Add host UTS namespace support for Add-Ons (#3596)

* Add host UTS namespace support for Add-Ons

Using the UTS host namespace is useful when running a mDNS responder
which learns the hostname from the gethostname syscall. This way the
add-on can use the system's hostname without further doing.

* Check host_uts default

* Adjust Security rating if host UTS mode and CAP_ADMIN is set

* Don't add hostname to DNS server if UTS namespace is disabled

* Simplify hostname logic

* Update supervisor/docker/addon.py

Co-authored-by: Mike Degatano <michael.degatano@gmail.com>

---------

Co-authored-by: Mike Degatano <michael.degatano@gmail.com>

supervisor/addons/model.py

@@ -34,6 +34,7 @@ from ..const import (
     ATTR_HOST_IPC,
     ATTR_HOST_NETWORK,
     ATTR_HOST_PID,
+    ATTR_HOST_UTS,
     ATTR_IMAGE,
     ATTR_INGRESS,
     ATTR_INGRESS_STREAM,
@@ -308,6 +309,11 @@ class AddonModel(CoreSysAttributes, ABC):
         """Return True if add-on run on host IPC namespace."""
         return self.data[ATTR_HOST_IPC]
 
+    @property
+    def host_uts(self) -> bool:
+        """Return True if add-on run on host UTS namespace."""
+        return self.data[ATTR_HOST_UTS]
+
     @property
     def host_dbus(self) -> bool:
         """Return True if add-on run on host D-BUS."""

supervisor/addons/utils.py

@@ -70,6 +70,10 @@ def rating_security(addon: AddonModel) -> int:
     if addon.host_pid:
         rating += -2
 
+    # UTS host namespace allows to set hostname only with SYS_ADMIN
+    if addon.host_uts and Capabilities.SYS_ADMIN in addon.privileged:
+        rating += -1
+
     # Docker Access & full Access
     if addon.access_docker_api or addon.with_full_access:
         rating = 1

supervisor/addons/validate.py

@@ -41,6 +41,7 @@ from ..const import (
     ATTR_HOST_IPC,
     ATTR_HOST_NETWORK,
     ATTR_HOST_PID,
+    ATTR_HOST_UTS,
     ATTR_IMAGE,
     ATTR_INGRESS,
     ATTR_INGRESS_ENTRY,
@@ -283,6 +284,7 @@ _SCHEMA_ADDON_CONFIG = vol.Schema(
         vol.Optional(ATTR_HOST_NETWORK, default=False): vol.Boolean(),
         vol.Optional(ATTR_HOST_PID, default=False): vol.Boolean(),
         vol.Optional(ATTR_HOST_IPC, default=False): vol.Boolean(),
+        vol.Optional(ATTR_HOST_UTS, default=False): vol.Boolean(),
         vol.Optional(ATTR_HOST_DBUS, default=False): vol.Boolean(),
         vol.Optional(ATTR_DEVICES): [str],
         vol.Optional(ATTR_UDEV, default=False): vol.Boolean(),

supervisor/api/addons.py

@@ -46,6 +46,7 @@ from ..const import (
     ATTR_HOST_IPC,
     ATTR_HOST_NETWORK,
     ATTR_HOST_PID,
+    ATTR_HOST_UTS,
     ATTR_HOSTNAME,
     ATTR_ICON,
     ATTR_INGRESS,
@@ -216,6 +217,7 @@ class APIAddons(CoreSysAttributes):
             ATTR_HOST_NETWORK: addon.host_network,
             ATTR_HOST_PID: addon.host_pid,
             ATTR_HOST_IPC: addon.host_ipc,
+            ATTR_HOST_UTS: addon.host_uts,
             ATTR_HOST_DBUS: addon.host_dbus,
             ATTR_PRIVILEGED: addon.privileged,
             ATTR_FULL_ACCESS: addon.with_full_access,

supervisor/const.py

@@ -181,6 +181,7 @@ ATTR_HOST_INTERNET = "host_internet"
 ATTR_HOST_IPC = "host_ipc"
 ATTR_HOST_NETWORK = "host_network"
 ATTR_HOST_PID = "host_pid"
+ATTR_HOST_UTS = "host_uts"
 ATTR_HOSTNAME = "hostname"
 ATTR_ICON = "icon"
 ATTR_ID = "id"

supervisor/docker/addon.py

@@ -265,6 +265,13 @@ class DockerAddon(DockerInterface):
             return "host"
         return None
 
+    @property
+    def uts_mode(self) -> str | None:
+        """Return UTS mode for add-on."""
+        if self.addon.host_uts:
+            return "host"
+        return None
+
     @property
     def capabilities(self) -> list[str] | None:
         """Generate needed capabilities."""
@@ -472,18 +479,22 @@ class DockerAddon(DockerInterface):
         # Cleanup
         self._stop()
 
+        # Don't set a hostname if no separate UTS namespace is used
+        hostname = None if self.uts_mode else self.addon.hostname
+
         # Create & Run container
         try:
             docker_container = self.sys_docker.run(
                 self.image,
                 tag=str(self.addon.version),
                 name=self.name,
-                hostname=self.addon.hostname,
+                hostname=hostname,
                 detach=True,
                 init=self.addon.default_init,
                 stdin_open=self.addon.with_stdin,
                 network_mode=self.network_mode,
                 pid_mode=self.pid_mode,
+                uts_mode=self.uts_mode,
                 ports=self.ports,
                 extra_hosts=self.network_mapping,
                 device_cgroup_rules=self.cgroups_rules,

supervisor/docker/manager.py

@@ -176,6 +176,7 @@ class DockerAPI:
         if dns:
             kwargs["dns"] = [str(self.network.dns)]
             kwargs["dns_search"] = [DNS_SUFFIX]
+            if hostname:
                 kwargs["domainname"] = DNS_SUFFIX
 
         # Setup network

tests/addons/test_config.py

@@ -23,6 +23,7 @@ def test_basic_config():
     assert not valid_config["host_ipc"]
     assert not valid_config["host_dbus"]
     assert not valid_config["host_pid"]
+    assert not valid_config["host_uts"]
 
     assert not valid_config["hassio_api"]
     assert not valid_config["homeassistant_api"]