MDEV-21960 Bind READ_ONLY ADMIN to @@read_only

mysql-test/suite/sys_vars/r/read_only_func.result

@@ -20,7 +20,7 @@ id	name
 CREATE user sameea;
 CONNECT  connn,localhost,sameea,,;
 SET Global read_ONLY=ON;
-ERROR 42000: Access denied; you need (at least one of) the SUPER privilege(s) for this operation
+ERROR 42000: Access denied; you need (at least one of) the SUPER, READ_ONLY ADMIN privilege(s) for this operation
 CREATE TABLE t2
 (
 id INT NOT NULL auto_increment,

mysql-test/suite/sys_vars/r/read_only_grant.result

+#
+# MDEV-21960 Bind READ_ONLY ADMIN to @@read_only
+#
+# Test that "SET read_only" is not allowed without READ_ONLY ADMIN or SUPER
+CREATE USER user1@localhost;
+GRANT ALL PRIVILEGES ON *.* TO user1@localhost;
+REVOKE READ_ONLY ADMIN, SUPER ON *.* FROM user1@localhost;
+connect user1,localhost,user1,,;
+connection user1;
+SET GLOBAL read_only=0;
+ERROR 42000: Access denied; you need (at least one of) the SUPER, READ_ONLY ADMIN privilege(s) for this operation
+SET read_only=0;
+ERROR HY000: Variable 'read_only' is a GLOBAL variable and should be set with SET GLOBAL
+SET SESSION read_only=0;
+ERROR HY000: Variable 'read_only' is a GLOBAL variable and should be set with SET GLOBAL
+disconnect user1;
+connection default;
+DROP USER user1@localhost;
+# Test that "SET read_only" is allowed with READ_ONLY ADMIN
+CREATE USER user1@localhost;
+GRANT READ_ONLY ADMIN ON *.* TO user1@localhost;
+connect user1,localhost,user1,,;
+connection user1;
+SET GLOBAL read_only=0;
+SET read_only=0;
+ERROR HY000: Variable 'read_only' is a GLOBAL variable and should be set with SET GLOBAL
+SET SESSION read_only=0;
+ERROR HY000: Variable 'read_only' is a GLOBAL variable and should be set with SET GLOBAL
+disconnect user1;
+connection default;
+DROP USER user1@localhost;
+# Test that "SET read_only" is allowed with SUPER
+CREATE USER user1@localhost;
+GRANT SUPER ON *.* TO user1@localhost;
+connect user1,localhost,user1,,;
+connection user1;
+SET GLOBAL read_only=0;
+SET read_only=0;
+ERROR HY000: Variable 'read_only' is a GLOBAL variable and should be set with SET GLOBAL
+SET SESSION read_only=0;
+ERROR HY000: Variable 'read_only' is a GLOBAL variable and should be set with SET GLOBAL
+disconnect user1;
+connection default;
+DROP USER user1@localhost;

mysql-test/suite/sys_vars/t/read_only_grant.test

+--source include/not_embedded.inc
+
+--echo #
+--echo # MDEV-21960 Bind READ_ONLY ADMIN to @@read_only
+--echo #
+
+--echo # Test that "SET read_only" is not allowed without READ_ONLY ADMIN or SUPER
+
+CREATE USER user1@localhost;
+GRANT ALL PRIVILEGES ON *.* TO user1@localhost;
+REVOKE READ_ONLY ADMIN, SUPER ON *.* FROM user1@localhost;
+--connect(user1,localhost,user1,,)
+--connection user1
+--error ER_SPECIFIC_ACCESS_DENIED_ERROR
+SET GLOBAL read_only=0;
+--error ER_GLOBAL_VARIABLE
+SET read_only=0;
+--error ER_GLOBAL_VARIABLE
+SET SESSION read_only=0;
+--disconnect user1
+--connection default
+DROP USER user1@localhost;
+
+--echo # Test that "SET read_only" is allowed with READ_ONLY ADMIN
+
+CREATE USER user1@localhost;
+GRANT READ_ONLY ADMIN ON *.* TO user1@localhost;
+--connect(user1,localhost,user1,,)
+--connection user1
+SET GLOBAL read_only=0;
+--error ER_GLOBAL_VARIABLE
+SET read_only=0;
+--error ER_GLOBAL_VARIABLE
+SET SESSION read_only=0;
+--disconnect user1
+--connection default
+DROP USER user1@localhost;
+
+--echo # Test that "SET read_only" is allowed with SUPER
+
+CREATE USER user1@localhost;
+GRANT SUPER ON *.* TO user1@localhost;
+--connect(user1,localhost,user1,,)
+--connection user1
+SET GLOBAL read_only=0;
+--error ER_GLOBAL_VARIABLE
+SET read_only=0;
+--error ER_GLOBAL_VARIABLE
+SET SESSION read_only=0;
+--disconnect user1
+--connection default
+DROP USER user1@localhost;

sql/privilege.h

@@ -325,7 +325,11 @@ constexpr privilege_t PRIV_SET_SYSTEM_VAR_SQL_LOG_BIN=
 
 
 /* Privileges related to --read-only */
+// Was super prior to 10.5.2
 constexpr privilege_t PRIV_IGNORE_READ_ONLY= READ_ONLY_ADMIN_ACL | SUPER_ACL;
+// Was super prior to 10.5.2
+constexpr privilege_t PRIV_SET_SYSTEM_GLOBAL_VAR_READ_ONLY=
+  READ_ONLY_ADMIN_ACL | SUPER_ACL;
 
 /*
   Privileges related to connection handling.

sql/sys_vars.cc

@@ -2822,7 +2822,9 @@ static bool fix_read_only(sys_var *self, THD *thd, enum_var_type type)
   transition (especially when transitioning from false to true) and
   synchronizes both booleans in the end.
 */
-static Sys_var_mybool Sys_readonly(
+static Sys_var_on_access_global<Sys_var_mybool,
+                                PRIV_SET_SYSTEM_GLOBAL_VAR_READ_ONLY>
+Sys_readonly(
        "read_only",
        "Make all non-temporary tables read-only, with the exception for "
        "replication (slave) threads and users with the SUPER privilege",

sql/sys_vars.ic

@@ -118,6 +118,17 @@ class Sys_var_on_access: public BASE
 };
 
 
+template<class BASE, privilege_t GLOBAL_PRIV>
+class Sys_var_on_access_global: public BASE
+{
+  using BASE::BASE;
+  bool on_check_access_global(THD *thd) const override
+  {
+    return check_global_access(thd, GLOBAL_PRIV);
+  }
+};
+
+
 /**
   A small wrapper class to pass getopt arguments as a pair
   to the Sys_var_* constructors. It improves type safety and helps