Use strn functions and improve error handling. Even if we know the strings are NULL terminated we use length terminated string functions after a first strlen this makes it easier to assert that at one point we know the string is terminated and afterwards use the length of that.

#include "certificate.h"
#ifdef Q_OS_LINUX
Certificate::Certificate(const QByteArray& asn1data) : mValid(false) {
}

Certificate::~Certificate() {
}
#endif