fix: Refresh client cert when it is rejected by the server.

Author: hessjcg

dialer.go

@@ -418,9 +418,11 @@ func (d *Dialer) Dial(ctx context.Context, icn string, opts ...DialOption) (conn
 	tlsConn := tls.Client(conn, ci.TLSConfig())
 	err = tlsConn.HandshakeContext(ctx)
 	if err != nil {
+		// TLS handshake errors are fatal and require a refresh. Remove the instance
+		// from the cache so that future calls to Dial() will block until the
+		// certificate is refreshed successfully.
 		d.logger.Debugf(ctx, "[%v] TLS handshake failed: %v", cn.String(), err)
-		// refresh the instance info in case it caused the handshake failure
-		c.ForceRefresh()
+		d.removeCached(ctx, cn, c, err)
 		_ = tlsConn.Close() // best effort close attempt
 		return nil, errtype.NewDialError("handshake failed", cn.String(), err)
 	}
@@ -435,7 +437,22 @@ func (d *Dialer) Dial(ctx context.Context, icn string, opts ...DialOption) (conn
 	iConn := newInstrumentedConn(tlsConn, func() {
 		n := atomic.AddUint64(c.openConnsCount, ^uint64(0)) // c.openConnsCount = c.openConnsCount - 1
 		trace.RecordOpenConnections(context.Background(), int64(n), d.dialerID, cn.String())
-	}, d.dialerID, cn.String())
+	},
+		func(err error) {
+			// ignore EOF
+			if err == io.EOF {
+				return
+			}
+			d.logger.Debugf(ctx, "[%v] IO Error on Read or Write: %v", cn.String(), err)
+			if d.isTLSError(err) {
+				// TLS handshake errors are fatal. Remove the instance from the cache
+				// so that future calls to Dial() will block until the certificate
+				// is refreshed successfully.
+				d.removeCached(ctx, cn, c, err)
+				_ = tlsConn.Close() // best effort close attempt
+			}
+		},
+		d.dialerID, cn.String())
 
 	// If this connection was opened using a Domain Name, then store it for later
 	// in case it needs to be forcibly closed.
@@ -446,12 +463,19 @@ func (d *Dialer) Dial(ctx context.Context, icn string, opts ...DialOption) (conn
 	}
 	return iConn, nil
 }
+func (d *Dialer) isTLSError(err error) bool {
+	if nErr, ok := err.(net.Error); ok {
+		return !nErr.Timeout() && // it's a permanent net error
+			strings.Contains(nErr.Error(), "tls") // it's a TLS-related error
+	}
+	return false
+}
 
 // removeCached stops all background refreshes and deletes the connection
 // info cache from the map of caches.
 func (d *Dialer) removeCached(
 	ctx context.Context,
-	i instance.ConnName, c connectionInfoCache, err error,
+	i instance.ConnName, c *monitoredCache, err error,
 ) {
 	d.logger.Debugf(
 		ctx,
@@ -461,8 +485,11 @@ func (d *Dialer) removeCached(
 	)
 	d.lock.Lock()
 	defer d.lock.Unlock()
-	c.Close()
-	delete(d.cache, createKey(i))
+	key := createKey(i)
+	if cachedC, ok := d.cache[key]; ok && cachedC == c {
+		delete(d.cache, key)
+	}
+	c.connectionInfoCache.Close()
 }
 
 // validClientCert checks that the ephemeral client certificate retrieved from
@@ -504,7 +531,7 @@ func (d *Dialer) EngineVersion(ctx context.Context, icn string) (string, error)
 	}
 	ci, err := c.ConnectionInfo(ctx)
 	if err != nil {
-		d.removeCached(ctx, cn, c.connectionInfoCache, err)
+		d.removeCached(ctx, cn, c, err)
 		return "", err
 	}
 	return ci.DBVersion, nil
@@ -528,17 +555,18 @@ func (d *Dialer) Warmup(ctx context.Context, icn string, opts ...DialOption) err
 	}
 	_, err = c.ConnectionInfo(ctx)
 	if err != nil {
-		d.removeCached(ctx, cn, c.connectionInfoCache, err)
+		d.removeCached(ctx, cn, c, err)
 	}
 	return err
 }
 
 // newInstrumentedConn initializes an instrumentedConn that on closing will
 // decrement the number of open connects and record the result.
-func newInstrumentedConn(conn net.Conn, closeFunc func(), dialerID, connName string) *instrumentedConn {
+func newInstrumentedConn(conn net.Conn, closeFunc func(), errFunc func(error), dialerID, connName string) *instrumentedConn {
 	return &instrumentedConn{
 		Conn:      conn,
 		closeFunc: closeFunc,
+		errFunc:   errFunc,
 		dialerID:  dialerID,
 		connName:  connName,
 	}
@@ -549,6 +577,7 @@ func newInstrumentedConn(conn net.Conn, closeFunc func(), dialerID, connName str
 type instrumentedConn struct {
 	net.Conn
 	closeFunc func()
+	errFunc   func(error)
 	mu        sync.RWMutex
 	closed    bool
 	dialerID  string
@@ -561,6 +590,8 @@ func (i *instrumentedConn) Read(b []byte) (int, error) {
 	bytesRead, err := i.Conn.Read(b)
 	if err == nil {
 		go trace.RecordBytesReceived(context.Background(), int64(bytesRead), i.connName, i.dialerID)
+	} else {
+		i.errFunc(err)
 	}
 	return bytesRead, err
 }
@@ -571,6 +602,8 @@ func (i *instrumentedConn) Write(b []byte) (int, error) {
 	bytesWritten, err := i.Conn.Write(b)
 	if err == nil {
 		go trace.RecordBytesSent(context.Background(), int64(bytesWritten), i.connName, i.dialerID)
+	} else {
+		i.errFunc(err)
 	}
 	return bytesWritten, err
 }

internal/mock/cloudsql.go

@@ -75,11 +75,13 @@ func (f FakeCSQLInstance) serverCACert() ([]byte, error) {
 	if f.signer != nil {
 		return f.signer(f.Cert, f.Key)
 	}
+
 	if f.serverCAMode == "" || f.serverCAMode == "GOOGLE_MANAGED_INTERNAL_CA" {
 		// legacy server mode, return only the server cert
 		return toPEMFormat(f.certs.serverCert)
 	}
 	return toPEMFormat(f.certs.casServerCertificate, f.certs.serverIntermediateCaCert, f.certs.serverCaCert)
+
 }
 
 // ClientCert creates an ephemeral client certificate signed with the Cloud SQL

internal/mock/sqladmin.go

@@ -102,38 +102,38 @@ func (r *Request) matches(hR *http.Request) bool {
 //
 // https://cloud.google.com/sql/docs/mysql/admin-api/rest/v1beta4/instances/get
 func InstanceGetSuccess(i FakeCSQLInstance, ct int) *Request {
-	var ips []*sqladmin.IpMapping
-	for ipType, addr := range i.ipAddrs {
-		if ipType == "PUBLIC" {
-			ips = append(ips, &sqladmin.IpMapping{IpAddress: addr, Type: "PRIMARY"})
-			continue
-		}
-		if ipType == "PRIVATE" {
-			ips = append(ips, &sqladmin.IpMapping{IpAddress: addr, Type: "PRIVATE"})
-		}
-	}
-
-	certBytes, err := i.serverCACert()
-	if err != nil {
-		panic(err)
-	}
-
-	db := &sqladmin.ConnectSettings{
-		BackendType:     i.backendType,
-		DatabaseVersion: i.dbVersion,
-		DnsName:         i.DNSName,
-		IpAddresses:     ips,
-		Region:          i.region,
-		ServerCaCert:    &sqladmin.SslCert{Cert: string(certBytes)},
-		PscEnabled:      i.pscEnabled,
-		ServerCaMode:    i.serverCAMode,
-	}
-
 	r := &Request{
 		reqMethod: http.MethodGet,
 		reqPath:   fmt.Sprintf("/sql/v1beta4/projects/%s/instances/%s/connectSettings", i.project, i.name),
 		reqCt:     ct,
 		handle: func(resp http.ResponseWriter, _ *http.Request) {
+			var ips []*sqladmin.IpMapping
+			for ipType, addr := range i.ipAddrs {
+				if ipType == "PUBLIC" {
+					ips = append(ips, &sqladmin.IpMapping{IpAddress: addr, Type: "PRIMARY"})
+					continue
+				}
+				if ipType == "PRIVATE" {
+					ips = append(ips, &sqladmin.IpMapping{IpAddress: addr, Type: "PRIVATE"})
+				}
+			}
+
+			certBytes, err := i.serverCACert()
+			if err != nil {
+				panic(err)
+			}
+
+			db := &sqladmin.ConnectSettings{
+				BackendType:     i.backendType,
+				DatabaseVersion: i.dbVersion,
+				DnsName:         i.DNSName,
+				IpAddresses:     ips,
+				Region:          i.region,
+				ServerCaCert:    &sqladmin.SslCert{Cert: string(certBytes)},
+				PscEnabled:      i.pscEnabled,
+				ServerCaMode:    i.serverCAMode,
+			}
+
 			b, err := db.MarshalJSON()
 			if err != nil {
 				http.Error(resp, err.Error(), http.StatusInternalServerError)