76 lines
2.3 KiB
JavaScript
76 lines
2.3 KiB
JavaScript
'use strict';
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var ASN1 = module.exports = function ASN1() {
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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 10+ 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 ];
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ASN1.parse = function parseAsn1(buf, depth) {
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if (depth >= 10) { 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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// 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(buf.slice(index, index + asn1.lengthSize).toString('hex'), 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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index += 1;
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adjust = -1;
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}
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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 + asn1.length + adjust);
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return asn1;
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}
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asn1.children = [];
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while (iters < 15 && index < buf.byteLength) {
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iters += 1;
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child = ASN1.parse(buf.slice(index, index + asn1.length), (depth || 0) + 1);
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index += (2 + child.lengthSize + child.length);
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asn1.children.push(child);
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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', Buffer.from([asn1.type]).toString('hex'), 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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module.exports = ASN1;
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