asn1.js/packer.js

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'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;
if ('number' === typeof hex) {
hex = Enc.numToHex(hex);
}
// 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._toArray = function toArray(next, opts) {
var typ = opts.json ? Enc.numToHex(next.type) : next.type;
var val = next.value;
if (val) {
if ('string' !== typeof val && opts.json) {
val = Enc.bufToHex(val);
}
return [typ, val];
}
return [
typ,
next.children.map(function(child) {
return toArray(child, opts);
})
];
};
ASN1._pack = function(arr) {
var typ = arr[0];
if ('number' === typeof arr[0]) {
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 if (arr[1].byteLength) {
str = Enc.bufToHex(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);
}
};
// TODO should this return a buffer?
ASN1.pack = function(asn1, opts) {
if (!opts) {
opts = {};
}
if (!Array.isArray(asn1)) {
asn1 = ASN1._toArray(asn1, { json: true });
}
var result = ASN1._pack(asn1);
if (opts.json) {
return result;
}
return Enc.hexToBuf(result);
};