Allow using caching_sha2_password for proxy auth

Up until now, mysql_native_password was used for auth. This is however
removed in MySQL 9.x and this is the default that Homebrew installs on
MacOS.

While we can also try to deal with installing older versions on MacOS,
alternatively we update the auth for the proxy to
caching_sha2_password.

The one thing that this breaks is very old MySQL 5.7 clients. Anything
older than MySQL 5.7.23 (released 2018-07-27) would break with this. We
don't really support 5.7 for the proxy anyway though.

Signed-off-by: Dirkjan Bussink <[email protected]>

authserver.go

@@ -0,0 +1,74 @@
+package psdbproxy
+
+import (
+	"crypto/rand"
+	"net"
+
+	"vitess.io/vitess/go/mysql"
+	querypb "vitess.io/vitess/go/vt/proto/query"
+)
+
+// cachingSha2AuthServerNone takes all comers.
+type cachingSha2AuthServerNone struct{}
+
+type noneGetter struct{}
+
+// AuthMethods returns the list of registered auth methods
+// implemented by this auth server.
+func (a *cachingSha2AuthServerNone) AuthMethods() []mysql.AuthMethod {
+	return []mysql.AuthMethod{&mysqlCachingSha2AuthMethod{}}
+}
+
+// DefaultAuthMethodDescription returns MysqlNativePassword as the default
+// authentication method for the auth server implementation.
+func (a *cachingSha2AuthServerNone) DefaultAuthMethodDescription() mysql.AuthMethodDescription {
+	return mysql.CachingSha2Password
+}
+
+// Get returns the empty string
+func (ng *noneGetter) Get() *querypb.VTGateCallerID {
+	return &querypb.VTGateCallerID{Username: "root"}
+}
+
+type mysqlCachingSha2AuthMethod struct{}
+
+func (n *mysqlCachingSha2AuthMethod) Name() mysql.AuthMethodDescription {
+	return mysql.CachingSha2Password
+}
+
+func (n *mysqlCachingSha2AuthMethod) HandleUser(conn *mysql.Conn, user string) bool {
+	return true
+}
+
+func (n *mysqlCachingSha2AuthMethod) AuthPluginData() ([]byte, error) {
+	salt, err := newSalt()
+	if err != nil {
+		return nil, err
+	}
+	return append(salt, 0), nil
+}
+
+func (n *mysqlCachingSha2AuthMethod) AllowClearTextWithoutTLS() bool {
+	return true
+}
+
+func (n *mysqlCachingSha2AuthMethod) HandleAuthPluginData(c *mysql.Conn, user string, serverAuthPluginData []byte, clientAuthPluginData []byte, remoteAddr net.Addr) (mysql.Getter, error) {
+	return &noneGetter{}, nil
+}
+
+func newSalt() ([]byte, error) {
+	salt := make([]byte, 20)
+	if _, err := rand.Read(salt); err != nil {
+		return nil, err
+	}
+
+	// Salt must be a legal UTF8 string.
+	for i := range len(salt) {
+		salt[i] &= 0x7f
+		if salt[i] == '\x00' || salt[i] == '$' {
+			salt[i]++
+		}
+	}
+
+	return salt, nil
+}

cmd/psdbproxy/main.go

@@ -7,6 +7,7 @@ import (
 	"github.com/planetscale/psdb/auth"
 	"github.com/planetscale/psdbproxy"
 	"github.com/spf13/pflag"
+	"vitess.io/vitess/go/mysql"
 )
 
 var (
@@ -40,7 +41,7 @@ func main() {
 
 	ch := make(chan error)
 	go func() {
-		ch <- s.ListenAndServe()
+		ch <- s.ListenAndServe(mysql.CachingSha2Password)
 	}()
 
 	logger.Info(

server.go

@@ -26,7 +26,7 @@ type Server struct {
 	mysql.UnimplementedHandler
 }
 
-func (s *Server) Serve(l net.Listener) error {
+func (s *Server) Serve(l net.Listener, authMethod mysql.AuthMethodDescription) error {
 	s.ensureSetup()
 
 	handler, err := s.handler()
@@ -37,9 +37,19 @@ func (s *Server) Serve(l net.Listener) error {
 		return err
 	}
 
+	var auth mysql.AuthServer
+	switch authMethod {
+	case mysql.CachingSha2Password:
+		auth = &cachingSha2AuthServerNone{}
+	case mysql.MysqlNativePassword:
+		auth = mysql.NewAuthServerNone()
+	default:
+		return fmt.Errorf("unsupported auth method: %v", authMethod)
+	}
+
 	listener, err := mysql.NewListenerWithConfig(mysql.ListenerConfig{
 		Listener:            l,
-		AuthServer:          mysql.NewAuthServerNone(),
+		AuthServer:          auth,
 		Handler:             handler,
 		ConnReadTimeout:     s.ReadTimeout,
 		ConnWriteTimeout:    30 * time.Second,
@@ -55,12 +65,12 @@ func (s *Server) Serve(l net.Listener) error {
 	return nil
 }
 
-func (s *Server) ListenAndServe() error {
+func (s *Server) ListenAndServe(authMethod mysql.AuthMethodDescription) error {
 	l, err := net.Listen("tcp", s.Addr)
 	if err != nil {
 		return err
 	}
-	return s.Serve(l)
+	return s.Serve(l, authMethod)
 }
 
 func (s *Server) Shutdown() {