PS-11143-[9.7] sql/auth: quiesce caching_sha2_password before teardown

sql/auth/sha2_password.cc

@@ -33,8 +33,10 @@
 #include <sys/types.h>
 #include <algorithm>
 #include <charconv>  // from_chars
-#include <iomanip>   /* std::setfill(), std::setw() */
-#include <iostream>  /* For debugging               */
+#include <condition_variable>
+#include <iomanip>  /* std::setfill(), std::setw() */
+#include <iostream> /* For debugging               */
+#include <mutex>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ -103,11 +105,43 @@ bool caching_sha2_enforce_storage_format = false;
 class THD;
 struct SYS_VAR;
 
+extern sha2_password::Caching_sha2_password *g_caching_sha2_password;
+
+class Caching_sha2_password_state {
+ public:
+  bool begin() {
+    std::lock_guard<std::mutex> lock(mutex);
+    if (shutting_down || g_caching_sha2_password == nullptr) return false;
+    ++active_calls;
+    return true;
+  }
+
+  void end() {
+    std::lock_guard<std::mutex> lock(mutex);
+    assert(active_calls > 0);
+    if (--active_calls == 0) cv.notify_all();
+  }
+
+  void start_shutdown() {
+    std::unique_lock<std::mutex> lock(mutex);
+    shutting_down = true;
+    cv.wait(lock, [&] { return active_calls == 0; });
+  }
+
+ private:
+  std::mutex mutex;
+  std::condition_variable cv;
+  size_t active_calls = 0;
+  bool shutting_down = false;
+};
+
 char *caching_sha2_rsa_private_key_path;
 char *caching_sha2_rsa_public_key_path;
 bool caching_sha2_auto_generate_rsa_keys = true;
 
 Rsa_authentication_keys *g_caching_sha2_rsa_keys = nullptr;
+int caching_sha2_digest_rounds = 0;
+static Caching_sha2_password_state g_caching_sha2_password_state;
 
 static bool init_event_tracking_authentication();
 static bool deinit_event_tracking_authentication();
@@ -1100,6 +1134,9 @@ static char perform_full_authentication = '\4';
 static int caching_sha2_password_authenticate(MYSQL_PLUGIN_VIO *vio,
                                               MYSQL_SERVER_AUTH_INFO *info) {
   DBUG_TRACE;
+  if (!g_caching_sha2_password_state.begin()) return CR_ERROR;
+  auto cleanup_guard =
+      create_scope_guard([&] { g_caching_sha2_password_state.end(); });
   uchar *pkt;
   int pkt_len;
   char scramble[SCRAMBLE_LENGTH + 1];
@@ -1326,6 +1363,9 @@ static int caching_sha2_password_authenticate(MYSQL_PLUGIN_VIO *vio,
 int caching_sha2_password_generate(char *outbuf, unsigned int *buflen,
                                    const char *inbuf, unsigned int inbuflen) {
   DBUG_TRACE;
+  if (!g_caching_sha2_password_state.begin()) return 1;
+  auto cleanup_guard =
+      create_scope_guard([&] { g_caching_sha2_password_state.end(); });
   const std::string source(inbuf, inbuflen);
   std::string serialized_string;
 
@@ -1372,6 +1412,9 @@ int caching_sha2_password_generate(char *outbuf, unsigned int *buflen,
 static int caching_sha2_password_validate(char *const inbuf,
                                           unsigned int buflen) {
   DBUG_TRACE;
+  if (!g_caching_sha2_password_state.begin()) return 1;
+  auto cleanup_guard =
+      create_scope_guard([&] { g_caching_sha2_password_state.end(); });
   const std::string serialized_string(inbuf, buflen);
   if (g_caching_sha2_password->validate_hash(serialized_string)) return 1;
   return 0;
@@ -1433,6 +1476,9 @@ static int caching_sha2_authentication_init(MYSQL_PLUGIN plugin_ref) {
 
 static int caching_sha2_authentication_deinit(void *arg [[maybe_unused]]) {
   DBUG_TRACE;
+
+  g_caching_sha2_password_state.start_shutdown();
+
   if (g_caching_sha2_password) {
     delete g_caching_sha2_password;
     g_caching_sha2_password = nullptr;
@@ -1461,6 +1507,12 @@ static int compare_caching_sha2_password_with_hash(
     const char *hash, unsigned long hash_length, const char *cleartext,
     unsigned long cleartext_length, int *is_error) {
   DBUG_TRACE;
+  if (!g_caching_sha2_password_state.begin()) {
+    *is_error = 1;
+    return -1;
+  }
+  auto cleanup_guard =
+      create_scope_guard([&] { g_caching_sha2_password_state.end(); });
 
   const std::string_view stored(hash, hash_length);
   const std::string plaintext_password(cleartext, cleartext_length);
@@ -1700,6 +1752,10 @@ bool Event_tracking_authentication_implementation::callback(
     If status is set to true, it indicates an error.
     In which case, don't touch the cache.
   */
+  if (!g_caching_sha2_password_state.begin()) return false;
+  auto cleanup_guard =
+      create_scope_guard([&] { g_caching_sha2_password_state.end(); });
+
   if (data->status) return false;
   switch (data->event_subclass) {
     case EVENT_TRACKING_AUTHENTICATION_FLUSH: