✨ zb,zm: Support Option<Header<'_>> parameter in property getters

This allows for fine-grained connecting-UID checking, in order to
be able to control who is able to access property values.

Signed-off-by: Razvan Cojocaru <rzvncj@gmail.com>

zbus/src/fdo/properties.rs

@@ -9,7 +9,7 @@ use zbus_names::InterfaceName;
 use zvariant::{OwnedValue, Value};
 
 use super::{Error, Result};
-use crate::{interface, message::Header, object_server::SignalEmitter, ObjectServer};
+use crate::{interface, message::Header, object_server::SignalEmitter, Connection, ObjectServer};
 
 /// Service-side implementation for the `org.freedesktop.DBus.Properties` interface.
 /// This interface is implemented automatically for any object registered to the
@@ -29,6 +29,7 @@ impl Properties {
         &self,
         interface_name: InterfaceName<'_>,
         property_name: &str,
+        #[zbus(connection)] conn: &Connection,
         #[zbus(object_server)] server: &ObjectServer,
         #[zbus(header)] header: Header<'_>,
     ) -> Result<OwnedValue> {
@@ -41,7 +42,12 @@ impl Properties {
                 Error::UnknownInterface(format!("Unknown interface '{interface_name}'"))
             })?;
 
-        let res = iface.instance.read().await.get(property_name).await;
+        let res = iface
+            .instance
+            .read()
+            .await
+            .get(property_name, server, conn, &Some(header))
+            .await;
         res.unwrap_or_else(|| {
             Err(Error::UnknownProperty(format!(
                 "Unknown property '{property_name}'"
@@ -72,7 +78,7 @@ impl Properties {
             .instance
             .read()
             .await
-            .set(property_name, &value, &emitter)
+            .set(property_name, &value, &emitter, &header)
         {
             zbus::object_server::DispatchResult::RequiresMut => {}
             zbus::object_server::DispatchResult::NotFound => {
@@ -88,7 +94,7 @@ impl Properties {
             .instance
             .write()
             .await
-            .set_mut(property_name, &value, &emitter)
+            .set_mut(property_name, &value, &emitter, &header)
             .await;
         res.unwrap_or_else(|| {
             Err(Error::UnknownProperty(format!(
@@ -113,7 +119,7 @@ impl Properties {
                 Error::UnknownInterface(format!("Unknown interface '{interface_name}'"))
             })?;
 
-        let res = iface.instance.read().await.get_all().await?;
+        let res = iface.instance.read().await.get_all(&Some(header)).await?;
         Ok(res)
     }
 

zbus/src/object_server/interface/mod.rs

@@ -17,8 +17,11 @@ use zbus_names::{InterfaceName, MemberName};
 use zvariant::{OwnedValue, Value};
 
 use crate::{
-    async_lock::RwLock, fdo, message::Message, object_server::SignalEmitter, Connection,
-    ObjectServer,
+    async_lock::RwLock,
+    fdo,
+    message::{self, Header, Message},
+    object_server::SignalEmitter,
+    Connection, ObjectServer,
 };
 
 /// This trait is used to dispatch messages to an interface instance.
@@ -45,10 +48,23 @@ pub trait Interface: Any + Send + Sync {
     }
 
     /// Get a property value. Returns `None` if the property doesn't exist.
-    async fn get(&self, property_name: &str) -> Option<fdo::Result<OwnedValue>>;
+    ///
+    /// Note: The header parameter will be None when the getter is used by the current process,
+    /// where we just query the value for administrative purposes. Since in that case there are no
+    /// "real" callers, it doesn't make sense to think of this parameter being relevant.
+    async fn get(
+        &self,
+        property_name: &str,
+        server: &ObjectServer,
+        connection: &Connection,
+        header: &Option<message::Header<'_>>,
+    ) -> Option<fdo::Result<OwnedValue>>;
 
     /// Return all the properties.
-    async fn get_all(&self) -> fdo::Result<HashMap<String, OwnedValue>>;
+    async fn get_all(
+        &self,
+        header: &Option<message::Header<'_>>,
+    ) -> fdo::Result<HashMap<String, OwnedValue>>;
 
     /// Set a property value.
     ///
@@ -60,8 +76,9 @@ pub trait Interface: Any + Send + Sync {
         property_name: &'call str,
         value: &'call Value<'_>,
         emitter: &'call SignalEmitter<'_>,
+        header: &'call message::Header<'_>,
     ) -> DispatchResult<'call> {
-        let _ = (property_name, value, emitter);
+        let _ = (property_name, value, emitter, header);
         DispatchResult::RequiresMut
     }
 
@@ -75,6 +92,7 @@ pub trait Interface: Any + Send + Sync {
         property_name: &str,
         value: &Value<'_>,
         emitter: &SignalEmitter<'_>,
+        header: &Header<'_>,
     ) -> Option<fdo::Result<()>>;
 
     /// Call a method.

zbus/src/object_server/node.rs

@@ -241,7 +241,7 @@ impl Node {
             .instance
             .read()
             .await
-            .get_all()
+            .get_all(&None)
             .await
     }
 }

zbus/tests/e2e.rs

@@ -262,6 +262,13 @@ impl MyIface {
         self.count
     }
 
+    #[instrument]
+    #[zbus(property)]
+    fn test_header_prop(&self, #[zbus(header)] header: Option<Header<'_>>) -> bool {
+        debug!("`TestHeaderProp` getter called: {:?}.", header);
+        header.is_some()
+    }
+
     #[instrument]
     #[zbus(property)]
     async fn hash_map(&self) -> HashMap<String, String> {
@@ -570,6 +577,7 @@ async fn my_iface_test(conn: Connection, event: Event) -> zbus::Result<u32> {
     drop(props_changed_stream);
 
     proxy.ping().await?;
+    assert_eq!(proxy.test_header_prop().await?, true);
     assert_eq!(proxy.count().await?, 1);
     assert_eq!(proxy.cached_count()?, None);