b60 bebfbc70
    289b7ec6 eaa127fa d4ef3085 04881d05
    d9d4d039 e6db99e5 1fa27cf8 c4ac5665
    f4292244 432aff97 ab9423a7 fc93a039
    655b59c3 8f0ccc92 ffeff47d 85845dd1
    6fa87e4f fe2ce6e0 a3014314 4e0811a1
    f7537e82 bd3af235 2ad7d2bb eb86d391
    67452301 efcdab89 98badcfe 10325476 ]],"(%w+)", function (s) table.insert(md5.consts, tonumber(s,16)) end)
    --67452301 efcdab89 98badcfe 10325476 ]],"(%w+)", function (s) tinsert(md5.consts,tonumber(s,16)) end)

function md5.transform(A,B,C,D,X)
  local f=function (x,y,z) return bit_or(bit_and(x,y),bit_and(-x-1,z)) end
  local g=function (x,y,z) return bit_or(bit_and(x,z),bit_and(y,-z-1)) end
  local h=function (x,y,z) return bit_xor(x,bit_xor(y,z)) end
  local i=function (x,y,z) return bit_xor(y,bit_or(x,-z-1)) end
  local z=function (f,a,b,c,d,x,s,ac)
        a=bit_and(a+f(b,c,d)+x+ac,md5.ff)
        -- be *very* careful that left shift does not cause rounding!
        return bit_or(bit_lshift(bit_and(a,bit_rshift(md5.ff,s)),s),bit_rshift(a,32-s))+b
      end
  local a,b,c,d=A,B,C,D
  local t=md5.consts

  a=z(f,a,b,c,d,X[ 0], 7,t[ 1])
  d=z(f,d,a,b,c,X[ 1],12,t[ 2])
  c=z(f,c,d,a,b,X[ 2],17,t[ 3])
  b=z(f,b,c,d,a,X[ 3],22,t[ 4])
  a=z(f,a,b,c,d,X[ 4], 7,t[ 5])
  d=z(f,d,a,b,c,X[ 5],12,t[ 6])
  c=z(f,c,d,a,b,X[ 6],17,t[ 7])
  b=z(f,b,c,d,a,X[ 7],22,t[ 8])
  a=z(f,a,b,c,d,X[ 8], 7,t[ 9])
  d=z(f,d,a,b,c,X[ 9],12,t[10])
  c=z(f,c,d,a,b,X[10],17,t[11])
  b=z(f,b,c,d,a,X[11],22,t[12])
  a=z(f,a,b,c,d,X[12], 7,t[13])
  d=z(f,d,a,b,c,X[13],12,t[14])
  c=z(f,c,d,a,b,X[14],17,t[15])
  b=z(f,b,c,d,a,X[15],22,t[16])

  a=z(g,a,b,c,d,X[ 1], 5,t[17])
  d=z(g,d,a,b,c,X[ 6], 9,t[18])
  c=z(g,c,d,a,b,X[11],14,t[19])
  b=z(g,b,c,d,a,X[ 0],20,t[20])
  a=z(g,a,b,c,d,X[ 5], 5,t[21])
  d=z(g,d,a,b,c,X[10], 9,t[22])
  c=z(g,c,d,a,b,X[15],14,t[23])
  b=z(g,b,c,d,a,X[ 4],20,t[24])
  a=z(g,a,b,c,d,X[ 9], 5,t[25])
  d=z(g,d,a,b,c,X[14], 9,t[26])
  c=z(g,c,d,a,b,X[ 3],14,t[27])
  b=z(g,b,c,d,a,X[ 8],20,t[28])
  a=z(g,a,b,c,d,X[13], 5,t[29])
  d=z(g,d,a,b,c,X[ 2], 9,t[30])
  c=z(g,c,d,a,b,X[ 7],14,t[31])
  b=z(g,b,c,d,a,X[12],20,t[32])

  a=z(h,a,b,c,d,X[ 5], 4,t[33])
  d=z(h,d,a,b,c,X[ 8],11,t[34])
  c=z(h,c,d,a,b,X[11],16,t[35])
  b=z(h,b,c,d,a,X[14],23,t[36])
  a=z(h,a,b,c,d,X[ 1], 4,t[37])
  d=z(h,d,a,b,c,X[ 4],11,t[38])
  c=z(h,c,d,a,b,X[ 7],16,t[39])
  b=z(h,b,c,d,a,X[10],23,t[40])
  a=z(h,a,b,c,d,X[13], 4,t[41])
  d=z(h,d,a,b,c,X[ 0],11,t[42])
  c=z(h,c,d,a,b,X[ 3],16,t[43])
  b=z(h,b,c,d,a,X[ 6],23,t[44])
  a=z(h,a,b,c,d,X[ 9], 4,t[45])
  d=z(h,d,a,b,c,X[12],11,t[46])
  c=z(h,c,d,a,b,X[15],16,t[47])
  b=z(h,b,c,d,a,X[ 2],23,t[48])

  a=z(i,a,b,c,d,X[ 0], 6,t[49])
  d=z(i,d,a,b,c,X[ 7],10,t[50])
  c=z(i,c,d,a,b,X[14],15,t[51])
  b=z(i,b,c,d,a,X[ 5],21,t[52])
  a=z(i,a,b,c,d,X[12], 6,t[53])
  d=z(i,d,a,b,c,X[ 3],10,t[54])
  c=z(i,c,d,a,b,X[10],15,t[55])
  b=z(i,b,c,d,a,X[ 1],21,t[56])
  a=z(i,a,b,c,d,X[ 8], 6,t[57])
  d=z(i,d,a,b,c,X[15],10,t[58])
  c=z(i,c,d,a,b,X[ 6],15,t[59])
  b=z(i,b,c,d,a,X[13],21,t[60])
  a=z(i,a,b,c,d,X[ 4], 6,t[61])
  d=z(i,d,a,b,c,X[11],10,t[62])
  c=z(i,c,d,a,b,X[ 2],15,t[63])
  b=z(i,b,c,d,a,X[ 9],21,t[64])

  return A+a,B+b,C+c,D+d
end

-- convert little-endian 32-bit int to a 4-char string
local function leIstr(i)
  local f=function (s) return string.char(bit_and(bit_rshift(i,s),255)) end
  return f(0)..f(8)..f(16)..f(24)
end

  -- convert raw string to big-endian int
  local function beInt(s)
    local v=0
    for i=1,string.len(s) do v=v*256+string.byte(s,i) end
    return v
  end
  -- convert raw string to little-endian int
  local function leInt(s)
    local v=0
    for i=string.len(s),1,-1 do v=v*256+string.byte(s,i) end
    return v
  end
  -- cut up a string in little-endian ints of given size
  local function leStrCuts(s,...)
    local o,r=1,{}
    for i=1,#arg do
      table.insert(r,leInt(string.sub(s,o,o+arg[i]-1)))
      o=o+arg[i]
    end
    return r
  end

function md5.Calc(s)
  local msgLen=string.len(s)
  local padLen=56- msgLen % 64
  if msgLen % 64 > 56 then padLen=padLen+64 end
  if padLen==0 then padLen=64 end
  s=s..string.char(128)..string.rep(string.char(0),padLen-1)
  s=s..leIstr(8*msgLen)..leIstr(0)
  assert(string.len(s) % 64 ==0)
  local t=md5.consts
  local a,b,c,d=t[65],t[66],t[67],t[68]
  for i=1,string.len(s),64 do
    local X=leStrCuts(string.sub(s,i,i+63),4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4)
    assert(#X==16)
    X[0]=table.remove(X,1) -- zero based!
    a,b,c,d=md5.transform(a,b,c,d,X)
  end
  local swap=function (w) return beInt(leIstr(w)) end
  return string.format("%08x%08x%08x%08x",swap(a),swap(b),swap(c),swap(d))
end

return md5.Calc("asdf"); -- 912ec803b2ce49e4a541068d495ab570

Hi, I was using this md5 implementation in a project I was working and and noticed an issue with calculating especially large strings. Especially long strings (roughly 3000+ characters) were all being encoded as 0000 0000 0000 0000.

It seemed that the issues is that the C implementation of md5 relies on the fact that a,b,c,d are uint32 and that they naturally buffer overflow. Our lua implementation needs to simulate this buffer overflow so I added these lines after the md5 transform:

a = a % (2^32)
b = b % (2^32)
c = c % (2^32)
d = d % (2^32)