rekey doesn't seem to work

[SushiTee]

Hi,
I'm trying to use this software to be able to us encryption for sqlite databases.
I'm trying to use database encryption with QT. I made it build already (at least the sqlite part + encryption). The wxWidgets stuff I don't really need.
So here is my problem.
Whenever I use rekey it fails to change the key.

        int rc = sqlite3_open_v2("test.sql", &db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0);

        if( rc ){
            qInfo() << "Can't open database";
            return;
        }else{
            qInfo() << "Opened database successfully ";
        }

        string pw = "blabla";
        if (!isDbEncrypted(db))
        {
            sqlite3_key(db, "", 0);
            sqlite3_rekey(db, pw.data(), pw.length());
            qInfo() << "Database was encrypted.";
        }
        else
        {
            sqlite3_key(db, pw.data(), pw.length());
            sqlite3_rekey(db, "", 0);
            qInfo() << "Database was decrypted.";
        }

        sqlite3_close(db);

I simply open a database. If it is not encrypted it will be encrypted and if it is already encrpted it will be decrypted. At least this is how it should be but it is not. If a new unencrypted DB is created it works fine but if I load the DB again after the encrption I get an error that the DB is corrupted or encrypted e´ven though I set the correct password with sqlite3_key(...).
I don't really get it. Am I missing something?

[utelle]

The culprit is most probably your function isDbEncrypted(), for which you didn't show the code.

For an existing encrypted database the call to sqlite3_key has to be the very first action after opening the database connection. I suspect that isDbEncrypted() performs some SQL and returns false if that fails, but then it is already too late to call sqlite3_key.

If my suspicion is correct, then you would have to first close the database connection, reopen it, and then call sqlite3_key with the correct password. Alternatively you could read the first 16 bytes of the database files. If they are equal to the zero-terminated string SQLite format 3, then the file is an unencrypted SQLite database file; otherwise it is an encrypted database file or not a database file at all.

BTW, if the database file is unencrypted and you want to encrypt (rekey) it, then you don't need to call sqlite3_key with an empty key first. Just call sqlite3_rekey with the new password.

[SushiTee]

Thank you. It works indeed.