From 55bb3260c12bae33b6a8eac73cbb6972f8517411 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Reynir=20Bj=C3=B6rnsson?= Date: Thu, 16 May 2024 13:58:08 +0200 Subject: [PATCH] Only schedule_exit() once MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If an exit has already been scheduled we should not schedule it again. Otherwise, the exit signal is never emitted if the peer reschedules the exit before the timeout occurs. schedule_exit() now only takes the context as argument. The signal is hard coded to SIGTERM, and the interval is read directly from the context options. Furthermore, schedule_exit() now returns a bool signifying whether an exit was scheduled; false if exit is already scheduled. The call sites are updated accordingly. A notable difference is that management is only notified *once* when an exit is scheduled - we no longer notify management on redundant exit. This patch was assigned a CVE number after already reviewed and ACKed, because it was discovered that a misbehaving client can use the (now fixed) server behaviour to avoid being disconnected by means of a managment interface "client-kill" command - the security issue here is "client can circumvent security policy set by management interface". This only affects previously authenticated clients, and only management client-kill, so normal renegotion / AUTH_FAIL ("your session ends") is not affected. CVE: 2024-28882 Change-Id: I9457f005f4ba970502e6b667d9dc4299a588d661 Signed-off-by: Reynir Björnsson Acked-by: Arne Schwabe Message-Id: <20240516120434.23499-1-gert@greenie.muc.de> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg28679.html Signed-off-by: Gert Doering --- src/openvpn/forward.c | 15 +++++++++++---- src/openvpn/forward.h | 2 +- src/openvpn/push.c | 12 +++++++----- 3 files changed, 19 insertions(+), 10 deletions(-) diff --git a/src/openvpn/forward.c b/src/openvpn/forward.c index 8d10f253..01165b2e 100644 --- a/src/openvpn/forward.c +++ b/src/openvpn/forward.c @@ -514,17 +514,24 @@ check_server_poll_timeout(struct context *c) } /* - * Schedule a signal n_seconds from now. + * Schedule a SIGTERM signal c->options.scheduled_exit_interval seconds from now. */ -void -schedule_exit(struct context *c, const int n_seconds, const int signal) +bool +schedule_exit(struct context *c) { + const int n_seconds = c->options.scheduled_exit_interval; + /* don't reschedule if already scheduled. */ + if (event_timeout_defined(&c->c2.scheduled_exit)) + { + return false; + } tls_set_single_session(c->c2.tls_multi); update_time(); reset_coarse_timers(c); event_timeout_init(&c->c2.scheduled_exit, n_seconds, now); - c->c2.scheduled_exit_signal = signal; + c->c2.scheduled_exit_signal = SIGTERM; msg(D_SCHED_EXIT, "Delayed exit in %d seconds", n_seconds); + return true; } /* diff --git a/src/openvpn/forward.h b/src/openvpn/forward.h index 6fb5a189..422c5913 100644 --- a/src/openvpn/forward.h +++ b/src/openvpn/forward.h @@ -303,7 +303,7 @@ void reschedule_multi_process(struct context *c); void process_ip_header(struct context *c, unsigned int flags, struct buffer *buf); -void schedule_exit(struct context *c, const int n_seconds, const int signal); +bool schedule_exit(struct context *c); static inline struct link_socket_info * get_link_socket_info(struct context *c) diff --git a/src/openvpn/push.c b/src/openvpn/push.c index 1b406b9c..d220eeb9 100644 --- a/src/openvpn/push.c +++ b/src/openvpn/push.c @@ -204,7 +204,11 @@ receive_exit_message(struct context *c) * */ if (c->options.mode == MODE_SERVER) { - schedule_exit(c, c->options.scheduled_exit_interval, SIGTERM); + if (!schedule_exit(c)) + { + /* Return early when we don't need to notify management */ + return; + } } else { @@ -391,7 +395,7 @@ __attribute__ ((format(__printf__, 4, 5))) void send_auth_failed(struct context *c, const char *client_reason) { - if (event_timeout_defined(&c->c2.scheduled_exit)) + if (!schedule_exit(c)) { msg(D_TLS_DEBUG, "exit already scheduled for context"); return; @@ -401,8 +405,6 @@ send_auth_failed(struct context *c, const char *client_reason) static const char auth_failed[] = "AUTH_FAILED"; size_t len; - schedule_exit(c, c->options.scheduled_exit_interval, SIGTERM); - len = (client_reason ? strlen(client_reason)+1 : 0) + sizeof(auth_failed); if (len > PUSH_BUNDLE_SIZE) { @@ -492,7 +494,7 @@ send_auth_pending_messages(struct tls_multi *tls_multi, void send_restart(struct context *c, const char *kill_msg) { - schedule_exit(c, c->options.scheduled_exit_interval, SIGTERM); + schedule_exit(c); send_control_channel_string(c, kill_msg ? kill_msg : "RESTART", D_PUSH); }