add ASN.1 parser

lib/asn1-parser.js

@@ -0,0 +1,147 @@
+// Copyright 2016-2018 AJ ONeal. All rights reserved
+// https://git.coolaj86.com/coolaj86/asn1-parser.js
+/* 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 = require('./encoding.js');
+var PEM = exports.PEM;
+
+//
+// Parser
+//
+
+ASN1.ELOOPN = 20; // I've seen 9 max in https certificates
+ASN1.ELOOP = "uASN1.js Error: iterated over " + ASN1.ELOOPN + "+ elements (probably a malformed file)";
+ASN1.EDEEPN = 60; // I've seen 29 deep in https certificates
+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 b64 = str.split(/\n/).filter(function (line) {
+    return !/-----/.test(line);
+  }).join('');
+  var der = Enc.base64ToBuf(b64);
+  return { bytes: der };
+};
+
+Enc.base64ToBuf = function (b64) {
+  return Buffer.from(b64, 'base64');
+};
+Enc.binToBuf = function (bin) {
+  return Buffer.from(bin, 'binary');
+};
+Enc.bufToHex = function (u8) {
+  return Buffer.from(u8).toString('hex');
+};
+Enc.numToHex = function (d) {
+  d = d.toString(16);
+  if (d.length % 2) {
+    return '0' + d;
+  }
+  return d;
+};
+
+}('undefined' !== typeof window ? window : module.exports));