CVE-2023-43633

On boot, the Pillar eve container checks for the existence and content of
/config/GlobalConfig/global.json.

If the file exists, it overrides the existing configuration on the device on boot.

This allows an attacker to change the systems configuration, which also includes some
debug functions.

This could be used to unlock the ssh with custom authorized_keys via the
debug.enable.ssh key, similar to the authorized_keys finding that was noted before.

Other usages include unlocking the usb to enable the keyboard via the debug.enable.usb
key, allowing VNC access via the app.allow.vnc key, and more.

An attacker could easily enable these debug functionalities without triggering the measured
boot mechanism implemented by EVE OS, and without marking the device as UUD
(Unknown Update Detected).
This is because the /config partition is not protected by measured boot, it is mutable and it
is not encrypted in any way.





An attacker can gain full control over the device without changing the PCR values, thereby not
triggering the measured boot mechanism, and having full access to the vault.




Note:

This issue was partially fixed in these commits (after disclosure to Zededa), where the config
partition measurement was added to PCR13:

 aa3501d6c57206ced222c33aea15a9169d629141

 5fef4d92e75838cc78010edaed5247dfbdae1889.

This issue was made viable in version 9.0.0 when the calculation was moved to PCR14 but it was not included in the measured boot.