AES not work properly in StringSource and StringSink functions in Qt

Question

I have using of Crypto++ library in Qt due to encrypt a string with AES method in CBC mode and using of StringSource and StringSink to define input and output string parameters.

First, i read all bytes from a file ("unicode" or "ASCII" encoding), then set it as the input parameter in StringSource function, then set a parameter as string(data-type) for output (cipher-text). just i want to get a string and encrypt it with "aes-cbc" and showing output.

Also, i know FileSource and FileSink are two functions(consist input and output stream parameters) for writing data to files! but i want to read file content as input-string.

My Code :

void Widget::onEncryptButton()
{
    QByteArray key = "qwertyuiopasdfgh";
    QByteArray iv = "wertyuiopasdfghj"
    QByteArray plain;
    string cipher;

    QFile fi("/home/msi/Desktop/input.txt");
    QFile fo("/home/msi/Desktop/output.enc");

    fi.open(QFile::ReadOnly);
    fo.open(QFile::WriteOnly);
    plain = fi.readAll();

    AESEncryption aese((byte*)key.constData(), AES::DEFAULT_KEYLENGTH);    // default is 16
    CBC_Mode_ExternalCipher::Encryption encryptor(aese, (byte*)iv.constData());
    StringSource(plain, true, new StreamTransformationFilter(encryptor, new StringSink(cipher)));

    QMessageBox::information(this, "", QString("%1, %2").arg(strlen(cipher.c_str())).arg(cipher.size()));    // just for viewing cipher length

    fo.write(cipher.c_str());
    fi.close();
    fo.close();
}

Now i have bellow problems :

• When i read a compact file content(e.g. 900 byte) and set it as input in StringSource, generated cipher will be incomplete (e.g. 320 byte)

• Output of strlen(cipher.c_str()) is different by cipher.size() in "QMessageBox"

• My code working truly When i read some files("unicode" or "ASCII", "larg" or "little" size) and sometimes working incorrectly. i dont understand which of the reason caused this problem?

• Even, i set some input-string directly (not reading from file) and fails again!

Regards!

Answer 1

I could be your plain, if it contains '\0'. Try to pass both, the data and the length:

StringSource((byte*)plain.constData(), plain.size(), true, new StreamTransformationFilter(encryptor, new StringSink(cipher)));