asn1-parser.js

// Copyright 2018 AJ ONeal. All rights reserved
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
;(function (exports) {
'use strict';

if (!exports.ASN1) { exports.ASN1 = {}; }
if (!exports.Enc) { exports.Enc = {}; }
if (!exports.PEM) { exports.PEM = {}; }

var ASN1 = exports.ASN1;
var Enc = exports.Enc;
var PEM = exports.PEM;

//
// Parser
//

// Although I've only seen 9 max in https certificates themselves,
// but each domain list could have up to 100
ASN1.ELOOPN = 102;
ASN1.ELOOP = "uASN1.js Error: iterated over " + ASN1.ELOOPN + "+ elements (probably a malformed file)";
// I've seen https certificates go 29 deep
ASN1.EDEEPN = 60;
ASN1.EDEEP = "uASN1.js Error: element nested " + ASN1.EDEEPN + "+ layers deep (probably a malformed file)";
// Container Types are Sequence 0x30, Container Array? (0xA0, 0xA1)
// Value Types are Boolean 0x01, Integer 0x02, Null 0x05, Object ID 0x06, String 0x0C, 0x16, 0x13, 0x1e Value Array? (0x82)
// Bit String (0x03) and Octet String (0x04) may be values or containers
// Sometimes Bit String is used as a container (RSA Pub Spki)
ASN1.CTYPES = [ 0x30, 0x31, 0xa0, 0xa1 ];
ASN1.VTYPES = [ 0x01, 0x02, 0x05, 0x06, 0x0c, 0x82 ];
ASN1.parse = function parseAsn1Helper(buf) {
  //var ws = '  ';
  function parseAsn1(buf, depth, eager) {
    if (depth.length >= ASN1.EDEEPN) { throw new Error(ASN1.EDEEP); }

    var index = 2; // we know, at minimum, data starts after type (0) and lengthSize (1)
    var asn1 = { type: buf[0], lengthSize: 0, length: buf[1] };
    var child;
    var iters = 0;
    var adjust = 0;
    var adjustedLen;

    // Determine how many bytes the length uses, and what it is
    if (0x80 & asn1.length) {
      asn1.lengthSize = 0x7f & asn1.length;
      // I think that buf->hex->int solves the problem of Endianness... not sure
      asn1.length = parseInt(Enc.bufToHex(buf.slice(index, index + asn1.lengthSize)), 16);
      index += asn1.lengthSize;
    }

    // High-order bit Integers have a leading 0x00 to signify that they are positive.
    // Bit Streams use the first byte to signify padding, which x.509 doesn't use.
    if (0x00 === buf[index] && (0x02 === asn1.type || 0x03 === asn1.type)) {
      // However, 0x00 on its own is a valid number
      if (asn1.length > 1) {
        index += 1;
        adjust = -1;
      }
    }
    adjustedLen = asn1.length + adjust;

    //console.warn(depth.join(ws) + '0x' + Enc.numToHex(asn1.type), index, 'len:', asn1.length, asn1);

    function parseChildren(eager) {
      asn1.children = [];
      //console.warn('1 len:', (2 + asn1.lengthSize + asn1.length), 'idx:', index, 'clen:', 0);
      while (iters < ASN1.ELOOPN && index < (2 + asn1.length + asn1.lengthSize)) {
        iters += 1;
        depth.length += 1;
        child = parseAsn1(buf.slice(index, index + adjustedLen), depth, eager);
        depth.length -= 1;
        // The numbers don't match up exactly and I don't remember why...
        // probably something with adjustedLen or some such, but the tests pass
        index += (2 + child.lengthSize + child.length);
        //console.warn('2 len:', (2 + asn1.lengthSize + asn1.length), 'idx:', index, 'clen:', (2 + child.lengthSize + child.length));
        if (index > (2 + asn1.lengthSize + asn1.length)) {
          if (!eager) { console.error(JSON.stringify(asn1, ASN1._replacer, 2)); }
          throw new Error("Parse error: child value length (" + child.length
            + ") is greater than remaining parent length (" + (asn1.length - index)
            + " = " + asn1.length + " - " + index + ")");
        }
        asn1.children.push(child);
        //console.warn(depth.join(ws) + '0x' + Enc.numToHex(asn1.type), index, 'len:', asn1.length, asn1);
      }
      if (index !== (2 + asn1.lengthSize + asn1.length)) {
        //console.warn('index:', index, 'length:', (2 + asn1.lengthSize + asn1.length));
        throw new Error("premature end-of-file");
      }
      if (iters >= ASN1.ELOOPN) { throw new Error(ASN1.ELOOP); }

      delete asn1.value;
      return asn1;
    }

    // Recurse into types that are _always_ containers
    if (-1 !== ASN1.CTYPES.indexOf(asn1.type)) { return parseChildren(eager); }

    // Return types that are _always_ values
    asn1.value = buf.slice(index, index + adjustedLen);
    if (-1 !== ASN1.VTYPES.indexOf(asn1.type)) { return asn1; }

    // For ambigious / unknown types, recurse and return on failure
    // (and return child array size to zero)
    try { return parseChildren(true); }
    catch(e) { asn1.children.length = 0; return asn1; }
  }

  var asn1 = parseAsn1(buf, []);
  var len = buf.byteLength || buf.length;
  if (len !== 2 + asn1.lengthSize + asn1.length) {
    throw new Error("Length of buffer does not match length of ASN.1 sequence.");
  }
  return asn1;
};
ASN1._replacer = function (k, v) {
  if ('type' === k) { return '0x' + Enc.numToHex(v); }
  if (v && 'value' === k) { return '0x' + Enc.bufToHex(v.data || v); }
  return v;
};

// don't replace the full parseBlock, if it exists
PEM.parseBlock = PEM.parseBlock || function (str) {
  var der = str.split(/\n/).filter(function (line) {
    return !/-----/.test(line);
  }).join('');
  return { der: Enc.base64ToBuf(der) };
};

Enc.base64ToBuf = function (b64) {
  return Enc.binToBuf(atob(b64));
};
Enc.binToBuf = function (bin) {
  var arr = bin.split('').map(function (ch) {
    return ch.charCodeAt(0);
  });
  return 'undefined' !== typeof Uint8Array ? new Uint8Array(arr) : arr;
};
Enc.bufToHex = function (u8) {
  var hex = [];
  var i, h;
  var len = (u8.byteLength || u8.length);

  for (i = 0; i < len; i += 1) {
    h = u8[i].toString(16);
    if (h.length % 2) { h = '0' + h; }
    hex.push(h);
  }

  return hex.join('').toLowerCase();
};
Enc.numToHex = function (d) {
  d = d.toString(16);
  if (d.length % 2) {
    return '0' + d;
  }
  return d;
};

}('undefined' !== typeof window ? window : module.exports));