Drop privileges when seeding Dell haptic config (#497)

The root-run package hook changed ownership of paths below a
user-controlled home directory. A config symlink could redirect chown to
an arbitrary root-owned file during installation or upgrade.

Run the config writer as the target desktop user and remove the privileged
ownership changes. This also prevents the missing-config path from writing
through a user-controlled pathname as root. Add regression coverage and
bump the package release.

Reported-by: piratemoo (Esther) <22439214+piratemoo@users.noreply.github.com>
Link: https://github.com/piratemoo/Arbitrary-File-Ownership-Change-via-Symlink-LPE

.github/workflows/test.yml

@@ -45,6 +45,7 @@ jobs:
               ./bin/sync-rebuilds --self-test
               ./bin/omarchy-pkgs self-test
               ./bin/omarchy-release self-test
+              ./tests/dell-xps-touchpad-haptics-install.sh
               ./tests/partial-release.sh
               ./tests/published-build-plan.sh
             '

pkgbuilds/dell-xps-touchpad-haptics/PKGBUILD

@@ -2,7 +2,7 @@
 
 pkgname=dell-xps-touchpad-haptics
 pkgver=1.0.0
-pkgrel=3
+pkgrel=4
 pkgdesc="Synaptics haptic touchpad presets for Dell XPS on Omarchy"
 arch=('x86_64')
 url="https://github.com/omacom-io/omarchy-pkgs"

pkgbuilds/dell-xps-touchpad-haptics/dell-xps-touchpad-haptics.install

@@ -3,6 +3,7 @@ _default_level="high"
 _env_path="/etc/dell-xps-touchpad-haptics.env"
 _legacy_env_path="/etc/omarchy-dell-haptic-touchpad.env"
 _legacy_override_dir="/etc/systemd/system/dell-xps-haptic-touchpad.service.d"
+_runuser_path="/usr/bin/runuser"
 
 _existing_home() {
   local line value
@@ -124,18 +125,13 @@ _ensure_user_config() {
   local config_dir="$home/.config/omarchy"
   local config_path="$config_dir/dell-haptic.conf"
 
-  if [[ ! -f $config_path ]] && ! env HOME="$home" USER="$user" LOGNAME="$user" \
+  if [[ ! -f $config_path ]] && ! "$_runuser_path" --user "$user" -- \
+    /usr/bin/env HOME="$home" USER="$user" LOGNAME="$user" \
     /usr/bin/dell-xps-touchpad-haptics set "$_default_level"; then
     echo ":: Failed to create ${config_path} for user '$user'." >&2
     return 1
   fi
 
-  if [[ -f $config_path ]]; then
-    chown "$user:$user" "$home/.config" 2>/dev/null || true
-    chown "$user:$user" "$config_dir" 2>/dev/null || true
-    chown "$user:$user" "$config_path" 2>/dev/null || true
-  fi
-
   return 0
 }
 

tests/dell-xps-touchpad-haptics-install.sh

@@ -0,0 +1,53 @@
+#!/bin/bash
+set -euo pipefail
+
+REPO_ROOT=$(realpath "${BASH_SOURCE[0]%/*}/..")
+INSTALL_SCRIPT="$REPO_ROOT/pkgbuilds/dell-xps-touchpad-haptics/dell-xps-touchpad-haptics.install"
+TEST_ROOT=$(mktemp -d)
+trap 'rm -rf "$TEST_ROOT"' EXIT
+
+# shellcheck source=/dev/null
+source "$INSTALL_SCRIPT"
+
+home="$TEST_ROOT/home"
+config_dir="$home/.config/omarchy"
+config_path="$config_dir/dell-haptic.conf"
+protected_file="$TEST_ROOT/protected"
+runuser_call="$TEST_ROOT/runuser-call"
+chown_call="$TEST_ROOT/chown-call"
+runuser_stub="$TEST_ROOT/runuser"
+mkdir -p "$config_dir"
+printf 'must remain unchanged\n' >"$protected_file"
+ln -s "$protected_file" "$config_path"
+
+chown() {
+  printf '%s\n' "$*" >>"$chown_call"
+}
+
+_ensure_user_config test-user "$home"
+[[ ! -e $chown_call ]]
+[[ ! -e $runuser_call ]]
+[[ $(cat "$protected_file") == 'must remain unchanged' ]]
+
+rm "$config_path"
+printf '%s\n' \
+  '#!/bin/bash' \
+  'set -euo pipefail' \
+  '[[ $1 == --user && $2 == test-user && $3 == -- && $4 == /usr/bin/env ]]' \
+  '[[ $5 == "HOME=$EXPECTED_HOME" && $6 == USER=test-user && $7 == LOGNAME=test-user ]]' \
+  '[[ $8 == /usr/bin/dell-xps-touchpad-haptics && $9 == set && ${10} == high ]]' \
+  'printf "%s\n" "$*" >>"$RUNUSER_CALL"' \
+  'printf "INTENSITY=100\n" >"$EXPECTED_CONFIG"' >"$runuser_stub"
+chmod +x "$runuser_stub"
+export EXPECTED_HOME="$home"
+export EXPECTED_CONFIG="$config_path"
+export RUNUSER_CALL="$runuser_call"
+_runuser_path="$runuser_stub"
+
+_ensure_user_config test-user "$home"
+[[ ! -e $chown_call ]]
+[[ -f $config_path && ! -L $config_path ]]
+[[ $(cat "$config_path") == 'INTENSITY=100' ]]
+grep -q '^--user test-user -- /usr/bin/env ' "$runuser_call"
+
+echo 'PASS: user config creation drops privileges and never chowns symlink targets'