133 lines
4.7 KiB
Kotlin
133 lines
4.7 KiB
Kotlin
package com.hexated
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import android.util.Base64
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import java.security.MessageDigest
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import java.security.SecureRandom
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import java.util.*
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import javax.crypto.Cipher
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import javax.crypto.spec.IvParameterSpec
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import javax.crypto.spec.SecretKeySpec
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import kotlin.math.min
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// code found on https://stackoverflow.com/a/63701411
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/**
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* Conforming with CryptoJS AES method
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*/
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// see https://gist.github.com/thackerronak/554c985c3001b16810af5fc0eb5c358f
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@Suppress("unused", "FunctionName", "SameParameterValue")
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object CryptoAES {
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private const val KEY_SIZE = 256
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private const val IV_SIZE = 128
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private const val HASH_CIPHER = "AES/CBC/PKCS5Padding"
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private const val AES = "AES"
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private const val KDF_DIGEST = "MD5"
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// Seriously crypto-js, what's wrong with you?
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private const val APPEND = "Salted__"
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/**
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* Encrypt
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* @param password passphrase
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* @param plainText plain string
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*/
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fun encrypt(password: String, plainText: String): String {
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val saltBytes = generateSalt(8)
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val key = ByteArray(KEY_SIZE / 8)
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val iv = ByteArray(IV_SIZE / 8)
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EvpKDF(password.toByteArray(), KEY_SIZE, IV_SIZE, saltBytes, key, iv)
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val keyS = SecretKeySpec(key, AES)
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val cipher = Cipher.getInstance(HASH_CIPHER)
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val ivSpec = IvParameterSpec(iv)
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cipher.init(Cipher.ENCRYPT_MODE, keyS, ivSpec)
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val cipherText = cipher.doFinal(plainText.toByteArray())
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// Thanks kientux for this: https://gist.github.com/kientux/bb48259c6f2133e628ad
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// Create CryptoJS-like encrypted!
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val sBytes = APPEND.toByteArray()
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val b = ByteArray(sBytes.size + saltBytes.size + cipherText.size)
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System.arraycopy(sBytes, 0, b, 0, sBytes.size)
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System.arraycopy(saltBytes, 0, b, sBytes.size, saltBytes.size)
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System.arraycopy(cipherText, 0, b, sBytes.size + saltBytes.size, cipherText.size)
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val bEncode = Base64.encode(b, Base64.NO_WRAP)
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return String(bEncode)
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}
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/**
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* Decrypt
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* Thanks Artjom B. for this: http://stackoverflow.com/a/29152379/4405051
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* @param password passphrase
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* @param cipherText encrypted string
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*/
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fun decrypt(password: String, cipherText: String): String {
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val ctBytes = Base64.decode(cipherText.toByteArray(), Base64.NO_WRAP)
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val saltBytes = Arrays.copyOfRange(ctBytes, 8, 16)
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val cipherTextBytes = Arrays.copyOfRange(ctBytes, 16, ctBytes.size)
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val key = ByteArray(KEY_SIZE / 8)
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val iv = ByteArray(IV_SIZE / 8)
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EvpKDF(password.toByteArray(), KEY_SIZE, IV_SIZE, saltBytes, key, iv)
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val cipher = Cipher.getInstance(HASH_CIPHER)
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val keyS = SecretKeySpec(key, AES)
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cipher.init(Cipher.DECRYPT_MODE, keyS, IvParameterSpec(iv))
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val plainText = cipher.doFinal(cipherTextBytes)
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return String(plainText)
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}
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private fun EvpKDF(
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password: ByteArray,
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keySize: Int,
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ivSize: Int,
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salt: ByteArray,
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resultKey: ByteArray,
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resultIv: ByteArray
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): ByteArray {
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return EvpKDF(password, keySize, ivSize, salt, 1, KDF_DIGEST, resultKey, resultIv)
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}
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@Suppress("NAME_SHADOWING")
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private fun EvpKDF(
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password: ByteArray,
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keySize: Int,
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ivSize: Int,
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salt: ByteArray,
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iterations: Int,
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hashAlgorithm: String,
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resultKey: ByteArray,
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resultIv: ByteArray
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): ByteArray {
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val keySize = keySize / 32
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val ivSize = ivSize / 32
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val targetKeySize = keySize + ivSize
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val derivedBytes = ByteArray(targetKeySize * 4)
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var numberOfDerivedWords = 0
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var block: ByteArray? = null
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val hash = MessageDigest.getInstance(hashAlgorithm)
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while (numberOfDerivedWords < targetKeySize) {
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if (block != null) {
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hash.update(block)
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}
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hash.update(password)
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block = hash.digest(salt)
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hash.reset()
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// Iterations
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for (i in 1 until iterations) {
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block = hash.digest(block!!)
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hash.reset()
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}
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System.arraycopy(
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block!!, 0, derivedBytes, numberOfDerivedWords * 4,
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min(block.size, (targetKeySize - numberOfDerivedWords) * 4)
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)
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numberOfDerivedWords += block.size / 4
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}
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System.arraycopy(derivedBytes, 0, resultKey, 0, keySize * 4)
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System.arraycopy(derivedBytes, keySize * 4, resultIv, 0, ivSize * 4)
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return derivedBytes // key + iv
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}
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private fun generateSalt(length: Int): ByteArray {
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return ByteArray(length).apply {
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SecureRandom().nextBytes(this)
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}
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}
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} |