host_firewall: FireHOL level1 as its own set firehol_v4 next to Spamhaus, daily updater and firewall.firehol opt-out

2026-10-24 17:31:45 +00:00
parent 312be161b9
commit c55a96c0ea
6 changed files with 238 additions and 5 deletions
@@ -0,0 +1,127 @@
+#!/usr/bin/python3
+# Managed by Ansible (role host_firewall), do not edit.
+"""Rebuilds the FireHOL level1 set firehol_v4 of table inet host.
+
+A failed download or sanity check exits non-zero before anything changes, so
+the previous set stays in place.
+"""
+import ipaddress
+import json
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+import time
+import urllib.request
+
+PERSISTED = "/etc/nftables.d/host-firehol.nft"
+URL = "https://raw.githubusercontent.com/firehol/blocklist-ipsets/master/firehol_level1.netset"
+USER_AGENT = "ruekov-host-firewall (nft-host-firehol)"
+
+# Lower bound that catches an empty or truncated answer.
+MIN_ENTRIES = 1000
+# A prefix this wide is a parse error, not a bad network.
+MIN_PREFIXLEN = 8
+# Private, CGNAT (NetBird), loopback, link-local and multicast/reserved space:
+# an entry overlapping one of these never lands in the set, so the own
+# infrastructure cannot block itself.
+EXCLUDED = [ipaddress.ip_network(n) for n in (
+    "0.0.0.0/8", "10.0.0.0/8", "100.64.0.0/10", "127.0.0.0/8",
+    "169.254.0.0/16", "172.16.0.0/12", "192.168.0.0/16", "224.0.0.0/3")]
+
+
+def fail(message):
+    print(f"nft-host-firehol: {message}", file=sys.stderr)
+    sys.exit(1)
+
+
+def fetch():
+    error = None
+    for attempt in range(3):
+        try:
+            request = urllib.request.Request(URL, headers={"User-Agent": USER_AGENT})
+            with urllib.request.urlopen(request, timeout=120) as response:
+                return response.read().decode("utf-8")
+        except OSError as e:
+            error = e
+            time.sleep(5 * (attempt + 1))
+    fail(f"download of {URL} failed: {error}")
+
+
+def own_addresses():
+    result = subprocess.run(["ip", "-j", "-4", "address", "show"], capture_output=True, text=True)
+    if result.returncode != 0:
+        fail(f"ip address show failed: {result.stderr.strip()}")
+    return [ipaddress.ip_address(a["local"]) for link in json.loads(result.stdout)
+            for a in link.get("addr_info", []) if a.get("family") == "inet"]
+
+
+def main():
+    networks = []
+    for line in fetch().splitlines():
+        line = line.strip()
+        if not line or line.startswith("#"):
+            continue
+        try:
+            networks.append(ipaddress.IPv4Network(line))
+        except ValueError:
+            fail(f"unparsable line: {line!r}")
+    if len(networks) < MIN_ENTRIES:
+        fail(f"only {len(networks)} entries")
+
+    own = own_addresses()
+    kept, excluded, own_skipped = [], 0, 0
+    for network in networks:
+        if any(network.overlaps(e) for e in EXCLUDED):
+            excluded += 1
+        elif any(address in network for address in own):
+            own_skipped += 1
+        else:
+            if network.prefixlen < MIN_PREFIXLEN:
+                fail(f"suspiciously wide prefix {network}")
+            kept.append(network)
+    merged = list(ipaddress.collapse_addresses(kept))
+    print(f"firehol_v4: {len(networks)} entries, {excluded} in private or reserved space and "
+          f"{own_skipped} holding an own address skipped -> {len(merged)} merged")
+
+    elements = ",\n\t\t".join(str(n) for n in merged) + ","
+    persisted = ("# Generated by nft-host-firehol, do not edit.\n"
+                 "table inet host {\n"
+                 "\tset firehol_v4 { type ipv4_addr; flags interval; auto-merge; elements = {\n"
+                 f"\t\t{elements}\n\t}} }}\n}}\n")
+
+    # Checked under another table name: a dry run against the live table
+    # name changes the live sets for its duration and unlisted addresses match.
+    check_rules = persisted.replace("table inet host {", "table inet host_firehol_check {")
+    checked = subprocess.run(["nft", "-c", "-f", "-"], input=check_rules, capture_output=True, text=True)
+    if checked.returncode != 0:
+        fail(f"nft rejects the set: {checked.stderr.strip()}")
+
+    with tempfile.TemporaryDirectory() as tmp:
+        previous = None
+        if os.path.exists(PERSISTED):
+            previous = os.path.join(tmp, "previous.nft")
+            shutil.copyfile(PERSISTED, previous)
+        with open(PERSISTED + ".new", "w", encoding="utf-8") as f:
+            f.write(persisted)
+        os.chmod(PERSISTED + ".new", 0o644)
+        os.replace(PERSISTED + ".new", PERSISTED)
+
+        # A reload replaces the whole table, sets included, in one transaction.
+        active = subprocess.run(["systemctl", "-q", "is-active", "nft-host.service"]).returncode == 0
+        if active:
+            reloaded = subprocess.run(["systemctl", "reload", "nft-host.service"], capture_output=True, text=True)
+            if reloaded.returncode != 0:
+                if previous:
+                    shutil.copyfile(previous, PERSISTED)
+                fail(f"reloading the rule set failed, kept the previous set: {reloaded.stderr.strip()}")
+        print("reloaded the rule set" if active else "persisted only")
+
+
+try:
+    main()
+except SystemExit:
+    raise
+except Exception as e:  # keep the previous set on any surprise
+    fail(f"{type(e).__name__}: {e}")
@@ -0,0 +1,8 @@
+[Unit]
+Description=Refresh the FireHOL set of the host firewall
+Wants=network-online.target
+After=network-online.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/local/sbin/nft-host-firehol
@@ -0,0 +1,10 @@
+[Unit]
+Description=Daily refresh of the host firewall FireHOL set
+
+[Timer]
+OnCalendar=daily
+RandomizedDelaySec=6h
+Persistent=true
+
+[Install]
+WantedBy=timers.target