Repository: nats-io/nats-server (go)

Issue:
Fix Gateways tlsconfig reload
### Proposed change

When reload config, we should update all config in "g.remotes", not only config in "opts.Gateway.Gateways".

![Image](https://github.com/user-attachments/assets/17656da1-c947-4aa1-b28b-420dde96e31c)

https://github.com/nats-io/nats-server/blob/323e97ef773599c92b2ad35fae3b3e9ba5694712/server/gateway.go#L424



### Use case


For example，we config like this, but we have implicit cluster "al-tt-cn-kk", so opts.Gateway.Gateways only contains "aa-ss-kk-4", g.remotes contains "al-tt-cn-kk" and "al-tt-cn-kk".

```
gateway: {
    gateways: [
      {
        "name": "aa-ss-kk-4",
        "urls": [
          "nats://127.0.0.1:7222"
        ]
      }
    ],
    name: al-cn-tt-5,
    port: 7222,
    tls: {
      ca_file: /Users/zego/GolandProjects/go-zego/istioTest/nats/spireserver/bundle.0.pem,
      cert_file: /Users/zego/GolandProjects/go-zego/istioTest/nats/spireserver/svid.0.pem,
      key_file: /Users/zego/GolandProjects/go-zego/istioTest/nats/spireserver/svid.0.key,
      verify: true,
      insecure: true, //不校验
      verify_cert_and_check_known_urls: true
    }
}

```

### Contribution


updateRemotesTLSConfig update follow.

```
// Update remote gateways TLS configurations after a config reload.
func (g *srvGateway) updateRemotesTLSConfig(opts *Options) {
	g.Lock()
	defer g.Unlock()
	for name, cfg := range g.remotes {
		if name == g.name {
			continue
		}
		cfg.Lock()
		var ro *RemoteGatewayOpts
		for _, r := range opts.Gateway.Gateways {
			if r.Name == name {
				ro = r
				break
			}
		}
		// If TLS config is in remote, use that one, otherwise,
		// use the TLS config from the main block.
		if ro != nil && ro.TLSConfig != nil {
			cfg.TLSConfig = ro.TLSConfig.Clone()
		} else if opts.Gateway.TLSConfig != nil {
			cfg.TLSConfig = opts.Gateway.TLSConfig.Clone()
		}
		// Ensure that OCSP callbacks are always setup after a reload if needed.
		mustStaple := opts.OCSPConfig != nil && opts.OCSPConfig.Mode == OCSPModeAlways
		if mustStaple && opts.Gateway.TLSConfig != nil {
			clientCB := opts.Gateway.TLSConfig.GetClientCertificate
			verifyCB := opts.Gateway.TLSConfig.VerifyConnection
			if mustStaple && cfg.TLSConfig != nil {
				if clientCB != nil && cfg.TLSConfig.GetClientCertificate == nil {
					cfg.TLSConfig.GetClientCertificate = clientCB
				}
				if verifyCB != nil && cfg.TLSConfig.VerifyConnection == nil {
					cfg.TLSConfig.VerifyConnection = verifyCB
				}
			}
		}
		cfg.Unlock()
	}
}
```

Pull request description:
[FIXED] Gateway: TLS configuration reload now applies to implicit remotes
When a config reload is issued and a server has implicit remote gateways (that is, gateways that were gossiped and not explicitly configured), the TLS changes were applied only to explicit remotes.

With this change, the changes to the main `tls{}` block will be applied to implicit remotes.

Credit to @song0071000 for the proposed changes in the code.

Resolves #6875

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>

Patch:
diff --git a/server/gateway.go b/server/gateway.go
index 6257e3f6..ca0e2474 100644
--- a/server/gateway.go
+++ b/server/gateway.go
@@ -424,38 +424,48 @@ func (s *Server) newGateway(opts *Options) error {
 func (g *srvGateway) updateRemotesTLSConfig(opts *Options) {
 	g.Lock()
 	defer g.Unlock()
-
-	for _, ro := range opts.Gateway.Gateways {
-		if ro.Name == g.name {
+	// Instead of going over opts.Gateway.Gateways, which would include only
+	// explicit remotes, we are going to go through g.remotes.
+	for name, cfg := range g.remotes {
+		if name == g.name {
 			continue
 		}
-		if cfg, ok := g.remotes[ro.Name]; ok {
-			cfg.Lock()
-			// If TLS config is in remote, use that one, otherwise,
-			// use the TLS config from the main block.
-			if ro.TLSConfig != nil {
-				cfg.TLSConfig = ro.TLSConfig.Clone()
-			} else if opts.Gateway.TLSConfig != nil {
-				cfg.TLSConfig = opts.Gateway.TLSConfig.Clone()
+		var ro *RemoteGatewayOpts
+		// We now need to go back and find the RemoteGatewayOpts but only if
+		// this remote is explicit (otherwise it won't be found).
+		if !cfg.isImplicit() {
+			for _, r := range opts.Gateway.Gateways {
+				if r.Name == name {
+					ro = r
+					break
+				}
 			}
-
-			// Ensure that OCSP callbacks are always setup after a reload if needed.
-			mustStaple := opts.OCSPConfig != nil && opts.OCSPConfig.Mode == OCSPModeAlways
-			if mustStaple && opts.Gateway.TLSConfig != nil {
-				clientCB := opts.Gateway.TLSConfig.GetClientCertificate
-				verifyCB := opts.Gateway.TLSConfig.VerifyConnection
-				if mustStaple && cfg.TLSConfig != nil {
-					if clientCB != nil && cfg.TLSConfig.GetClientCertificate == nil {
-						cfg.TLSConfig.GetClientCertificate = clientCB
-					}
-					if verifyCB != nil && cfg.TLSConfig.VerifyConnection == nil {
-						cfg.TLSConfig.VerifyConnection = verifyCB
-					}
+		}
+		cfg.Lock()
+		// If we have an `ro` (that means an explicitly defined remote gateway)
+		// and it has an explicit TLS config, use that one, otherwise (no explicit
+		// TLS config in the remote, or implicit remote), use the TLS config from
+		// the main block.
+		if ro != nil && ro.TLSConfig != nil {
+			cfg.TLSConfig = ro.TLSConfig.Clone()
+		} else if opts.Gateway.TLSConfig != nil {
+			cfg.TLSConfig = opts.Gateway.TLSConfig.Clone()
+		}
+		// Ensure that OCSP callbacks are always setup after a reload if needed.
+		mustStaple := opts.OCSPConfig != nil && opts.OCSPConfig.Mode == OCSPModeAlways
+		if mustStaple && opts.Gateway.TLSConfig != nil {
+			clientCB := opts.Gateway.TLSConfig.GetClientCertificate
+			verifyCB := opts.Gateway.TLSConfig.VerifyConnection
+			if mustStaple && cfg.TLSConfig != nil {
+				if clientCB != nil && cfg.TLSConfig.GetClientCertificate == nil {
+					cfg.TLSConfig.GetClientCertificate = clientCB
+				}
+				if verifyCB != nil && cfg.TLSConfig.VerifyConnection == nil {
+					cfg.TLSConfig.VerifyConnection = verifyCB
 				}
 			}
-
-			cfg.Unlock()
 		}
+		cfg.Unlock()
 	}
 }
 


Test patch:
diff --git a/server/gateway_test.go b/server/gateway_test.go
index 8813ab57..3febf8d7 100644
--- a/server/gateway_test.go
+++ b/server/gateway_test.go
@@ -6458,6 +6458,65 @@ func TestGatewayTLSConfigReloadForRemote(t *testing.T) {
 	waitForOutboundGateways(t, srvB, 1, time.Second)
 }
 
+func TestGatewayTLSConfigReloadForImplicitRemote(t *testing.T) {
+	SetGatewaysSolicitDelay(5 * time.Millisecond)
+	defer ResetGatewaysSolicitDelay()
+
+	template := `
+		listen: 127.0.0.1:-1
+		gateway {
+			name: "A"
+			listen: "127.0.0.1:-1"
+			tls {
+				cert_file: "../test/configs/certs/srva-cert.pem"
+				key_file:  "../test/configs/certs/srva-key.pem"
+				%s
+				verify: true
+			}
+		}
+	`
+	confA := createConfFile(t, fmt.Appendf(nil, template, `ca_file:   "../test/configs/certs/ca.pem"`))
+	srvA, optsA := RunServerWithConfig(confA)
+	defer srvA.Shutdown()
+
+	optsB := testGatewayOptionsFromToWithTLS(t, "B", "A", []string{fmt.Sprintf("nats://127.0.0.1:%d", optsA.Gateway.Port)})
+	srvB := runGatewayServer(optsB)
+	defer srvB.Shutdown()
+
+	waitForInboundGateways(t, srvA, 1, time.Second)
+	waitForOutboundGateways(t, srvA, 1, time.Second)
+	waitForInboundGateways(t, srvB, 1, time.Second)
+	waitForOutboundGateways(t, srvB, 1, time.Second)
+
+	// We will verify that the config reload of the tls{} block is applied to
+	// the implicit remote (from A to B) by removing the ca_file.
+	reloadUpdateConfig(t, srvA, confA, fmt.Sprintf(template, ""))
+
+	// Get the remote from A to B
+	cfg := srvA.getRemoteGateway("B")
+	require_NotNil(t, cfg)
+	cfg.Lock()
+	tc := cfg.TLSConfig
+	cfg.Unlock()
+	require_NotNil(t, tc)
+	// The CA should have been removed.
+	require_True(t, tc.ClientCAs == nil)
+
+	// Reset the connection attempts, since we are going to close the connection
+	// from A to B and make sure that connection keeps failing.
+	cfg.resetConnAttempts()
+
+	// Get the outbound connection and close it.
+	c := srvA.getOutboundGatewayConnection("B")
+	require_NotNil(t, c)
+	c.mu.Lock()
+	c.nc.Close()
+	c.mu.Unlock()
+
+	// Verify that we fail to connect from A to B now.
+	waitForGatewayFailedConnect(t, srvA, "B", true, time.Second)
+}
+
 func TestGatewayAuthDiscovered(t *testing.T) {
 	SetGatewaysSolicitDelay(5 * time.Millisecond)
 	defer ResetGatewaysSolicitDelay()