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executor: forbid user to drop important system table #7471

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merged 8 commits into from
Aug 29, 2018
Merged

executor: forbid user to drop important system table #7471

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3c9d354
executor: forbid user to drop important system table
tiancaiamao Aug 23, 2018
a7fd95c
fix CI
tiancaiamao Aug 23, 2018
8bbeac7
address comment
tiancaiamao Aug 23, 2018
ad05169
Merge branch 'master' into forbit-drop-system-table
tiancaiamao Aug 23, 2018
a9f82e6
address comment
tiancaiamao Aug 27, 2018
a0a844e
address comment
tiancaiamao Aug 29, 2018
d872685
Merge branch 'master' into forbit-drop-system-table
tiancaiamao Aug 29, 2018
27b89fd
update comment
tiancaiamao Aug 29, 2018
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20 changes: 20 additions & 0 deletions executor/ddl.go
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ import (
"github.com/pingcap/tidb/infoschema"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/mysql"
"github.com/pingcap/tidb/privilege/privileges"
"github.com/pingcap/tidb/sessionctx/variable"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/chunk"
Expand Down Expand Up @@ -154,8 +155,19 @@ func (e *DDLExec) executeCreateIndex(s *ast.CreateIndexStmt) error {
return errors.Trace(err)
}

var errForbidDrop = errors.New("Drop mysql tables is forbidden")

func (e *DDLExec) executeDropDatabase(s *ast.DropDatabaseStmt) error {
dbName := model.NewCIStr(s.Name)

// Protect important system table from been dropped by a mistake.
// I can hardly find a case that a user really need to do this.
if dbName.L == "mysql" {
if !privileges.SkipWithGrant {
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Why we need to consider the privileges.SkipWithGrant?

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I know it's a rare case, but how about that we really want to do it?

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We need a "backdoor".

return errors.Trace(errForbidDrop)
}
}

err := domain.GetDomain(e.ctx).DDL().DropSchema(e.ctx, dbName)
if infoschema.ErrDatabaseNotExists.Equal(err) {
if s.IfExists {
Expand Down Expand Up @@ -198,6 +210,14 @@ func (e *DDLExec) executeDropTable(s *ast.DropTableStmt) error {
return errors.Trace(err)
}

// Protect important system table from been dropped by a mistake.
// I can hardly find a case that a user really need to do this.
if tn.Schema.L == "mysql" {
if !privileges.SkipWithGrant {
return errors.Trace(errForbidDrop)
}
}

if config.CheckTableBeforeDrop {
log.Warnf("admin check table `%s`.`%s` before drop.", fullti.Schema.O, fullti.Name.O)
sql := fmt.Sprintf("admin check table `%s`.`%s`", fullti.Schema.O, fullti.Name.O)
Expand Down
6 changes: 6 additions & 0 deletions executor/ddl_test.go
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Expand Up @@ -128,6 +128,9 @@ func (s *testSuite) TestCreateDropDatabase(c *C) {
c.Assert(err.Error(), Equals, plan.ErrNoDB.Error())
_, err = tk.Exec("select * from t;")
c.Assert(err.Error(), Equals, plan.ErrNoDB.Error())

_, err = tk.Exec("drop database mysql")
c.Assert(err, NotNil)
}

func (s *testSuite) TestCreateDropTable(c *C) {
Expand All @@ -137,6 +140,9 @@ func (s *testSuite) TestCreateDropTable(c *C) {
tk.MustExec("drop table if exists drop_test")
tk.MustExec("create table drop_test (a int)")
tk.MustExec("drop table drop_test")

_, err := tk.Exec("drop table mysql.user")
c.Assert(err, NotNil)
}

func (s *testSuite) TestCreateDropIndex(c *C) {
Expand Down
6 changes: 6 additions & 0 deletions privilege/privileges/cache_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -200,6 +200,12 @@ func (s *testCacheSuite) TestAbnormalMySQLTable(c *C) {
c.Assert(err, IsNil)
defer se.Close()

saveSkipWithGrant := privileges.SkipWithGrant
defer func() {
privileges.SkipWithGrant = saveSkipWithGrant
}()
privileges.SkipWithGrant = true

// Simulate the case mysql.user is synchronized from MySQL.
mustExec(c, se, "DROP TABLE mysql.user;")
mustExec(c, se, "USE mysql;")
Expand Down