96 lines
4.2 KiB
Diff
96 lines
4.2 KiB
Diff
From 37a4dc5835731a1f7a81f1b67c45b8dfb556dd1c Mon Sep 17 00:00:00 2001
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From: hongjinghao <q1204531485@163.com>
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Date: Mon, 5 Jun 2023 18:17:06 +0100
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Subject: [PATCH] bus: Assign a serial number for messages from the driver
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Normally, it's enough to rely on a message being given a serial number
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by the DBusConnection just before it is actually sent. However, in the
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rare case where the policy blocks the driver from sending a message
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(due to a deny rule or the outgoing message quota being full), we need
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to get a valid serial number sooner, so that we can copy it into the
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DBUS_HEADER_FIELD_REPLY_SERIAL field (which is mandatory) in the error
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message sent to monitors. Otherwise, the dbus-daemon will crash with
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an assertion failure if at least one Monitoring client is attached,
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because zero is not a valid serial number to copy.
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This fixes a denial-of-service vulnerability: if a privileged user is
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monitoring the well-known system bus using a Monitoring client like
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dbus-monitor or `busctl monitor`, then an unprivileged user can cause
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denial-of-service by triggering this crash. A mitigation for this
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vulnerability is to avoid attaching Monitoring clients to the system
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bus when they are not needed. If there are no Monitoring clients, then
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the vulnerable code is not reached.
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Co-authored-by: Simon McVittie <smcv@collabora.com>
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Resolves: dbus/dbus#457
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(cherry picked from commit b159849e031000d1dbc1ab876b5fc78a3ce9b534)
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---
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bus/connection.c | 15 +++++++++++++++
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dbus/dbus-connection-internal.h | 2 ++
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dbus/dbus-connection.c | 11 ++++++++++-
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3 files changed, 27 insertions(+), 1 deletion(-)
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diff --git a/bus/connection.c b/bus/connection.c
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index b35834338..215f02307 100644
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--- a/bus/connection.c
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+++ b/bus/connection.c
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@@ -2350,6 +2350,21 @@ bus_transaction_send_from_driver (BusTransaction *transaction,
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if (!dbus_message_set_sender (message, DBUS_SERVICE_DBUS))
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return FALSE;
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+ /* Make sure the message has a non-zero serial number, otherwise
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+ * bus_transaction_capture_error_reply() will not be able to mock up
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+ * a corresponding reply for it. Normally this would be delayed until
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+ * the first time we actually send the message out from a
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+ * connection, when the transaction is committed, but that's too late
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+ * in this case.
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+ */
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+ if (dbus_message_get_serial (message) == 0)
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+ {
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+ dbus_uint32_t next_serial;
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+
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+ next_serial = _dbus_connection_get_next_client_serial (connection);
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+ dbus_message_set_serial (message, next_serial);
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+ }
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+
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if (bus_connection_is_active (connection))
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{
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if (!dbus_message_set_destination (message,
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diff --git a/dbus/dbus-connection-internal.h b/dbus/dbus-connection-internal.h
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index 483573212..ba79b1928 100644
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--- a/dbus/dbus-connection-internal.h
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+++ b/dbus/dbus-connection-internal.h
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@@ -54,6 +54,8 @@ DBUS_PRIVATE_EXPORT
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DBusConnection * _dbus_connection_ref_unlocked (DBusConnection *connection);
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DBUS_PRIVATE_EXPORT
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void _dbus_connection_unref_unlocked (DBusConnection *connection);
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+DBUS_PRIVATE_EXPORT
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+dbus_uint32_t _dbus_connection_get_next_client_serial (DBusConnection *connection);
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void _dbus_connection_queue_received_message_link (DBusConnection *connection,
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DBusList *link);
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dbus_bool_t _dbus_connection_has_messages_to_send_unlocked (DBusConnection *connection);
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diff --git a/dbus/dbus-connection.c b/dbus/dbus-connection.c
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index c525b6dc1..09cef2788 100644
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--- a/dbus/dbus-connection.c
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+++ b/dbus/dbus-connection.c
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@@ -1456,7 +1456,16 @@ _dbus_connection_unref_unlocked (DBusConnection *connection)
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_dbus_connection_last_unref (connection);
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}
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-static dbus_uint32_t
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+/**
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+ * Allocate and return the next non-zero serial number for outgoing messages.
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+ *
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+ * This method is only valid to call from single-threaded code, such as
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+ * the dbus-daemon, or with the connection lock held.
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+ *
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+ * @param connection the connection
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+ * @returns A suitable serial number for the next message to be sent on the connection.
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+ */
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+dbus_uint32_t
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_dbus_connection_get_next_client_serial (DBusConnection *connection)
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{
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dbus_uint32_t serial;
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--
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GitLab
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