Harden existing key-based SSH setups

migrations/1788124236.sh

@@ -0,0 +1,77 @@
+echo "Disable SSH password authentication on existing key-based setups"
+
+config=/etc/ssh/sshd_config.d/10-omarchy-hardening.conf
+authorized_keys="$HOME/.ssh/authorized_keys"
+
+as_root() {
+  if (( EUID == 0 )); then
+    "$@"
+  else
+    sudo "$@"
+  fi
+}
+
+# The fixed setup command writes this file itself. Its presence is also the
+# machine-wide completion state, so migrations run by another account no-op.
+if [[ -e $config || -L $config ]]; then
+  exit 0
+fi
+
+# Earlier versions enabled sshd before importing the key, but did not leave a
+# marker saying that Omarchy configured it. Limit the repair to a daemon that is
+# enabled or currently exposed and a user who already has a usable authorized
+# key. A machine that never set SSH up exits without prompting for privileges.
+if ! systemctl is-enabled --quiet sshd.service 2>/dev/null &&
+  ! systemctl is-active --quiet sshd.service 2>/dev/null; then
+  exit 0
+fi
+
+if [[ ! -f $authorized_keys || -L $authorized_keys || ! -s $authorized_keys || ! -r $authorized_keys ]] ||
+  ! ssh-keygen -lf "$authorized_keys" >/dev/null 2>&1; then
+  echo "Leaving SSH password authentication unchanged because $authorized_keys has no usable public key."
+  exit 0
+fi
+
+echo "Disabling SSH password authentication on the existing key-based SSH setup..."
+if ! as_root install -Dm644 /dev/stdin "$config" <<'CONF'
+# Written by Omarchy once an SSH key was already authorized.
+# Delete this file and reload sshd to allow password logins again.
+PasswordAuthentication no
+KbdInteractiveAuthentication no
+CONF
+then
+  echo "Administrator privileges are required to harden the existing SSH setup. Run omarchy-migrate again from a terminal." >&2
+  exit 1
+fi
+
+# Syntax alone is insufficient because sshd uses the first value it reads. If
+# another administrator rule wins, remove our ineffective file and keep the
+# migration pending rather than claiming the machine is protected.
+if ! as_root sshd -t; then
+  as_root rm -f -- "$config" || true
+  echo "sshd rejected the hardening config. Fix the SSH configuration and run omarchy-migrate again." >&2
+  exit 1
+fi
+
+effective_config=$(as_root sshd -T) || {
+  as_root rm -f -- "$config" || true
+  echo "Could not inspect sshd's effective configuration. Run omarchy-migrate again after fixing SSH." >&2
+  exit 1
+}
+
+if ! grep -qixF "passwordauthentication no" <<<"$effective_config" ||
+  ! grep -qixF "kbdinteractiveauthentication no" <<<"$effective_config"; then
+  as_root rm -f -- "$config" || true
+  echo "Another SSH rule keeps password authentication enabled. Fix its ordering and run omarchy-migrate again." >&2
+  exit 1
+fi
+
+# An enabled but deliberately stopped daemon picks the file up on its next
+# start. Reload only a daemon that is currently serving connections so existing
+# sessions survive while new ones get the hardened policy.
+if systemctl is-active --quiet sshd.service 2>/dev/null; then
+  if ! as_root systemctl reload sshd.service; then
+    echo "The hardening config is valid but sshd could not reload it. Run omarchy-migrate again after fixing the service." >&2
+    exit 1
+  fi
+fi

test/shell.d/sshd-hardening-migration-test.sh

@@ -0,0 +1,121 @@
+#!/bin/bash
+
+set -euo pipefail
+
+source "$(dirname "$0")/base-test.sh"
+
+test_dir=$(mktemp -d)
+trap 'rm -rf "$test_dir"' EXIT
+
+migration="$ROOT/migrations/1788124236.sh"
+stub_bin="$test_dir/bin"
+mkdir -p "$stub_bin"
+
+cat >"$stub_bin/systemctl" <<'STUB'
+#!/bin/bash
+printf 'systemctl %s\n' "$*" >>"${CALL_LOG:?}"
+case "$1 $2" in
+"is-enabled --quiet") [[ ${SSHD_ENABLED:-0} == 1 ]] ;;
+"is-active --quiet") [[ ${SSHD_ACTIVE:-0} == 1 ]] ;;
+"reload sshd.service") [[ ${SSHD_RELOAD_VALID:-1} == 1 ]] ;;
+*) exit 2 ;;
+esac
+STUB
+
+cat >"$stub_bin/sshd" <<'STUB'
+#!/bin/bash
+printf 'sshd %s\n' "$*" >>"${CALL_LOG:?}"
+case $1 in
+-t) [[ ${SSHD_SYNTAX_VALID:-1} == 1 ]] ;;
+-T)
+  printf 'PasswordAuthentication %s\n' "${SSHD_PASSWORD_AUTH:-no}"
+  printf 'KbdInteractiveAuthentication %s\n' "${SSHD_KBD_AUTH:-no}"
+  ;;
+*) exit 2 ;;
+esac
+STUB
+
+cat >"$stub_bin/sudo" <<'STUB'
+#!/bin/bash
+printf 'sudo %s\n' "$*" >>"${CALL_LOG:?}"
+exec "$@"
+STUB
+
+chmod +x "$stub_bin"/*
+
+ssh-keygen -q -t ed25519 -N "" -f "$test_dir/key"
+public_key=$(<"$test_dir/key.pub")
+
+run_migration() {
+  local scenario=$1
+  local home="$test_dir/$scenario/home"
+  local root="$test_dir/$scenario/root"
+  local config="$root/etc/ssh/sshd_config.d/10-omarchy-hardening.conf"
+
+  mkdir -p "$home/.ssh" "${config%/*}"
+  : >"$test_dir/$scenario.calls"
+  if [[ ${AUTHORIZED_KEY_STATE:-valid} == "valid" ]]; then
+    printf '%s\n' "$public_key" >"$home/.ssh/authorized_keys"
+  elif [[ $AUTHORIZED_KEY_STATE == "invalid" ]]; then
+    printf 'not a public key\n' >"$home/.ssh/authorized_keys"
+  fi
+
+  # Keep the privileged production destination fixed in the shipped migration.
+  # For this isolated test only, rewrite that one assignment in the input fed to
+  # bash so no scenario can touch the host's /etc.
+  sed "s|^config=/etc/ssh/sshd_config.d/10-omarchy-hardening.conf$|config=$config|" "$migration" |
+    HOME="$home" CALL_LOG="$test_dir/$scenario.calls" PATH="$stub_bin:$PATH" \
+      SSHD_ENABLED="${SSHD_ENABLED:-0}" SSHD_ACTIVE="${SSHD_ACTIVE:-0}" \
+      SSHD_SYNTAX_VALID="${SSHD_SYNTAX_VALID:-1}" \
+      SSHD_PASSWORD_AUTH="${SSHD_PASSWORD_AUTH:-no}" \
+      SSHD_KBD_AUTH="${SSHD_KBD_AUTH:-no}" \
+      SSHD_RELOAD_VALID="${SSHD_RELOAD_VALID:-1}" \
+      bash -euo pipefail
+}
+
+SSHD_ENABLED=0 SSHD_ACTIVE=0 run_migration disabled
+[[ ! -e $test_dir/disabled/root/etc/ssh/sshd_config.d/10-omarchy-hardening.conf ]] ||
+  fail "SSH migration leaves a disabled daemon alone"
+! grep -q '^sudo ' "$test_dir/disabled.calls" || fail "disabled SSH does not prompt for privileges"
+pass "SSH migration no-ops when sshd is not enabled or active"
+
+AUTHORIZED_KEY_STATE=missing SSHD_ENABLED=1 run_migration no-key >/dev/null
+[[ ! -e $test_dir/no-key/root/etc/ssh/sshd_config.d/10-omarchy-hardening.conf ]] ||
+  fail "SSH migration must not disable passwords without an authorized key"
+! grep -q '^sudo ' "$test_dir/no-key.calls" || fail "missing SSH key does not prompt for privileges"
+
+AUTHORIZED_KEY_STATE=invalid SSHD_ENABLED=1 run_migration invalid-key >/dev/null
+[[ ! -e $test_dir/invalid-key/root/etc/ssh/sshd_config.d/10-omarchy-hardening.conf ]] ||
+  fail "SSH migration must not trust a malformed authorized_keys file"
+pass "SSH migration requires a usable authorized key before disabling passwords"
+
+SSHD_ENABLED=1 SSHD_ACTIVE=1 run_migration active >/dev/null
+config="$test_dir/active/root/etc/ssh/sshd_config.d/10-omarchy-hardening.conf"
+grep -qxF "PasswordAuthentication no" "$config" || fail "SSH migration disables password authentication"
+grep -qxF "KbdInteractiveAuthentication no" "$config" || fail "SSH migration disables keyboard-interactive authentication"
+grep -qxF "sudo sshd -t" "$test_dir/active.calls" || fail "SSH migration validates sshd syntax"
+grep -qxF "sudo sshd -T" "$test_dir/active.calls" || fail "SSH migration validates effective sshd settings"
+grep -qxF "sudo systemctl reload sshd.service" "$test_dir/active.calls" || fail "SSH migration reloads an active daemon"
+pass "SSH migration hardens and reloads an existing key-based SSH setup"
+
+SSHD_ENABLED=1 SSHD_ACTIVE=0 run_migration stopped >/dev/null
+[[ -e $test_dir/stopped/root/etc/ssh/sshd_config.d/10-omarchy-hardening.conf ]] ||
+  fail "SSH migration hardens an enabled but stopped daemon"
+! grep -qF 'reload sshd.service' "$test_dir/stopped.calls" || fail "SSH migration must not start or reload a stopped daemon"
+pass "SSH migration hardens an enabled daemon without starting it"
+
+if SSHD_ENABLED=1 SSHD_ACTIVE=1 SSHD_PASSWORD_AUTH=yes run_migration ineffective >"$test_dir/ineffective.output" 2>&1; then
+  fail "SSH migration must fail when password authentication remains effective"
+fi
+[[ ! -e $test_dir/ineffective/root/etc/ssh/sshd_config.d/10-omarchy-hardening.conf ]] ||
+  fail "SSH migration removes an ineffective config"
+! grep -qF 'reload sshd.service' "$test_dir/ineffective.calls" || fail "SSH migration must not reload ineffective hardening"
+pass "SSH migration stays pending when another rule keeps password authentication enabled"
+
+if SSHD_ENABLED=1 SSHD_ACTIVE=1 SSHD_SYNTAX_VALID=0 run_migration invalid-config >"$test_dir/invalid-config.output" 2>&1; then
+  fail "SSH migration must fail when sshd rejects its config"
+fi
+[[ ! -e $test_dir/invalid-config/root/etc/ssh/sshd_config.d/10-omarchy-hardening.conf ]] ||
+  fail "SSH migration removes a rejected config"
+! grep -qF 'reload sshd.service' "$test_dir/invalid-config.calls" || fail "SSH migration must not reload rejected hardening"
+pass "SSH migration fails safely when sshd rejects the config"