Module: S3SwfUpload::Signature

Included in:
S3UploadsController
Defined in:
lib/s3_swf_upload/signature.rb

Instance Method Summary collapse

Instance Method Details

#assert(expr) ⇒ Object

Absolute barebones “unit” tests

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# File 'lib/s3_swf_upload/signature.rb', line 16

def assert(expr)
  raise 'Assertion failed' unless (expr)
end

#b64_hmac_sha1(key, data) ⇒ Object

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# File 'lib/s3_swf_upload/signature.rb', line 11

def b64_hmac_sha1(key, data)
  return binb2b64(core_hmac_sha1(key, data))
end

#binb2b64(binarray) ⇒ Object

Convert an array of big-endian words to a base-64 string

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# File 'lib/s3_swf_upload/signature.rb', line 178

def binb2b64(binarray)
  tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  str = ""

  #for(var i = 0; i < binarray.length * 4; i += 3)
  i = 0
  while(i < binarray.length * 4)
    triplet = (((binarray[i   >> 2].to_i >> 8 * (3 -  i   %4)) & 0xFF) << 16) |
                 (((binarray[i+1 >> 2].to_i >> 8 * (3 - (i+1)%4)) & 0xFF) << 8 ) |
                  ((binarray[i+2 >> 2].to_i >> 8 * (3 - (i+2)%4)) & 0xFF)
    #for(var j = 0; j < 4; j++)
    j = 0
    while(j < 4)
      if(i * 8 + j * 6 > binarray.length * 32)
        str += $b64pad
      else
        str += tab[(triplet >> 6*(3-j)) & 0x3F].chr
      end
      j += 1
    end
    i += 3
  end
  return str
end

#binb2hex(binarray) ⇒ Object

Convert an array of big-endian words to a hex string.

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# File 'lib/s3_swf_upload/signature.rb', line 164

def binb2hex(binarray)
  hex_tab = $hexcase ? "0123456789ABCDEF" : "0123456789abcdef"
  str = ""
  #for(var i = 0; i < binarray.length * 4; i++)
  i = 0
  while(i < binarray.length * 4)
    str += hex_tab[(binarray[i>>2] >> ((3 - i%4)*8+4)) & 0xF].chr +
           hex_tab[(binarray[i>>2] >> ((3 - i%4)*8  )) & 0xF].chr
    i += 1
  end
  return str;
end

#core_hmac_sha1(key, data) ⇒ Object

Calculate the HMAC-SHA1 of a key and some data

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# File 'lib/s3_swf_upload/signature.rb', line 104

def core_hmac_sha1(key, data)
  bkey = str2binb(key)
  if(bkey.length > 16) 
    bkey = core_sha1(bkey, key.length * $chrsz)
  end

  ipad = Array.new(16, 0)
  opad = Array.new(16, 0)
  #for(var i = 0; i < 16; i++)
  i = 0
  while(i < 16)
    ipad[i] = (bkey[i] || 0) ^ 0x36363636
    opad[i] = (bkey[i] || 0) ^ 0x5C5C5C5C
    i += 1
  end

  hash = core_sha1((ipad + str2binb(data)), 512 + data.length * $chrsz)
  return core_sha1((opad + hash), 512 + 160)
end

#core_sha1(x, len) ⇒ Object

Calculate the SHA-1 of an array of big-endian words, and a bit length

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# File 'lib/s3_swf_upload/signature.rb', line 37

def core_sha1(x, len)
  # append padding
  x[len >> 5] ||= 0
  x[len >> 5] |= 0x80 << (24 - len % 32)
  x[((len + 64 >> 9) << 4) + 15] = len

  w = Array.new(80, 0)
  a =  1732584193
  b = -271733879
  c = -1732584194
  d =  271733878
  e = -1009589776

  #for(var i = 0; i < x.length; i += 16)
  i = 0
  while(i < x.length)
    olda = a
    oldb = b
    oldc = c
    oldd = d
    olde = e

    #for(var j = 0; j < 80; j++)
    j = 0
    while(j < 80)
      if(j < 16) 
        w[j] = x[i + j] || 0
      else 
        w[j] = rol(w[j-3] ^ w[j-8] ^ w[j-14] ^ w[j-16], 1)
      end

      t = safe_add(safe_add(rol(a, 5), sha1_ft(j, b, c, d)),
                   safe_add(safe_add(e, w[j]), sha1_kt(j)))
      e = d
      d = c
      c = rol(b, 30)
      b = a
      a = t
      j += 1
    end

    a = safe_add(a, olda)
    b = safe_add(b, oldb)
    c = safe_add(c, oldc)
    d = safe_add(d, oldd)
    e = safe_add(e, olde)
    i += 16
  end
  return [a, b, c, d, e]
end

#hex_sha1(s) ⇒ Object

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# File 'lib/s3_swf_upload/signature.rb', line 7

def hex_sha1(s)
  return binb2hex(core_sha1(str2binb(s), s.length * $chrsz))
end

#rol(num, cnt) ⇒ Object

Bitwise rotate a 32-bit number to the left.

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# File 'lib/s3_swf_upload/signature.rb', line 132

def rol(num, cnt)
  #return (num << cnt) | (num >>> (32 - cnt))
  return (num.js_shl(cnt)) | (num.js_shr_zf(32 - cnt))
end

#safe_add(x, y) ⇒ Object

Add integers, wrapping at 2^32. This uses 16-bit operations internally to work around bugs in some JS interpreters.

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# File 'lib/s3_swf_upload/signature.rb', line 126

def safe_add(x, y)
  v = (x+y) % (2**32)
  return v > 2**31 ? v- 2**32 : v
end

#self_test ⇒ Object

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# File 'lib/s3_swf_upload/signature.rb', line 20

def self_test
  num, cnt = [1732584193, 5]

  assert(core_sha1(str2binb('abc'), 'abc'.length) == [-519653305, -1566383753, -2070791546, -753729183, -204968198])
  assert(rol(num, cnt) == -391880660)
  assert(safe_add(2042729798, num) == -519653305)
  assert((num.js_shl(cnt)) == -391880672)
  assert((num.js_shr_zf(32 - cnt)) == 12)
  assert(sha1_ft(0, -271733879, -1732584194, 271733878) == -1732584194)
  assert(sha1_kt(0) == 1518500249)
  assert(safe_add(safe_add(rol(num, cnt), sha1_ft(0, -271733879, -1732584194, 271733878)), safe_add(safe_add(-1009589776, 1902273280), sha1_kt(0))) == 286718899)
  assert(str2binb('foo bar hey there') == [1718578976, 1650553376, 1751480608, 1952998770, 1694498816])
  assert(hex_sha1("abc") == "a9993e364706816aba3e25717850c26c9cd0d89d")
  assert(b64_hmac_sha1("foo", "abc") == "frFXMR9cNoJdsSPnjebZpBhUKzI=")
end

#sha1_ft(t, b, c, d) ⇒ Object

Perform the appropriate triplet combination function for the current iteration

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# File 'lib/s3_swf_upload/signature.rb', line 90

def sha1_ft(t, b, c, d)
  return (b & c) | ((~b) & d) if(t < 20) 
  return b ^ c ^ d if(t < 40)
  return (b & c) | (b & d) | (c & d) if(t < 60)
  return b ^ c ^ d;
end

#sha1_kt(t) ⇒ Object

Determine the appropriate additive constant for the current iteration

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# File 'lib/s3_swf_upload/signature.rb', line 98

def sha1_kt(t)
  return (t < 20) ?  1518500249 : (t < 40) ?  1859775393 :
         (t < 60) ? -1894007588 : -899497514
end

#str2binb(str) ⇒ Object

Convert an 8-bit or 16-bit string to an array of big-endian words In 8-bit function, characters >255 have their hi-byte silently ignored.

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# File 'lib/s3_swf_upload/signature.rb', line 139

def str2binb(str)
  bin = []
  mask = (1 << $chrsz) - 1
  #for(var i = 0; i < str.length * $chrsz; i += $chrsz)
  i = 0
  while(i < str.length * $chrsz)
    bin[i>>5] ||= 0
    bin[i>>5] |= (str[i / $chrsz].ord & mask) << (32 - $chrsz - i%32)
    i += $chrsz
  end
  return bin
end