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A turkish researcher found a flaw allowing the access to root account without password on MacOS High Sierra.
This flaw is critical because easily executable. It can be used locally or remotely if the device has an active VNC protocol (screen sharing activated). This flaw grants access to all device’s permissions. The attacker can do whatever he wants.
The access to the authentication panel to tape the administrator password is the only thing needed. This panel is available from any account on the device (locally or remotely via VNC protocol).
The flaw comes from the mistakenly activated root account on MacOS High Sierra. This root account is an inheritance of the UNIX system from which MacOS is developed. It is present and used in the Linux world but normally is deactivated (available but deactivated) on Mac, replaced with administrator accounts that cannot access system files.
How to protect yourself
You just need to set a password for this root account. Never loose this password.
In command lines from whatever administrator account on the device
If you want the technical informations for Limawi, take a look here.
The running of SSL/TLS
SSL/TLS is a protocol that provides server identity verification (for instance a web server like Limawi, in that case we speak about https because the protocol to access a web server is called http). This identity verification works with a certificate sent from the server.
Here is the protocol step by step (technical terms are present in the graphs):
- The client software asks the server its identity.
- The server sends a certificate signed by the certification authority trusted by both the client software and the server to the client software.
- The client software checks if the signature belongs to the certification authority it trusts.
- It sends a request to this certification authority to check if it ensures that the certificate is still valid.
- The client software and the server agree on a session key that will encrypt informations during a limited period (this time passed, another session key will take the place, the details for Limawi are explained in the graphs about the session key).
- The client software and the server can communicate in a secure way.
The HSTS extension
The HSTS extension is a http protocol extension (the protocol that loads webpages) reinforcing the SSL/TLS use.