Android: prefer CharArray over String

lambdapioneer · Feb 23, 2024 · 4552b92 · 4552b92
1 parent 73bc771
commit 4552b92
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Showing 17 changed files with 133 additions and 68 deletions.
diff --git a/android/app/src/main/java/com/lambdapioneer/sloth/app/models/HiddenSlothViewModel.kt b/android/app/src/main/java/com/lambdapioneer/sloth/app/models/HiddenSlothViewModel.kt
@@ -47,14 +47,14 @@ class HiddenSlothViewModel(
         runLongTaskInBackground {
             val data = content.encodeToByteArray()
             if (useCachedSecrets) {
-                val cachedSecrets = hiddenSloth.computeCachedSecrets(pw = password)
+                val cachedSecrets = hiddenSloth.computeCachedSecrets(pw = password.toCharArray())
                 hiddenSloth.encryptToStorageWithCachedSecrets(
                     cachedSecrets = cachedSecrets,
                     data = data
                 )
             } else {
                 hiddenSloth.encryptToStorage(
-                    pw = password,
+                    pw = password.toCharArray(),
                     data = data,
                 )
             }
@@ -64,10 +64,10 @@ class HiddenSlothViewModel(
     fun load(password: String, useCachedSecrets: Boolean) {
         runLongTaskInBackground {
             val contentBytes = if (useCachedSecrets) {
-                val cachedSecrets = hiddenSloth.computeCachedSecrets(pw = password)
+                val cachedSecrets = hiddenSloth.computeCachedSecrets(pw = password.toCharArray())
                 hiddenSloth.decryptFromStorageWithCachedSecrets(cachedSecrets)
             } else {
-                hiddenSloth.decryptFromStorage(pw = password)
+                hiddenSloth.decryptFromStorage(pw = password.toCharArray())
             }
             this.output.value = contentBytes.decodeToString()
         }

diff --git a/android/app/src/main/java/com/lambdapioneer/sloth/app/models/LongSlothViewModel.kt b/android/app/src/main/java/com/lambdapioneer/sloth/app/models/LongSlothViewModel.kt
@@ -32,13 +32,13 @@ class LongSlothViewModel(
 
     fun generateKey(password: String) {
         runLongTaskInBackground {
-            key.value = longSloth.createNewKey(pw = password)
+            key.value = longSloth.createNewKey(pw = password.toCharArray())
         }
     }
 
     fun deriveKey(password: String) {
         runLongTaskInBackground {
-            key.value = longSloth.deriveForExistingKey(pw = password)
+            key.value = longSloth.deriveForExistingKey(pw = password.toCharArray())
         }
     }
 

diff --git a/...libsodium/src/main/java/com/lambdapioneer/sloth/pwhash_libsodium/LibSodiumArgon2PwHash.kt b/...libsodium/src/main/java/com/lambdapioneer/sloth/pwhash_libsodium/LibSodiumArgon2PwHash.kt
@@ -3,6 +3,9 @@ package com.lambdapioneer.sloth.pwhash_libsodium
 import com.goterl.lazysodium.SodiumAndroid
 import com.lambdapioneer.sloth.crypto.PwHash
 import com.lambdapioneer.sloth.utils.secureRandomBytes
+import java.nio.CharBuffer
+import java.util.Arrays
+import com.goterl.lazysodium.interfaces.PwHash as LibSodiumPwHash
 
 
 class LibSodiumArgon2PwHash(
@@ -18,25 +21,33 @@ class LibSodiumArgon2PwHash(
 
     override fun deriveHash(
         salt: ByteArray,
-        password: String,
+        password: CharArray,
         outputLengthInBytes: Int,
     ): ByteArray {
         require(salt.size == SALT_LEN)
         require(outputLengthInBytes > 0)
         require(password.isNotEmpty())
 
-        val passwordBytes = password.encodeToByteArray()
+        val passwordCharBuffer = CharBuffer.wrap(password)
+        val passwordBytes = Charsets.UTF_16.encode(passwordCharBuffer).array()
+
         val result = ByteArray(outputLengthInBytes)
 
-        val libSodiumResult = libSodium.crypto_pwhash(
-            result, result.size.toLong(),
-            passwordBytes, passwordBytes.size.toLong(),
-            salt,
-            params.opsLimit,
-            params.memLimit,
-            com.goterl.lazysodium.interfaces.PwHash.Alg.PWHASH_ALG_ARGON2ID13.value,
-        )
-        check(libSodiumResult == 0)
+        try {
+            val libSodiumResult = libSodium.crypto_pwhash(
+                /* outputHash = */ result,
+                /* outputHashLen = */ result.size.toLong(),
+                /* password = */ passwordBytes,
+                /* passwordLen = */ passwordBytes.size.toLong(),
+                /* salt = */ salt,
+                /* opsLimit = */ params.opsLimit,
+                /* memLimit = */ params.memLimit,
+                /* alg = */ LibSodiumPwHash.Alg.PWHASH_ALG_ARGON2ID13.value,
+            )
+            check(libSodiumResult == 0)
+        } finally {
+            Arrays.fill(passwordBytes, 0x00)
+        }
 
         return result
     }
@@ -46,7 +57,7 @@ class LibSodiumArgon2PwHash(
     }
 
     companion object {
-        private const val SALT_LEN = com.goterl.lazysodium.interfaces.PwHash.SALTBYTES
+        private const val SALT_LEN = LibSodiumPwHash.SALTBYTES
     }
 }
 
diff --git a/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/SlothLibTest.kt b/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/SlothLibTest.kt
@@ -34,7 +34,7 @@ class SlothLibTest {
     fun testLongSloth_runThrough() {
         val instance = createInstance()
 
-        val pw = "password"
+        val pw = "password".toCharArray()
         val storage = OnDiskStorage(context)
         val identifier1 = "longsloth_test_1"
         val longSloth1 = instance.getLongSlothInstance(
@@ -90,7 +90,7 @@ class SlothLibTest {
 
         val data = "hello".toByteArray()
         val data2 = "hola".toByteArray()
-        val pw = "password"
+        val pw = "password".toCharArray()
 
         // create a HiddenSloth instance
         val params = HiddenSlothParams(payloadMaxLength = 1 * MIB)
@@ -131,12 +131,13 @@ class SlothLibTest {
 
         // does not decrypt under a different passphrase
         assertThatExceptionOfType(SlothDecryptionFailed::class.java).isThrownBy {
-            hiddenSloth1.decryptFromStorage("wrong passphrase")
+            hiddenSloth1.decryptFromStorage("wrong passphrase".toCharArray())
         }
 
         // does not decrypt under a different passphrase with pre-computed secrets
         assertThatExceptionOfType(SlothDecryptionFailed::class.java).isThrownBy {
-            val wrongCachedSecrets = hiddenSloth1.computeCachedSecrets("wrong passphrase")
+            val wrongCachedSecrets =
+                hiddenSloth1.computeCachedSecrets("wrong passphrase".toCharArray())
             hiddenSloth1.decryptFromStorageWithCachedSecrets(wrongCachedSecrets)
         }
 

diff --git a/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/SlothParameterBenchmarkTest.kt b/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/SlothParameterBenchmarkTest.kt
@@ -69,7 +69,7 @@ class SlothParameterBenchmarkTest {
         )
 
         val waitingTime = measureWaitingTime {
-            longSloth.createNewKey(pw = "passphrase")
+            longSloth.createNewKey(pw = "passphrase".toCharArray())
         }
         assertThat(waitingTime).isGreaterThan(targetDuration)
         assertThat(waitingTime).isLessThan(targetDuration.multipliedBy(5))

diff --git a/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/crypto/Pbkdf2PwHashTest.kt b/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/crypto/Pbkdf2PwHashTest.kt
@@ -15,58 +15,58 @@ class Pbkdf2PwHashTest {
 
     @Test
     fun testHash_whenSameInput_thenSameOutput() {
-        val h1 = instance.deriveHash(salt, "test", 32)
-        val h2 = instance.deriveHash(salt, "test", 32)
+        val h1 = instance.deriveHash(salt, "test".toCharArray(), 32)
+        val h2 = instance.deriveHash(salt, "test".toCharArray(), 32)
 
         assertThat(h1).isEqualTo(h2)
     }
 
     @Test
     fun testHash_whenInteractiveParameters_thenSucceeds() {
         val instance = Pbkdf2PwHash(Pbkdf2PwHashParams.INTERACTIVE)
-        val h1 = instance.deriveHash(salt, "test", 32)
+        val h1 = instance.deriveHash(salt, "test".toCharArray(), 32)
 
         assertThat(h1).isNotEmpty()
     }
 
     @Test
     fun testHash_whenOwaspParameters_thenSucceeds() {
         val instance = Pbkdf2PwHash(Pbkdf2PwHashParams.OWASP)
-        val h1 = instance.deriveHash(salt, "test", 32)
+        val h1 = instance.deriveHash(salt, "test".toCharArray(), 32)
 
         assertThat(h1).isNotEmpty()
     }
 
     @Test
     fun testHash_whenOwaspSha256Parameters_thenSucceeds() {
         val instance = Pbkdf2PwHash(Pbkdf2PwHashParams.OWASP_SHA256)
-        val h1 = instance.deriveHash(salt, "test", 32)
+        val h1 = instance.deriveHash(salt, "test".toCharArray(), 32)
 
         assertThat(h1).isNotEmpty()
     }
 
     @Test
     fun testHash_whenLongKeyLength_thenSucceeds() {
         val len = 10 * 1024 * 1024 // 10 MiB
-        val h = instance.deriveHash(salt, "test", len)
+        val h = instance.deriveHash(salt, "test".toCharArray(), len)
 
         assertThat(h).hasSize(len)
     }
 
     @Test
     fun testHash_whenDifferentSalt_thenDifferentOutput() {
-        val h1 = instance.deriveHash(salt, "test", 32)
+        val h1 = instance.deriveHash(salt, "test".toCharArray(), 32)
 
         val differentSalt = instance.createSalt()
-        val h2 = instance.deriveHash(differentSalt, "test", 32)
+        val h2 = instance.deriveHash(differentSalt, "test".toCharArray(), 32)
 
         assertThat(h1).isNotEqualTo(h2)
     }
 
     @Test
     fun testHash_whenDifferentPassword_thenDifferentOutput() {
-        val h1 = instance.deriveHash(salt, "test", 32)
-        val h2 = instance.deriveHash(salt, "different", 32)
+        val h1 = instance.deriveHash(salt, "test".toCharArray(), 32)
+        val h2 = instance.deriveHash(salt, "different".toCharArray(), 32)
 
         assertThat(h1).isNotEqualTo(h2)
     }

diff --git a/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/impl/HiddenSlothImplTest.kt b/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/impl/HiddenSlothImplTest.kt
@@ -18,7 +18,7 @@ import java.io.File
 import javax.crypto.AEADBadTagException
 
 private val DEFAULT_HANDLE = "handle".encodeToByteArray()
-private const val DEFAULT_PASSWORD = "password"
+private val DEFAULT_PASSWORD = "password".toCharArray()
 
 @RunWith(AndroidJUnit4::class)
 class HiddenSlothImplTest {
@@ -121,7 +121,7 @@ class HiddenSlothImplTest {
 
         instance.init(storage, DEFAULT_HANDLE)
         instance.encrypt(storage, DEFAULT_PASSWORD, data)
-        instance.decrypt(storage, "wrong passphrase")
+        instance.decrypt(storage, "wrong passphrase".toCharArray())
     }
 
     @Test(expected = AEADBadTagException::class)

diff --git a/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/impl/LongSlothImplTest.kt b/android/sloth/src/androidTest/java/com/lambdapioneer/sloth/impl/LongSlothImplTest.kt
@@ -6,14 +6,15 @@ import com.lambdapioneer.sloth.crypto.Pbkdf2PwHash
 import com.lambdapioneer.sloth.storage.OnDiskStorage
 import com.lambdapioneer.sloth.testing.createSecureElementOrSkip
 import com.lambdapioneer.sloth.utils.secureRandomBytes
+import com.lambdapioneer.sloth.utils.secureRandomChars
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
 import java.io.File
 
 private val DEFAULT_HANDLE = "handle".encodeToByteArray()
-private const val DEFAULT_PASSWORD = "password"
+private val DEFAULT_PASSWORD = "password".toCharArray()
 private const val DEFAULT_OUTPUT_LENGTH = 32
 
 @RunWith(AndroidJUnit4::class)
@@ -51,7 +52,7 @@ class LongSlothImplTest {
     @Test
     fun whenKeyGenWithLongPassword_thenYieldSameKey() {
         val instance = createInstance()
-        val pw = secureRandomBytes(255).decodeToString()
+        val pw = secureRandomChars(255)
 
         val k1 = instance.keyGen(
             storage = storage,
@@ -82,7 +83,7 @@ class LongSlothImplTest {
 
         val k2 = instance.derive(
             storage = storage,
-            pw = "not the default password",
+            pw = "not the default password".toCharArray(),
             outputLengthBytes = DEFAULT_OUTPUT_LENGTH
         )
 

diff --git a/android/sloth/src/main/java/com/lambdapioneer/sloth/HiddenSloth.kt b/android/sloth/src/main/java/com/lambdapioneer/sloth/HiddenSloth.kt
@@ -75,7 +75,7 @@ class HiddenSloth internal constructor(
      * [identifier]. The storage must have been previous initialized using [onAppStart].
      */
     fun encryptToStorage(
-        pw: String,
+        pw: CharArray,
         data: ByteArray,
     ) {
         check(isInitialized)
@@ -92,7 +92,7 @@ class HiddenSloth internal constructor(
      * (b) the password is wrong, or (c) the storage has been tampered with.
      */
     fun decryptFromStorage(
-        pw: String,
+        pw: CharArray,
     ): ByteArray {
         check(isInitialized)
         val namespacedStorage = storage.getOrCreateNamespace(identifier)
@@ -112,7 +112,7 @@ class HiddenSloth internal constructor(
      * calls to [encryptToStorageWithCachedSecrets] and [decryptFromStorageWithCachedSecrets].
      */
     fun computeCachedSecrets(
-        pw: String,
+        pw: CharArray,
         authenticateStorage: Boolean = true,
     ): HiddenSlothCachedSecrets {
         check(isInitialized)

diff --git a/android/sloth/src/main/java/com/lambdapioneer/sloth/LongSloth.kt b/android/sloth/src/main/java/com/lambdapioneer/sloth/LongSloth.kt
@@ -37,7 +37,7 @@ class LongSloth internal constructor(
      * @param outputLengthBytes The length of the output key in bytes. Defaults to 32 bytes.
      */
     fun createNewKey(
-        pw: String,
+        pw: CharArray,
         outputLengthBytes: Int = 32,
     ): ByteArray {
         val namespacedHandle = identifierToHandle(identifier)
@@ -58,7 +58,7 @@ class LongSloth internal constructor(
      * @param outputLengthBytes The length of the output key in bytes. Defaults to 32 bytes.
      */
     fun deriveForExistingKey(
-        pw: String,
+        pw: CharArray,
         outputLengthBytes: Int = 32,
     ): ByteArray {
         val namespacedStorage = storage.getOrCreateNamespace(identifier)

diff --git a/android/sloth/src/main/java/com/lambdapioneer/sloth/crypto/Pbkdf2PwHash.kt b/android/sloth/src/main/java/com/lambdapioneer/sloth/crypto/Pbkdf2PwHash.kt
@@ -15,12 +15,12 @@ class Pbkdf2PwHash(
 
     override fun deriveHash(
         salt: ByteArray,
-        password: String,
+        password: CharArray,
         outputLengthInBytes: Int,
     ): ByteArray {
         val factory = SecretKeyFactory.getInstance(params.algorithm)
         val keySpec = PBEKeySpec(
-            /* password = */ password.toCharArray(),
+            /* password = */ password,
             /* salt = */ salt,
             /* iterationCount = */ params.iterationCount,
             /* keyLength = */ 8 * outputLengthInBytes

diff --git a/android/sloth/src/main/java/com/lambdapioneer/sloth/crypto/PwHash.kt b/android/sloth/src/main/java/com/lambdapioneer/sloth/crypto/PwHash.kt
@@ -20,5 +20,5 @@ interface PwHash {
      * @param password The password to use for the hash function.
      * @param outputLengthInBytes The length of the output hash in bytes.
      */
-    fun deriveHash(salt: ByteArray, password: String, outputLengthInBytes: Int): ByteArray
+    fun deriveHash(salt: ByteArray, password: CharArray, outputLengthInBytes: Int): ByteArray
 }