asn1.js 8.4 KB
;(function () {
'use strict';
var ASN1 = window.ASN1 = {};
var Enc = window.Encoding;
// Copyright 2018 AJ ONeal. All rights reserved
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */


//
// Parser
//

// Although I've only seen 9 max in https certificates themselves,
// but each domain list could have up to 100
ASN1.ELOOPN = 102;
ASN1.ELOOP =
	'uASN1.js Error: iterated over ' +
	ASN1.ELOOPN +
	'+ elements (probably a malformed file)';
// I've seen https certificates go 29 deep
ASN1.EDEEPN = 60;
ASN1.EDEEP =
	'uASN1.js Error: element nested ' +
	ASN1.EDEEPN +
	'+ layers deep (probably a malformed file)';
// Container Types are Sequence 0x30, Container Array? (0xA0, 0xA1)
// Value Types are Boolean 0x01, Integer 0x02, Null 0x05, Object ID 0x06, String 0x0C, 0x16, 0x13, 0x1e Value Array? (0x82)
// Bit String (0x03) and Octet String (0x04) may be values or containers
// Sometimes Bit String is used as a container (RSA Pub Spki)
ASN1.CTYPES = [0x30, 0x31, 0xa0, 0xa1];
ASN1.VTYPES = [0x01, 0x02, 0x05, 0x06, 0x0c, 0x82];
ASN1.parseVerbose = function parseAsn1Helper(buf, opts) {
	if (!opts) {
		opts = {};
	}
	//var ws = '  ';
	function parseAsn1(buf, depth, eager) {
		if (depth.length >= ASN1.EDEEPN) {
			throw new Error(ASN1.EDEEP);
		}

		var index = 2; // we know, at minimum, data starts after type (0) and lengthSize (1)
		var asn1 = { type: buf[0], lengthSize: 0, length: buf[1] };
		var child;
		var iters = 0;
		var adjust = 0;
		var adjustedLen;

		// Determine how many bytes the length uses, and what it is
		if (0x80 & asn1.length) {
			asn1.lengthSize = 0x7f & asn1.length;
			// I think that buf->hex->int solves the problem of Endianness... not sure
			asn1.length = parseInt(
				Enc.bufToHex(buf.slice(index, index + asn1.lengthSize)),
				16
			);
			index += asn1.lengthSize;
		}

		// High-order bit Integers have a leading 0x00 to signify that they are positive.
		// Bit Streams use the first byte to signify padding, which x.509 doesn't use.
		if (0x00 === buf[index] && (0x02 === asn1.type || 0x03 === asn1.type)) {
			// However, 0x00 on its own is a valid number
			if (asn1.length > 1) {
				index += 1;
				adjust = -1;
			}
		}
		adjustedLen = asn1.length + adjust;

		//console.warn(depth.join(ws) + '0x' + Enc.numToHex(asn1.type), index, 'len:', asn1.length, asn1);

		function parseChildren(eager) {
			asn1.children = [];
			//console.warn('1 len:', (2 + asn1.lengthSize + asn1.length), 'idx:', index, 'clen:', 0);
			while (
				iters < ASN1.ELOOPN &&
				index < 2 + asn1.length + asn1.lengthSize
			) {
				iters += 1;
				depth.length += 1;
				child = parseAsn1(
					buf.slice(index, index + adjustedLen),
					depth,
					eager
				);
				depth.length -= 1;
				// The numbers don't match up exactly and I don't remember why...
				// probably something with adjustedLen or some such, but the tests pass
				index += 2 + child.lengthSize + child.length;
				//console.warn('2 len:', (2 + asn1.lengthSize + asn1.length), 'idx:', index, 'clen:', (2 + child.lengthSize + child.length));
				if (index > 2 + asn1.lengthSize + asn1.length) {
					if (!eager) {
						console.error(JSON.stringify(asn1, ASN1._replacer, 2));
					}
					throw new Error(
						'Parse error: child value length (' +
							child.length +
							') is greater than remaining parent length (' +
							(asn1.length - index) +
							' = ' +
							asn1.length +
							' - ' +
							index +
							')'
					);
				}
				asn1.children.push(child);
				//console.warn(depth.join(ws) + '0x' + Enc.numToHex(asn1.type), index, 'len:', asn1.length, asn1);
			}
			if (index !== 2 + asn1.lengthSize + asn1.length) {
				//console.warn('index:', index, 'length:', (2 + asn1.lengthSize + asn1.length));
				throw new Error('premature end-of-file');
			}
			if (iters >= ASN1.ELOOPN) {
				throw new Error(ASN1.ELOOP);
			}

			delete asn1.value;
			return asn1;
		}

		// Recurse into types that are _always_ containers
		if (-1 !== ASN1.CTYPES.indexOf(asn1.type)) {
			return parseChildren(eager);
		}

		// Return types that are _always_ values
		asn1.value = buf.slice(index, index + adjustedLen);
		if (opts.json) {
			asn1.value = Enc.bufToHex(asn1.value);
		}
		if (-1 !== ASN1.VTYPES.indexOf(asn1.type)) {
			return asn1;
		}

		// For ambigious / unknown types, recurse and return on failure
		// (and return child array size to zero)
		try {
			return parseChildren(true);
		} catch (e) {
			asn1.children.length = 0;
			return asn1;
		}
	}

	var asn1 = parseAsn1(buf, []);
	var len = buf.byteLength || buf.length;
	if (len !== 2 + asn1.lengthSize + asn1.length) {
		throw new Error(
			'Length of buffer does not match length of ASN.1 sequence.'
		);
	}
	return asn1;
};
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.parse = function(opts) {
	var opts2 = { json: false !== opts.json };
	var verbose = ASN1.parseVerbose(opts.der, opts2);
	if (opts.verbose) {
		return verbose;
	}
	return ASN1._toArray(verbose, opts2);
};
ASN1._replacer = function(k, v) {
	if ('type' === k) {
		return '0x' + Enc.numToHex(v);
	}
	if (v && 'value' === k) {
		return '0x' + Enc.bufToHex(v.data || v);
	}
	return v;
};


//
// 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);
};
}());