*: add back salt (#134)

pkg/proxy/backend/authenticator.go

@@ -50,6 +50,7 @@ type Authenticator struct {
 	serverAddr                  string
 	user                        string
 	attrs                       []byte // no need to parse
+	salt                        []byte
 	capability                  uint32 // client capability
 	collation                   uint8
 	proxyProtocol               bool
@@ -104,7 +105,7 @@ func (auth *Authenticator) handshakeFirstTime(logger *zap.Logger, clientIO *pnet
 		proxyCapability ^= pnet.ClientSSL
 	}
 
-	if err := clientIO.WriteInitialHandshake(proxyCapability.Uint32(), make([]byte, 20), mysql.AuthNativePassword); err != nil {
+	if err := clientIO.WriteInitialHandshake(proxyCapability.Uint32(), auth.salt, mysql.AuthNativePassword); err != nil {
 		return err
 	}
 	pkt, isSSL, err := clientIO.ReadSSLRequestOrHandshakeResp()

pkg/proxy/backend/backend_conn_mgr.go

@@ -90,11 +90,16 @@ type BackendConnManager struct {
 // NewBackendConnManager creates a BackendConnManager.
 func NewBackendConnManager(logger *zap.Logger, nsmgr *namespace.NamespaceManager, connectionID uint64, proxyProtocol, requireBackendTLS bool) *BackendConnManager {
 	mgr := &BackendConnManager{
-		logger:         logger,
-		connectionID:   connectionID,
-		cmdProcessor:   NewCmdProcessor(),
-		nsmgr:          nsmgr,
-		authenticator:  &Authenticator{supportedServerCapabilities: supportedServerCapabilities, proxyProtocol: proxyProtocol, requireBackendTLS: requireBackendTLS},
+		logger:       logger,
+		connectionID: connectionID,
+		cmdProcessor: NewCmdProcessor(),
+		nsmgr:        nsmgr,
+		authenticator: &Authenticator{
+			supportedServerCapabilities: supportedServerCapabilities,
+			proxyProtocol:               proxyProtocol,
+			requireBackendTLS:           requireBackendTLS,
+			salt:                        GenerateSalt(20),
+		},
 		signalReceived: make(chan struct{}, 1),
 		redirectResCh:  make(chan *redirectResult, 1),
 	}

pkg/proxy/backend/util.go

@@ -0,0 +1,33 @@
+// Copyright 2022 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package backend
+
+import _ "unsafe"
+
+//go:linkname Uint32N runtime.fastrandn
+func Uint32N(a uint64) uint64
+
+// Buf generates a random string using ASCII characters but avoid separator character.
+// Ref https://github.com/mysql/mysql-server/blob/5.7/mysys_ssl/crypt_genhash_impl.cc#L435.
+func GenerateSalt(size int) []byte {
+	buf := make([]byte, size)
+	for i := range buf {
+		buf[i] = byte(Uint32N(127))
+		for buf[i] == 0 || buf[i] == byte('$') {
+			buf[i] = byte(Uint32N(127))
+		}
+	}
+	return buf
+}