236 lines
7.3 KiB
JavaScript
236 lines
7.3 KiB
JavaScript
'use strict';
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//
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// A dumbed-down, minimal ASN.1 parser / packer combo
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//
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// Note: generally I like to write congruent code
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// (i.e. output can be used as input and vice-versa)
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// However, this seemed to be more readable and easier
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// to use written as-is, asymmetrically.
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// (I also generally prefer to export objects rather
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// functions but, yet again, asthetics one in this case)
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var Enc = require('./encoding.js');
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//
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// Packer
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//
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// Almost every ASN.1 type that's important for CSR
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// can be represented generically with only a few rules.
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var ASN1 = module.exports = function ASN1(/*type, hexstrings...*/) {
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var args = Array.prototype.slice.call(arguments);
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var typ = args.shift();
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var str = args.join('').replace(/\s+/g, '').toLowerCase();
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var len = (str.length/2);
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var lenlen = 0;
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var hex = typ;
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// We can't have an odd number of hex chars
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if (len !== Math.round(len)) {
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throw new Error("invalid hex");
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}
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// The first byte of any ASN.1 sequence is the type (Sequence, Integer, etc)
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// The second byte is either the size of the value, or the size of its size
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// 1. If the second byte is < 0x80 (128) it is considered the size
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// 2. If it is > 0x80 then it describes the number of bytes of the size
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// ex: 0x82 means the next 2 bytes describe the size of the value
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// 3. The special case of exactly 0x80 is "indefinite" length (to end-of-file)
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if (len > 127) {
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lenlen += 1;
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while (len > 255) {
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lenlen += 1;
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len = len >> 8;
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}
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}
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if (lenlen) { hex += Enc.numToHex(0x80 + lenlen); }
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return hex + Enc.numToHex(str.length/2) + str;
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};
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// The Integer type has some special rules
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ASN1.UInt = function UINT() {
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var str = Array.prototype.slice.call(arguments).join('');
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var first = parseInt(str.slice(0, 2), 16);
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// If the first byte is 0x80 or greater, the number is considered negative
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// Therefore we add a '00' prefix if the 0x80 bit is set
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if (0x80 & first) { str = '00' + str; }
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return ASN1('02', str);
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};
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// The Bit String type also has a special rule
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ASN1.BitStr = function BITSTR() {
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var str = Array.prototype.slice.call(arguments).join('');
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// '00' is a mask of how many bits of the next byte to ignore
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return ASN1('03', '00' + str);
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};
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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.VTYPES = [ 0x02, 0x03, 0x05, 0x06, 0x0c, 0x82 ];
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ASN1.parse = function parseAsn1(buf, depth, ws) {
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if (!ws) { ws = ''; }
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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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// this is a primitive value type
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if (-1 !== ASN1.VTYPES.indexOf(asn1.type)) {
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asn1.value = buf.slice(index, index + adjustedLen);
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return asn1;
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}
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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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console.error(JSON.stringify(asn1, function (k, v) {
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if ('value' === k) { return '0x' + Enc.bufToHex(v.data); } return v;
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}, 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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return asn1;
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};
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/*
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ASN1._stringify = function(asn1) {
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//console.log(JSON.stringify(asn1, null, 2));
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//console.log(asn1);
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var ws = '';
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function write(asn1) {
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console.log(ws, 'ch', Enc.numToHex(asn1.type), asn1.length);
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if (!asn1.children) {
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return;
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}
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asn1.children.forEach(function (a) {
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ws += '\t';
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write(a);
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ws = ws.slice(1);
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});
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}
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write(asn1);
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};
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*/
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ASN1.tpl = function (asn1) {
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//console.log(JSON.stringify(asn1, null, 2));
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//console.log(asn1);
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var sp = ' ';
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var ws = sp;
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var i = 0;
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var vars = [];
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var str = ws;
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function write(asn1, k) {
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str += "\n" + ws;
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var val;
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if ('number' !== typeof k) {
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// ignore
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} else {
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str += ', ';
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}
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if (0x02 === asn1.type) {
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str += "ASN1.UInt(";
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} else if (0x03 === asn1.type) {
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str += "ASN1.BitStr(";
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} else {
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str += "ASN1('" + Enc.numToHex(asn1.type) + "'";
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}
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if (!asn1.children) {
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if (0x05 !== asn1.type) {
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if (0x06 !== asn1.type) {
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val = asn1.value || new Uint8Array(0);
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vars.push("\n// 0x" + Enc.numToHex(val.byteLength) + " (" + val.byteLength + " bytes)\nopts.tpl" + i + " = '"
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+ Enc.bufToHex(val) + "';");
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if (0x02 !== asn1.type && 0x03 !== asn1.type) {
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str += ", ";
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}
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str += "Enc.bufToHex(opts.tpl" + i + ")";
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} else {
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str += ", '" + Enc.bufToHex(asn1.value) + "'";
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}
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} else {
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console.warn("XXXXXXXXXXXXXXXXXXXXX");
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}
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str += ")";
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return ;
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}
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asn1.children.forEach(function (a, j) {
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i += 1;
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ws += sp;
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write(a, j);
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ws = ws.slice(sp.length);
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});
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str += "\n" + ws + ")";
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}
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write(asn1);
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console.log('var opts = {};');
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console.log(vars.join('\n') + '\n');
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console.log();
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console.log('function buildSchema(opts) {');
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console.log(sp + 'return Enc.hexToBuf(' + str.slice(3) + ');');
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console.log('}');
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console.log();
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console.log('buildSchema(opts);');
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};
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module.exports = ASN1;
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