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

This commit is contained in:
AJ ONeal 2018-11-25 21:17:00 -07:00
commit baf56d7466
5 changed files with 307 additions and 0 deletions

96
README.md Normal file
View File

@ -0,0 +1,96 @@
# BlueCrypt ASN.1 Parser
An ASN.1 parser in less than 100 lines of Vanilla JavaScript,
part of the BlueCrypt suite.
<br>
<small>(< 150 with newlines and comments)</small>
| < 100 lines of code | 1.1k gzipped | 2.5k minified | 4.7k with comments |
# Features
* [x] Complete ASN.1 parser
* [x] Parses x.509 certificates
* [x] PEM (base64-encoded DER)
* [x] VanillaJS, Zero Dependencies
* [x] Browsers (back to ES5.1)
* [ ] Node.js (built, publishing soon)
* [ ] Online Demo (built, publishing soon)
![](https://i.imgur.com/gV7w7bM.png)
<!--
# Demo
<https://coolaj86.com/demos/asn1-parser/>
-->
# Usage
```html
<script src="https://git.coolaj86.com/coolaj86/asn1-parser.js/raw/branch/master/asn1-parser.js"></script>
```
```js
'use strict";
var ASN1 = window.ASN1 // 62 lines
var Enc = window.Enc // 27 lines
var PEM = window.PEM // 6 lines
var pem = [ '-----BEGIN EC PRIVATE KEY-----'
+ 'MHcCAQEEIImMnaNu2jRjvQwVFnhhDw/KDYtS2Q6n8T5kJYniwY1UoAoGCCqGSM49'
+ 'AwEHoUQDQgAEIT1SWLxsacPiE5Z16jkopAn8/+85rMjgyCokrnjDft6Y/YnA4A50'
+ 'yZe7CnFsqeDcpnPbubP6cpYiVcnevNIYyg=='
+ '-----END EC PRIVATE KEY-----'
].join('\n');
var der = PEM.parseBlock(pem).der;
var json = ASN1.parse(der);
console.log(json);
```
```json
{ "type": 48 /*0x30*/, "lengthSize": 0, "length": 89
, "children": [
{ "type": 48 /*0x30*/, "lengthSize": 0, "length": 19
, "children": [
{ "type": 6, "lengthSize": 0, "length": 7, "value": <0x2a8648ce3d0201> },
{ "type": 6, "lengthSize": 0, "length": 8, "value": <0x2a8648ce3d030107> }
]
},
{ "type": 3, "lengthSize": 0, "length": 66,
"value": "<0x04213d5258bc6c69c3e2139675ea3928a409fcffef39acc8e0c82a24ae78c37ede98fd89c0e00e74c997bb0a716ca9e0dca673dbb9b3fa72962255c9debcd218ca>"
}
]
}
```
Note: `value` will be a `Uint8Array`, not a hex string.
### Optimistic Parsing
This is a dumbed-down, minimal ASN1 parser.
Rather than incorporating knowledge of each possible x509 schema
to know whether to traverse deeper into a value container,
it always tries to dive in (and backs out when parsing fails).
It is possible that it will produce false positives, but not likely
in real-world scenarios (PEM, x509, CSR, etc).
I'd be interested to hear if you encounter such a case.
### 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 Parser](https://git.coolaj86.com/coolaj86/asn1-parser.js) |
MPL-2.0

142
asn1-parser.js Normal file
View File

@ -0,0 +1,142 @@
;(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
//
ASN1.ELOOP = "uASN1.js Error: iterated over 15+ elements (probably a malformed file)";
ASN1.EDEEP = "uASN1.js Error: element nested 20+ layers deep (probably a malformed file)";
// Container Types are Sequence 0x30, Octect String 0x04, Array? (0xA0, 0xA1)
// Value Types are Integer 0x02, Bit String 0x03, Null 0x05, Object ID 0x06,
// Sometimes Bit String is used as a container (RSA Pub Spki)
ASN1.CTYPES = [ 0x30, 0x31, 0xa0, 0xa1 ];
ASN1.parse = function parseAsn1(buf, depth, ws) {
if (!ws) { ws = ''; }
if (!depth) { depth = 0; }
if (depth >= 20) { 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(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 < 15 && index < (2 + asn1.length + asn1.lengthSize)) {
iters += 1;
child = ASN1.parse(buf.slice(index, index + adjustedLen), (depth || 0) + 1, ws + ' ');
// 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(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 >= 15) { throw new Error(ASN1.ELOOP); }
delete asn1.value;
return asn1;
}
// We want to fail if we know for sure that it's bad
if (-1 !== ASN1.CTYPES.indexOf(asn1.type)) {
return parseChildren();
}
asn1.value = buf.slice(index, index + adjustedLen);
try {
return parseChildren(true);
} catch(e) {
// leaving iterable array as a matter of convenience
asn1.children = [];
return asn1;
}
};
ASN1._replacer = function (k, v) {
if ('type' === k) { return '0x' + Enc.numToHex(v); }
if ('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));

43
index.html Normal file
View File

@ -0,0 +1,43 @@
<!DOCTYPE html>
<html>
<head>
<title>ASN.1 Parser - BlueCrypt</title>
<style>
textarea {
width: 42em;
height: 10em;
}
</style>
</head>
<body>
<h1>BlueCrypt ASN.1 Parser</h1>
<textarea class="js-input" placeholder="Paste a PEM here">-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEIT1SWLxsacPiE5Z16jkopAn8/+85
rMjgyCokrnjDft6Y/YnA4A50yZe7CnFsqeDcpnPbubP6cpYiVcnevNIYyg==
-----END PUBLIC KEY-----</textarea>
<pre><code class="js-hex"> </code></pre>
<pre><code class="js-json"> </code></pre>
<script src="./asn1-parser.js"></script>
<script>
var $input = document.querySelector('.js-input');
function convert() {
console.log('change');
var pem = PEM.parseBlock(document.querySelector('.js-input').value);
var hex = Enc.bufToHex(pem.der);
console.log(hex);
document.querySelector('.js-hex').innerText = hex
.match(/.{2}/g).join(' ').match(/.{1,24}/g).join(' ').match(/.{1,50}/g).join('\n');
var json = ASN1.parse(pem.der);
document.querySelector('.js-json').innerText = JSON.stringify(json, ASN1._replacer, 2);
}
$input.addEventListener('keyup', convert);
convert();
</script>
</body>
</html>

26
package.json Normal file
View File

@ -0,0 +1,26 @@
{
"name": "asn1-parser",
"version": "1.0.0",
"description": "An ASN.1 parser in less than 100 lines of Vanilla JavaScript, part of the BlueCrypt suite.",
"homepage": "https://git.coolaj86.com/coolaj86/asn1-parser.js",
"main": "asn1-parser.js",
"directories": {
"lib": "lib"
},
"repository": {
"type": "git",
"url": "https://git.coolaj86.com/coolaj86/asn1-parser.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"
}

BIN
screenshot.png Normal file

Binary file not shown.

After

Width:  |  Height:  |  Size: 108 KiB