// Copyright 2011 Mark Cavage <mcavage@gmail.com> All rights reserved.
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const assert = require('assert')
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const ASN1 = require('./types')
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const errors = require('./errors')
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// --- Globals
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const newInvalidAsn1Error = errors.newInvalidAsn1Error
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// --- API
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function Reader (data) {
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if (!data || !Buffer.isBuffer(data)) { throw new TypeError('data must be a node Buffer') }
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this._buf = data
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this._size = data.length
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// These hold the "current" state
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this._len = 0
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this._offset = 0
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}
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Object.defineProperty(Reader.prototype, Symbol.toStringTag, { value: 'BerReader' })
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Object.defineProperty(Reader.prototype, 'length', {
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enumerable: true,
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get: function () { return (this._len) }
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})
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Object.defineProperty(Reader.prototype, 'offset', {
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enumerable: true,
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get: function () { return (this._offset) }
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})
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Object.defineProperty(Reader.prototype, 'remain', {
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get: function () { return (this._size - this._offset) }
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})
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Object.defineProperty(Reader.prototype, 'buffer', {
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get: function () { return (this._buf.slice(this._offset)) }
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})
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/**
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* Reads a single byte and advances offset; you can pass in `true` to make this
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* a "peek" operation (i.e., get the byte, but don't advance the offset).
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*
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* @param {Boolean} peek true means don't move offset.
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* @return {Number} the next byte, null if not enough data.
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*/
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Reader.prototype.readByte = function (peek) {
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if (this._size - this._offset < 1) { return null }
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const b = this._buf[this._offset] & 0xff
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if (!peek) { this._offset += 1 }
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return b
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}
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Reader.prototype.peek = function () {
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return this.readByte(true)
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}
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/**
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* Reads a (potentially) variable length off the BER buffer. This call is
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* not really meant to be called directly, as callers have to manipulate
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* the internal buffer afterwards.
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*
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* As a result of this call, you can call `Reader.length`, until the
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* next thing called that does a readLength.
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*
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* @return {Number} the amount of offset to advance the buffer.
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* @throws {InvalidAsn1Error} on bad ASN.1
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*/
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Reader.prototype.readLength = function (offset) {
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if (offset === undefined) { offset = this._offset }
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if (offset >= this._size) { return null }
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let lenB = this._buf[offset++] & 0xff
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if (lenB === null) { return null }
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if ((lenB & 0x80) === 0x80) {
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lenB &= 0x7f
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if (lenB === 0) { throw newInvalidAsn1Error('Indefinite length not supported') }
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if (lenB > 4) { throw newInvalidAsn1Error('encoding too long') }
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if (this._size - offset < lenB) { return null }
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this._len = 0
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for (let i = 0; i < lenB; i++) { this._len = (this._len << 8) + (this._buf[offset++] & 0xff) }
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} else {
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// Wasn't a variable length
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this._len = lenB
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}
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return offset
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}
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/**
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* Parses the next sequence in this BER buffer.
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*
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* To get the length of the sequence, call `Reader.length`.
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*
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* @return {Number} the sequence's tag.
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*/
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Reader.prototype.readSequence = function (tag) {
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const seq = this.peek()
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if (seq === null) { return null }
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if (tag !== undefined && tag !== seq) {
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throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
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': got 0x' + seq.toString(16))
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}
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const o = this.readLength(this._offset + 1) // stored in `length`
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if (o === null) { return null }
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this._offset = o
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return seq
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}
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Reader.prototype.readInt = function () {
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return this._readTag(ASN1.Integer)
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}
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Reader.prototype.readBoolean = function (tag) {
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return (this._readTag(tag || ASN1.Boolean) !== 0)
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}
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Reader.prototype.readEnumeration = function () {
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return this._readTag(ASN1.Enumeration)
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}
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Reader.prototype.readString = function (tag, retbuf) {
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if (!tag) { tag = ASN1.OctetString }
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const b = this.peek()
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if (b === null) { return null }
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if (b !== tag) {
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throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
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': got 0x' + b.toString(16))
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}
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const o = this.readLength(this._offset + 1) // stored in `length`
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if (o === null) { return null }
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if (this.length > this._size - o) { return null }
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this._offset = o
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if (this.length === 0) { return retbuf ? Buffer.alloc(0) : '' }
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const str = this._buf.slice(this._offset, this._offset + this.length)
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this._offset += this.length
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return retbuf ? str : str.toString('utf8')
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}
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Reader.prototype.readOID = function (tag) {
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if (!tag) { tag = ASN1.OID }
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const b = this.readString(tag, true)
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if (b === null) { return null }
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const values = []
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let value = 0
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for (let i = 0; i < b.length; i++) {
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const byte = b[i] & 0xff
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value <<= 7
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value += byte & 0x7f
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if ((byte & 0x80) === 0) {
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values.push(value)
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value = 0
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}
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}
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value = values.shift()
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values.unshift(value % 40)
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values.unshift((value / 40) >> 0)
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return values.join('.')
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}
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Reader.prototype._readTag = function (tag) {
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assert.ok(tag !== undefined)
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const b = this.peek()
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if (b === null) { return null }
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if (b !== tag) {
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throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
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': got 0x' + b.toString(16))
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}
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const o = this.readLength(this._offset + 1) // stored in `length`
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if (o === null) { return null }
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if (this.length > 4) { throw newInvalidAsn1Error('Integer too long: ' + this.length) }
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if (this.length > this._size - o) { return null }
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this._offset = o
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const fb = this._buf[this._offset]
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let value = 0
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let i
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for (i = 0; i < this.length; i++) {
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value <<= 8
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value |= (this._buf[this._offset++] & 0xff)
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}
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if ((fb & 0x80) === 0x80 && i !== 4) { value -= (1 << (i * 8)) }
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return value >> 0
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}
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// --- Exported API
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module.exports = Reader
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