asn1-packer.js

lib/asn1-packer.js

@@ -0,0 +1,110 @@
+'use strict';
+
+var ASN1 = module.exports;
+var Enc = require('./encoding.js');
+
+//
+// Packer
+//
+
+// Almost every ASN.1 type that's important for CSR
+// can be represented generically with only a few rules.
+ASN1.Any = function (/*type, hexstrings...*/) {
+  var args = Array.prototype.slice.call(arguments);
+  var typ = args.shift();
+  var str = args.join('').replace(/\s+/g, '').toLowerCase();
+  var len = (str.length/2);
+  var lenlen = 0;
+  var hex = typ;
+
+  // We can't have an odd number of hex chars
+  if (len !== Math.round(len)) {
+    throw new Error("invalid hex");
+  }
+
+  // The first byte of any ASN.1 sequence is the type (Sequence, Integer, etc)
+  // The second byte is either the size of the value, or the size of its size
+
+  // 1. If the second byte is < 0x80 (128) it is considered the size
+  // 2. If it is > 0x80 then it describes the number of bytes of the size
+  //    ex: 0x82 means the next 2 bytes describe the size of the value
+  // 3. The special case of exactly 0x80 is "indefinite" length (to end-of-file)
+
+  if (len > 127) {
+    lenlen += 1;
+    while (len > 255) {
+      lenlen += 1;
+      len = len >> 8;
+    }
+  }
+
+  if (lenlen) { hex += Enc.numToHex(0x80 + lenlen); }
+  return hex + Enc.numToHex(str.length/2) + str;
+};
+
+// The Integer type has some special rules
+ASN1.UInt = function UINT() {
+  var str = Array.prototype.slice.call(arguments).join('');
+  var first = parseInt(str.slice(0, 2), 16);
+
+  // If the first byte is 0x80 or greater, the number is considered negative
+  // Therefore we add a '00' prefix if the 0x80 bit is set
+  if (0x80 & first) { str = '00' + str; }
+
+  return ASN1.Any('02', str);
+};
+
+// The Bit String type also has a special rule
+ASN1.BitStr = function BITSTR() {
+  var str = Array.prototype.slice.call(arguments).join('');
+  // '00' is a mask of how many bits of the next byte to ignore
+  return ASN1.Any('03', '00' + str);
+};
+
+ASN1._pack = function (arr) {
+  var typ = Enc.numToHex(arr[0]);
+  var str = '';
+  if (Array.isArray(arr[1])) {
+    arr[1].forEach(function (a) {
+      str += ASN1._pack(a);
+    });
+  } else if ('string' === typeof arr[1]) {
+    str = arr[1];
+  } else {
+    throw new Error("unexpected array");
+  }
+  if ('03' === typ) {
+    return ASN1.BitStr(str);
+  } else if ('02' === typ) {
+    return ASN1.UInt(str);
+  } else {
+    return ASN1.Any(typ, str);
+  }
+};
+ASN1.pack = function (arr) {
+  return Enc.hexToBuf(ASN1._pack(arr));
+};
+
+Enc.bufToBase64 = function (u8) {
+  var bin = '';
+  u8.forEach(function (i) {
+    bin += String.fromCharCode(i);
+  });
+  return btoa(bin);
+};
+
+Enc.hexToBuf = function (hex) {
+  var arr = [];
+  hex.match(/.{2}/g).forEach(function (h) {
+    arr.push(parseInt(h, 16));
+  });
+  return 'undefined' !== typeof Uint8Array ? new Uint8Array(arr) : arr;
+};
+
+Enc.numToHex = function (d) {
+  d = d.toString(16);
+  if (d.length % 2) {
+    return '0' + d;
+  }
+  return d;
+};