BUG 12610784: SET PASSWORD INCORRECTLY KEEP AN OLD EMPTY PASSWORD

The check for empty password in the user account was checking the wrong field.
Fixed to check the proper password hash.
Test case added.
Fixed native_password and old_password plugins that suffered from the same
problems.
Unambuguated the auth_string ACL_USER member : previously it was used for 
both password and the authentication string (depending on the plugin). Now
fixed to contain either the authentication string specified or empty string.

mysql-test/r/plugin_auth.result

@@ -447,4 +447,11 @@ ORDER BY COLUMN_NAME;
 IS_NULLABLE	COLUMN_NAME
 YES	authentication_string
 YES	plugin
+#
+# Bug #12610784: SET PASSWORD INCORRECTLY KEEP AN OLD EMPTY PASSWORD
+#
+CREATE USER bug12610784@localhost;
+SET PASSWORD FOR bug12610784@localhost = PASSWORD('secret');
+ERROR 28000: Access denied for user 'bug12610784'@'localhost' (using password: NO)
+DROP USER bug12610784@localhost;
 End of 5.5 tests

mysql-test/t/plugin_auth.test

@@ -512,4 +512,19 @@ SELECT IS_NULLABLE, COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS
   ORDER BY COLUMN_NAME;
 
 
+--echo #
+--echo # Bug #12610784: SET PASSWORD INCORRECTLY KEEP AN OLD EMPTY PASSWORD
+--echo #
+
+CREATE USER bug12610784@localhost; 
+SET PASSWORD FOR bug12610784@localhost = PASSWORD('secret');
+--disable_query_log
+--error ER_ACCESS_DENIED_ERROR
+connect(b12610784,localhost,bug12610784,,test);
+--enable_query_log
+connect(b12610784,localhost,bug12610784,secret,test);
+connection default;
+disconnect b12610784;
+DROP USER bug12610784@localhost;
+
 --echo End of 5.5 tests

sql/sql_acl.cc

@@ -825,8 +825,6 @@ static my_bool acl_load(THD *thd, TABLE_LIST *tables)
 
     char *password= get_field(&mem, table->field[2]);
     uint password_len= password ? strlen(password) : 0;
-    user.auth_string.str= password ? password : const_cast<char*>("");
-    user.auth_string.length= password_len;
     set_user_salt(&user, password, password_len);
 
     if (set_user_plugin(&user, password_len))
@@ -915,7 +913,7 @@ static my_bool acl_load(THD *thd, TABLE_LIST *tables)
           char *tmpstr= get_field(&mem, table->field[next_field++]);
           if (tmpstr)
           {
-            if (user.auth_string.length)
+            if (password_len)
             {
               sql_print_warning("'user' entry '%s@%s' has both a password "
                                 "and an authentication plugin specified. The "
@@ -1483,8 +1481,8 @@ static void acl_insert_user(const char *user, const char *host,
   {
     acl_user.plugin= password_len == SCRAMBLED_PASSWORD_CHAR_LENGTH_323 ?
       old_password_plugin_name : native_password_plugin_name;
-    acl_user.auth_string.str= strmake_root(&mem, password, password_len);
-    acl_user.auth_string.length= password_len;
+    acl_user.auth_string.str= const_cast<char*>("");
+    acl_user.auth_string.length= 0;
   }
 
   acl_user.access=privileges;
@@ -8380,7 +8378,7 @@ static bool parse_com_change_user_packet(MPVIO_EXT *mpvio, uint packet_length)
         old_password_plugin, otherwise MySQL will think that server 
         and client plugins don't match.
       */
-      if (mpvio->acl_user->auth_string.length == 0)
+      if (mpvio->acl_user->salt_len == 0)
         mpvio->acl_user_plugin= old_password_plugin_name;
     }
   }
@@ -8685,7 +8683,7 @@ static ulong parse_client_handshake_packet(MPVIO_EXT *mpvio,
         old_password_plugin, otherwise MySQL will think that server 
         and client plugins don't match.
       */
-      if (mpvio->acl_user->auth_string.length == 0)
+      if (mpvio->acl_user->salt_len == 0)
         mpvio->acl_user_plugin= old_password_plugin_name;
     }
   }
@@ -9473,7 +9471,7 @@ static int native_password_authenticate(MYSQL_PLUGIN_VIO *vio,
 #endif
 
   if (pkt_len == 0) /* no password */
-    DBUG_RETURN(info->auth_string[0] ? CR_ERROR : CR_OK);
+    DBUG_RETURN(mpvio->acl_user->salt_len != 0 ? CR_ERROR : CR_OK);
 
   info->password_used= PASSWORD_USED_YES;
   if (pkt_len == SCRAMBLE_LENGTH)
@@ -9522,7 +9520,7 @@ static int old_password_authenticate(MYSQL_PLUGIN_VIO *vio,
     pkt_len= strnlen((char*)pkt, pkt_len);
 
   if (pkt_len == 0) /* no password */
-    return info->auth_string[0] ? CR_ERROR : CR_OK;
+    return mpvio->acl_user->salt_len != 0 ? CR_ERROR : CR_OK;
 
   if (secure_auth(mpvio))
     return CR_ERROR;