From 116c83ce93baef7ccbb3d55d5d142fc844667459 Mon Sep 17 00:00:00 2001
From: Jonathan Lebon <jonathan@jlebon.com>
Date: Wed, 3 Nov 2021 12:23:32 -0400
Subject: [PATCH] 15fcos: add 35coreos-iptables dracut module

This implements the proposal agreed upon in:
https://github.com/coreos/fedora-coreos-tracker/issues/676

On first boot and subsequent boots, we look for
`/etc/fedora-coreos/iptables-legacy.stamp`. If found, we move the system
back to iptables-legacy. If any modifications already exist to the
configuration, we do nothing.
---
 .../coreos-enable-iptables-legacy.service     | 19 ++++++
 .../coreos-enable-iptables-legacy.sh          | 62 +++++++++++++++++++
 .../35coreos-iptables/module-setup.sh         | 17 +++++
 tests/kola/firewall/iptables-legacy/config.bu | 28 +++++++++
 .../test.sh}                                  |  7 +--
 tests/kola/firewall/iptables-nft/test.sh      | 18 ++++++
 6 files changed, 147 insertions(+), 4 deletions(-)
 create mode 100644 overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/coreos-enable-iptables-legacy.service
 create mode 100755 overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/coreos-enable-iptables-legacy.sh
 create mode 100644 overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/module-setup.sh
 create mode 100644 tests/kola/firewall/iptables-legacy/config.bu
 rename tests/kola/firewall/{iptables-legacy => iptables-legacy/test.sh} (69%)
 create mode 100755 tests/kola/firewall/iptables-nft/test.sh

diff --git a/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/coreos-enable-iptables-legacy.service b/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/coreos-enable-iptables-legacy.service
new file mode 100644
index 0000000000..1df5092224
--- /dev/null
+++ b/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/coreos-enable-iptables-legacy.service
@@ -0,0 +1,19 @@
+[Unit]
+Description=CoreOS Enable iptables-legacy
+ConditionPathExists=/etc/initrd-release
+DefaultDependencies=false
+ConditionPathExists=/sysroot/etc/coreos/iptables-legacy.stamp
+ConditionKernelCommandLine=!ignition.firstboot
+
+# On first boot, allow Ignition config to install stamp file.
+After=ignition-files.service
+
+# On subsequent boots, just make sure the deployment is accessible.
+After=ostree-prepare-root.service
+
+Before=initrd.target
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/sbin/coreos-enable-iptables-legacy
diff --git a/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/coreos-enable-iptables-legacy.sh b/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/coreos-enable-iptables-legacy.sh
new file mode 100755
index 0000000000..547a275473
--- /dev/null
+++ b/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/coreos-enable-iptables-legacy.sh
@@ -0,0 +1,62 @@
+#!/bin/bash
+set -euo pipefail
+
+declare -A SYMLINKS=(
+    [ip6tables]=ip6tables-legacy
+    [ip6tables-restore]=ip6tables-legacy-restore
+    [ip6tables-save]=ip6tables-legacy-save
+    [iptables]=iptables-legacy
+    [iptables-restore]=iptables-legacy-restore
+    [iptables-save]=iptables-legacy-save
+)
+
+# sanity-check the stamp file is present
+if [ ! -e /sysroot/etc/coreos/iptables-legacy.stamp ]; then
+    exit 0
+fi
+
+# if legacy doesn't exist on the host anymore, do nothing
+for legacy in "${SYMLINKS[@]}"; do
+    path=/sysroot/usr/sbin/$legacy
+    if [ ! -e "$path" ]; then
+        echo "Executable $path no longer present; exiting."
+        exit 0
+    fi
+done
+
+symlink_is_default() {
+    local symlink=$1; shift
+    # check that the deployment is still using the symlink (i.e. the user didn't
+    # do something funky), and that the OSTree default is still symlink-based
+    # (i.e. that we didn't change strategy and forgot to update this script)
+    if [ ! -L "/sysroot/$symlink" ] || [ ! -L "/sysroot/usr/$symlink" ]; then
+        return 1
+    fi
+    # compare symlink targets between deployment and OSTree default
+    if [ "$(readlink "/sysroot/$symlink")" != "$(readlink "/sysroot/usr/$symlink")" ]; then
+        return 1
+    fi
+}
+
+# If there are any modifications to the symlinks, do nothing. This is basically
+# like `ostree admin config-diff` but more focused and lighter/safer than doing
+# a bwrap call and grepping output.
+for symlink in "${!SYMLINKS[@]}"; do
+    symlink=/etc/alternatives/$symlink
+    if ! symlink_is_default "$symlink"; then
+        echo "Symlink $symlink is not default; exiting without modifying."
+        exit 0
+    fi
+done
+
+# Update symlinks for legacy backend!
+for symlink in "${!SYMLINKS[@]}"; do
+    target=${SYMLINKS[$symlink]}
+    symlink=/etc/alternatives/$symlink
+    ln -vsf "/usr/sbin/$target" "/sysroot/$symlink"
+    # symlink labels don't matter, but relabel to appease unlabeled_t scanners
+    coreos-relabel "$symlink"
+done
+
+rm /sysroot/etc/coreos/iptables-legacy.stamp
+echo "Updated /sysroot to use iptables-legacy."
diff --git a/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/module-setup.sh b/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/module-setup.sh
new file mode 100644
index 0000000000..677f3f6188
--- /dev/null
+++ b/overlay.d/15fcos/usr/lib/dracut/modules.d/35coreos-iptables/module-setup.sh
@@ -0,0 +1,17 @@
+install_and_enable_unit() {
+    unit="$1"; shift
+    target="$1"; shift
+    inst_simple "$moddir/$unit" "$systemdsystemunitdir/$unit"
+    # note we `|| exit 1` here so we error out if e.g. the units are missing
+    # see https://github.com/coreos/fedora-coreos-config/issues/799
+    systemctl -q --root="$initdir" add-requires "$target" "$unit" || exit 1
+}
+
+install() {
+    inst_simple readlink
+
+    inst_simple "$moddir/coreos-enable-iptables-legacy.sh" \
+        "/usr/sbin/coreos-enable-iptables-legacy"
+    install_and_enable_unit "coreos-enable-iptables-legacy.service" \
+        "initrd.target"
+}
diff --git a/tests/kola/firewall/iptables-legacy/config.bu b/tests/kola/firewall/iptables-legacy/config.bu
new file mode 100644
index 0000000000..c7092c4022
--- /dev/null
+++ b/tests/kola/firewall/iptables-legacy/config.bu
@@ -0,0 +1,28 @@
+variant: fcos
+version: 1.4.0
+storage:
+  links:
+    - path: /etc/alternatives/iptables
+      target: /usr/sbin/iptables-legacy
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/iptables-restore
+      target: /usr/sbin/iptables-legacy-restore
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/iptables-save
+      target: /usr/sbin/iptables-legacy-save
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/ip6tables
+      target: /usr/sbin/ip6tables-legacy
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/ip6tables-restore
+      target: /usr/sbin/ip6tables-legacy-restore
+      overwrite: true
+      hard: false
+    - path: /etc/alternatives/ip6tables-save
+      target: /usr/sbin/ip6tables-legacy-save
+      overwrite: true
+      hard: false
diff --git a/tests/kola/firewall/iptables-legacy b/tests/kola/firewall/iptables-legacy/test.sh
similarity index 69%
rename from tests/kola/firewall/iptables-legacy
rename to tests/kola/firewall/iptables-legacy/test.sh
index 9e45b15c89..e210116731 100755
--- a/tests/kola/firewall/iptables-legacy
+++ b/tests/kola/firewall/iptables-legacy/test.sh
@@ -3,7 +3,7 @@
 # is using the `nf_tables` backend.
 # TODO: modify this test to check for `nf_tables` backend when FCOS switches.
 #       See https://github.com/coreos/fedora-coreos-config/pull/1324
-# kola: { "distros": "fcos", "exclusive": false }
+# kola: { "distros": "fcos", "exclusive": true }
 set -xeuo pipefail
 
 ok() {
@@ -15,10 +15,9 @@ fatal() {
     exit 1
 }
 
-# Make sure we're still on legacy iptables for now
-# https://github.com/coreos/fedora-coreos-tracker/issues/676#issuecomment-928028451
+# Make sure we're on legacy iptables
 if ! iptables --version | grep legacy; then
     iptables --version # output for logs
     fatal "iptables version is not legacy"
 fi
-ok "iptables still in legacy mode"
+ok "iptables in legacy mode"
diff --git a/tests/kola/firewall/iptables-nft/test.sh b/tests/kola/firewall/iptables-nft/test.sh
new file mode 100755
index 0000000000..89f75fcfb7
--- /dev/null
+++ b/tests/kola/firewall/iptables-nft/test.sh
@@ -0,0 +1,18 @@
+#!/bin/bash
+# kola: { "exclusive": false }
+set -xeuo pipefail
+
+ok() {
+    echo "ok" "$@"
+}
+
+fatal() {
+    echo "$@" >&2
+    exit 1
+}
+
+if ! iptables --version | grep nf_tables; then
+    iptables --version # output for logs
+    fatal "iptables version is not nft"
+fi
+ok "iptables in nft mode"