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/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