> Linux doesn't distinguish between trusted LANs [...] and public untrusted LANs
Gotta be the annoying and point out here that Linux is a kernel. Fedora Workstation, for instance, has firewalld installed & enabled by default, which does apply different policies to different network zones. Hook a default system up to a hostile coffee shop, and TCP/UDP ports <= 1024 are blocked by the default FedoraWorkstation zone. NetworkManager connections have a 'zone' property that the user can change to 'home', 'trusted', etc.
> Also, the fact that your printer infra can run arbitrary code as root, code supplied by the remote printer itself, is another level of crazy
Only, it seems, if non-default legacy printer drivers (foomatic) and discovery services (cups-browsed) are present. And doesn't cups run backends as an unprivileged 'lp' user? And confined by MAC (again, in the Red Hat world, SELinux confines it to the cupsd_t domain). So not _that_ crazy.
Disabling foomatic seems hard since the PPD can be distributed by the attacker and foomatic-rip is part of the cups-filter package. But yes, lp user + SELinux should be enough to make this not a 9.9.
I actaully didn't realise that foomatic is part of cups-filters now?! On the other hand - it's only 'activated' by cups-browsed, if I understand correctly, at least by the currently disclosed set of vulnerabilities... let's hope an attacker can't craft a printer that will trick cups itself into configuring a dodgy print destination...
Gotta be the annoying and point out here that Linux is a kernel. Fedora Workstation, for instance, has firewalld installed & enabled by default, which does apply different policies to different network zones. Hook a default system up to a hostile coffee shop, and TCP/UDP ports <= 1024 are blocked by the default FedoraWorkstation zone. NetworkManager connections have a 'zone' property that the user can change to 'home', 'trusted', etc.
> Also, the fact that your printer infra can run arbitrary code as root, code supplied by the remote printer itself, is another level of crazy
Only, it seems, if non-default legacy printer drivers (foomatic) and discovery services (cups-browsed) are present. And doesn't cups run backends as an unprivileged 'lp' user? And confined by MAC (again, in the Red Hat world, SELinux confines it to the cupsd_t domain). So not _that_ crazy.