acme.js/lib/asn1/packer.js

92 lines
2.2 KiB
JavaScript

'use strict';
var ASN1 = module.exports;
var Enc = require('@root/encoding/hex');
//
// Packer
//
// Almost every ASN.1 type that's important for CSR
// can be represented generically with only a few rules.
function Any(/*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;
}
ASN1.Any = Any;
// 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 Any('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 Any('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 Any(typ, str);
}
};