v1.0.0: An ASN.1 packer in <100 lines of Vanilla JavaScript, part of the BlueCrypt suite

README.md

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+# Bluecrypt ASN.1 Packer
+
+An ASN.1 builder in less than 100 lines of Vanilla JavaScript,
+part of the Bluecrypt suite.
+<br>
+<small>(< 150 with newlines and comments)</small>
+
+# Features
+
+| <100 lines of code | <1k gzipped | 1.8k minified | 3.3k with comments |
+
+* [x] Complete ASN.1 packer
+  * [x] Parses x.509 certificates
+  * [x] PEM (base64-encoded DER)
+* [x] VanillaJS, Zero Dependencies
+  * [x] Browsers (even old ones)
+  * [x] Online [Demo](https://coolaj86.com/demos/asn1-packer/)
+  * [ ] Node.js (built, publishing soon)
+
+# Demo
+
+<https://coolaj86.com/demos/asn1-packer/>
+
+<img border="1" src="https://i.imgur.com/phGeuMw.png" />
+
+# Usage
+
+```html
+<script src="https://git.coolaj86.com/coolaj86/asn1-packer.js/raw/branch/master/asn1-packer.js"></script>
+```
+
+```js
+'use strict';
+
+var ASN1 = window.ASN1  // 62 lines
+var Enc = window.Enc    // 27 lines
+var PEM = window.PEM    //  6 lines
+
+var arr = [
+  0x30,
+  [
+    [ 0x30, [ [ 0x06, "2a8648ce3d0201" ], [ 0x06, "2a8648ce3d030107" ] ] ],
+    [ 0x03, "04213d5258bc6c69c3e2139675ea3928a409fcffef39acc8e0c82a24ae78c37ede98fd89c0e00e74c997bb0a716ca9e0dca673dbb9b3fa72962255c9debcd218ca" ]
+  ]
+];
+
+var hex = ASN1.pack(arr);
+var buf = Enc.hexToBuf(hex);
+var pem = PEM.packBlock({ type: "PUBLIC KEY", bytes: buf });
+
+console.log(pem);
+```
+
+```
+-----BEGIN PUBLIC KEY-----
+MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEIT1SWLxsacPiE5Z16jkopAn8/+85
+rMjgyCokrnjDft6Y/YnA4A50yZe7CnFsqeDcpnPbubP6cpYiVcnevNIYyg==
+-----END PUBLIC KEY-----
+```
+
+### Simple Packing
+
+All types are handled by the same rules except for Integer (0x02)
+and Bit String (0x03), which require special padding.
+
+This is sufficient for RSA and EC keypairs, and CSRs.
+
+I don't know of any format for which it is not sufficient,
+but if you find one I'd like to know about it.
+
+### Zero Dependencies
+
+> A little copying is better than a little dependency - Golang Proverbs by Rob Pike
+
+Rather than requiring hundreds (or thousands) of lines of dependencies,
+this library takes the approach of including from other libraries in its suite
+to produce a small, focused file that does exactly what it needs to do.
+
+# Legal
+
+[Bluecrypt VanillaJS ASN.1 Packer](https://git.coolaj86.com/coolaj86/asn1-packer.js) |
+MPL-2.0

asn1-packer.js

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+;(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;
+
+//
+// Packer
+//
+
+// Almost every ASN.1 type that's important for CSR
+// can be represented generically with only a few rules.
+exports.ASN1 = function ASN1(/*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('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('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(typ, str);
+  }
+};
+Object.keys(ASN1).forEach(function (k) {
+  exports.ASN1[k] = ASN1[k];
+});
+ASN1 = exports.ASN1;
+
+PEM.packBlock = function (opts) {
+  // TODO allow for headers?
+  return '-----BEGIN ' + opts.type + '-----\n'
+    + Enc.bufToBase64(opts.bytes).match(/.{1,64}/g).join('\n') + '\n'
+    + '-----END ' + opts.type + '-----'
+  ;
+};
+
+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;
+};
+
+}('undefined' !== typeof window ? window : module.exports));

index.html

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+<!DOCTYPE html>
+<html>
+<head>
+  <title>ASN.1 Packer - Bluecrypt</title>
+  <style>
+    textarea {
+      width: 42em;
+      height: 10em;
+    }
+  </style>
+</head>
+<body>
+  <h1>Bluecrypt ASN.1 Packer</h1>
+
+  <input type="text" class="js-type" placeholder="PEM header (i.e. PUBLIC KEY)" value="PUBLIC KEY">
+  <br>
+  <textarea class="js-input" placeholder="Paste a PEM here">[
+  48,
+  [
+    [
+      48,
+      [
+        [
+          6,
+          "2a8648ce3d0201"
+        ],
+        [
+          6,
+          "2a8648ce3d030107"
+        ]
+      ]
+    ],
+    [
+      3,
+      "04213d5258bc6c69c3e2139675ea3928a409fcffef39acc8e0c82a24ae78c37ede98fd89c0e00e74c997bb0a716ca9e0dca673dbb9b3fa72962255c9debcd218ca"
+    ]
+  ]
+]</textarea>
+
+  <pre><code class="js-hex"> </code></pre>
+
+  <pre><code class="js-pem"> </code></pre>
+
+  <br>
+  <p>Made with <a href="https://git.coolaj86.com/coolaj86/asn1-packer/">asn1-packer.js</a></p>
+
+  <script src="./asn1-packer.js"></script>
+  <script>
+    var $input = document.querySelector('.js-input');
+
+    function convert() {
+      console.log('keyup');
+      var json;
+
+      try {
+        var typ = document.querySelector('.js-type').value;
+        var text = document.querySelector('.js-input').value;
+        var arr = JSON.parse(text);
+        var hex = ASN1.pack(arr);
+        var buf = Enc.hexToBuf(hex);
+        var pem = PEM.packBlock({ type: typ, bytes: buf });
+        document.querySelector('.js-hex').innerText = hex
+          .match(/.{2}/g).join(' ').match(/.{1,24}/g).join(' ').match(/.{1,50}/g).join('\n');
+        document.querySelector('.js-pem').innerText = pem;
+      } catch(e) {
+        pem = { error: { message: e.message } };
+        document.querySelector('.js-pem').innerText = JSON.stringify(pem);
+      }
+    }
+
+    $input.addEventListener('keyup', convert);
+    convert();
+  </script>
+</body>
+</html>

package.json

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+{
+  "name": "asn1-packer",
+  "version": "1.0.0",
+  "description": "An ASN.1 packer in less than 100 lines of Vanilla JavaScript, part of the Bluecrypt suite.",
+  "homepage": "https://git.coolaj86.com/coolaj86/asn1-packer.js",
+  "main": "asn1-packer.js",
+  "scripts": {
+    "prepare": "uglifyjs asn1-packer.js > asn1-packer.min.js"
+  },
+  "directories": {
+    "lib": "lib"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://git.coolaj86.com/coolaj86/asn1-packer.js"
+  },
+  "keywords": [
+    "zero-dependency",
+    "ASN.1",
+    "X.509",
+    "PEM",
+    "DER",
+    "asn1",
+    "x509",
+    "VanillaJS"
+  ],
+  "author": "AJ ONeal <coolaj86@gmail.com> (https://coolaj86.com/)",
+  "license": "MPL-2.0"
+}