On 8/22/21 11:49 AM, Peng Liang wrote:
Hi all, When we change the user for QEMU process (change "user" and "group" in /etc/libvirt/qemu.conf) to a normal user, we found that libvirtd will also change the ownership of /var/cache/libvirt/qemu but will keep the ownership of /var/cache/libvirt/qemu/capabilities as root. Is it secure to put files/directories owned by root in a directory owned by a normal user? Could the normal user replace the root's file with a new one?
No, the capabilities directory lacks write perms: drwxr-xr-x 2 root root 234 Aug 20 17:11 /var/cache/libvirt/qemu/capabilities/ and caps files themselves are RW by root only: -rw------- 1 root root 144215 Aug 20 15:38 926803a9278e445ec919c2b6cbd8c1c449c75b26dcb1686b774314180376c725.xml Therefore, I don't think a regular user could spoof capabilities.
Does it need to set sticky bit on /var/cache/libvirt/qemu or keep the ownership of /var/cache/libvirt/qemu as root?
No, setting sticky bit would make caps files owned by root:group and I don't think we want that (even though, not even group can write caps files). I hope this answers your concern. Michal