From a4e2856d06f3abba98fc542795075ec7322cdde7 Mon Sep 17 00:00:00 2001
From: Wim Taymans <wtaymans@redhat.com>
Date: Thu, 7 May 2026 14:08:30 +0200
Subject: [PATCH] pulse-server: block arbitrary filter-graphs

Add a special 'blocked' spa-libs value that returns EPERM when trying to
load the factory.

Only allow loading the LADSPA filter.graph nodes for the LADSPA sink and
source. The most problematic part is the pipe filter, that allows it to
spawn arbirary programs as part of the filter.graph.

You can add a filter-graph to any stream with stream_props.
---
 doc/dox/config/pipewire.conf.5.md | 3 +++
 src/daemon/pipewire-pulse.conf.in | 6 ++++++
 src/pipewire/context.c            | 4 ++--
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/doc/dox/config/pipewire.conf.5.md b/doc/dox/config/pipewire.conf.5.md
index 8c551ba55..12d2ea855 100644
--- a/doc/dox/config/pipewire.conf.5.md
+++ b/doc/dox/config/pipewire.conf.5.md
@@ -358,6 +358,8 @@ factory-name and the plugin where the factory can be found.
 Factory names can contain a wildcard to group several related factories into one
 plugin. The plugin is loaded from the first matching factory-name.
 
+A special `blocked` value for the plugin disables the factory-name.
+
 ## Example
 
 ```
@@ -374,6 +376,7 @@ context.spa-libs = {
     api.jack.*      = jack/libspa-jack
     support.*       = support/libspa-support
     video.convert.* = videoconvert/libspa-videoconvert
+    #filter.graph   = blocked
 }
 ```
 
diff --git a/src/daemon/pipewire-pulse.conf.in b/src/daemon/pipewire-pulse.conf.in
index bf4b93c77..3b427fbd6 100644
--- a/src/daemon/pipewire-pulse.conf.in
+++ b/src/daemon/pipewire-pulse.conf.in
@@ -22,6 +22,12 @@ context.properties = {
 context.spa-libs = {
     audio.convert.* = audioconvert/libspa-audioconvert
     support.*       = support/libspa-support
+    # because the pulse server allows dynamic loading of streams and modules
+    # inside the server, we must be careful with the filter-graph. Only allow
+    # LADSPA filters.
+    filter.graph.plugin.ladspa = filter-graph/libspa-filter-graph-plugin-ladspa
+    filter.graph.plugin.* = blocked
+    filter.graph = filter-graph/libspa-filter-graph
 }
 
 context.modules = [
diff --git a/src/pipewire/context.c b/src/pipewire/context.c
index 63a3ae9c9..eb89ca752 100644
--- a/src/pipewire/context.c
+++ b/src/pipewire/context.c
@@ -1067,8 +1067,8 @@ struct spa_handle *pw_context_load_spa_handle(struct pw_context *context,
 	lib = pw_context_find_spa_lib(context, factory_name);
 	if (lib == NULL && info != NULL)
 		lib = spa_dict_lookup(info, SPA_KEY_LIBRARY_NAME);
-	if (lib == NULL) {
-		errno = ENOENT;
+	if (lib == NULL || spa_streq(lib, "blocked")) {
+		errno = lib ? EPERM : ENOENT;
 		pw_log_warn("%p: no library for %s: %m",
 				context, factory_name);
 		return NULL;