SQLiteOutOfMemoryException out of memory (code 7), no clear indication as to why

[frapontillo]

Since we updated our library from android-database-sqlcipher to sqlcipher-android we've been getting multiple instances of these crashes:

Fatal Exception: android.database.sqlite.SQLiteOutOfMemoryException
out of memory (code 7): , while compiling: SELECT COUNT(*) FROM sqlite_schema;
net.zetetic.database.sqlcipher.SQLiteConnection.nativePrepareStatement (SQLiteConnection.java)
net.zetetic.database.sqlcipher.SQLiteConnection.acquirePreparedStatement (SQLiteConnection.java:973)
net.zetetic.database.sqlcipher.SQLiteConnection.executeForLong (SQLiteConnection.java:628)
net.zetetic.database.sqlcipher.SQLiteConnection.open (SQLiteConnection.java:240)
net.zetetic.database.sqlcipher.SQLiteConnection.open (SQLiteConnection.java:202)
net.zetetic.database.sqlcipher.SQLiteConnectionPool.openConnectionLocked (SQLiteConnectionPool.java:474)
net.zetetic.database.sqlcipher.SQLiteConnectionPool.open (SQLiteConnectionPool.java:188)
net.zetetic.database.sqlcipher.SQLiteConnectionPool.open (SQLiteConnectionPool.java:180)
net.zetetic.database.sqlcipher.SQLiteDatabase.openInner (SQLiteDatabase.java:1028)
net.zetetic.database.sqlcipher.SQLiteDatabase.open (SQLiteDatabase.java)
net.zetetic.database.sqlcipher.SQLiteDatabase.openDatabase (SQLiteDatabase.java:840)
net.zetetic.database.sqlcipher.SQLiteOpenHelper.getDatabaseLocked (SQLiteOpenHelper.java:359)
net.zetetic.database.sqlcipher.SQLiteOpenHelper.getWritableDatabase (SQLiteOpenHelper.java:278)
net.zetetic.database.sqlcipher.SupportHelper.getWritableDatabase (SupportHelper.java:60)
androidx.room.driver.SupportSQLiteDriver.open (SupportSQLiteDriver.android.kt:26)
androidx.room.driver.SupportSQLiteConnectionPool.getSupportConnection (SupportSQLiteConnectionPool.android.kt:35)
androidx.room.driver.SupportSQLiteConnectionPool.useConnection (SupportSQLiteConnectionPool.android.kt)
androidx.room.RoomConnectionManager.useConnection (RoomConnectionManager.android.kt:126)
androidx.room.RoomDatabase.useConnection$room_runtime_release (RoomDatabase.android.kt:593)
androidx.room.util.DBUtil__DBUtil_androidKt$performBlocking$1.invokeSuspend (DBUtil.android.kt:247)
androidx.room.util.DBUtil__DBUtil_androidKt$performBlocking$1.invoke (DBUtil.android.kt:2)
androidx.room.util.DBUtil__DBUtil_androidKt$performBlocking$1.invoke (DBUtil.android.kt:1)

This is just an example, we get the same android.database.sqlite.SQLiteOutOfMemoryException when SqlCipher calls getReadableDatabase, on multiple databases and on both Room and Content Provider.

This happens across all kinds of devices and OS versions, so it is not a limited subset of our user base.

Devices	OS

We have 2 databases, one accessed via Room, one via Content Providers.

At app startup, I see:

Database keying operation returned:0
Database keying operation returned:0
Database keying operation returned:0
Database keying operation returned:0
Database keying operation returned:0

Does this mean at least one of the 2 databases gets opened multiple times? I am providing access to these databases via singletons, so this shouldn't be happening, unless there is a race condition somewhere.

Is there any way to understand the actual reason behind this error?

[sjlombardo]

Hello @frapontillo. It is possible for SQLCipher to bubble up an "out of memory" exception, but it is rare. The most common causes follow

1. Library startup / initialization failure
2. Errors from the low level cryptographic provider operations
3. API misuse causing an unsafe internal state for the library
4. Failure to allocate memory

The common thread is that something unexpected has happened that SQLCipher determines will affect its operation in an unrecoverable way. Rather than risk database corruption SQLCipher will internally cease operation which gets interpreted as an out of memory condition (which is a safe way to prevent the SQLite library code from further manipulating a DB.

By contrast, the multiple "Database keying operation returned: 0" messages at startup are generally to be expected since the library will use a connection pool in WAL mode.

Given the exception is being thrown in the open() method, is your application doing anything with a SQLiteDatabaseHook, either in preKey or postKey?

The most direct way to troubleshoot this would be to enable the SQLCipher log by executing the following statements early in the application lifecycle:

PRAGMA cipher_log = '/path/to/a/writable/log/file';
PRAGMA cipher_log_level = TRACE;

If you are able to reproduce this error locally on a device or an emulator, can you please do that, capture the log file, and then send it over for analysis?

[frapontillo]

We have this in our hook:

val databaseHook = object : SQLiteDatabaseHook {

    override fun preKey(connection: SQLiteConnection?) {
        connection?.executeRaw("PRAGMA cipher_memory_security = OFF;", null, null)
    }

    override fun postKey(connection: SQLiteConnection?) {
        connection?.executeRaw("PRAGMA cipher_migrate;", null, null)
    }
}

I guess the issue could be with cipher_migrate being done on every connection. I'll try and do that conditionally rather than on every connection as explained here.

I will also remove "PRAGMA cipher_memory_security = OFF;" as it seems like it is the default now.