Implement cryptography extensions

android/uhabits-android/src/androidTest/java/org/isoron/uhabits/utils/EncryptionExtTest.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2016-2020 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.isoron.uhabits.utils
+
+import org.isoron.uhabits.*
+import org.junit.*
+import java.io.*
+
+class EncryptionExtTest : BaseAndroidTest() {
+    @Test
+    fun test_encrypt_decrypt_string() {
+        val original = "Hello world!"
+        val key = generateEncryptionKey()
+        val encrypted = original.encrypt(key)
+        val decrypted = encrypted.decrypt(key)
+        assertEquals("Hello world!", decrypted)
+    }
+
+    @Test
+    fun test_encrypt_decrypt_file() {
+        val original = File.createTempFile("file", ".txt")
+        val writer = PrintWriter(original.outputStream())
+        writer.println("hello world")
+        writer.println("encryption test")
+        writer.close()
+
+        val key = generateEncryptionKey()
+        val encrypted = original.encryptToString(key)
+
+        val decrypted = File.createTempFile("file", ".txt")
+        encrypted.decryptToFile(key, decrypted)
+        assertEquals("hello world\nencryption test\n", decrypted.readText())
+    }
+}

android/uhabits-android/src/main/java/org/isoron/uhabits/utils/EncryptionExt.kt

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2016-2020 Álinson Santos Xavier <isoron@gmail.com>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.utils
+
+import android.util.*
+import java.io.*
+import java.nio.*
+import java.nio.charset.StandardCharsets.*
+import javax.crypto.*
+import javax.crypto.spec.*
+
+fun ByteArray.encrypt(key: String): ByteArray {
+    val keySpec = SecretKeySpec(Base64.decode(key, Base64.DEFAULT), "AES")
+    val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
+    cipher.init(Cipher.ENCRYPT_MODE, keySpec)
+    val encrypted = cipher.doFinal(this)
+    return ByteBuffer
+            .allocate(16 + encrypted.size)
+            .put(cipher.iv)
+            .put(encrypted)
+            .array()
+}
+
+fun ByteArray.decrypt(key: String): ByteArray {
+    val buffer = ByteBuffer.wrap(this)
+    val iv = ByteArray(16)
+    buffer.get(iv)
+    val encrypted = ByteArray(buffer.remaining())
+    buffer.get(encrypted)
+    val keySpec = SecretKeySpec(Base64.decode(key, Base64.DEFAULT), "AES")
+    val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
+    cipher.init(Cipher.DECRYPT_MODE, keySpec, IvParameterSpec(iv))
+    return cipher.doFinal(encrypted)
+}
+
+fun String.encrypt(key: String): String {
+    return Base64.encodeToString(this.toByteArray().encrypt(key), Base64.DEFAULT)
+}
+
+fun String.decrypt(key: String): String {
+    return String(Base64.decode(this, Base64.DEFAULT).decrypt(key), UTF_8)
+}
+
+fun String.decryptToFile(key: String, output: File)
+{
+    val outputStream = FileOutputStream(output)
+    output.writeBytes(Base64.decode(this, Base64.DEFAULT).decrypt(key))
+    outputStream.close()
+}
+
+fun File.encryptToString(key: String): String {
+    val bytes = ByteArray(this.length().toInt())
+    val inputStream = FileInputStream(this)
+    inputStream.read(bytes)
+    inputStream.close()
+    return Base64.encodeToString(bytes.encrypt(key), Base64.DEFAULT)
+}
+
+fun generateEncryptionKey(): String {
+    return try {
+        val keygen = KeyGenerator.getInstance("AES")
+        keygen.init(256)
+        val key = keygen.generateKey()
+        Base64.encodeToString(key.encoded, Base64.DEFAULT)
+    } catch (e: Exception) {
+        throw RuntimeException(e)
+    }
+}