#!/usr/bin/env bash
# policy: usr_ctl_dnshostfile — grant specific IPA users write access to
# /etc/hosts via a POSIX ACL. Default (no membership) leaves /etc/hosts at
# its normal root-only permissions — membership is what GRANTS the right,
# it does not restrict anything for non-members.
#
# Scope: /etc/hosts only, deliberately not /etc/resolv.conf. On systems using
# systemd-resolved, /etc/resolv.conf is usually a symlink to a stub file on
# tmpfs that gets regenerated on boot/network changes, so a static ACL there
# would silently vanish; covering it properly would mean resolving and
# re-applying to whatever the symlink currently targets on every run, which
# is a deliberate follow-up rather than something folded in here silently.
#
# Requires: the 'acl' package (setfacl/getfacl) on the client.
# Security note: this is a real grant, not a cosmetic one — a member can
# redirect any hostname to any IP on this machine (local DNS override), which
# is enough to locally spoof a login page or update server. Grant deliberately.

HOSTS_FILE="/etc/hosts"
DNSHOST_STATE="$STATE_DIR/dnshostfile-acl-users"
[[ -f "$DNSHOST_STATE" ]] || touch "$DNSHOST_STATE"

if ! command -v setfacl &>/dev/null; then
    warn "usr_ctl_dnshostfile: setfacl not found (install the 'acl' package) — skipping"
else
    _dnshost_grp_exists=false
    grep -qxF "usr_ctl_dnshostfile" <<< "$_ALL_USER_GROUPS" && _dnshost_grp_exists=true

    _DNSHOST_USERS=()
    if [[ "$_dnshost_grp_exists" == true ]]; then
        while IFS= read -r _u; do
            [[ -z "$_u" ]] && continue
            _DNSHOST_USERS+=("$_u")
        done < <(_ipa_group_member_users usr_ctl_dnshostfile)
    fi

    _dnshost_in_desired() {
        local n="$1"
        for _d in "${_DNSHOST_USERS[@]+"${_DNSHOST_USERS[@]}"}"; do [[ "$_d" == "$n" ]] && return 0; done
        return 1
    }

    # Grant: add an ACL entry for every currently-desired user (idempotent).
    for _u in "${_DNSHOST_USERS[@]+"${_DNSHOST_USERS[@]}"}"; do
        getent passwd "$_u" &>/dev/null || continue
        if ! getfacl "$HOSTS_FILE" 2>/dev/null | grep -qxF "user:${_u}:rw-"; then
            setfacl -m "u:${_u}:rw" "$HOSTS_FILE" \
                && log "usr_ctl_dnshostfile: granted $_u write access to $HOSTS_FILE" \
                || warn "usr_ctl_dnshostfile: setfacl grant failed for $_u"
        fi
    done

    # Revert: remove the ACL entry for anyone previously granted who is no
    # longer in the group (or the group was deleted entirely).
    _NEW_DNSHOST_STATE=()
    while IFS= read -r _old_u; do
        [[ -z "$_old_u" ]] && continue
        if _dnshost_in_desired "$_old_u"; then
            _NEW_DNSHOST_STATE+=("$_old_u")
        else
            setfacl -x "u:${_old_u}" "$HOSTS_FILE" 2>/dev/null \
                && log "usr_ctl_dnshostfile: revoked $_old_u write access to $HOSTS_FILE"
        fi
    done < "$DNSHOST_STATE"

    if [[ ${#_DNSHOST_USERS[@]} -gt 0 ]]; then
        printf '%s\n' "${_DNSHOST_USERS[@]}" | sort -u > "$DNSHOST_STATE"
    else
        > "$DNSHOST_STATE"
    fi
    unset _dnshost_grp_exists _DNSHOST_USERS _u _NEW_DNSHOST_STATE _old_u
fi