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JavaScript generic ASN.1 parser (mirror)
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121#!/usr/bin/env node'use strict';
const fs = require('fs'), Base64 = require('./base64.js'), ASN1 = require('./asn1.js'), rfc = require('./rfcasn1.json'), colYellow = "\x1b[33m", colBlue = "\x1b[34m", colReset = "\x1b[0m";
function searchType(name) { for (const r of Object.values(rfc)) if (name in r.types) { // console.log(name + ' found in ' + r.name); return r.types[name]; } throw 'Type not found: ' + name;}
function translate(def, tn) { const id = def?.id; if (def?.type == 'tag' && !def.explicit) // def.type = def.content[0].type; def = def.content[0].type; while (def?.type == 'defined' || def?.type?.type == 'defined') { const name = def?.type?.type ? def.type.name : def.name; def = Object.assign({}, def); def.type = searchType(name).type; } if (def?.type?.name == 'CHOICE') { for (let c of def.type.content) { c = translate(c); if (tn == c.type.name || tn == c.name) { def = Object.assign({}, def); def.type = c.type.name ? c.type : c; break; } } } if (id) def = Object.assign({}, def, { id }); return def ?? { type: {} };}
function firstUpper(s) { return s[0].toUpperCase() + s.slice(1);}
function print(value, def, stats, indent) { if (indent === undefined) indent = ''; stats ??= {}; stats.total ??= 0; stats.recognized ??= 0; stats.defs ??= {}; let tn = value.typeName(); def = translate(def, tn); tn = tn.replaceAll('_', ' '); if (stats) ++stats.total; let name = ''; if (def?.type) { if (def.id) name += colBlue + def.id + colReset; if (typeof def.type == 'object' && def.name) name = (name ? name + ' ' : '') + def.name; if (stats && name != '') ++stats.recognized; if (name) name += ' '; } let s = indent + name + colYellow + value.typeName() + colReset + " @" + value.stream.pos; if (value.length >= 0) s += "+"; s += value.length; if (value.tag.tagConstructed) s += " (constructed)"; else if ((value.tag.isUniversal() && ((value.tag.tagNumber == 0x03) || (value.tag.tagNumber == 0x04))) && (value.sub !== null)) s += " (encapsulates)"; let content = value.content(); if (content) s += ": " + content.replace(/\n/g, '|'); s += "\n"; if (value.sub !== null) { indent += ' '; if (def?.type?.type) def = def.type; let j = def?.content ? 0 : -1; for (const subval of value.sub) { let type; if (j >= 0) { if (def.typeOf) type = def.content[0]; else { let tn = subval.typeName(); //.replaceAll('_', ' '); do { type = def.content[j++]; // type = translate(type, tn); if (type?.type?.type) type = type.type; } while (type && ('optional' in type || 'default' in type) && type.name != 'ANY' && type.name != tn); if (type?.type == 'defined') stats.defs[type.id] = subval.content().split(/\n/); else if (type?.definedBy && stats.defs?.[type.definedBy]?.[1]) // hope current OIDs contain the type name (will need to parse from RFC itself) type = searchType(firstUpper(stats.defs[type.definedBy][1])); } } s += print(subval, type, stats, indent); } } return s;}
let content = fs.readFileSync(process.argv[3]);try { // try PEM first content = Base64.unarmor(content);} catch (e) { // try DER/BER then}let result = ASN1.decode(content);content = null;let stats = {};console.log(print(result, searchType(process.argv[2]), stats));console.log('Stats:', (stats.recognized * 100 / stats.total).toFixed(2) + '%');// console.log('Defs:', stats.defs);