Brains Not Brawn Blog: SHA256 and classic ASP VBSCRIPT for intercom.io secure settings and others

I've recently been using intercom.io to manage my member communication and they require a secure mode to be enabled that passes a hashed value with each session.

On the back end I needed to create javascript that looked like this:

The user hash needed to be a SHA256 hash of the users email address and the unique "salt" or secret key provided by intercom.io on a user account basis.

The problem was that I'm using Vbscript/classic ASP so was having trouble sorting this out with the limited VBScript library.

The solution was found courtesy of:

/*
 * A JavaScript implementation of the Secure Hash Algorithm, SHA-256, as defined
 * in FIPS 180-2
 * Version 2.2 Copyright Angel Marin, Paul Johnston 2000 - 2009.
 * Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
 * Distributed under the BSD License
 * See http://pajhome.org.uk/crypt/md5 for details.
 * Adapted into a WSC for use in classic ASP by Daniel O'Malley
 * (based on an SHA-1 example by Erik Oosterwaal)
 * for use with the Amazon Product Advertising API
 */

Basically you create a stand alone file called sha256.wsc that lives in the same directory as the function - then pass in the appropriate variables.

VBScript Function:

The contents for sha256.wsc follow at the end of the post. Good luck and happy coding

<?xml version="1.0"?>
<component>
<?component error="true" debug="true"?>
<registration
 description="sha256"
 progid="sha256.WSC"
 version="1.00"
 classid="{E2EA9DA9-6B72-437B-85E8-4542DA19F7E6}"
>
</registration>

<property name="hexcase">
  <get/>
  <put/>
 </property>
 <property name="b64pad">
  <get/>
  <put/>
 </property>

<method name="b64_hmac_sha256">
  <parameter name="k"/>
  <parameter name="d"/>
 </method>
</public>

/* properties */
function get_hexcase()   {get_hexcase = hexcase};
function put_hexcase(newValue) {hexcase  = newValue};

function get_b64pad()   {get_b64pad  = b64pad};
function put_b64pad(newValue) {b64pad   = newValue};

/* methods */
/*

/*
 * A JavaScript implementation of the Secure Hash Algorithm, SHA-256, as defined
 * in FIPS 180-2
 * Version 2.2 Copyright Angel Marin, Paul Johnston 2000 - 2009.
 * Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
 * Distributed under the BSD License
 * See http://pajhome.org.uk/crypt/md5 for details.
 * Adapted into a WSC for use in classic ASP by Daniel O'Malley
 * (based on an SHA-1 example by Erik Oosterwaal)
 * for use with the Amazon Product Advertising API
 */

/*
 * Configurable variables
 */
var hexcase = 1;  /* hex output format. 0 - lowercase; 1 - uppercase  */
var b64pad  = "="; /* base-64 pad character.  */

/*
 * Below is the signature-generation function for Amazon that takes two parameters:
 * k - your Amazon AWS "secret access key"
 * d - the data you wish to encode (the string to sign)
 * The function passes these parameters through HMAC-SHA256 hashing/encoding, then returns a 
 * base-64 encoded string which you then use as your signature for the Amazon API call
 */

function b64_hmac_sha256(k, d)
  {
/* To avoid any ambiguity over use of linefeed characters, the line below replaces
 * any line break, carriage return or other whitespace in the input with a "\n" character
 * since that's what Amazon requires
 */
/*d=d.replace ( /\s/g, "\n");*/
/*return rstr2b64(rstr_hmac_sha256(str2rstr_utf8(k), str2rstr_utf8(d)));*/

/*return output in hex*/
return rstr2any(rstr_hmac_sha256(str2rstr_utf8(k), str2rstr_utf8(d)), "0123456789abcdef");

}

/*
 * Calculate the HMAC-sha256 of a key and some data (raw strings)
 */
function rstr_hmac_sha256(key, data)
{
  var bkey = rstr2binb(key);
  if(bkey.length > 16) bkey = binb_sha256(bkey, key.length * 8);

var ipad = Array(16), opad = Array(16);
  for(var i = 0; i < 16; i++)
  {
    ipad[i] = bkey[i] ^ 0x36363636;
    opad[i] = bkey[i] ^ 0x5C5C5C5C;
  }

var hash = binb_sha256(ipad.concat(rstr2binb(data)), 512 + data.length * 8);
  return binb2rstr(binb_sha256(opad.concat(hash), 512 + 256));
}

/*
 * Convert a raw string to a hex string
 */
function rstr2hex(input)
{
  try { hexcase } catch(e) { hexcase=0; }
  var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
  var output = "";
  var x;
  for(var i = 0; i < input.length; i++)
  {
    x = input.charCodeAt(i);
    output += hex_tab.charAt((x >>> 4) & 0x0F)
           +  hex_tab.charAt( x        & 0x0F);
  }
  return output;
}

/*
 * Convert a raw string to a base-64 string
 */
function rstr2b64(input)
{
  try { b64pad } catch(e) { b64pad=''; }
  var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  var output = "";
  var len = input.length;
  for(var i = 0; i < len; i += 3)
  {
    var triplet = (input.charCodeAt(i) << 16)
                | (i + 1 < len ? input.charCodeAt(i+1) << 8 : 0)
                | (i + 2 < len ? input.charCodeAt(i+2)      : 0);
    for(var j = 0; j < 4; j++)
    {
      if(i * 8 + j * 6 > input.length * 8) output += b64pad;
      else output += tab.charAt((triplet >>> 6*(3-j)) & 0x3F);
    }
  }
  return output;
}

/*
 * Convert a raw string to an arbitrary string encoding
 */
function rstr2any(input, encoding)
{
  var divisor = encoding.length;
  var remainders = Array();
  var i, q, x, quotient;

/* Convert to an array of 16-bit big-endian values, forming the dividend */
  var dividend = Array(Math.ceil(input.length / 2));
  for(i = 0; i < dividend.length; i++)
  {
    dividend[i] = (input.charCodeAt(i * 2) << 8) | input.charCodeAt(i * 2 + 1);
  }

/*
   * Repeatedly perform a long division. The binary array forms the dividend,
   * the length of the encoding is the divisor. Once computed, the quotient
   * forms the dividend for the next step. We stop when the dividend is zero.
   * All remainders are stored for later use.
   */
  while(dividend.length > 0)
  {
    quotient = Array();
    x = 0;
    for(i = 0; i < dividend.length; i++)
    {
      x = (x << 16) + dividend[i];
      q = Math.floor(x / divisor);
      x -= q * divisor;
      if(quotient.length > 0 || q > 0)
        quotient[quotient.length] = q;
    }
    remainders[remainders.length] = x;
    dividend = quotient;
  }

/* Convert the remainders to the output string */
  var output = "";
  for(i = remainders.length - 1; i >= 0; i--)
    output += encoding.charAt(remainders[i]);

/* Append leading zero equivalents */
  var full_length = Math.ceil(input.length * 8 /
                                    (Math.log(encoding.length) / Math.log(2)))
  for(i = output.length; i < full_length; i++)
    output = encoding[0] + output;

return output;
}

/*
 * Encode a string as utf-8.
 * For efficiency, this assumes the input is valid utf-16.
 */
function str2rstr_utf8(input)
{
  var output = "";
  var i = -1;
  var x, y;

while(++i < input.length)
  {
    /* Decode utf-16 surrogate pairs */
    x = input.charCodeAt(i);
    y = i + 1 < input.length ? input.charCodeAt(i + 1) : 0;
    if(0xD800 <= x && x <= 0xDBFF && 0xDC00 <= y && y <= 0xDFFF)
    {
      x = 0x10000 + ((x & 0x03FF) << 10) + (y & 0x03FF);
      i++;
    }

/* Encode output as utf-8 */
    if(x <= 0x7F)
      output += String.fromCharCode(x);
    else if(x <= 0x7FF)
      output += String.fromCharCode(0xC0 | ((x >>> 6 ) & 0x1F),
                                    0x80 | ( x         & 0x3F));
    else if(x <= 0xFFFF)
      output += String.fromCharCode(0xE0 | ((x >>> 12) & 0x0F),
                                    0x80 | ((x >>> 6 ) & 0x3F),
                                    0x80 | ( x         & 0x3F));
    else if(x <= 0x1FFFFF)
      output += String.fromCharCode(0xF0 | ((x >>> 18) & 0x07),
                                    0x80 | ((x >>> 12) & 0x3F),
                                    0x80 | ((x >>> 6 ) & 0x3F),
                                    0x80 | ( x         & 0x3F));
  }
  return output;
}

/*
 * Encode a string as utf-16
 */
function str2rstr_utf16le(input)
{
  var output = "";
  for(var i = 0; i < input.length; i++)
    output += String.fromCharCode( input.charCodeAt(i)        & 0xFF,
                                  (input.charCodeAt(i) >>> 8) & 0xFF);
  return output;
}

function str2rstr_utf16be(input)
{
  var output = "";
  for(var i = 0; i < input.length; i++)
    output += String.fromCharCode((input.charCodeAt(i) >>> 8) & 0xFF,
                                   input.charCodeAt(i)        & 0xFF);
  return output;
}

/*
 * Convert a raw string to an array of big-endian words
 * Characters >255 have their high-byte silently ignored.
 */
function rstr2binb(input)
{
  var output = Array(input.length >> 2);
  for(var i = 0; i < output.length; i++)
    output[i] = 0;
  for(var i = 0; i < input.length * 8; i += 8)
    output[i>>5] |= (input.charCodeAt(i / 8) & 0xFF) << (24 - i % 32);
  return output;
}

/*
 * Convert an array of big-endian words to a string
 */
function binb2rstr(input)
{
  var output = "";
  for(var i = 0; i < input.length * 32; i += 8)
    output += String.fromCharCode((input[i>>5] >>> (24 - i % 32)) & 0xFF);
  return output;
}

/*
 * Main sha256 function, with its support functions
 */
function sha256_S (X, n) {return ( X >>> n ) | (X << (32 - n));}
function sha256_R (X, n) {return ( X >>> n );}
function sha256_Ch(x, y, z) {return ((x & y) ^ ((~x) & z));}
function sha256_Maj(x, y, z) {return ((x & y) ^ (x & z) ^ (y & z));}
function sha256_Sigma0256(x) {return (sha256_S(x, 2) ^ sha256_S(x, 13) ^ sha256_S(x, 22));}
function sha256_Sigma1256(x) {return (sha256_S(x, 6) ^ sha256_S(x, 11) ^ sha256_S(x, 25));}
function sha256_Gamma0256(x) {return (sha256_S(x, 7) ^ sha256_S(x, 18) ^ sha256_R(x, 3));}
function sha256_Gamma1256(x) {return (sha256_S(x, 17) ^ sha256_S(x, 19) ^ sha256_R(x, 10));}
function sha256_Sigma0512(x) {return (sha256_S(x, 28) ^ sha256_S(x, 34) ^ sha256_S(x, 39));}
function sha256_Sigma1512(x) {return (sha256_S(x, 14) ^ sha256_S(x, 18) ^ sha256_S(x, 41));}
function sha256_Gamma0512(x) {return (sha256_S(x, 1)  ^ sha256_S(x, 8) ^ sha256_R(x, 7));}
function sha256_Gamma1512(x) {return (sha256_S(x, 19) ^ sha256_S(x, 61) ^ sha256_R(x, 6));}

var sha256_K = new Array
(
  1116352408, 1899447441, -1245643825, -373957723, 961987163, 1508970993,
  -1841331548, -1424204075, -670586216, 310598401, 607225278, 1426881987,
  1925078388, -2132889090, -1680079193, -1046744716, -459576895, -272742522,
  264347078, 604807628, 770255983, 1249150122, 1555081692, 1996064986,
  -1740746414, -1473132947, -1341970488, -1084653625, -958395405, -710438585,
  113926993, 338241895, 666307205, 773529912, 1294757372, 1396182291,
  1695183700, 1986661051, -2117940946, -1838011259, -1564481375, -1474664885,
  -1035236496, -949202525, -778901479, -694614492, -200395387, 275423344,
  430227734, 506948616, 659060556, 883997877, 958139571, 1322822218,
  1537002063, 1747873779, 1955562222, 2024104815, -2067236844, -1933114872,
  -1866530822, -1538233109, -1090935817, -965641998
);

function binb_sha256(m, l)
{
  var HASH = new Array(1779033703, -1150833019, 1013904242, -1521486534,
                       1359893119, -1694144372, 528734635, 1541459225);
  var W = new Array(64);
  var a, b, c, d, e, f, g, h;
  var i, j, T1, T2;

/* append padding */
  m[l >> 5] |= 0x80 << (24 - l % 32);
  m[((l + 64 >> 9) << 4) + 15] = l;

for(i = 0; i < m.length; i += 16)
  {
    a = HASH[0];
    b = HASH[1];
    c = HASH[2];
    d = HASH[3];
    e = HASH[4];
    f = HASH[5];
    g = HASH[6];
    h = HASH[7];

for(j = 0; j < 64; j++)
    {
      if (j < 16) W[j] = m[j + i];
      else W[j] = safe_add(safe_add(safe_add(sha256_Gamma1256(W[j - 2]), W[j - 7]),
                                            sha256_Gamma0256(W[j - 15])), W[j - 16]);

T1 = safe_add(safe_add(safe_add(safe_add(h, sha256_Sigma1256(e)), sha256_Ch(e, f, g)),
                                                          sha256_K[j]), W[j]);
      T2 = safe_add(sha256_Sigma0256(a), sha256_Maj(a, b, c));
      h = g;
      g = f;
      f = e;
      e = safe_add(d, T1);
      d = c;
      c = b;
      b = a;
      a = safe_add(T1, T2);
    }

HASH[0] = safe_add(a, HASH[0]);
    HASH[1] = safe_add(b, HASH[1]);
    HASH[2] = safe_add(c, HASH[2]);
    HASH[3] = safe_add(d, HASH[3]);
    HASH[4] = safe_add(e, HASH[4]);
    HASH[5] = safe_add(f, HASH[5]);
    HASH[6] = safe_add(g, HASH[6]);
    HASH[7] = safe_add(h, HASH[7]);
  }
  return HASH;
}

function safe_add (x, y)
{
  var lsw = (x & 0xFFFF) + (y & 0xFFFF);
  var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
  return (msw << 16) | (lsw & 0xFFFF);
}

]]>
</script>
</component>

Brains Not Brawn Blog

5/16/14

SHA256 and classic ASP VBSCRIPT for intercom.io secure settings and others

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