/run/user/1000 bypasses /run's `noexec` as it is its own mount point. We might want to look into restricting that too.
- lock down interpreters / compilers (interpreter lock) (compiler lock)
Allow minimal privileges via mount options
- Noexec on everything possible
- Nodev everywhere except / and chroot partitions
- Nosetuid everywhere except /
- Consider making /var/tmp link to /tmp, or maybe mount –bind option
A reasonable /etc/fstab:LABEL=/ / ext3 defaults 1 1 LABEL=/tmp /tmp ext3 defaults,nosuid,noexec,nodev 1 2 LABEL=/var/log/audit /var/log/audit ext3 defaults,nosuid,noexec,nodev 1 2 LABEL=/home /home ext3 defaults,nosuid,nodev 1 2 LABEL=/var /var ext3 defaults,nosuid 1 2 LABEL=/boot /boot ext3 defaults,nosuid,noexec,nodev 1 2 /tmp /var/tmp ext3 defaults,bind,nosuid,noexec,nodev 1 2 tmpfs /dev/shm tmpfs defaults,nosuid,noexec,nodev 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 LABEL=SWAP-sda6 swap swap defaults 0 0
Once you have your partitions broken out and sized accordingly, you can begin to restrict the various mount points as much as possible. You should add nodev, noexec, and nosuid wherever possible. An example of a decently restricted /etc/fstab file is below:/dev/VG_OS/lv_root / ext3 defaults 1 1 /dev/VG_OS/lv_tmp /tmp ext3 defaults,nosuid,noexec,nodev 1 2 /dev/VG_OS/lv_vartmp /var/tmp ext3 defaults,nosuid,noexec,nodev 1 2 /dev/data_vol/lv_home /home ext3 defaults,nosuid,nodev 1 2 /dev/VG_OS/lv_var /var ext3 defaults,nosuid 1 2 /dev/data_vol/lv_web /var/www ext3 defaults,nosuid,nodev 1 2 /dev/sda1 /boot ext3 defaults,nosuid,noexec,nodev 1 2 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 /dev/_VG_OS/lv_swap swap swap defaults 0 0
Obviously you'll need to modify this example to suit your own system. LVM, volume names, labels etc are all subject to change. Please don't copy this example verbatim and expect it to work for you.
The webserver mount can also be set noexec, however this will impact cgi based applications, as well as server side includes which rely on the execute bit hack. If you're not using cgi applications, I would recommend at least testing noexec and using it if there are no negative side-effects.
Following the principle of least privilege, file systems should be mounted with the most restrictive mount options possible (without losing functionality).
Relevant mount options are:
- nodev: Do not interpret character or block special devices on the file system.
- nosuid: Do not allow set-user-identifier or set-group-identifier bits to take effect.
- noexec: Do not allow direct execution of any binaries on the mounted file system.
- Setting noexec on /home disallows executable scripts and breaks Wine* and Steam.
- Some packages (building nvidia-dkms for example) may require exec on /var.
- Wine does not need the exec flag for opening Windows executables. It is only needed when Wine itself is installed in /home.
File systems used for data should always be mounted with nodev, nosuid and noexec.
Potential file system mounts to consider: