From ecb67d012bfa5c292894c5a5a9554a85771f7d48 Mon Sep 17 00:00:00 2001
From: Franziska Kunsmann <hi@kunsmann.eu>
Date: Thu, 3 Jun 2021 13:57:50 +0200
Subject: [PATCH] bundles/nftables: introduce

---
 bundles/nftables/files/nftables.conf | 72 ++++++++++++++++++++++
 bundles/nftables/items.py            | 35 +++++++++++
 bundles/nftables/metadata.py         | 91 ++++++++++++++++++++++++++++
 3 files changed, 198 insertions(+)
 create mode 100644 bundles/nftables/files/nftables.conf
 create mode 100644 bundles/nftables/items.py
 create mode 100644 bundles/nftables/metadata.py

diff --git a/bundles/nftables/files/nftables.conf b/bundles/nftables/files/nftables.conf
new file mode 100644
index 0000000..f417856
--- /dev/null
+++ b/bundles/nftables/files/nftables.conf
@@ -0,0 +1,72 @@
+#!/usb/sbin/nft -f
+
+flush ruleset
+
+table inet filter {
+    chain input {
+        type filter hook input priority 0
+        policy drop
+
+        tcp flags syn tcp option maxseg size 1-500 drop
+
+        ct state { established, related } accept
+        ct state invalid drop
+
+        iif lo accept
+
+        icmp type timestamp-request drop
+        icmp type timestamp-reply drop
+        ip protocol icmp accept
+
+        ip6 nexthdr ipv6-icmp accept
+% for ruleset, rules in sorted(node.metadata.get('nftables/rules/input', {}).items()):
+
+        # ${ruleset}
+%  for rule in rules:
+        ${rule}
+%  endfor
+        # / ${ruleset}
+% endfor
+    }
+
+    chain output {
+        type filter hook output priority 0
+        policy accept
+    }
+
+    chain forward {
+        type filter hook forward priority 0
+        policy drop
+
+        icmp type timestamp-request drop
+        icmp type timestamp-reply drop
+
+% for ruleset, rules in sorted(node.metadata.get('nftables/rules/forward', {}).items()):
+
+        # ${ruleset}
+%  for rule in rules:
+        ${rule}
+%  endfor
+        # / ${ruleset}
+% endfor
+    }
+}
+
+table nat {
+    chain prerouting {
+        type nat hook prerouting priority -100
+
+% for rule in node.metadata.get('nftables/rules/nat_prerouting', []):
+        ${rule}
+% endfor
+    }
+    chain postrouting {
+        type nat hook postrouting priority 100
+
+% for rule in node.metadata.get('nftables/rules/nat_postrouting', []):
+        ${rule}
+% endfor
+    }
+}
+
+include "/etc/nftables-rules.d/*-*"
diff --git a/bundles/nftables/items.py b/bundles/nftables/items.py
new file mode 100644
index 0000000..f755916
--- /dev/null
+++ b/bundles/nftables/items.py
@@ -0,0 +1,35 @@
+if node.has_bundle('pacman'):
+    package = 'pkg_pacman:nftables'
+else:
+    package = 'pkg_apt:nftables'
+
+directories = {
+    # used by other bundles
+    '/etc/nftables-rules.d': {
+        'purge': True,
+        'triggers': {
+            'svc_systemd:nftables:reload',
+        },
+    },
+}
+
+files = {
+    '/etc/nftables.conf': {
+        'content_type': 'mako',
+        'needs': {
+            'directory:/etc/nftables-rules.d',
+        },
+        'triggers': {
+            'svc_systemd:nftables:reload',
+        },
+    },
+}
+
+svc_systemd = {
+    'nftables': {
+        'needs': {
+            'file:/etc/nftables.conf',
+            package,
+        },
+    },
+}
diff --git a/bundles/nftables/metadata.py b/bundles/nftables/metadata.py
new file mode 100644
index 0000000..a960c32
--- /dev/null
+++ b/bundles/nftables/metadata.py
@@ -0,0 +1,91 @@
+from bundlewrap.exceptions import BundleError
+
+defaults = {
+    'apt': {
+        'packages': {
+            'nftables': {},
+
+            # XXX remove after all systems have been migrated
+        },
+    },
+    'pacman': {
+        'packages': {
+            'nftables': {},
+            'iptables-nft': {
+                # uninstalls iptables automatically
+                'needed_by': {
+                    'pkg_pacman:nftables',
+                },
+            },
+        },
+    },
+}
+
+if not node.has_bundle('vmhost'):
+    # see comment in bundles/vmhost/items.py
+    defaults['apt']['packages']['iptables'] = {
+        'installed': False,
+        'needed_by': {
+            'pkg_apt:nftables',
+        },
+    }
+
+@metadata_reactor.provides(
+    'nftables/rules/input/port_rules',
+)
+def port_rules_to_nftables(metadata):
+    # Using this, bundles can simply set up port based rules. This
+    # reactor will then take care of converting those rules to actual
+    # nftables rules
+    ruleset = set()
+
+    # Plese note we do not set any defaults for ports. Bundles are
+    # expected to know themselves which default to use.
+    for portdef, targets in metadata.get('firewall/port_rules', {}).items():
+        if '/' in portdef:
+            port, proto = portdef.split('/', 2)
+
+            if proto not in {'udp'}:
+                raise BundleError(f'firewall/port_rules: illegal identifier {portdef} in metadata for {node.name}')
+        else:
+            port = portdef
+            proto = 'tcp'
+
+        for target in targets:
+            if port == '*' and target == '*':
+                raise BundleError('firewall/port_rules: setting both port and target to * is unsupported')
+
+            comment = f'# port_rules {target}'
+
+            if port != '*':
+                if ':' in port:
+                    parts = port.split(':')
+                    port_str = f'dport {{ {parts[0]}-{parts[1]} }} '
+                else:
+                    port_str = f'dport {port} '
+                prefix = ''
+            else:
+                port_str = ''
+                prefix = 'meta l4proto '
+
+            if target == '*':
+                ruleset.add(f'{prefix}{proto} {port_str}accept {comment}')
+            else:
+                resolved = repo.libs.tools.resolve_identifier(repo, target)
+
+                for address in resolved['ipv4']:
+                    ruleset.add(f'{prefix}{proto} {port_str}ip saddr {address} accept {comment}')
+
+                for address in resolved['ipv6']:
+                    ruleset.add(f'{prefix}{proto} {port_str}ip6 saddr {address} accept {comment}')
+
+    return {
+        'nftables': {
+            'rules': {
+                # order does not matter here.
+                'input': {
+                    'port_rules': sorted(ruleset),
+                },
+            },
+        },
+    }