AJ ONeal
6 years ago
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baf56d7466
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# BlueCrypt ASN.1 Parser |
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An ASN.1 parser in less than 100 lines of Vanilla JavaScript, |
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part of the BlueCrypt suite. |
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<br> |
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<small>(< 150 with newlines and comments)</small> |
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| < 100 lines of code | 1.1k gzipped | 2.5k minified | 4.7k with comments | |
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# Features |
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* [x] Complete ASN.1 parser |
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* [x] Parses x.509 certificates |
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* [x] PEM (base64-encoded DER) |
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* [x] VanillaJS, Zero Dependencies |
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* [x] Browsers (back to ES5.1) |
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* [ ] Node.js (built, publishing soon) |
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* [ ] Online Demo (built, publishing soon) |
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![](https://i.imgur.com/gV7w7bM.png) |
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<!-- |
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# Demo |
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<https://coolaj86.com/demos/asn1-parser/> |
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--> |
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# Usage |
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```html |
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<script src="https://git.coolaj86.com/coolaj86/asn1-parser.js/raw/branch/master/asn1-parser.js"></script> |
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``` |
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```js |
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'use strict"; |
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var ASN1 = window.ASN1 // 62 lines |
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var Enc = window.Enc // 27 lines |
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var PEM = window.PEM // 6 lines |
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var pem = [ '-----BEGIN EC PRIVATE KEY-----' |
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+ 'MHcCAQEEIImMnaNu2jRjvQwVFnhhDw/KDYtS2Q6n8T5kJYniwY1UoAoGCCqGSM49' |
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+ 'AwEHoUQDQgAEIT1SWLxsacPiE5Z16jkopAn8/+85rMjgyCokrnjDft6Y/YnA4A50' |
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+ 'yZe7CnFsqeDcpnPbubP6cpYiVcnevNIYyg==' |
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+ '-----END EC PRIVATE KEY-----' |
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].join('\n'); |
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var der = PEM.parseBlock(pem).der; |
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var json = ASN1.parse(der); |
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console.log(json); |
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``` |
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```json |
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{ "type": 48 /*0x30*/, "lengthSize": 0, "length": 89 |
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, "children": [ |
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{ "type": 48 /*0x30*/, "lengthSize": 0, "length": 19 |
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, "children": [ |
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{ "type": 6, "lengthSize": 0, "length": 7, "value": <0x2a8648ce3d0201> }, |
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{ "type": 6, "lengthSize": 0, "length": 8, "value": <0x2a8648ce3d030107> } |
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] |
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}, |
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{ "type": 3, "lengthSize": 0, "length": 66, |
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"value": "<0x04213d5258bc6c69c3e2139675ea3928a409fcffef39acc8e0c82a24ae78c37ede98fd89c0e00e74c997bb0a716ca9e0dca673dbb9b3fa72962255c9debcd218ca>" |
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} |
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] |
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} |
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``` |
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Note: `value` will be a `Uint8Array`, not a hex string. |
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### Optimistic Parsing |
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This is a dumbed-down, minimal ASN1 parser. |
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Rather than incorporating knowledge of each possible x509 schema |
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to know whether to traverse deeper into a value container, |
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it always tries to dive in (and backs out when parsing fails). |
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It is possible that it will produce false positives, but not likely |
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in real-world scenarios (PEM, x509, CSR, etc). |
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I'd be interested to hear if you encounter such a case. |
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### Zero Dependencies |
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> A little copying is better than a little dependency - Golang Proverbs by Rob Pike |
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Rather than requiring hundreds (or thousands) of lines of dependencies, |
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this library takes the approach of including from other libraries in its suite |
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to produce a small, focused file that does exactly what it needs to do. |
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# Legal |
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[BlueCrypt VanillaJS ASN.1 Parser](https://git.coolaj86.com/coolaj86/asn1-parser.js) | |
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MPL-2.0 |
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;(function (exports) { |
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'use strict'; |
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if (!exports.ASN1) { exports.ASN1 = {}; } |
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if (!exports.Enc) { exports.Enc = {}; } |
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if (!exports.PEM) { exports.PEM = {}; } |
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var ASN1 = exports.ASN1; |
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var Enc = exports.Enc; |
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var PEM = exports.PEM; |
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//
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// Parser
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//
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ASN1.ELOOP = "uASN1.js Error: iterated over 15+ elements (probably a malformed file)"; |
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ASN1.EDEEP = "uASN1.js Error: element nested 20+ layers deep (probably a malformed file)"; |
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// Container Types are Sequence 0x30, Octect String 0x04, Array? (0xA0, 0xA1)
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// Value Types are Integer 0x02, Bit String 0x03, Null 0x05, Object ID 0x06,
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// Sometimes Bit String is used as a container (RSA Pub Spki)
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ASN1.CTYPES = [ 0x30, 0x31, 0xa0, 0xa1 ]; |
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ASN1.parse = function parseAsn1(buf, depth, ws) { |
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if (!ws) { ws = ''; } |
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if (!depth) { depth = 0; } |
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if (depth >= 20) { throw new Error(ASN1.EDEEP); } |
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var index = 2; // we know, at minimum, data starts after type (0) and lengthSize (1)
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var asn1 = { type: buf[0], lengthSize: 0, length: buf[1] }; |
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var child; |
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var iters = 0; |
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var adjust = 0; |
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var adjustedLen; |
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// Determine how many bytes the length uses, and what it is
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if (0x80 & asn1.length) { |
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asn1.lengthSize = 0x7f & asn1.length; |
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// I think that buf->hex->int solves the problem of Endianness... not sure
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asn1.length = parseInt(Enc.bufToHex(buf.slice(index, index + asn1.lengthSize)), 16); |
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index += asn1.lengthSize; |
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} |
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// High-order bit Integers have a leading 0x00 to signify that they are positive.
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// Bit Streams use the first byte to signify padding, which x.509 doesn't use.
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if (0x00 === buf[index] && (0x02 === asn1.type || 0x03 === asn1.type)) { |
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// However, 0x00 on its own is a valid number
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if (asn1.length > 1) { |
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index += 1; |
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adjust = -1; |
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} |
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} |
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adjustedLen = asn1.length + adjust; |
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//console.warn(ws + '0x' + Enc.numToHex(asn1.type), index, 'len:', asn1.length, asn1);
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function parseChildren(eager) { |
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asn1.children = []; |
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//console.warn('1 len:', (2 + asn1.lengthSize + asn1.length), 'idx:', index, 'clen:', 0);
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while (iters < 15 && index < (2 + asn1.length + asn1.lengthSize)) { |
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iters += 1; |
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child = ASN1.parse(buf.slice(index, index + adjustedLen), (depth || 0) + 1, ws + ' '); |
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// The numbers don't match up exactly and I don't remember why...
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// probably something with adjustedLen or some such, but the tests pass
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index += (2 + child.lengthSize + child.length); |
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//console.warn('2 len:', (2 + asn1.lengthSize + asn1.length), 'idx:', index, 'clen:', (2 + child.lengthSize + child.length));
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if (index > (2 + asn1.lengthSize + asn1.length)) { |
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if (!eager) { console.error(JSON.stringify(asn1, ASN1._replacer, 2)); } |
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throw new Error("Parse error: child value length (" + child.length |
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+ ") is greater than remaining parent length (" + (asn1.length - index) |
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+ " = " + asn1.length + " - " + index + ")"); |
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} |
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asn1.children.push(child); |
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//console.warn(ws + '0x' + Enc.numToHex(asn1.type), index, 'len:', asn1.length, asn1);
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} |
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if (index !== (2 + asn1.lengthSize + asn1.length)) { |
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//console.warn('index:', index, 'length:', (2 + asn1.lengthSize + asn1.length));
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throw new Error("premature end-of-file"); |
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} |
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if (iters >= 15) { throw new Error(ASN1.ELOOP); } |
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delete asn1.value; |
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return asn1; |
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} |
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// We want to fail if we know for sure that it's bad
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if (-1 !== ASN1.CTYPES.indexOf(asn1.type)) { |
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return parseChildren(); |
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} |
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asn1.value = buf.slice(index, index + adjustedLen); |
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try { |
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return parseChildren(true); |
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} catch(e) { |
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// leaving iterable array as a matter of convenience
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asn1.children = []; |
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return asn1; |
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} |
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}; |
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ASN1._replacer = function (k, v) { |
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if ('type' === k) { return '0x' + Enc.numToHex(v); } |
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if ('value' === k) { return '0x' + Enc.bufToHex(v.data || v); } |
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return v; |
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}; |
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// don't replace the full parseBlock, if it exists
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PEM.parseBlock = PEM.parseBlock || function (str) { |
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var der = str.split(/\n/).filter(function (line) { |
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return !/-----/.test(line); |
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}).join(''); |
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return { der: Enc.base64ToBuf(der) }; |
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}; |
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Enc.base64ToBuf = function (b64) { |
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return Enc.binToBuf(atob(b64)); |
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}; |
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Enc.binToBuf = function (bin) { |
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var arr = bin.split('').map(function (ch) { |
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return ch.charCodeAt(0); |
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}); |
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return 'undefined' !== typeof Uint8Array ? new Uint8Array(arr) : arr; |
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}; |
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Enc.bufToHex = function (u8) { |
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var hex = []; |
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var i, h; |
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var len = (u8.byteLength || u8.length); |
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for (i = 0; i < len; i += 1) { |
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h = u8[i].toString(16); |
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if (h.length % 2) { h = '0' + h; } |
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hex.push(h); |
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} |
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return hex.join('').toLowerCase(); |
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}; |
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Enc.numToHex = function (d) { |
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d = d.toString(16); |
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if (d.length % 2) { |
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return '0' + d; |
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} |
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return d; |
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}; |
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}('undefined' !== typeof window ? window : module.exports)); |
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<!DOCTYPE html> |
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<html> |
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<head> |
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<title>ASN.1 Parser - BlueCrypt</title> |
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<style> |
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textarea { |
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width: 42em; |
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height: 10em; |
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} |
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</style> |
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</head> |
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<body> |
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<h1>BlueCrypt ASN.1 Parser</h1> |
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<textarea class="js-input" placeholder="Paste a PEM here">-----BEGIN PUBLIC KEY----- |
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MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEIT1SWLxsacPiE5Z16jkopAn8/+85 |
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rMjgyCokrnjDft6Y/YnA4A50yZe7CnFsqeDcpnPbubP6cpYiVcnevNIYyg== |
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-----END PUBLIC KEY-----</textarea> |
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<pre><code class="js-hex"> </code></pre> |
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<pre><code class="js-json"> </code></pre> |
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<script src="./asn1-parser.js"></script> |
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<script> |
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var $input = document.querySelector('.js-input'); |
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function convert() { |
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console.log('change'); |
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var pem = PEM.parseBlock(document.querySelector('.js-input').value); |
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var hex = Enc.bufToHex(pem.der); |
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console.log(hex); |
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document.querySelector('.js-hex').innerText = hex |
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.match(/.{2}/g).join(' ').match(/.{1,24}/g).join(' ').match(/.{1,50}/g).join('\n'); |
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var json = ASN1.parse(pem.der); |
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document.querySelector('.js-json').innerText = JSON.stringify(json, ASN1._replacer, 2); |
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} |
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$input.addEventListener('keyup', convert); |
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convert(); |
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</script> |
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</body> |
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</html> |
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{ |
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"name": "asn1-parser", |
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"version": "1.0.0", |
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"description": "An ASN.1 parser in less than 100 lines of Vanilla JavaScript, part of the BlueCrypt suite.", |
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"homepage": "https://git.coolaj86.com/coolaj86/asn1-parser.js", |
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"main": "asn1-parser.js", |
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"directories": { |
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"lib": "lib" |
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}, |
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"repository": { |
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"type": "git", |
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"url": "https://git.coolaj86.com/coolaj86/asn1-parser.js" |
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}, |
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"keywords": [ |
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"zero-dependency", |
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"ASN.1", |
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"X.509", |
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"PEM", |
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"DER", |
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"asn1", |
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"x509", |
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"VanillaJS" |
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], |
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"author": "AJ ONeal <coolaj86@gmail.com> (https://coolaj86.com/)", |
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"license": "MPL-2.0" |
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} |
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