fix(docker): run hostexec as container user

.changeset/hostexec-container-user.md

@@ -0,0 +1,5 @@
+---
+"@jmfederico/pi-web": patch
+---
+
+Run Docker host command bridge commands as the PI WEB container user by default, with `hostexec --root` for administrative commands.

docker/README.md

@@ -16,7 +16,7 @@ By design, the runtime containers get deliberate host access so PI WEB agents ca
 - `/var/run/docker.sock` is mounted into the containers. The Docker socket is root-equivalent on the host.
 - `/srv`, `/opt`, and `/home` are mounted read/write.
 - `/` is mounted read-only at `/host` for inspection.
-- `hostexec` can start a temporary privileged helper container and run explicit commands in the host namespaces.
+- `hostexec` can start a temporary privileged helper container and run explicit commands in the host namespaces. Commands run as the container user by default, and `hostexec --root` can still run explicit administrative commands as root.
 
 Only install this on machines where the PI WEB user, the selected workspaces, and the browser/API clients are trusted. Review scripts before piping them to `sh` if you do not already trust this repository.
 
@@ -150,16 +150,16 @@ If you use a reverse proxy, keep the container bound to localhost or a private a
 
 ## `hostexec` examples
 
-`hostexec <command...>` is the only host command bridge provided by this Docker setup. It intentionally does not abstract package managers or detect distributions.
+`hostexec [--root] <command...>` is the only host command bridge provided by this Docker setup. It intentionally does not abstract package managers or detect distributions. By default, commands run as the same numeric user/group as the PI WEB container. Use `--root` only for administrative host commands.
 
 Run it from a PI WEB session, a PI WEB terminal, or by execing into the runtime container:
 
 ```bash
 hostexec uname -a
 hostexec systemctl status docker
-hostexec zypper refresh
-hostexec sh -lc 'zypper refresh && zypper dup -y'
-hostexec apt-get update
+hostexec --root zypper refresh
+hostexec --root sh -lc 'zypper refresh && zypper dup -y'
+hostexec --root apt-get update
 ```
 
 From the host shell, for a quick smoke test:
@@ -169,7 +169,7 @@ cd ~/.local/share/pi-web-docker
 docker compose exec web hostexec uname -a
 ```
 
-`hostexec` starts a temporary privileged helper container through the mounted Docker socket, enters the host namespaces with `nsenter`, and runs exactly the command you passed. Treat it like running a privileged host command.
+`hostexec` starts a temporary privileged helper container through the mounted Docker socket, enters the host namespaces with `nsenter`, and runs exactly the command you passed. Treat it like privileged host access even when the final command drops back to the container user.
 
 ## Development Docker setup
 

docker/bin/hostexec

@@ -3,13 +3,36 @@ set -euo pipefail
 
 usage() {
   cat >&2 <<'EOF'
-Usage: hostexec <command...>
+Usage: hostexec [--root] [--] <command...>
 
 Run a command on the Docker host by starting a temporary privileged helper
 container through the mounted Docker socket and entering the host namespaces.
+Commands run as the current container UID/GID by default. Use --root to keep
+root privileges for administrative host commands.
 EOF
 }
 
+run_as_root=false
+while [ "$#" -gt 0 ]; do
+  case "$1" in
+    --root)
+      run_as_root=true
+      shift
+      ;;
+    --help|-h)
+      usage
+      exit 0
+      ;;
+    --)
+      shift
+      break
+      ;;
+    *)
+      break
+      ;;
+  esac
+done
+
 if [ "$#" -eq 0 ]; then
   usage
   exit 64
@@ -30,19 +53,71 @@ if [[ "$docker_host" == unix://* ]]; then
 fi
 
 helper_image="${HOSTEXEC_IMAGE:-alpine:3.22}"
+target_uid="$(id -u)"
+target_gid="$(id -g)"
 tty_args=(--interactive)
 if [ -t 0 ] && [ -t 1 ]; then
   tty_args+=(--tty)
 fi
 
+docker_args=(
+  --rm
+  "${tty_args[@]}"
+  --pull=missing
+  --privileged
+  --security-opt label=disable
+  --pid=host
+  --network=host
+  --volume /:/host:rw
+)
+
+if [ "$run_as_root" = true ] || { [ "$target_uid" = 0 ] && [ "$target_gid" = 0 ]; }; then
+  exec docker run \
+    "${docker_args[@]}" \
+    "$helper_image" \
+    nsenter -t 1 -m -u -i -n -p -- "$@"
+fi
+
+run_as_container_user='target_uid="${HOSTEXEC_TARGET_UID:?}"
+target_gid="${HOSTEXEC_TARGET_GID:?}"
+
+target_user=""
+if command -v getent >/dev/null 2>&1; then
+  passwd_entry="$(getent passwd "$target_uid" || true)"
+  if [ -n "$passwd_entry" ]; then
+    target_user="${passwd_entry%%:*}"
+  fi
+fi
+
+if [ -n "$target_user" ]; then
+  if command -v runuser >/dev/null 2>&1; then
+    exec runuser -u "$target_user" -- "$@"
+  fi
+
+  if command -v su >/dev/null 2>&1; then
+    exec su -s /bin/sh -c '\''exec "$@"'\'' -- "$target_user" hostexec-su "$@"
+  fi
+fi
+
+if command -v setpriv >/dev/null 2>&1; then
+  if [ -n "$target_user" ]; then
+    exec setpriv --reuid "$target_uid" --regid "$target_gid" --init-groups -- "$@"
+  fi
+
+  exec setpriv --reuid "$target_uid" --regid "$target_gid" --clear-groups -- "$@"
+fi
+
+if command -v nsenter >/dev/null 2>&1; then
+  exec nsenter -t 1 -m -u -i -n -p -S "$target_uid" -G "$target_gid" -- "$@"
+fi
+
+echo "hostexec: unable to switch to host uid:gid $target_uid:$target_gid" >&2
+exit 69
+'
+
 exec docker run \
-  --rm \
-  "${tty_args[@]}" \
-  --pull=missing \
-  --privileged \
-  --security-opt label=disable \
-  --pid=host \
-  --network=host \
-  --volume /:/host:rw \
+  "${docker_args[@]}" \
+  --env HOSTEXEC_TARGET_UID="$target_uid" \
+  --env HOSTEXEC_TARGET_GID="$target_gid" \
   "$helper_image" \
-  nsenter -t 1 -m -u -i -n -p -- "$@"
+  nsenter -t 1 -m -u -i -n -p -- /bin/sh -c "$run_as_container_user" hostexec-user "$@"