main/modules/05-create-user.sh

#!/usr/bin/env bash
# 05-create-user — create a daily-driver sudo user when running as direct root.
#
# Why this exists: `makepkg` (yay / AUR) refuses to run as root. On a fresh VPS
# that lands you in as root with no SUDO_USER, we create a non-root sudoer,
# copy root's authorized_keys to it, configure passwordless sudo with
# !tty_tickets + a long timestamp_timeout, and retarget the config steps
# (zsh, nvim, nvm, docker group) at that user's $HOME.
#
# Behaviour:
#   - Not root                            -> skip (you're already a normal user).
#   - Root + SUDO_USER set                -> skip (you sudoed in; that user is the target).
#   - Root + no SUDO_USER + Arch          -> auto-create (AUR needs it), confirm name.
#   - Root + no SUDO_USER + Debian/Ubuntu -> ask y/N (optional, apt works as root).
#   - --create-user flag                  -> force prompt regardless.
#   - --username NAME                     -> override default name, no prompt.
#   - --yes (no --username)               -> default to 'mk' silently (no stall).
#
# Passwordless, no user password (NOPASSWD). Idempotent: re-runs re-sync
# authorized_keys + sudoers rather than failing.

step_name="create-user"
step_desc="create a sudo user (passwordless) + copy root's ssh keys + retarget config"
step_run="run_create_user"

run_create_user() {
  log "create-user step"

  # not root -> nothing to do, target stays as current user
  if (( EUID != 0 )); then
    echo "  not root — target stays $USER ($HOME)"
    export TARGET_USER="$USER" TARGET_HOME="$HOME"
    return
  fi

  # root but came in via sudo -> use that invoking user, don't create a new one
  if [[ -z "${SUDO_USER:-}" ]]; then _handle_direct_root; else _handle_sudoed_root; fi
}

# ── direct root (logged in as root; the case that actually needs a new user) ─
_handle_direct_root() {
  local should_create=0

  if (( CREATE_USER )) || [[ -n "${USERNAME_ARG:-}" ]]; then
    [[ -n "${USERNAME_ARG:-}" ]] && log "--username given: forcing user creation"
    should_create=1
  elif [[ "$DISTRO" == "arch" ]]; then
    # AUR/makepkg cannot run as root — we genuinely need a non-root sudoer.
    echo "  running as direct root on Arch: a non-root sudoer is needed for yay/AUR."
    yn "Create a sudo user now? (recommended)" y && should_create=1
  else
    # Debian/Ubuntu: apt works as root, so this is convenience (key-first login).
    yn "Create a daily-driver sudo user? (optional — apt works as root)" n && should_create=1
  fi

  if (( ! should_create )); then
    echo "  skipping user creation — config will target root ($HOME)"
    warn "on Arch you won't be able to build AUR packages (yay/angie) as root"
    export TARGET_USER="root" TARGET_HOME="$HOME"
    return
  fi

  local user="${USERNAME_ARG:-}"
  if [[ -z "$user" ]]; then
    local default="mk"
    read -rp "  username [$default]: " user
    [[ -z "$user" ]] && user="$default"
  fi

  _create_or_sync_user "$user"
}

# ── root via sudo: use the invoking user, don't create another ───────────────
_handle_sudoed_root() {
  local user="$SUDO_USER"
  local home; home="$(getent passwd "$user" | cut -d: -f6)"
  log "running as root via sudo — using invoking user '$user' as target"
  # ensure they have passwordless sudo + the ssh key + sudo group, then retarget
  _create_or_sync_user "$user" skip_create
  export TARGET_USER="$user" TARGET_HOME="$home"
}

# ── the meat: create if missing, sync sudoers, sync authorized_keys ──────────
_create_or_sync_user() { # username [skip_create]
  local user="$1"
  local skip_create="${2:-}"

  if [[ "$skip_create" != "skip_create" ]]; then
    if id "$user" >/dev/null 2>&1; then
      ok "user '$user' already exists — syncing config only"
    else
      local shell_bin; shell_bin="$(command -v zsh 2>/dev/null || echo /bin/bash)"
      local groups
      case "$DISTRO" in
        arch)   groups="wheel" ;;
        debian) groups="sudo,adm" ;;
      esac
      log "creating user '$user' (shell=$shell_bin, groups=$groups)"
      useradd -m -s "$shell_bin" -G "$groups" "$user"
      # passwordless account: clear the password field entirely
      passwd -d "$user" >/dev/null 2>&1 || true
      # unlock the account so SSH key login still works after passwd -d
      usermod -p "" "$user" 2>/dev/null || true
      ok "user '$user' created (no password set; ssh-key login only)"
    fi
  fi

  local home; home="$(getent passwd "$user" | cut -d: -f6)"

  _sync_authorized_keys "$user" "$home"
  _install_sudoers "$user"

  export TARGET_USER="$user" TARGET_HOME="$home"
  ok "config target retargeted: user=$user home=$home"
}

# ── copy root's authorized_keys to the target user (idempotent) ──────────────
_sync_authorized_keys() { # user home
  local user="$1" home="$2"
  local src="/root/.ssh/authorized_keys"
  if [[ ! -f "$src" ]]; then
    warn "no /root/.ssh/authorized_keys — add your key manually:"
    echo "  install -d -m 700 -o $user -g $user $home/.ssh"
    echo "  # then: paste your pubkey into $home/.ssh/authorized_keys (chmod 600)"
    return
  fi
  install -d -m 700 -o "$user" -g "$user" "$home/.ssh"
  install -m 600 -o "$user" -g "$user" "$src" "$home/.ssh/authorized_keys"
  local n; n=$(grep -cE '^[^#]' "$src" 2>/dev/null || echo 0)
  ok "copied $n authorized key(s) to $home/.ssh/authorized_keys"
  warn "sanity-check these are YOUR keys (fingerprints):"
  ssh-keygen -lf "$src" 2>/dev/null | sed 's/^/    /' || true
}

# ── write /etc/sudoers.d/<user>: NOPASSWD, !tty_tickets, 7-day cache ─────────
_install_sudoers() { # user
  local user="$1" file="/etc/sudoers.d/${user}"
  log "configuring sudoers for '$user' (passwordless, !tty_tickets, 7d timeout)"
  # write to a temp, validate with visudo -c, then move into place atomically
  local tmp; tmp="$(mktemp)"
  cat > "$tmp" <<EOF
# managed by bootstrap — passwordless sudo for $user
Defaults:$user !tty_tickets
Defaults:$user timestamp_timeout=10080
$user ALL=(ALL) NOPASSWD:ALL
EOF
  # visudo must see proper perms (0440) to be happy
  chmod 0440 "$tmp"
  if visudo -cf "$tmp" >/dev/null 2>&1; then
    install -m 0440 -o root -g root "$tmp" "$file"
    ok "sudoers installed: $file"
  else
    err "visudo -c rejected the sudoers snippet — NOT installed, inspect aborted"
    cat "$tmp" | sed 's/^/  /'
  fi
  rm -f "$tmp"
}