#!/bin/bash
#
# Copyright Security Onion Solutions LLC and/or licensed to Security Onion Solutions LLC under one
# or more contributor license agreements. Licensed under the Elastic License 2.0 as shown at
# https://securityonion.net/license; you may not use this file except in compliance with the
# Elastic License 2.0.
#
# so-kernel-upgrade — install the UEK8 (6.x) kernel and make it the boot default.
#
# Security Onion is moving off the EL9 stock kernel (RHCK, 5.14) and UEK7 (5.15) onto UEK8
# (6.x). Three things have to happen, and the tool has to drive each one:
#
#   1. Populate. The manager mirrors the UEK8 packages into /nsm/kernelrepo via so-repo-sync,
#      and serves them to the grid over https://<manager>/kernelrepo. Until that sync runs the
#      repo is valid but EMPTY -- dnf resolves it happily and installs nothing, with no error.
#   2. Install. A node on RHCK has no kernel-uek* package at all, so there is nothing for
#      'dnf update' to upgrade. A node on UEK7 does have kernel-uek installed, so
#      'dnf install kernel-uek' reports "Nothing to do" and exits 0 without installing 6.x.
#      Both cases need an explicit install of the UEK8 NEVRA.
#   3. Boot it. Whether a newly installed UEK8 kernel becomes the boot default depends on the
#      RUNNING kernel's flavor. kernel-install/grubby (with UPDATEDEFAULT=yes) only auto-promote
#      within the running kernel's flavor lineage:
#        - From UEK7 (5.x, kernel-uek) the install stays in the kernel-uek lineage and IS
#          auto-promoted, so no grubby change is needed -- just make sure the repo is populated
#          and install UEK8.
#        - From the stock EL9 kernel (RHCK, 5.14, no UEK) it is a flavor CROSS that is NOT
#          auto-promoted, so the box keeps booting RHCK until grubby is told otherwise.
#      This tool inspects the running kernel and only runs 'grubby --set-default' for RHCK.
#
# Every one of those failure modes is silent by default. This tool handles each case and fails
# loudly when it cannot, rather than reporting success while changing nothing.
#
# Manager vs minion: only the manager owns /nsm/kernelrepo, so only the manager can populate
# it. If the repo is empty here, a manager runs so-repo-sync itself; a minion has no way to
# fix it and exits non-zero telling the admin to sync the manager first.
#
# Idempotent: an already-installed, already-default UEK8 kernel is left alone. It only sets
# the boot default; it does NOT reboot -- the admin reboots the node on their own schedule.

. /usr/sbin/so-common

# Client-side repo id (what dnf enables on this node, from repo/client/oracle.sls) vs the
# reposync-side section in repodownload.conf that the manager mirrors from (mirrors the
# securityonion/securityonionsync split for the main repo).
KERNEL_REPO="securityonionkernel"
KERNEL_REPO_SYNC="securityonionkernelsync"
KERNEL_PKG="kernel-uek"
KERNEL_REPO_DIR="/nsm/kernelrepo"
REPOSYNC_CONF="/opt/so/conf/reposync/repodownload.conf"
GLOBAL_PILLAR="/opt/so/saltstack/local/pillar/global/soc_global.sls"

log() { echo "[so-kernel-upgrade] $*"; }
die() { echo "[so-kernel-upgrade] ERROR: $*" >&2; exit 1; }

command -v grubby >/dev/null 2>&1 || die "grubby not found"
command -v dnf >/dev/null 2>&1 || die "dnf not found"

ARCH="$(rpm -E '%{_arch}')"

is_airgap() {
    [ -f "$GLOBAL_PILLAR" ] && grep -q 'airgap: *[Tt]rue' "$GLOBAL_PILLAR"
}

# Newest installed UEK8 (6.x) kernel known to the bootloader. UEK8 vmlinuz paths look like
# /boot/vmlinuz-6.12.0-204.92.4.2.el9uek.x86_64; UEK7 (5.15) and RHCK (5.14) won't match.
find_uek8() {
    grubby --info=ALL 2>/dev/null \
        | sed -n 's/^kernel="\(.*\)"$/\1/p' \
        | grep -E '/vmlinuz-6\.[0-9]+.*uek' \
        | sort -V | tail -1
}

# Classify the RUNNING kernel (uname -r) -- this, not what's installed, is what decides whether
# a UEK8 install auto-promotes to the boot default:
#   uek8  6.x UEK    already on the target line; nothing to do
#   uek7  5.x UEK    a UEK8 install stays in the kernel-uek lineage and auto-promotes (no grubby)
#   rhck  5.14 EL9   crossing into the UEK flavor does NOT auto-promote (needs grubby --set-default)
running_flavor() {
    case "$(uname -r)" in
        6.*uek*) echo uek8 ;;
        *uek*)   echo uek7 ;;
        *)       echo rhck ;;
    esac
}

# Newest UEK8 kernel-uek NEVRA offered by the kernel repo, empty if the repo has none.
# Restricted to the kernel repo so a UEK7 kernel-uek in the main repo can't be picked up,
# and filtered to 6.x so we never "succeed" by reinstalling the 5.15 we already have.
uek8_available() {
    dnf -q repoquery --disablerepo='*' --enablerepo="$KERNEL_REPO" \
        --arch="$ARCH" --latest-limit=1 \
        --qf '%{name}-%{evr}.%{arch}\n' "$KERNEL_PKG" 2>/dev/null \
        | grep -E "^${KERNEL_PKG}-6\." | tail -1
}

kernelrepo_rpm_count() {
    find "$KERNEL_REPO_DIR" -maxdepth 1 -name '*.rpm' 2>/dev/null | wc -l
}

# The kernel repo starts life as valid-but-empty (kernelrepo_init_empty in
# salt/manager/init.sls) and is filled by so-repo-sync. During a soup, so-repo-sync runs
# BEFORE the highstate deploys the [securityonionkernelsync] section into repodownload.conf, so
# the first kernel-aware soup leaves the repo empty until the next nightly sync.
sync_kernel_repo() {
    if is_airgap; then
        log "airgap install: $KERNEL_REPO_DIR is populated from the airgap ISO, not by so-repo-sync."
        return 1
    fi
    if ! grep -q "^\[${KERNEL_REPO_SYNC}\]" "$REPOSYNC_CONF" 2>/dev/null; then
        log "$REPOSYNC_CONF has no [${KERNEL_REPO_SYNC}] section -- run a highstate to deploy it."
        return 1
    fi

    log "populating $KERNEL_REPO_DIR with so-repo-sync (mirrors upstream; can take several minutes)"
    su socore -c '/usr/sbin/so-repo-sync' || { log "so-repo-sync failed"; return 1; }

    dnf -q clean expire-cache >/dev/null 2>&1
    return 0
}

# Make the kernel repo actually able to serve a UEK8 package, or fail trying.
ensure_kernel_repo() {
    # The repo is assigned by the repo.client highstate, and only once NICs are pinned by MAC
    # (/opt/so/state/nic_names_pinned) so the kernel swap can't renumber interfaces SO binds
    # by name. skip_if_unavailable=1 means a broken repo is silently ignored, so check first.
    if ! dnf -q repolist --enabled 2>/dev/null | awk '{print $1}' | grep -qx "$KERNEL_REPO"; then
        log "repo '$KERNEL_REPO' is not enabled on this node."
        log "Run a highstate first; the repo is skipped until /opt/so/state/nic_names_pinned"
        log "exists (run so-nic-pin) and this node's salt matches the version this release ships."
        die "kernel repo unavailable"
    fi

    [ -n "$(uek8_available)" ] && return 0

    log "repo '$KERNEL_REPO' is enabled but offers no UEK8 $KERNEL_PKG package"

    if ! is_manager_node; then
        log "This is a minion; it consumes the kernel repo from the manager and cannot populate it."
        log "On the manager, run:  su socore -c /usr/sbin/so-repo-sync"
        log "then re-run this script here."
        die "manager's kernel repo is empty"
    fi

    log "this is a manager and $KERNEL_REPO_DIR holds $(kernelrepo_rpm_count) rpm(s)"
    sync_kernel_repo || die "could not populate $KERNEL_REPO_DIR"

    [ -n "$(uek8_available)" ] \
        || die "so-repo-sync completed but $KERNEL_REPO still offers no UEK8 $KERNEL_PKG"
}

reboot_notice() {
    [ "$(uname -r)" = "$(basename "$1" | sed 's/^vmlinuz-//')" ] \
        || log "REBOOT REQUIRED to start using the UEK8 kernel (currently running $(uname -r))."
}

# Keep future kernel updates on the UEK line rather than falling back to RHCK. Oracle ships
# /etc/sysconfig/kernel; only rewrite it when it's actually pointing somewhere else.
set_default_kernel_conf() {
    if [ -f /etc/sysconfig/kernel ] && ! grep -q '^DEFAULTKERNEL=kernel-uek-core$' /etc/sysconfig/kernel; then
        log "setting DEFAULTKERNEL=kernel-uek-core in /etc/sysconfig/kernel"
        sed -i 's/^DEFAULTKERNEL=.*/DEFAULTKERNEL=kernel-uek-core/' /etc/sysconfig/kernel
    fi
}

# Make sure a UEK8 kernel is installed, leaving its boot entry in INSTALLED_UEK8. If one is
# already present we leave the repo alone -- it may be disabled or empty and we don't need it
# just to flip the boot default. Otherwise install the explicit NEVRA, not the bare package
# name: on a UEK7 node 'dnf install kernel-uek' sees 5.15 already present, prints "Nothing to
# do" and exits 0 without installing 6.x.
ensure_uek8_installed() {
    INSTALLED_UEK8="$(find_uek8)"
    if [ -n "$INSTALLED_UEK8" ]; then
        log "UEK8 kernel already installed: $INSTALLED_UEK8"
        return 0
    fi

    ensure_kernel_repo
    local nevra; nevra="$(uek8_available)"
    log "installing $nevra from $KERNEL_REPO"
    dnf -y install "$nevra" || die "failed to install $nevra"

    INSTALLED_UEK8="$(find_uek8)"
    [ -n "$INSTALLED_UEK8" ] || die "$nevra installed but no 6.x UEK boot entry appeared -- check 'grubby --info=ALL'"
    log "installed UEK8 kernel: $INSTALLED_UEK8"
}

case "$(running_flavor)" in
uek8)
    # Already on the 6.x UEK line. A plain 'dnf update' keeps this node current within the
    # lineage and auto-promotes newer builds, so there is nothing for this tool to do.
    log "already running a UEK8 kernel ($(uname -r)); nothing to do."
    exit 0
    ;;

uek7)
    # On a 5.x UEK kernel. Installing UEK8 stays inside the kernel-uek lineage, so dnf/grubby
    # (UPDATEDEFAULT=yes) auto-promote it and we do NOT touch grubby. A node still on UEK7
    # usually means the kernel repo was empty when it last updated, so populate it and install.
    log "running UEK7 kernel ($(uname -r)); the kernel repo was likely not yet populated when"
    log "this node last updated. Populating it and installing UEK8 -- the update stays on the"
    log "kernel-uek line, so it becomes the boot default automatically (no grubby change needed)."
    set_default_kernel_conf
    ensure_uek8_installed

    now="$(grubby --default-kernel 2>/dev/null)"
    if [ "$now" = "$INSTALLED_UEK8" ]; then
        log "boot default auto-promoted to UEK8 kernel: $INSTALLED_UEK8"
    else
        log "WARNING: expected the UEK8 kernel to auto-promote but the default is still"
        log "'${now:-unknown}'. Run 'grubby --set-default=$INSTALLED_UEK8' to force it."
    fi
    reboot_notice "$INSTALLED_UEK8"
    ;;

rhck)
    # On the stock EL9 kernel (5.14, no UEK installed). Crossing from RHCK into the UEK flavor
    # does NOT auto-promote -- kernel-install/grubby only auto-promote within the running
    # kernel's flavor lineage -- so after installing we must set the boot default explicitly.
    log "running stock EL9 (RHCK) kernel ($(uname -r)); installing UEK8 and setting it as the"
    log "boot default explicitly (a RHCK->UEK flavor change does not auto-promote)."
    set_default_kernel_conf
    ensure_uek8_installed
    target="$INSTALLED_UEK8"

    current="$(grubby --default-kernel 2>/dev/null)"
    if [ "$current" = "$target" ]; then
        log "UEK8 kernel is already the boot default: $target"
        reboot_notice "$target"
        exit 0
    fi

    log "current default kernel: ${current:-unknown}"
    log "switching boot default to UEK8 kernel: $target"
    grubby --set-default="$target" || die "grubby --set-default failed for $target"

    # Verify the change actually took before claiming success.
    now="$(grubby --default-kernel 2>/dev/null)"
    [ "$now" = "$target" ] || die "default kernel is still '${now:-unknown}' after set-default"

    log "boot default is now $target"
    reboot_notice "$target"
    ;;
esac