73 lines
2.2 KiB
JavaScript
73 lines
2.2 KiB
JavaScript
'use strict';
|
|
|
|
//
|
|
// A dumbed-down, minimal ASN.1 parser / packer combo
|
|
//
|
|
// Note: generally I like to write congruent code
|
|
// (i.e. output can be used as input and vice-versa)
|
|
// However, this seemed to be more readable and easier
|
|
// to use written as-is, asymmetrically.
|
|
// (I also generally prefer to export objects rather
|
|
// functions but, yet again, asthetics one in this case)
|
|
|
|
var Enc = require('./encoding.js');
|
|
|
|
//
|
|
// Packer
|
|
//
|
|
|
|
// Almost every ASN.1 type that's important for CSR
|
|
// can be represented generically with only a few rules.
|
|
var ASN1 = module.exports = 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)) {
|
|
console.error(arguments);
|
|
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);
|
|
};
|