Demi Marie Obenour <demiobenour@gmail.com> writes:
This means that a breach of crosvm is not guaranteed to be fatal.
The Wayland socket is still only accessible by root, so crosvm must run as root. The known container escape via /proc/self/exe is blocked by bwrap being on a read-only filesystem. Container escapes via /proc are blocked by remounting /proc read-only. Crosvm does not have CAP_SYS_ADMIN so it cannot change mounts.
The two remaining steps are:
- Run crosvm as an unprivileged user. - Enable seccomp to block most system calls.
The latter should be done from within crosvm itself.
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com> --- host/rootfs/default.nix | 4 ++-- .../template/data/service/vhost-user-gpu/run | 24 +++++++++++++++++++++- 2 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/host/rootfs/default.nix b/host/rootfs/default.nix index ca2084f26d58be5e0e1695634e125032c50f82b2..4716bb7298515b2940cad09bb55e42c196ce7ebc 100644 --- a/host/rootfs/default.nix +++ b/host/rootfs/default.nix @@ -10,7 +10,7 @@ pkgsMusl.callPackage (
{ spectrum-host-tools, spectrum-router , lib, stdenvNoCC, nixos, runCommand, writeClosure, erofs-utils, s6-rc -, btrfs-progs, busybox, cloud-hypervisor, cosmic-files, crosvm +, btrfs-progs, bubblewrap, busybox, cloud-hypervisor, cosmic-files, crosvm , cryptsetup, dejavu_fonts, dbus, execline, foot, fuse3, iproute2 , inotify-tools, jq, kmod, mdevd, mesa, mount-flatpak, s6 , s6-linux-init, socat, systemd, util-linuxMinimal, virtiofsd @@ -25,7 +25,7 @@ let trivial;
packages = [ - btrfs-progs cloud-hypervisor cosmic-files crosvm cryptsetup dbus + btrfs-progs bubblewrap cloud-hypervisor cosmic-files crosvm cryptsetup dbus execline fuse3 inotify-tools iproute2 jq kmod mdevd mount-flatpak s6 s6-linux-init s6-rc socat spectrum-host-tools spectrum-router util-linuxMinimal virtiofsd xdg-desktop-portal-spectrum-host diff --git a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run index 0b4f6a00bc7aed0e721454d584d3bcd47fb18e2a..9b5dfad91944bd2c6c8994f387ab91394c68c1df 100755 --- a/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run +++ b/host/rootfs/image/etc/s6-linux-init/run-image/service/vm-services/template/data/service/vhost-user-gpu/run @@ -1,10 +1,32 @@ #!/bin/execlineb -P # SPDX-License-Identifier: EUPL-1.2+ # SPDX-FileCopyrightText: 2025 Alyssa Ross <hi@alyssa.is> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com>
You add a copyright line here, but not in subsequent patches. Is that on purpose?
s6-ipcserver -1a 0700 -C 1 -b 1 env/crosvm.sock
-crosvm --no-syslog device gpu +bwrap + --unshare-all + --unshare-user
--unshare-all doesn't imply --unshare-user?
+ --bind /run/user/0/wayland-1 /run/user/0/wayland-1 + --ro-bind /usr /usr + --ro-bind /lib /lib + --tmpfs /tmp + --dev /dev + --tmpfs /dev/shm + --ro-bind /nix /nix + --disable-userns + --proc /proc + --remount-ro /proc + --ro-bind /dev/null /proc/timer_list + --tmpfs /proc/scsi + --remount-ro /proc/scsi + --ro-bind /dev/null /proc/kcore + --ro-bind /dev/null /proc/sysrq-trigger + --tmpfs /proc/acpi + --remount-ro /proc/acpi + -- + crosvm --no-syslog device gpu
No indent necessary here. This is a chain-loading program like many others we use in execline scripts. We don't indent for those or the rightwards drift would be ridiculous!
--fd 0 --wayland-sock /run/user/0/wayland-1 --params "{\"context-types\":\"cross-domain\"}"