From 18ce601629fd233b1a7d50c7aa8dddfaca44cd63 Mon Sep 17 00:00:00 2001
From: Lingyu Song <songlingyu@pingcap.com>
Date: Tue, 25 Feb 2020 21:40:07 +0800
Subject: [PATCH] server: fix connection reset caused by alias length overflow
 (#14870)

---
 server/column.go      | 13 +++++++++++--
 server/column_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/server/column.go b/server/column.go
index 195061c3be875..677dc702eec13 100644
--- a/server/column.go
+++ b/server/column.go
@@ -17,6 +17,8 @@ import (
 	"github.com/pingcap/parser/mysql"
 )
 
+const maxColumnNameSize = 256
+
 // ColumnInfo contains information of a column
 type ColumnInfo struct {
 	Schema             string
@@ -35,12 +37,19 @@ type ColumnInfo struct {
 
 // Dump dumps ColumnInfo to bytes.
 func (column *ColumnInfo) Dump(buffer []byte) []byte {
+	nameDump, orgnameDump := []byte(column.Name), []byte(column.OrgName)
+	if len(nameDump) > maxColumnNameSize {
+		nameDump = nameDump[0:maxColumnNameSize]
+	}
+	if len(orgnameDump) > maxColumnNameSize {
+		orgnameDump = orgnameDump[0:maxColumnNameSize]
+	}
 	buffer = dumpLengthEncodedString(buffer, []byte("def"))
 	buffer = dumpLengthEncodedString(buffer, []byte(column.Schema))
 	buffer = dumpLengthEncodedString(buffer, []byte(column.Table))
 	buffer = dumpLengthEncodedString(buffer, []byte(column.OrgTable))
-	buffer = dumpLengthEncodedString(buffer, []byte(column.Name))
-	buffer = dumpLengthEncodedString(buffer, []byte(column.OrgName))
+	buffer = dumpLengthEncodedString(buffer, nameDump)
+	buffer = dumpLengthEncodedString(buffer, orgnameDump)
 
 	buffer = append(buffer, 0x0c)
 
diff --git a/server/column_test.go b/server/column_test.go
index b5baca7e1586e..c87f972811aed 100644
--- a/server/column_test.go
+++ b/server/column_test.go
@@ -50,3 +50,27 @@ func (s ColumnTestSuite) TestDumpColumn(c *C) {
 	c.Assert(dumpType(mysql.TypeEnum), Equals, mysql.TypeString)
 	c.Assert(dumpType(mysql.TypeBit), Equals, mysql.TypeBit)
 }
+
+func (s ColumnTestSuite) TestColumnNameLimit(c *C) {
+	aLongName := make([]byte, 0, 300)
+	for i := 0; i < 300; i++ {
+		aLongName = append(aLongName, 'a')
+	}
+	info := ColumnInfo{
+		Schema:             "testSchema",
+		Table:              "testTable",
+		OrgTable:           "testOrgTable",
+		Name:               string(aLongName),
+		OrgName:            "testOrgName",
+		ColumnLength:       1,
+		Charset:            106,
+		Flag:               0,
+		Decimal:            1,
+		Type:               14,
+		DefaultValueLength: 2,
+		DefaultValue:       []byte{5, 2},
+	}
+	r := info.Dump(nil)
+	exp := []byte{0x3, 0x64, 0x65, 0x66, 0xa, 0x74, 0x65, 0x73, 0x74, 0x53, 0x63, 0x68, 0x65, 0x6d, 0x61, 0x9, 0x74, 0x65, 0x73, 0x74, 0x54, 0x61, 0x62, 0x6c, 0x65, 0xc, 0x74, 0x65, 0x73, 0x74, 0x4f, 0x72, 0x67, 0x54, 0x61, 0x62, 0x6c, 0x65, 0xfc, 0x0, 0x1, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0x61, 0xb, 0x74, 0x65, 0x73, 0x74, 0x4f, 0x72, 0x67, 0x4e, 0x61, 0x6d, 0x65, 0xc, 0x6a, 0x0, 0x1, 0x0, 0x0, 0x0, 0xe, 0x0, 0x0, 0x1, 0x0, 0x0, 0x2, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x5, 0x2}
+	c.Assert(r, DeepEquals, exp)
+}