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@ -17,19 +17,61 @@
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* with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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@file:Suppress("UnstableApiUsage")
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package org.isoron.uhabits.utils
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import android.util.*
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import com.google.common.io.*
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import java.io.*
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import java.nio.*
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import java.nio.charset.StandardCharsets.*
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import java.util.zip.*
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import javax.crypto.*
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import javax.crypto.spec.*
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fun ByteArray.encrypt(key: String): ByteArray {
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val keySpec = SecretKeySpec(Base64.decode(key, Base64.DEFAULT), "AES")
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/**
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* Encryption key which can be used with [File.encryptToString], [String.decryptToFile],
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* [ByteArray.encrypt] and [ByteArray.decrypt].
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*
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* To randomly generate a new key, use [EncryptionKey.generate]. To load a key from a
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* Base64-encoded string, use [EncryptionKey.fromBase64].
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*/
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class EncryptionKey private constructor(
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val base64: String,
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val secretKey: SecretKey,
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) {
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companion object {
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fun fromBase64(base64: String): EncryptionKey {
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val keySpec = SecretKeySpec(Base64.decode(base64, Base64.DEFAULT), "AES")
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return EncryptionKey(base64, keySpec)
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}
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private fun fromSecretKey(spec: SecretKey): EncryptionKey {
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val base64 = Base64.encodeToString(spec.encoded, Base64.DEFAULT).trim()
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return EncryptionKey(base64, spec)
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}
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fun generate(): EncryptionKey {
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try {
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val generator = KeyGenerator.getInstance("AES").apply { init(256) }
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return fromSecretKey(generator.generateKey())
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} catch (e: Exception) {
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throw RuntimeException(e)
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}
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}
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}
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}
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/**
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* Encrypts the byte stream using the provided symmetric encryption key.
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*
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* The initialization vector (16 bytes) is prepended to the cipher text. To decrypt the result, use
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* [ByteArray.decrypt], providing the same key.
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*/
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fun ByteArray.encrypt(key: EncryptionKey): ByteArray {
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val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
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cipher.init(Cipher.ENCRYPT_MODE, keySpec)
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cipher.init(Cipher.ENCRYPT_MODE, key.secretKey)
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val encrypted = cipher.doFinal(this)
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return ByteBuffer
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.allocate(16 + encrypted.size)
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@ -38,48 +80,50 @@ fun ByteArray.encrypt(key: String): ByteArray {
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.array()
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}
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fun ByteArray.decrypt(key: String): ByteArray {
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/**
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* Decrypts a byte stream generated by [ByteArray.encrypt].
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*/
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fun ByteArray.decrypt(key: EncryptionKey): ByteArray {
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val buffer = ByteBuffer.wrap(this)
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val iv = ByteArray(16)
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buffer.get(iv)
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val encrypted = ByteArray(buffer.remaining())
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buffer.get(encrypted)
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val keySpec = SecretKeySpec(Base64.decode(key, Base64.DEFAULT), "AES")
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val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
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cipher.init(Cipher.DECRYPT_MODE, keySpec, IvParameterSpec(iv))
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cipher.init(Cipher.DECRYPT_MODE, key.secretKey, IvParameterSpec(iv))
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return cipher.doFinal(encrypted)
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}
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fun String.encrypt(key: String): String {
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return Base64.encodeToString(this.toByteArray().encrypt(key), Base64.DEFAULT)
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}
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fun String.decrypt(key: String): String {
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return String(Base64.decode(this, Base64.DEFAULT).decrypt(key), UTF_8)
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}
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fun String.decryptToFile(key: String, output: File)
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{
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val outputStream = FileOutputStream(output)
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output.writeBytes(Base64.decode(this, Base64.DEFAULT).decrypt(key))
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outputStream.close()
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}
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fun File.encryptToString(key: String): String {
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val bytes = ByteArray(this.length().toInt())
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val inputStream = FileInputStream(this)
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inputStream.read(bytes)
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inputStream.close()
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return Base64.encodeToString(bytes.encrypt(key), Base64.DEFAULT)
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/**
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* Takes a string produced by [File.encryptToString], decodes it with Base64, decompresses it with
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* gzip, decrypts it with the provided key, then writes the output to the specified file.
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*/
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fun String.decryptToFile(key: EncryptionKey, output: File) {
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val bytes = Base64.decode(this, Base64.DEFAULT).decrypt(key)
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ByteArrayInputStream(bytes).use { bytesInputStream ->
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GZIPInputStream(bytesInputStream).use { gzipInputStream ->
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FileOutputStream(output).use { fileOutputStream ->
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ByteStreams.copy(gzipInputStream, fileOutputStream)
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}
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}
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}
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}
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fun generateEncryptionKey(): String {
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return try {
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val keygen = KeyGenerator.getInstance("AES")
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keygen.init(256)
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val key = keygen.generateKey()
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Base64.encodeToString(key.encoded, Base64.DEFAULT).trim()
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} catch (e: Exception) {
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throw RuntimeException(e)
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/**
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* Compresses the file with gzip, encrypts it using the the provided key, then returns a string
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* containing the Base64-encoded cipher bytes.
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*
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* To decrypt and decompress the cipher text back into a file, use [String.decryptToFile].
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*/
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fun File.encryptToString(key: EncryptionKey): String {
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ByteArrayOutputStream().use { bytesOutputStream ->
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FileInputStream(this).use { inputStream ->
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GZIPOutputStream(bytesOutputStream).use { gzipOutputStream ->
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ByteStreams.copy(inputStream, gzipOutputStream)
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val bytes = bytesOutputStream.toByteArray()
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return Base64.encodeToString(bytes.encrypt(key), Base64.DEFAULT)
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}
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}
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}
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}
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