fix: harden server-initiated HTTP against SSRF and DNS rebinding

Route all server-initiated outbound HTTP through one SSRF-protected layer:

- Resolve each host once, validate every resolved address (private,
  loopback, link-local, CGNAT 100.64/10, multicast, reserved, unspecified,
  IPv4-mapped IPv6), and reject if any is unsafe.
- Pin the connection to the validated address via curl's RESOLVE option so
  curl cannot re-resolve to a rebound IP (closes the validate-then-connect
  TOCTOU). Uses getaddrinfo so IPv6 records are checked too.
- Add a sync SafeTransport and safehttp.post, and move the webhook and
  recipe-action paths off raw requests.post so they are guarded like the
  scraper.
- Add HTTP_ALLOW_LIST / HTTP_DISALLOW_LIST settings (deny > allow > default)
  so operators can reach an internal server or block extra hosts.

Apprise notifications egress through the third-party library and are not
covered here.

tests/unit_tests/pkgs/test_safehttp.py

@@ -0,0 +1,189 @@
+import http.server
+import ipaddress
+import socket
+import threading
+
+import httpx
+import pytest
+
+from mealie.pkgs import safehttp
+from mealie.pkgs.safehttp import transport as safehttp_transport
+from mealie.pkgs.safehttp.transport import (
+    AsyncSafeTransport,
+    InvalidDomainError,
+    is_blocked_ip,
+)
+
+
+def _request(url: str) -> httpx.Request:
+    return httpx.Request("GET", url)
+
+
+def _patch_resolver(monkeypatch, ips: list[str]) -> None:
+    def fake_getaddrinfo(host, port, *args, **kwargs):
+        return [(socket.AF_INET, socket.SOCK_STREAM, 6, "", (ip, port)) for ip in ips]
+
+    monkeypatch.setattr(safehttp_transport.socket, "getaddrinfo", fake_getaddrinfo)
+
+
+@pytest.mark.parametrize(
+    ("ip", "blocked"),
+    [
+        ("8.8.8.8", False),
+        ("2606:4700:4700::1111", False),
+        ("10.0.0.1", True),
+        ("172.16.5.5", True),
+        ("192.168.1.1", True),
+        ("127.0.0.1", True),
+        ("169.254.169.254", True),  # cloud metadata / link-local
+        ("100.64.0.1", True),  # CGNAT, not covered by is_private on all versions
+        ("0.0.0.0", True),
+        ("224.0.0.1", True),  # multicast
+        ("::1", True),
+        ("fe80::1", True),
+        ("fc00::1", True),
+        ("::ffff:127.0.0.1", True),  # IPv4-mapped loopback
+    ],
+)
+def test_is_blocked_ip(ip: str, blocked: bool):
+    assert is_blocked_ip(ipaddress.ip_address(ip)) is blocked
+
+
+def test_blocks_host_resolving_to_private(monkeypatch):
+    _patch_resolver(monkeypatch, ["10.0.0.5"])
+    transport = AsyncSafeTransport()
+    with pytest.raises(InvalidDomainError):
+        transport._validate(_request("https://evil.example/"))
+
+
+def test_allows_public_host_and_returns_pin(monkeypatch):
+    _patch_resolver(monkeypatch, ["93.184.216.34"])
+    transport = AsyncSafeTransport()
+    resolve = transport._validate(_request("https://example.test/path"))
+    assert resolve == ["example.test:443:93.184.216.34"]
+
+
+def test_pin_covers_all_resolved_addresses(monkeypatch):
+    _patch_resolver(monkeypatch, ["93.184.216.34", "93.184.216.35"])
+    transport = AsyncSafeTransport()
+    resolve = transport._validate(_request("http://example.test/"))
+    assert resolve == ["example.test:80:93.184.216.34", "example.test:80:93.184.216.35"]
+
+
+def test_rejects_when_any_resolved_address_is_unsafe(monkeypatch):
+    # one public, one private -> reject the whole request
+    _patch_resolver(monkeypatch, ["93.184.216.34", "127.0.0.1"])
+    transport = AsyncSafeTransport()
+    with pytest.raises(InvalidDomainError):
+        transport._validate(_request("https://mixed.example/"))
+
+
+def test_ip_literal_public_needs_no_pin():
+    transport = AsyncSafeTransport()
+    assert transport._validate(_request("https://93.184.216.34/")) is None
+
+
+def test_ip_literal_metadata_blocked():
+    transport = AsyncSafeTransport()
+    with pytest.raises(InvalidDomainError):
+        transport._validate(_request("http://169.254.169.254/latest/meta-data/"))
+
+
+def test_ipv6_resolution_is_validated(monkeypatch):
+    _patch_resolver(monkeypatch, ["::1"])
+    transport = AsyncSafeTransport()
+    with pytest.raises(InvalidDomainError):
+        transport._validate(_request("https://v6.example/"))
+
+
+def test_allow_list_bypasses_block(monkeypatch):
+    _patch_resolver(monkeypatch, ["10.0.0.5"])
+    transport = AsyncSafeTransport(allow_hosts=["internal.example"])
+    resolve = transport._validate(_request("https://internal.example/"))
+    assert resolve == ["internal.example:443:10.0.0.5"]
+
+
+def test_allow_list_cidr_bypasses_block(monkeypatch):
+    _patch_resolver(monkeypatch, ["10.1.2.3"])
+    transport = AsyncSafeTransport(allow_hosts=["10.0.0.0/8"])
+    assert transport._validate(_request("https://internal.example/")) == ["internal.example:443:10.1.2.3"]
+
+
+def test_deny_list_overrides_allow(monkeypatch):
+    _patch_resolver(monkeypatch, ["93.184.216.34"])
+    transport = AsyncSafeTransport(allow_hosts=["blocked.example"], deny_hosts=["blocked.example"])
+    with pytest.raises(InvalidDomainError):
+        transport._validate(_request("https://blocked.example/"))
+
+
+def test_deny_list_blocks_public_host(monkeypatch):
+    _patch_resolver(monkeypatch, ["93.184.216.34"])
+    transport = AsyncSafeTransport(deny_hosts=["93.184.216.0/24"])
+    with pytest.raises(InvalidDomainError):
+        transport._validate(_request("https://public.example/"))
+
+
+def test_unresolvable_host_is_rejected(monkeypatch):
+    def boom(host, port, *args, **kwargs):
+        raise socket.gaierror("no such host")
+
+    monkeypatch.setattr(safehttp_transport.socket, "getaddrinfo", boom)
+    transport = AsyncSafeTransport()
+    with pytest.raises(InvalidDomainError):
+        transport._validate(_request("https://nope.invalid/"))
+
+
+class _LocalServer:
+    def __init__(self):
+        class Handler(http.server.BaseHTTPRequestHandler):
+            def do_GET(self):
+                self.send_response(200)
+                self.end_headers()
+                self.wfile.write(b"OK")
+
+            def do_POST(self):
+                self.send_response(200)
+                self.end_headers()
+                self.wfile.write(b"OK")
+
+            def log_message(self, *args):
+                pass
+
+        self.server = http.server.HTTPServer(("127.0.0.1", 0), Handler)
+        self.port = self.server.server_address[1]
+        self.thread = threading.Thread(target=self.server.serve_forever, daemon=True)
+
+    def __enter__(self):
+        self.thread.start()
+        return self
+
+    def __exit__(self, *exc):
+        self.server.shutdown()
+
+
+@pytest.mark.asyncio
+async def test_async_transport_pins_connection_to_validated_ip(monkeypatch):
+    with _LocalServer() as server:
+        # host does not really resolve to localhost; the resolver + pin make it so
+        _patch_resolver(monkeypatch, ["127.0.0.1"])
+        transport = AsyncSafeTransport(allow_hosts=["pinned.example"])
+        async with httpx.AsyncClient(transport=transport) as client:
+            resp = await client.get(f"http://pinned.example:{server.port}/")
+        assert resp.status_code == 200
+        assert resp.text == "OK"
+
+
+def test_sync_post_blocks_loopback_by_default():
+    with _LocalServer() as server:
+        with pytest.raises(InvalidDomainError):
+            safehttp.post(f"http://127.0.0.1:{server.port}/", json={"x": 1})
+
+
+def test_sync_post_allows_configured_host():
+    with _LocalServer() as server:
+        resp = safehttp.post(
+            f"http://127.0.0.1:{server.port}/",
+            json={"x": 1},
+            allow_hosts=["127.0.0.1"],
+        )
+        assert resp.status_code == 200