On 7/28/25 19:13, Demi Marie Obenour wrote:
> This moves various calls to mkdir(1) to very early boot, before any
> services are running.  This has two advantages:
> 
> 1. These directories are guaranteed to exist.  Code can just assume that
>    they are there without checking for them.
> 
> 2. Malicious code running as an unprivileged user cannot create
>    directories under /tmp before legitimate code has done so.
> 
> The following directories are created under /tmp:
> 
> - /tmp/.font-unix (used by obsolete X Font Server) is created with mode
>   0000.
> - The directories used by X11 are created with 1700 permissions:
>   - /tmp/.X11-unix (X server)
>   - /tmp/.ICE-unix (Inter-Client Exchange)
>   - /tmp/.XIM-unix (X Input Methods)
> - $XDG_RUNTIME_DIR (/run/user/0) is created with 0700 permissions, as
>   expected by the XDG specification.
> 
> The copyright notice for directory creation is not kept because making
> one directories with well-known names and permissions is not
> copyrightable and the code has been rewritten.
> 
> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
> ---
> Changes since v6:
> 
> - Add missing S-o-b
> - Add comments explaining why each directory needs to be created.
> - Fix spelling errors in commit messages.
> 
> Changes since v5:
> 
> - Remove "directories" service in favor of creating the directories from
>   rc.init.
> ---
>  img/app/etc/s6-linux-init/scripts/rc.init  | 13 +++++++++++++
>  img/app/etc/s6-rc/wayland-proxy-virtwl/run | 10 ----------
>  2 files changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/img/app/etc/s6-linux-init/scripts/rc.init b/img/app/etc/s6-linux-init/scripts/rc.init
> index c5a59245ff3761e94acb974edde967806fb3b234..7744286d0282bb8e0cc40973c6a6eae4c9401630 100755
> --- a/img/app/etc/s6-linux-init/scripts/rc.init
> +++ b/img/app/etc/s6-linux-init/scripts/rc.init
> @@ -1,10 +1,23 @@
>  #!/bin/execlineb -P
>  # SPDX-License-Identifier: EUPL-1.2+
>  # SPDX-FileCopyrightText: 2020-2022 Alyssa Ross <hi@alyssa.is>
> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com>
>  
>  if { s6-rc-init -c /etc/s6-rc /run/service }
>  
>  if { modprobe overlay }
>  if { mount -a --mkdir }
>  
> +# X Font Server is obsolete
> +if { mkdir -m 0000 /tmp/.font-unix }
> +
> +# /tmp/.X11-unix: X11 server
> +# /tmp/.ICE-unix: X11 Inter-Client Exchange
> +# /tmp/.XIM-unix: X11 input methods
> +# Some documentation states sticky bit is required.
> +if { mkdir -m 1700 /tmp/.X11-unix /tmp/.ICE-unix /tmp/.XIM-unix }
> +
> +# /run/user/0: "$XDG_RUNTIME_DIR"
> +if { mkdir -m 0700 /run/user/0 }
> +
>  s6-rc change ok-all
> diff --git a/img/app/etc/s6-rc/wayland-proxy-virtwl/run b/img/app/etc/s6-rc/wayland-proxy-virtwl/run
> index 0715d912953c8a1d326059dfd37c29799fcbb053..c1e0e088c789ab8c5fde7e50c9f4b856fff0e477 100755
> --- a/img/app/etc/s6-rc/wayland-proxy-virtwl/run
> +++ b/img/app/etc/s6-rc/wayland-proxy-virtwl/run
> @@ -1,16 +1,6 @@
>  #!/bin/execlineb -P
>  # SPDX-License-Identifier: EUPL-1.2+
>  # SPDX-FileCopyrightText: 2023-2024 Alyssa Ross <hi@alyssa.is>
> -#
> -# Directory creation (if it's copyrightable):
> -# SPDX-License-Identifier: MIT
> -# SPDX-FileCopyrightText: 2022 Unikie
> -
> -foreground { mkdir /tmp/.X11-unix }
> -foreground {
> -  umask 077
> -  mkdir /run/user/0
> -}
>  
>  s6-ipcserver-socketbinder -B /run/user/0/wayland-0
>  fdmove -c 3 0

Whoops, forgot to run `git config --global format.thread shallow` before sending.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)