commit 254b23ab9d82a85892d01499100cde0b3d8b6931
Author: David Goulet <dgoulet@xxxxxxxxxxxxxx>
Date: Wed Mar 9 13:47:27 2022 -0500
hs: Schedule mainloop event on dirinfo change
Due to a possible Guard subsystem recursion, when the HS client gets
notified that the directory information has changed, it must run it in a
seperate mainloop event to avoid such issue.
See the ticket for more information on the recursion. This also fixes a
fatal assert.
Fixes #40579
Signed-off-by: David Goulet <dgoulet@xxxxxxxxxxxxxx>
---
changes/ticket40579 | 3 +++
src/feature/hs/hs_client.c | 48 ++++++++++++++++++++++++++++++++++++++++------
2 files changed, 45 insertions(+), 6 deletions(-)
diff --git a/changes/ticket40579 b/changes/ticket40579
new file mode 100644
index 0000000000..e2558c1102
--- /dev/null
+++ b/changes/ticket40579
@@ -0,0 +1,3 @@
+ o Minor bugfixes (onion service, client):
+ - Fix a fatal assert due to a guard subsystem recursion triggered by the
+ onion service client. Fixes bug 40579; bugfix on 0.3.5.1-alpha.
diff --git a/src/feature/hs/hs_client.c b/src/feature/hs/hs_client.c
index 4b4e268542..6c9645f0b8 100644
--- a/src/feature/hs/hs_client.c
+++ b/src/feature/hs/hs_client.c
@@ -38,6 +38,7 @@
#include "lib/crypt_ops/crypto_format.h"
#include "lib/crypt_ops/crypto_rand.h"
#include "lib/crypt_ops/crypto_util.h"
+#include "lib/evloop/compat_libevent.h"
#include "core/or/cpath_build_state_st.h"
#include "feature/dircommon/dir_connection_st.h"
@@ -46,11 +47,30 @@
#include "core/or/origin_circuit_st.h"
#include "core/or/socks_request_st.h"
+#include "trunnel/hs/cell_introduce1.h"
+
+/** This event is activated when we are notified that directory information has
+ * changed. It must be done asynchronous from the call due to possible
+ * recursion from the caller of that notification. See #40579. */
+static struct mainloop_event_t *dir_info_changed_ev = NULL;
+
/** Client-side authorizations for hidden services; map of service identity
* public key to hs_client_service_authorization_t *. */
static digest256map_t *client_auths = NULL;
-#include "trunnel/hs/cell_introduce1.h"
+/** Mainloop callback. Scheduled to run when we are notified of a directory
+ * info change. See hs_client_dir_info_changed(). */
+static void
+dir_info_changed_callback(mainloop_event_t *event, void *arg)
+{
+ (void) event;
+ (void) arg;
+
+ /* We have possibly reached the minimum directory information or new
+ * consensus so retry all pending SOCKS connection in
+ * AP_CONN_STATE_RENDDESC_WAIT state in order to fetch the descriptor. */
+ retry_all_socks_conn_waiting_for_desc();
+}
/** Return a human-readable string for the client fetch status code. */
static const char *
@@ -2584,6 +2604,9 @@ hs_client_free_all(void)
/* Purge the hidden service request cache. */
hs_purge_last_hid_serv_requests();
client_service_authorization_free_all();
+
+ /* This is NULL safe. */
+ mainloop_event_free(dir_info_changed_ev);
}
/** Purge all potentially remotely-detectable state held in the hidden
@@ -2609,14 +2632,27 @@ hs_client_purge_state(void)
log_info(LD_REND, "Hidden service client state has been purged.");
}
-/** Called when our directory information has changed. */
+/** Called when our directory information has changed.
+ *
+ * The work done in that function has to either be kept within the HS subsystem
+ * or else scheduled as a mainloop event. In other words, this function can't
+ * call outside to another subsystem to avoid risking recursion problems. */
void
hs_client_dir_info_changed(void)
{
- /* We have possibly reached the minimum directory information or new
- * consensus so retry all pending SOCKS connection in
- * AP_CONN_STATE_RENDDESC_WAIT state in order to fetch the descriptor. */
- retry_all_socks_conn_waiting_for_desc();
+ /* Make sure the mainloop has been initialized. Code path exist that reaches
+ * this before it is. */
+ if (!tor_libevent_is_initialized()) {
+ return;
+ }
+
+ /* Lazily create the event. HS Client subsystem doesn't have an init function
+ * and so we do it here before activating it. */
+ if (!dir_info_changed_ev) {
+ dir_info_changed_ev = mainloop_event_new(dir_info_changed_callback, NULL);
+ }
+ /* Activate it to run immediately. */
+ mainloop_event_activate(dir_info_changed_ev);
}
#ifdef TOR_UNIT_TESTS
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