fix(https): redirect only the certificate's hostnames, with 302

The force-HTTPS snippet was 'redir https://{host}{uri} permanent':
- every Host was redirected, including a bare IP that the tls-internal
  block has no certificate for — devices reaching the box by IP (no mDNS
  on Android / older Windows, the console IP fallback) couldn't load the
  UI at all
- 301 is cached by browsers, so switching HTTPS off kept bouncing them to
  a dead :443

Now a host matcher limits the redirect to <hostname>.local and <hostname>
and it's a 302. Self-update rewrites the old snippet if it is still the
untouched legacy content. Browsers that already cached the old 301 keep it
until their cache is cleared.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wq1hzUp4ZmCKHDuLKCnu73

furtka/https.py

@@ -36,7 +36,11 @@ from pathlib import Path
 CA_CERT_PATH = Path("/var/lib/caddy/pki/authorities/local/root.crt")
 SNIPPET_DIR = Path("/etc/caddy/furtka.d")
 REDIRECT_SNIPPET = SNIPPET_DIR / "redirect.caddyfile"
-REDIRECT_CONTENT = "redir https://{host}{uri} permanent\n"
+# Pre-26.21 redirect: permanent (browsers cache a 301 indefinitely, so
+# turning HTTPS off left them bouncing to a dead :443) and for every Host —
+# including a bare IP, which has no certificate, so devices that reach the
+# box by IP (no mDNS on Android / older Windows) couldn't load the UI at all.
+LEGACY_REDIRECT_CONTENT = "redir https://{host}{uri} permanent\n"
 HTTPS_SNIPPET_DIR = Path("/etc/caddy/furtka-https.d")
 HTTPS_SNIPPET = HTTPS_SNIPPET_DIR / "https.caddyfile"
 HOSTNAME_FILE = Path("/etc/hostname")
@@ -62,6 +66,19 @@ def _read_hostname(hostname_file: Path = HOSTNAME_FILE) -> str:
     return value or "furtka"
 
 
+def _redirect_snippet_content(hostname: str) -> str:
+    """HTTP→HTTPS redirect for the names the HTTPS block has a cert for.
+
+    Only those hosts are redirected: an IP or any other name keeps plain
+    HTTP instead of landing on a TLS handshake that can't succeed. 302 so
+    switching HTTPS off takes effect in browsers immediately.
+    """
+    return (
+        f"@furtka_https_host host {hostname}.local {hostname}\n"
+        "redir @furtka_https_host https://{host}{uri} 302\n"
+    )
+
+
 def _https_snippet_content(hostname: str) -> str:
     """Caddy site block the HTTPS toggle installs at opt-in.
 
@@ -151,8 +168,9 @@ def set_force_https(
     previous_https = https_snippet.read_text() if had_https else None
 
     if enabled:
-        snippet.write_text(REDIRECT_CONTENT)
+        hostname = _read_hostname(hostname_file)
-        https_snippet.write_text(_https_snippet_content(_read_hostname(hostname_file)))
+        snippet.write_text(_redirect_snippet_content(hostname))
+        https_snippet.write_text(_https_snippet_content(hostname))
     else:
         if had_redirect:
             snippet.unlink()

furtka/updater.py

@@ -192,6 +192,20 @@ def _maybe_migrate_preserve_https() -> None:
     )
 
 
+def _maybe_migrate_redirect_snippet() -> None:
+    """26.21 migration: swap the old catch-all 301 redirect for the
+    hostname-scoped 302 one, so boxes reached by IP can load the UI again
+    and turning HTTPS off stops sticking in browser caches."""
+    from furtka import https
+
+    redirect_snippet = _CADDY_SNIPPET_DIR / "redirect.caddyfile"
+    if not redirect_snippet.is_file():
+        return
+    if redirect_snippet.read_text() != https.LEGACY_REDIRECT_CONTENT:
+        return
+    redirect_snippet.write_text(https._redirect_snippet_content(_current_hostname()))
+
+
 def _refresh_caddyfile(source: Path) -> bool:
     """Copy the shipped Caddyfile to /etc/caddy/ iff it differs. Returns True
     if the file changed (so caddy needs more than a bare reload).
@@ -215,6 +229,7 @@ def _refresh_caddyfile(source: Path) -> bool:
     # hostname block is gone, so the redirect would 301 to a dead :443.
     # Preserve intent by writing the HTTPS listener snippet too.
     _maybe_migrate_preserve_https()
+    _maybe_migrate_redirect_snippet()
     rendered = source.read_text().replace(_CADDYFILE_HOSTNAME_MARKER, _current_hostname())
     if _CADDYFILE_LIVE.is_file() and rendered == _CADDYFILE_LIVE.read_text():
         return False

tests/test_https.py

@@ -113,7 +113,7 @@ def test_set_force_enable_writes_both_snippets_and_reloads(tmp_path):
 
     result = https.set_force_https(True, reload_caddy=fake_reload, **p)
     assert result is True
-    assert p["snippet"].read_text() == https.REDIRECT_CONTENT
+    assert p["snippet"].read_text() == https._redirect_snippet_content("testbox")
     written = p["https_snippet"].read_text()
     assert "testbox.local, testbox" in written
     assert "tls internal" in written
@@ -135,7 +135,7 @@ def test_set_force_disable_removes_both_snippets(tmp_path):
     p = _paths(tmp_path)
     p["snippet_dir"].mkdir()
     p["https_snippet_dir"].mkdir()
-    p["snippet"].write_text(https.REDIRECT_CONTENT)
+    p["snippet"].write_text(https._redirect_snippet_content("testbox"))
     p["https_snippet"].write_text("furtka.local { tls internal }\n")
 
     result = https.set_force_https(False, reload_caddy=lambda: None, **p)
@@ -199,10 +199,16 @@ def test_systemctl_missing_raises_and_rolls_back(tmp_path):
     assert not p["https_snippet"].exists()
 
 
-def test_redirect_snippet_content_is_caddy_redir_directive():
+def test_redirect_snippet_only_covers_cert_names_and_is_temporary():
-    # Lock the exact directive. A regression here silently stops the
+    # Lock the exact directives. A regression here silently stops the
     # redirect from taking effect even though the file-swap looks fine.
-    assert https.REDIRECT_CONTENT.strip() == "redir https://{host}{uri} permanent"
+    # Only the names the tls-internal block has a cert for are redirected
+    # (an IP would hit a failing TLS handshake), and 302 so switching HTTPS
+    # off isn't stuck in browser caches like the old 301 was.
+    assert https._redirect_snippet_content("mybox") == (
+        "@furtka_https_host host mybox.local mybox\n"
+        "redir @furtka_https_host https://{host}{uri} 302\n"
+    )
 
 
 def test_https_snippet_content_has_tls_internal_and_routes(tmp_path):

tests/test_updater.py

@@ -539,3 +539,31 @@ def test_health_check_survives_read_timeout(updater, monkeypatch):
     monkeypatch.setattr("urllib.request.urlopen", slow)
     monkeypatch.setattr(updater.time, "sleep", lambda _s: None)
     assert updater._health_check("http://127.0.0.1:7000/api/apps", deadline_s=0.05) is False
+
+
+def test_refresh_caddyfile_migrates_legacy_301_redirect(updater, tmp_path):
+    from furtka import https
+
+    snippet_dir = tmp_path / "etc_caddy" / "furtka.d"
+    snippet_dir.mkdir(parents=True)
+    (tmp_path / "etc_caddy" / "furtka-https.d").mkdir()
+    (tmp_path / "etc_caddy" / "furtka-https.d" / "https.caddyfile").write_text("x\n")
+    redirect = snippet_dir / "redirect.caddyfile"
+    redirect.write_text(https.LEGACY_REDIRECT_CONTENT)
+    src = tmp_path / "Caddyfile.src"
+    src.write_text("# caddy\n")
+    updater._refresh_caddyfile(src)
+    assert redirect.read_text() == https._redirect_snippet_content("testbox")
+
+
+def test_refresh_caddyfile_leaves_custom_redirect_alone(updater, tmp_path):
+    snippet_dir = tmp_path / "etc_caddy" / "furtka.d"
+    snippet_dir.mkdir(parents=True)
+    (tmp_path / "etc_caddy" / "furtka-https.d").mkdir()
+    (tmp_path / "etc_caddy" / "furtka-https.d" / "https.caddyfile").write_text("x\n")
+    redirect = snippet_dir / "redirect.caddyfile"
+    redirect.write_text("# hand-edited\n")
+    src = tmp_path / "Caddyfile.src"
+    src.write_text("# caddy\n")
+    updater._refresh_caddyfile(src)
+    assert redirect.read_text() == "# hand-edited\n"