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systemd/SOURCES/0314-sd-bus-introduce-API-f...

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From 8efdae75ddf035c8c04983820f8d8cf767cc17b1 Mon Sep 17 00:00:00 2001
From: Jan Synacek <jsynacek@redhat.com>
Date: Fri, 31 Jan 2020 11:34:45 +0100
Subject: [PATCH] sd-bus: introduce API for re-enqueuing incoming messages
When authorizing via PolicyKit we want to process incoming method calls
twice: once to process and figure out that we need PK authentication,
and a second time after we aquired PK authentication to actually execute
the operation. With this new call sd_bus_enqueue_for_read() we have a
way to put an incoming message back into the read queue for this
purpose.
This might have other uses too, for example debugging.
Related: CVE-2020-1712
---
src/libsystemd/libsystemd.sym | 1 +
src/libsystemd/sd-bus/sd-bus.c | 24 ++++++++++++++++++++++++
src/systemd/sd-bus.h | 1 +
3 files changed, 26 insertions(+)
diff --git a/src/libsystemd/libsystemd.sym b/src/libsystemd/libsystemd.sym
index 1eec17db50..e9972593a6 100644
--- a/src/libsystemd/libsystemd.sym
+++ b/src/libsystemd/libsystemd.sym
@@ -569,4 +569,5 @@ global:
sd_event_source_get_inotify_mask;
sd_event_source_set_destroy_callback;
sd_event_source_get_destroy_callback;
+ sd_bus_enqueue_for_read;
} LIBSYSTEMD_238;
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index e49d58137d..68ad6cbe89 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -4120,3 +4120,27 @@ _public_ int sd_bus_get_n_queued_write(sd_bus *bus, uint64_t *ret) {
*ret = bus->wqueue_size;
return 0;
}
+
+_public_ int sd_bus_enqueue_for_read(sd_bus *bus, sd_bus_message *m) {
+ int r;
+
+ assert_return(bus, -EINVAL);
+ assert_return(bus = bus_resolve(bus), -ENOPKG);
+ assert_return(m, -EINVAL);
+ assert_return(m->sealed, -EINVAL);
+ assert_return(!bus_pid_changed(bus), -ECHILD);
+
+ if (!BUS_IS_OPEN(bus->state))
+ return -ENOTCONN;
+
+ /* Re-enqeue a message for reading. This is primarily useful for PolicyKit-style authentication,
+ * where we want accept a message, then determine we need to interactively authenticate the user, and
+ * when we have that process the message again. */
+
+ r = bus_rqueue_make_room(bus);
+ if (r < 0)
+ return r;
+
+ bus->rqueue[bus->rqueue_size++] = bus_message_ref_queued(m, bus);
+ return 0;
+}
diff --git a/src/systemd/sd-bus.h b/src/systemd/sd-bus.h
index 54c4b1ca83..9ba757b13d 100644
--- a/src/systemd/sd-bus.h
+++ b/src/systemd/sd-bus.h
@@ -193,6 +193,7 @@ int sd_bus_process(sd_bus *bus, sd_bus_message **r);
int sd_bus_process_priority(sd_bus *bus, int64_t max_priority, sd_bus_message **r);
int sd_bus_wait(sd_bus *bus, uint64_t timeout_usec);
int sd_bus_flush(sd_bus *bus);
+int sd_bus_enqueue_for_read(sd_bus *bus, sd_bus_message *m);
sd_bus_slot* sd_bus_get_current_slot(sd_bus *bus);
sd_bus_message* sd_bus_get_current_message(sd_bus *bus);