decrypter.js
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var aes = require('./aes')
var Transform = require('cipher-base')
var inherits = require('inherits')
var modes = require('./modes')
var StreamCipher = require('./streamCipher')
var AuthCipher = require('./authCipher')
var ebtk = require('evp_bytestokey')
inherits(Decipher, Transform)
function Decipher (mode, key, iv) {
if (!(this instanceof Decipher)) {
return new Decipher(mode, key, iv)
}
Transform.call(this)
this._cache = new Splitter()
this._last = void 0
this._cipher = new aes.AES(key)
this._prev = new Buffer(iv.length)
iv.copy(this._prev)
this._mode = mode
this._autopadding = true
}
Decipher.prototype._update = function (data) {
this._cache.add(data)
var chunk
var thing
var out = []
while ((chunk = this._cache.get(this._autopadding))) {
thing = this._mode.decrypt(this, chunk)
out.push(thing)
}
return Buffer.concat(out)
}
Decipher.prototype._final = function () {
var chunk = this._cache.flush()
if (this._autopadding) {
return unpad(this._mode.decrypt(this, chunk))
} else if (chunk) {
throw new Error('data not multiple of block length')
}
}
Decipher.prototype.setAutoPadding = function (setTo) {
this._autopadding = !!setTo
return this
}
function Splitter () {
if (!(this instanceof Splitter)) {
return new Splitter()
}
this.cache = new Buffer('')
}
Splitter.prototype.add = function (data) {
this.cache = Buffer.concat([this.cache, data])
}
Splitter.prototype.get = function (autoPadding) {
var out
if (autoPadding) {
if (this.cache.length > 16) {
out = this.cache.slice(0, 16)
this.cache = this.cache.slice(16)
return out
}
} else {
if (this.cache.length >= 16) {
out = this.cache.slice(0, 16)
this.cache = this.cache.slice(16)
return out
}
}
return null
}
Splitter.prototype.flush = function () {
if (this.cache.length) {
return this.cache
}
}
function unpad (last) {
var padded = last[15]
var i = -1
while (++i < padded) {
if (last[(i + (16 - padded))] !== padded) {
throw new Error('unable to decrypt data')
}
}
if (padded === 16) {
return
}
return last.slice(0, 16 - padded)
}
var modelist = {
ECB: require('./modes/ecb'),
CBC: require('./modes/cbc'),
CFB: require('./modes/cfb'),
CFB8: require('./modes/cfb8'),
CFB1: require('./modes/cfb1'),
OFB: require('./modes/ofb'),
CTR: require('./modes/ctr'),
GCM: require('./modes/ctr')
}
function createDecipheriv (suite, password, iv) {
var config = modes[suite.toLowerCase()]
if (!config) {
throw new TypeError('invalid suite type')
}
if (typeof iv === 'string') {
iv = new Buffer(iv)
}
if (typeof password === 'string') {
password = new Buffer(password)
}
if (password.length !== config.key / 8) {
throw new TypeError('invalid key length ' + password.length)
}
if (iv.length !== config.iv) {
throw new TypeError('invalid iv length ' + iv.length)
}
if (config.type === 'stream') {
return new StreamCipher(modelist[config.mode], password, iv, true)
} else if (config.type === 'auth') {
return new AuthCipher(modelist[config.mode], password, iv, true)
}
return new Decipher(modelist[config.mode], password, iv)
}
function createDecipher (suite, password) {
var config = modes[suite.toLowerCase()]
if (!config) {
throw new TypeError('invalid suite type')
}
var keys = ebtk(password, false, config.key, config.iv)
return createDecipheriv(suite, keys.key, keys.iv)
}
exports.createDecipher = createDecipher
exports.createDecipheriv = createDecipheriv