5.1.5 Ensure Sealed System Volume (SSV) Is Enabled

Information

Sealed System Volume is a security feature introduced in macOS 11.0 Big Sur.

During system installation, a SHA-256 cryptographic hash is calculated for all immutable system files and stored in a Merkle tree which itself is hashed as the Seal. Both are stored in the metadata of the snapshot created of the System volume.

The seal is verified by the boot loader at startup. macOS will not boot if system files have been tampered with. If validation fails, the user will be instructed to reinstall the operating system.

During read operations for files located in the Sealed System Volume, a hash is calculated and compared to the value stored in the Merkle tree.

Rationale:

Running without Sealed System Volume on a production system could run the risk of Apple software, that integrates directly with macOS, being modified.

Impact:

Apple Software that integrates with the operating system could become compromised.

Solution

Perform the following to enable System Integrity Protection:

Reboot into the Recovery Partition (reboot and hold down Command + R)

Select an administrator's account and enter that account's password

Select Utilities

Select Terminal

Run the following command:

$ sudo /usr/bin/csrutil enable authenticated-root

Successfully enabled System authenticated root.
Restart the machine for the changes to take effect.



Reboot the computer

Note: You cannot enable Sealed System Volume from the booted operating system. If the remediation is attempted in the booted OS and not the Recovery Partition the output will give the error csrutil: This tool needs to be executed from Recovery OS.

See Also

https://workbench.cisecurity.org/files/3573