privilege: add DDL and DML privilege check for system tables (#15095) (…

…#15417) (#15445)

infoschema/perfschema/tables.go

@@ -14,6 +14,8 @@
 package perfschema
 
 import (
+	"strings"
+
 	"github.com/pingcap/parser/model"
 	"github.com/pingcap/tidb/infoschema"
 	"github.com/pingcap/tidb/kv"
@@ -36,6 +38,17 @@ const (
 	tableNameTiDBProfileGoroutines                  = "tidb_profile_goroutines"
 )
 
+var tableList = []string{
+	tableNameEventsStatementsSummaryByDigest,
+	tableNameTiDBProfileCPU,
+	tableNameTiDBProfileMemory,
+	tableNameTiDBProfileMutex,
+	tableNameTiDBProfileAllocs,
+	tableNameTiDBProfileBlock,
+	tableNameTiDBProfileGoroutines,
+	tableNameEventsStatementsSummaryByDigestHistory,
+}
+
 // perfSchemaTable stands for the fake table all its data is in the memory.
 type perfSchemaTable struct {
 	infoschema.VirtualTable
@@ -45,6 +58,16 @@ type perfSchemaTable struct {
 
 var pluginTable = make(map[string]func(autoid.Allocators, *model.TableInfo) (table.Table, error))
 
+// IsPredefinedTable judges whether this table is predefined.
+func IsPredefinedTable(tableName string) bool {
+	for _, name := range tableList {
+		if strings.EqualFold(tableName, name) {
+			return true
+		}
+	}
+	return false
+}
+
 // RegisterTable registers a new table into TiDB.
 func RegisterTable(tableName, sql string,
 	tableFromMeta func(autoid.Allocators, *model.TableInfo) (table.Table, error)) {

infoschema/perfschema/tables_test.go

@@ -20,6 +20,7 @@ import (
 	. "github.com/pingcap/check"
 	"github.com/pingcap/failpoint"
 	"github.com/pingcap/tidb/domain"
+	"github.com/pingcap/tidb/infoschema/perfschema"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/session"
 	"github.com/pingcap/tidb/store/mockstore"
@@ -56,6 +57,11 @@ func (s *testTableSuite) TearDownSuite(c *C) {
 	s.store.Close()
 }
 
+func (s *testTableSuite) TestPredefinedTables(c *C) {
+	c.Assert(perfschema.IsPredefinedTable("EVENTS_statements_summary_by_digest"), IsTrue)
+	c.Assert(perfschema.IsPredefinedTable("statements"), IsFalse)
+}
+
 func (s *testTableSuite) TestPerfSchemaTables(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 

privilege/privileges/privileges.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/pingcap/parser/auth"
 	"github.com/pingcap/parser/mysql"
+	"github.com/pingcap/tidb/infoschema/perfschema"
 	"github.com/pingcap/tidb/privilege"
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/types"
@@ -52,15 +53,29 @@ func (p *UserPrivileges) RequestVerification(activeRoles []*auth.RoleIdentity, d
 		return true
 	}
 
-	// Skip check for INFORMATION_SCHEMA database.
+	// Skip check for system databases.
 	// See https://dev.mysql.com/doc/refman/5.7/en/information-schema.html
-	if strings.EqualFold(db, "INFORMATION_SCHEMA") {
+	dbLowerName := strings.ToLower(db)
+	switch dbLowerName {
+	case util.InformationSchemaName.L:
 		switch priv {
 		case mysql.CreatePriv, mysql.AlterPriv, mysql.DropPriv, mysql.IndexPriv, mysql.CreateViewPriv,
 			mysql.InsertPriv, mysql.UpdatePriv, mysql.DeletePriv:
 			return false
 		}
 		return true
+	// We should be very careful of limiting privileges, so ignore `mysql` for now.
+	case util.PerformanceSchemaName.L:
+		// CREATE and DROP privileges are not limited in the older versions, so ignore them now.
+		// User may have created some tables in these schema, but predefined tables can't be altered or modified.
+		if dbLowerName == util.PerformanceSchemaName.L && perfschema.IsPredefinedTable(table) {
+			switch priv {
+			case mysql.AlterPriv, mysql.DropPriv, mysql.IndexPriv, mysql.InsertPriv, mysql.UpdatePriv, mysql.DeletePriv:
+				return false
+			case mysql.SelectPriv:
+				return true
+			}
+		}
 	}
 
 	mysqlPriv := p.Handle.Get()

privilege/privileges/privileges_test.go

@@ -880,8 +880,7 @@ func (s *testPrivilegeSuite) TestAnalyzeTable(c *C) {
 
 }
 
-func (s *testPrivilegeSuite) TestInformationSchema(c *C) {
-
+func (s *testPrivilegeSuite) TestSystemSchema(c *C) {
 	// This test tests no privilege check for INFORMATION_SCHEMA database.
 	se := newSession(c, s.store, s.dbName)
 	mustExec(c, se, `CREATE USER 'u1'@'localhost';`)
@@ -894,6 +893,15 @@ func (s *testPrivilegeSuite) TestInformationSchema(c *C) {
 	c.Assert(strings.Contains(err.Error(), "denied to user"), IsTrue)
 	_, err = se.Execute(context.Background(), "update information_schema.tables set table_name = 'tst' where table_name = 'mysql'")
 	c.Assert(strings.Contains(err.Error(), "privilege check fail"), IsTrue)
+
+	// Test performance_schema.
+	mustExec(c, se, `select * from performance_schema.events_statements_summary_by_digest`)
+	_, err = se.Execute(context.Background(), "drop table performance_schema.events_statements_summary_by_digest")
+	c.Assert(strings.Contains(err.Error(), "denied to user"), IsTrue)
+	_, err = se.Execute(context.Background(), "update performance_schema.events_statements_summary_by_digest set table_names = 'tst'")
+	c.Assert(strings.Contains(err.Error(), "privilege check fail"), IsTrue)
+	_, err = se.Execute(context.Background(), "delete from performance_schema.events_statements_summary_by_digest")
+	c.Assert(strings.Contains(err.Error(), "privilege check fail"), IsTrue)
 }
 
 func (s *testPrivilegeSuite) TestAdminCommand(c *C) {