A container may declare the capabilities it is granted (hq ADR 0169)

Exactly the names declared reach the runtime, named in the spec so a change
recreates the container; a name that is not a capability's is refused and a
privileged container stays undeclarable. For a seat holder whose runtime
changes the machine's packet filter.

internal/apply/left_out_test.go

@@ -134,3 +134,42 @@ func TestALeftOutModuleIsNeitherRemovedNorForgotten(t *testing.T) {
 		t.Fatalf("keeping the left-out module's container was not said: %+v", report.Outcomes)
 	}
 }
+
+// A container's capabilities reach the runtime and are part of its spec (novox/hq ADR 0169).
+func TestACapabilityReachesTheRuntimeAndTheSpec(t *testing.T) {
+	var ran []string
+	run := func(_ context.Context, name string, args ...string) (string, error) {
+		if name != "docker" {
+			return "", errors.New("not installed")
+		}
+		switch args[0] {
+		case "info":
+			return "29.0.0\n", nil
+		case "container":
+			return "false\t\n", errors.New("no such container")
+		case "run":
+			ran = args
+			return "deadbeef\n", nil
+		}
+		return "", nil
+	}
+	d := parseTrusted(t, `{"declaration":1,"resources":[
+	  {"id":"fw","type":"container","name":"fw","image":"`+pinned+`","network":"host","capabilities":["NET_ADMIN"]}
+	]}`)
+	_, _, _ = Apply(context.Background(), archHost(t), d, store.State{}, store.OriginCarried, run, nil, nil)
+	granted := false
+	for i, a := range ran {
+		if a == "--cap-add" && i+1 < len(ran) && ran[i+1] == "NET_ADMIN" {
+			granted = true
+		}
+	}
+	if !granted {
+		t.Fatalf("the capability was not granted: %v", ran)
+	}
+	with := d.Resources[0].(*declaration.Container)
+	without := *with
+	without.Capabilities = nil
+	if containerSpec(with, inputs{}) == containerSpec(&without, inputs{}) {
+		t.Fatal("a capability is not part of the container's spec")
+	}
+}