Avoid SQLCipher key derivation (#6774)

* Avoid SQLCipher key derivation by manually providing the generated as a raw key: this needs a series of DB re-key operations, performed as part of a 'dummy' DB migration

* Set key generation length to 32 bytes in `RandomSecretPassphraseProvider`.

* Use `ClientSecret` for handling the keys for SQLCipher. Move `ClientSecret` to `:libraries:androidutils` so it's shared.

libraries/androidutils/src/main/kotlin/io/element/android/libraries/androidutils/crypto/ClientSecret.kt

@@ -5,9 +5,7 @@
  * Please see LICENSE files in the repository root for full details.
  */
 
-package io.element.android.libraries.matrix.impl
+package io.element.android.libraries.androidutils.crypto
-
-import okio.ByteString.Companion.decodeHex
 
 /**
  * Represents a client secret used to encrypt/decrypt data from databases, which can be either a passphrase or a raw key.
@@ -17,7 +15,7 @@ sealed interface ClientSecret {
      * A passphrase that can be used to derive a key for encryption/decryption.
      */
     data class Passphrase(val value: String) : ClientSecret {
-        override fun formattedAsString(): String = toString()
+        override fun formattedAsString(): String = value
     }
 
     /**
@@ -57,10 +55,18 @@ sealed interface ClientSecret {
             val regex = Regex("^x'([0-9a-fA-F]+)'$")
             val rawKeyMatch = regex.matchEntire(secret)
             return if (rawKeyMatch != null) {
-                RawKey(rawKeyMatch.groupValues[1].decodeHex().toByteArray())
+                RawKey(rawKeyMatch.groupValues[1].hexToByteArray())
             } else {
                 Passphrase(secret)
             }
         }
+
+        /**
+         * Create a [ClientSecret] from raw bytes, which will be treated as a raw key.
+         */
+        fun fromRawBytes(bytes: ByteArray): ClientSecret = when (bytes.size) {
+            32 -> RawKey(bytes)
+            else -> Passphrase(bytes.toHexString())
+        }
     }
 }

libraries/cachestore/impl/src/main/kotlin/io/element/android/libraries/cachestore/impl/di/CacheStoreModule.kt

@@ -16,7 +16,9 @@ import dev.zacsweers.metro.SingleIn
 import io.element.android.libraries.cachestore.impl.CacheDatabase
 import io.element.android.libraries.di.annotations.ApplicationContext
 import io.element.encrypteddb.SqlCipherDriverFactory
-import io.element.encrypteddb.passphrase.RandomSecretPassphraseProvider
+import io.element.encrypteddb.passphrase.RandomDatabaseSecretProvider
+import io.element.encrypteddb.utils.ReplaceDatabaseKey
+import timber.log.Timber
 
 @BindingContainer
 @ContributesTo(AppScope::class)
@@ -35,9 +37,20 @@ object CacheStoreModule {
             parentDir.mkdirs()
         }
 
-        val passphraseProvider = RandomSecretPassphraseProvider(context, secretFile)
+        val rekeyMigrationVersion = 2L
+        val passphraseProvider = RandomDatabaseSecretProvider(context, secretFile)
         val driver = SqlCipherDriverFactory(passphraseProvider)
-            .create(CacheDatabase.Schema, "$name.db", context)
+            .create(
+                schema = CacheDatabase.Schema,
+                name = "$name.db",
+                context = context
+            ) { db, oldVersion, newVersion ->
+                Timber.d("Migrating $name database from version $oldVersion to $newVersion")
+                if (rekeyMigrationVersion in oldVersion..newVersion) {
+                    ReplaceDatabaseKey(passphraseProvider).replaceKey(name, db)
+                }
+            }
+
         return CacheDatabase(driver)
     }
 }

libraries/cachestore/impl/src/main/sqldelight/migrations/1.sqm

@@ -0,0 +1,8 @@
+-- Migrate DB from version 1
+-- Initial schema for CacheData table
+
+CREATE TABLE IF NOT EXISTS CacheData (
+    key TEXT NOT NULL PRIMARY KEY,
+    value TEXT NOT NULL,
+    updatedAt INTEGER NOT NULL
+);

libraries/cachestore/impl/src/main/sqldelight/migrations/2.sqm

@@ -0,0 +1,2 @@
+-- Migrate DB from version 2
+-- Dummy migration to trigger a re-key

libraries/encrypted-db/src/main/kotlin/io/element/encrypteddb/SqlCipherDriverFactory.kt

@@ -9,30 +9,54 @@
 package io.element.encrypteddb
 
 import android.content.Context
+import androidx.sqlite.db.SupportSQLiteDatabase
 import app.cash.sqldelight.db.QueryResult
 import app.cash.sqldelight.db.SqlDriver
 import app.cash.sqldelight.db.SqlSchema
 import app.cash.sqldelight.driver.android.AndroidSqliteDriver
-import io.element.encrypteddb.passphrase.PassphraseProvider
+import io.element.android.libraries.androidutils.crypto.ClientSecret
+import io.element.encrypteddb.passphrase.DatabaseSecretProvider
 import net.zetetic.database.sqlcipher.SupportOpenHelperFactory
 
 /**
  * Creates an encrypted version of the [SqlDriver] using SQLCipher's [SupportOpenHelperFactory].
- * @param passphraseProvider Provides the passphrase needed to use the SQLite database with SQLCipher.
+ * @param databaseSecretProvider Provides the passphrase needed to use the SQLite database with SQLCipher.
  */
 class SqlCipherDriverFactory(
-    private val passphraseProvider: PassphraseProvider,
+    private val databaseSecretProvider: DatabaseSecretProvider,
 ) {
+    companion object {
+        init {
+            System.loadLibrary("sqlcipher")
+        }
+    }
+
     /**
      * Returns a valid [SqlDriver] with SQLCipher support.
      * @param schema The SQLite DB schema.
      * @param name The name of the database to create.
      * @param context Android [Context], used to instantiate the driver.
+     * @param onUpgradeCallback Optional callback to handle database upgrades, which will be called in the [AndroidSqliteDriver.Callback.onUpgrade] method.
      */
-    fun create(schema: SqlSchema<QueryResult.Value<Unit>>, name: String, context: Context): SqlDriver {
+    fun create(
-        System.loadLibrary("sqlcipher")
+        schema: SqlSchema<QueryResult.Value<Unit>>,
-        val passphrase = passphraseProvider.getPassphrase()
+        name: String,
-        val factory = SupportOpenHelperFactory(passphrase)
+        context: Context,
-        return AndroidSqliteDriver(schema = schema, context = context, name = name, factory = factory)
+        onUpgradeCallback: ((driver: SupportSQLiteDatabase, oldVersion: Int, newVersion: Int) -> Unit)? = null,
+    ): SqlDriver {
+        val key = when (val secret = databaseSecretProvider.getSecret()) {
+            // For a raw key, we need the blob representation (`x'...'`) as bytes
+            is ClientSecret.RawKey -> secret.formattedAsString().toByteArray()
+            // For a passphrase, we need the bytes for the hex string representation
+            is ClientSecret.Passphrase -> secret.formattedAsString().hexToByteArray()
+        }
+        val factory = SupportOpenHelperFactory(key)
+        return AndroidSqliteDriver(schema = schema, context = context, name = name, factory = factory, callback = object : AndroidSqliteDriver.Callback(
+                schema
+            ) {
+            override fun onUpgrade(db: SupportSQLiteDatabase, oldVersion: Int, newVersion: Int) {
+                onUpgradeCallback?.invoke(db, oldVersion, newVersion)
+            }
+        })
     }
 }

libraries/encrypted-db/src/main/kotlin/io/element/encrypteddb/passphrase/DatabaseSecretProvider.kt

@@ -8,12 +8,19 @@
 
 package io.element.encrypteddb.passphrase
 
+import io.element.android.libraries.androidutils.crypto.ClientSecret
+
 /**
  * An abstraction to implement secure providers for SQLCipher passphrases.
  */
-interface PassphraseProvider {
+interface DatabaseSecretProvider {
     /**
-     * Returns a passphrase for SQLCipher in [ByteArray] format.
+     * Returns a secret for SQLCipher.
      */
-    fun getPassphrase(): ByteArray
+    fun getSecret(): ClientSecret
+
+    /**
+     * Resets the passphrase, for example by deleting the persisted secret. Returns `true` if the reset was successful, `false` otherwise.
+     */
+    fun reset(): Boolean
 }

libraries/encrypted-db/src/main/kotlin/io/element/encrypteddb/passphrase/RandomDatabaseSecretProvider.kt

@@ -9,35 +9,41 @@
 package io.element.encrypteddb.passphrase
 
 import android.content.Context
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 import io.element.encrypteddb.crypto.EncryptedFile
 import java.io.File
 import java.security.SecureRandom
 
 /**
- * Provides a secure passphrase for SQLCipher by generating a random secret and storing it into an [EncryptedFile].
+ * Provides a secure secret for SQLCipher by generating a random secret and storing it into an [EncryptedFile].
  * @param context Android [Context], used by [EncryptedFile] for cryptographic operations.
  * @param file Destination file where the key will be stored.
- * @param secretSize Length of the generated secret.
+ * @param secretSizeBytes Length of the generated secret.
  */
-class RandomSecretPassphraseProvider(
+class RandomDatabaseSecretProvider(
     private val context: Context,
     private val file: File,
-    private val secretSize: Int = 256,
+    private val secretSizeBytes: Int = 32,
-) : PassphraseProvider {
+) : DatabaseSecretProvider {
-    override fun getPassphrase(): ByteArray {
+    override fun getSecret(): ClientSecret {
         val encryptedFile = EncryptedFile(context, file)
-        return if (!file.exists()) {
+        val bytes = if (!file.exists()) {
             val secret = generateSecret()
             encryptedFile.openFileOutput().use { it.write(secret) }
             secret
         } else {
             encryptedFile.openFileInput().use { it.readBytes() }
         }
+        return ClientSecret.fromRawBytes(bytes)
+    }
+
+    override fun reset(): Boolean {
+        return file.delete()
     }
 
     private fun generateSecret(): ByteArray {
-        val buffer = ByteArray(size = secretSize)
+        // Generate a random secret of the specified size using a secure random generator.
-        SecureRandom().nextBytes(buffer)
+        return ByteArray(size = secretSizeBytes)
-        return buffer
+            .also { SecureRandom().nextBytes(it) }
     }
 }

libraries/encrypted-db/src/main/kotlin/io/element/encrypteddb/utils/ReplaceDatabaseKey.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.encrypteddb.utils
+
+import androidx.sqlite.db.SupportSQLiteDatabase
+import io.element.encrypteddb.passphrase.RandomDatabaseSecretProvider
+import timber.log.Timber
+
+/**
+ * A utility class to replace the encryption key of an existing SQLCipher database.
+ * This is used during database migrations when we want to change the encryption key.
+ *
+ * @param databaseSecretProvider The provider for generating new secrets.
+ */
+class ReplaceDatabaseKey(
+    private val databaseSecretProvider: RandomDatabaseSecretProvider
+) {
+    fun replaceKey(name: String, database: SupportSQLiteDatabase) {
+        Timber.d("Re-keying database $name")
+        // Reset the passphrase provider to generate a new passphrase
+        databaseSecretProvider.reset()
+
+        // Get the new secret and convert it to the format expected by SQLCipher
+        val newSecret = databaseSecretProvider.getSecret()
+        val key = newSecret.formattedAsString()
+
+        // Use the PRAGMA rekey command to change the encryption key of the database
+        database.query("PRAGMA rekey = \"$key\";").close()
+
+        // Verify that the database can be accessed with the new key by running a simple query
+        val result = database.query("select count(*) from sqlite_master").use { cursor ->
+            if (cursor.moveToNext()) cursor.getLong(0) else -1L
+        }
+        if (result >= 0) {
+            Timber.d("Re-keying database $name completed")
+        } else {
+            Timber.e("Re-keying database $name didn't work as expected.")
+        }
+    }
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustMatrixClientFactory.kt

@@ -9,6 +9,7 @@
 package io.element.android.libraries.matrix.impl
 
 import dev.zacsweers.metro.Inject
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 import io.element.android.libraries.core.coroutine.CoroutineDispatchers
 import io.element.android.libraries.core.data.ByteUnit
 import io.element.android.libraries.core.data.megaBytes

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/auth/RustMatrixAuthenticationService.kt

@@ -12,6 +12,7 @@ import dev.zacsweers.metro.AppScope
 import dev.zacsweers.metro.ContributesBinding
 import dev.zacsweers.metro.SingleIn
 import io.element.android.features.enterprise.api.EnterpriseService
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 import io.element.android.libraries.core.coroutine.CoroutineDispatchers
 import io.element.android.libraries.core.extensions.mapFailure
 import io.element.android.libraries.core.extensions.runCatchingExceptions
@@ -30,7 +31,6 @@ import io.element.android.libraries.matrix.api.core.SessionId
 import io.element.android.libraries.matrix.api.core.UserId
 import io.element.android.libraries.matrix.api.verification.SessionVerifiedStatus
 import io.element.android.libraries.matrix.impl.ClientBuilderSlidingSync
-import io.element.android.libraries.matrix.impl.ClientSecret
 import io.element.android.libraries.matrix.impl.RustMatrixClientFactory
 import io.element.android.libraries.matrix.impl.auth.qrlogin.QrErrorMapper
 import io.element.android.libraries.matrix.impl.auth.qrlogin.SdkQrCodeLoginData

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/keys/DefaultSecretGenerator.kt

@@ -11,7 +11,7 @@ package io.element.android.libraries.matrix.impl.keys
 import android.util.Base64
 import dev.zacsweers.metro.AppScope
 import dev.zacsweers.metro.ContributesBinding
-import io.element.android.libraries.matrix.impl.ClientSecret
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 import java.security.SecureRandom
 
 @ContributesBinding(AppScope::class)

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/keys/SecretGenerator.kt

@@ -8,7 +8,7 @@
 
 package io.element.android.libraries.matrix.impl.keys
 
-import io.element.android.libraries.matrix.impl.ClientSecret
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 
 private const val PASSPHRASE_SIZE = 256
 private const val KEY_SIZE = 32

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/storage/SqliteStoreBuilder.kt

@@ -7,9 +7,9 @@
 
 package io.element.android.libraries.matrix.impl.storage
 
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 import io.element.android.libraries.core.data.ByteUnit
 import io.element.android.libraries.core.data.megaBytes
-import io.element.android.libraries.matrix.impl.ClientSecret
 import io.element.android.libraries.matrix.impl.paths.SessionPaths
 import org.matrix.rustcomponents.sdk.ClientBuilder
 import org.matrix.rustcomponents.sdk.SqliteStoreBuilder as SdkSqliteStoreBuilder

libraries/matrix/impl/src/test/kotlin/io/element/android/libraries/matrix/impl/auth/FakeSecretGenerator.kt

@@ -8,7 +8,7 @@
 
 package io.element.android.libraries.matrix.impl.auth
 
-import io.element.android.libraries.matrix.impl.ClientSecret
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 import io.element.android.libraries.matrix.impl.keys.SecretGenerator
 import io.element.android.libraries.matrix.test.A_PASSPHRASE
 

libraries/matrix/impl/src/test/kotlin/io/element/android/libraries/matrix/impl/keys/DefaultSecretGeneratorTest.kt

@@ -9,7 +9,7 @@
 package io.element.android.libraries.matrix.impl.keys
 
 import com.google.common.truth.Truth.assertThat
-import io.element.android.libraries.matrix.impl.ClientSecret
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner

libraries/matrix/impl/src/test/kotlin/io/element/android/libraries/matrix/impl/storage/FakeSqliteStoreBuilder.kt

@@ -7,7 +7,7 @@
 
 package io.element.android.libraries.matrix.impl.storage
 
-import io.element.android.libraries.matrix.impl.ClientSecret
+import io.element.android.libraries.androidutils.crypto.ClientSecret
 import org.matrix.rustcomponents.sdk.ClientBuilder
 
 class FakeSqliteStoreBuilder : SqliteStoreBuilder {

libraries/push/impl/src/main/kotlin/io/element/android/libraries/push/impl/history/di/PushHistoryModule.kt

@@ -17,7 +17,9 @@ import dev.zacsweers.metro.SingleIn
 import io.element.android.libraries.di.annotations.ApplicationContext
 import io.element.android.libraries.push.impl.PushDatabase
 import io.element.encrypteddb.SqlCipherDriverFactory
-import io.element.encrypteddb.passphrase.RandomSecretPassphraseProvider
+import io.element.encrypteddb.passphrase.RandomDatabaseSecretProvider
+import io.element.encrypteddb.utils.ReplaceDatabaseKey
+import timber.log.Timber
 
 @BindingContainer
 @ContributesTo(AppScope::class)
@@ -36,9 +38,20 @@ object PushHistoryModule {
             parentDir.mkdirs()
         }
 
-        val passphraseProvider = RandomSecretPassphraseProvider(context, secretFile)
+        val rekeyMigrationVersion = 2L
+        val passphraseProvider = RandomDatabaseSecretProvider(context, secretFile)
         val driver = SqlCipherDriverFactory(passphraseProvider)
-            .create(PushDatabase.Schema, "$name.db", context)
+            .create(
+                schema = PushDatabase.Schema,
+                name = "$name.db",
+                context = context
+            ) { db, oldVersion, newVersion ->
+                Timber.d("Migrating $name database from version $oldVersion to $newVersion")
+                if (rekeyMigrationVersion in oldVersion..newVersion) {
+                    ReplaceDatabaseKey(passphraseProvider).replaceKey(name, db)
+                }
+            }
+
         return PushDatabase(driver)
     }
 }

libraries/push/impl/src/main/sqldelight/migrations/2.sqm

@@ -0,0 +1,2 @@
+-- Migrate DB from version 2
+-- Dummy migration to trigger a re-key

libraries/session-storage/impl/src/main/kotlin/io/element/android/libraries/sessionstorage/impl/di/SessionStorageModule.kt

@@ -17,7 +17,9 @@ import dev.zacsweers.metro.SingleIn
 import io.element.android.libraries.di.annotations.ApplicationContext
 import io.element.android.libraries.sessionstorage.impl.SessionDatabase
 import io.element.encrypteddb.SqlCipherDriverFactory
-import io.element.encrypteddb.passphrase.RandomSecretPassphraseProvider
+import io.element.encrypteddb.passphrase.RandomDatabaseSecretProvider
+import io.element.encrypteddb.utils.ReplaceDatabaseKey
+import timber.log.Timber
 
 @BindingContainer
 @ContributesTo(AppScope::class)
@@ -36,9 +38,20 @@ object SessionStorageModule {
             parentDir.mkdirs()
         }
 
-        val passphraseProvider = RandomSecretPassphraseProvider(context, secretFile)
+        val rekeyMigrationVersion = 11L
+        val passphraseProvider = RandomDatabaseSecretProvider(context, secretFile)
         val driver = SqlCipherDriverFactory(passphraseProvider)
-            .create(SessionDatabase.Schema, "$name.db", context)
+            .create(
+                schema = SessionDatabase.Schema,
+                name = "$name.db",
+                context = context,
+            ) { db, oldVersion, newVersion ->
+                Timber.d("Migrating $name database from version $oldVersion to $newVersion")
+                if (rekeyMigrationVersion in oldVersion..newVersion) {
+                    ReplaceDatabaseKey(passphraseProvider).replaceKey(name, db)
+                }
+            }
+
         return SessionDatabase(driver)
     }
 }

libraries/session-storage/impl/src/main/sqldelight/migrations/11.sqm

@@ -0,0 +1,2 @@
+-- Migrate DB from version 11
+-- Dummy migration to trigger a re-key

services/analytics/impl/src/main/kotlin/io/element/android/services/analytics/impl/watchers/DefaultAnalyticsColdStartWatcher.kt

@@ -57,7 +57,7 @@ class DefaultAnalyticsColdStartWatcher(
     override fun onRoomListVisible() {
         if (isColdStart.getAndSet(false)) {
             analyticsService.finishLongRunningTransaction(AnalyticsLongRunningTransaction.ColdStart) {
-                Timber.d("Room list is visible, finishing cold start check. Elapsed: ${it.duration}")
+                Timber.d("Room list is visible, finishing cold start check after ${it.duration}")
             }
         }
     }