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124 lines
3.1 KiB
124 lines
3.1 KiB
var AuthCipher = require('./authCipher')
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var Buffer = require('safe-buffer').Buffer
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var MODES = require('./modes')
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var StreamCipher = require('./streamCipher')
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var Transform = require('cipher-base')
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var aes = require('./aes')
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var ebtk = require('evp_bytestokey')
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var inherits = require('inherits')
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function Decipher (mode, key, iv) {
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Transform.call(this)
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this._cache = new Splitter()
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this._last = void 0
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this._cipher = new aes.AES(key)
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this._prev = Buffer.from(iv)
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this._mode = mode
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this._autopadding = true
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}
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inherits(Decipher, Transform)
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Decipher.prototype._update = function (data) {
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this._cache.add(data)
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var chunk
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var thing
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var out = []
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while ((chunk = this._cache.get(this._autopadding))) {
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thing = this._mode.decrypt(this, chunk)
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out.push(thing)
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}
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return Buffer.concat(out)
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}
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Decipher.prototype._final = function () {
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var chunk = this._cache.flush()
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if (this._autopadding) {
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return unpad(this._mode.decrypt(this, chunk))
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} else if (chunk) {
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throw new Error('data not multiple of block length')
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}
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}
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Decipher.prototype.setAutoPadding = function (setTo) {
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this._autopadding = !!setTo
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return this
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}
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function Splitter () {
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this.cache = Buffer.allocUnsafe(0)
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}
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Splitter.prototype.add = function (data) {
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this.cache = Buffer.concat([this.cache, data])
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}
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Splitter.prototype.get = function (autoPadding) {
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var out
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if (autoPadding) {
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if (this.cache.length > 16) {
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out = this.cache.slice(0, 16)
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this.cache = this.cache.slice(16)
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return out
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}
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} else {
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if (this.cache.length >= 16) {
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out = this.cache.slice(0, 16)
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this.cache = this.cache.slice(16)
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return out
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}
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}
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return null
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}
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Splitter.prototype.flush = function () {
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if (this.cache.length) return this.cache
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}
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function unpad (last) {
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var padded = last[15]
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if (padded < 1 || padded > 16) {
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throw new Error('unable to decrypt data')
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}
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var i = -1
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while (++i < padded) {
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if (last[(i + (16 - padded))] !== padded) {
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throw new Error('unable to decrypt data')
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}
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}
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if (padded === 16) return
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return last.slice(0, 16 - padded)
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}
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function createDecipheriv (suite, password, iv) {
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var config = MODES[suite.toLowerCase()]
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if (!config) throw new TypeError('invalid suite type')
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if (typeof iv === 'string') iv = Buffer.from(iv)
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if (config.mode !== 'GCM' && iv.length !== config.iv) throw new TypeError('invalid iv length ' + iv.length)
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if (typeof password === 'string') password = Buffer.from(password)
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if (password.length !== config.key / 8) throw new TypeError('invalid key length ' + password.length)
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if (config.type === 'stream') {
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return new StreamCipher(config.module, password, iv, true)
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} else if (config.type === 'auth') {
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return new AuthCipher(config.module, password, iv, true)
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}
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return new Decipher(config.module, password, iv)
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}
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function createDecipher (suite, password) {
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var config = MODES[suite.toLowerCase()]
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if (!config) throw new TypeError('invalid suite type')
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var keys = ebtk(password, false, config.key, config.iv)
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return createDecipheriv(suite, keys.key, keys.iv)
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}
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exports.createDecipher = createDecipher
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exports.createDecipheriv = createDecipheriv
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