feat(插件代理): 同源反向代理 —— VNC 不再暴露额外端口

问题：登录返回的 view_url 是 http://127.0.0.1:60100/vnc.html，WebUI 直接把它
嵌进 iframe。远程运维打开必白屏 —— 127.0.0.1 在客户端指向客户端自己，且
websockify/x11vnc 只绑回环，换服务器 IP 也连不上（实测 LAN IP 访问 000）。

★ 教训：只验证"服务端截图有画面"就宣布 VNC 可用是不充分的。四层链路里
①X 渲染 ②noVNC 客户端渲染 一直是好的，白屏真因在第④层「客户端如何拿到地址」。

内核新增通用「插件前缀代理」能力（不是为 channels 写的专用反向代理）：
- plugin.http 支持 prefix = true：声明前缀路由，承接所有子路径
- handler 返回 { proxy = "http://127.0.0.1:PORT" }，内核每次请求都问一遍
  ⇒ 会话停止/过期后插件不再给目标，旧地址自然失效（撤销点唯一）
- 鉴权与角色门禁复用现有链路，无旁路
- statusRecorder 增加 Unwrap()，让 Hijack 穿透访问日志中间件（否则 WebSocket 升级失败）
- 目标只允许带显式端口的**字面回环 IP**（用户拍板方案 A）：拒绝 https、localhost
  主机名、无端口、带 userinfo/path/query；理由是主机名可能被 hosts/DNS 改写
- 拒绝跨站 Origin（WebSocket 带环境 Cookie，否则第三方网页可借管理员会话开隧道）
- 不向插件后端转发 Authorization/Cookie/api_key

channels 接入：
- 新增 channels/browser/proxy/:session（prefix=true）
- 会话代号 = seq-随机8位，防猜到活跃会话
- view_url 改为网关同源路径，noVNC 的 WebSocket 走同前缀 /websockify
- 会话过期即回收浏览器栈并返回 404

判据（每条咬真实外部效应）：
- 静态资源转发
- 真实 HTTP 101 升级 + 双向数据回传（只断言静态转发不够 —— 升级是白屏真考点）
- 网关凭据不泄漏（在服务端断言请求头）
- 非法目标全拒（公网/localhost/https/无端口/带 path、query、userinfo）
- 跨站 Origin 403
- 未鉴权 401、过期会话 404、非子路径 404

回归：go test -tags luajit ./... 9 包全绿

internal/gateway/plugin_http_routes.go

@@ -55,6 +55,15 @@ func (g *Gateway) handlePluginHTTP(w http.ResponseWriter, r *http.Request) {
 	for i := range matches {
 		h := matches[i]
 		p, ok := matchHandlerPath(h.Path, rest)
+		if h.Prefix {
+			pattern := strings.Trim(h.Path, "/")
+			parts := strings.Split(strings.Trim(rest, "/"), "/")
+			n := len(strings.Split(pattern, "/"))
+			ok = len(parts) >= n
+			if ok {
+				p, ok = matchHandlerPath(pattern, strings.Join(parts[:n], "/"))
+			}
+		}
 		if !ok {
 			continue
 		}
@@ -116,6 +125,16 @@ func (g *Gateway) handlePluginHTTP(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadGateway, "plugin_error", err.Error())
 		return
 	}
+	if resp.Proxy != "" {
+		if !chosen.Prefix {
+			writeError(w, http.StatusBadGateway, "plugin_error", "proxy response requires prefix=true")
+			return
+		}
+		parts := strings.Split(strings.Trim(rest, "/"), "/")
+		n := len(strings.Split(strings.Trim(chosen.Path, "/"), "/"))
+		g.servePluginProxy(w, r, resp.Proxy, pluginHTTPPrefix+strings.Join(parts[:n], "/"))
+		return
+	}
 	lua.WriteHandlerResponse(w, resp)
 }
 

internal/gateway/plugin_proxy.go

@@ -0,0 +1,54 @@
+package gateway
+
+import (
+	"net"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"strings"
+)
+
+// servePluginProxy forwards a plugin-owned prefix to an explicit loopback
+// origin. No destination or path may be supplied by the client. Authentication
+// and endpoint authorization have already completed before this is called.
+func (g *Gateway) servePluginProxy(w http.ResponseWriter, r *http.Request, target, prefix string) {
+	u, err := url.Parse(target)
+	if err != nil || u.Scheme != "http" || u.User != nil || u.RawQuery != "" || u.Fragment != "" || (u.Path != "" && u.Path != "/") {
+		writeError(w, http.StatusBadGateway, "plugin_proxy", "proxy must name a loopback HTTP origin")
+		return
+	}
+	ip := net.ParseIP(u.Hostname())
+	if ip == nil || !ip.IsLoopback() || u.Port() == "" {
+		writeError(w, http.StatusBadGateway, "plugin_proxy", "proxy requires a literal loopback address and port")
+		return
+	}
+	// WebSocket requests are browser-initiated and carry ambient cookies. Do not
+	// allow a foreign website to use an administrator's session to open a tunnel.
+	if origin := r.Header.Get("Origin"); origin != "" {
+		o, e := url.Parse(origin)
+		if e != nil || !strings.EqualFold(o.Host, r.Host) {
+			writeError(w, http.StatusForbidden, "forbidden", "cross-origin proxy request refused")
+			return
+		}
+	}
+	proxy := httputil.NewSingleHostReverseProxy(u)
+	director := proxy.Director
+	proxy.Director = func(out *http.Request) {
+		director(out)
+		out.URL.Path = strings.TrimPrefix(r.URL.Path, prefix)
+		if out.URL.Path == "" {
+			out.URL.Path = "/"
+		}
+		out.URL.RawPath = ""
+		out.Host = u.Host
+		out.Header.Del("Authorization")
+		out.Header.Del("Cookie")
+		q := out.URL.Query()
+		q.Del("api_key")
+		out.URL.RawQuery = q.Encode()
+	}
+	proxy.ErrorHandler = func(w http.ResponseWriter, r *http.Request, err error) {
+		writeError(w, http.StatusBadGateway, "plugin_proxy", "plugin service unavailable")
+	}
+	proxy.ServeHTTP(w, r)
+}

internal/gateway/plugin_proxy_security_test.go

@@ -0,0 +1,66 @@
+package gateway
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestPluginProxyRejectsUnsafeTargetsAndOrigin(t *testing.T) {
+	g, _ := gatewayWithSpy(t)
+	for _, target := range []string{"http://example.com:80", "http://localhost:80", "https://127.0.0.1:80", "http://127.0.0.1", "http://u:p@127.0.0.1:80", "http://127.0.0.1:80/path", "http://127.0.0.1:80/?x=1"} {
+		rr := httptest.NewRecorder()
+		g.servePluginProxy(rr, httptest.NewRequest("GET", "http://gateway/api/plugins/http/relay/s/live.js", nil), target, "/api/plugins/http/relay/s")
+		if rr.Code != 502 {
+			t.Errorf("unsafe target %q accepted: %d", target, rr.Code)
+		}
+	}
+	rr := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "http://gateway/api/plugins/http/relay/s/websockify", nil)
+	req.Header.Set("Origin", "https://evil.example")
+	g.servePluginProxy(rr, req, "http://127.0.0.1:12345", "/api/plugins/http/relay/s")
+	if rr.Code != 403 {
+		t.Fatalf("foreign origin accepted: %d", rr.Code)
+	}
+}
+
+func TestPluginPrefixProxyAuthorizationAndRevocation(t *testing.T) {
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { t.Error("denied request reached backend") }))
+	defer backend.Close()
+	g, _ := gatewayWithSpy(t)
+	src := `local p={name="relaydeny",http={{path="relaydeny/:session",prefix=true,roles={"admin"},handler="proxy"}}}
+ function p.proxy(req) return {status=404,body="expired session"} end
+ return p`
+	if err := g.core.Plugins().LoadSource("relaydeny", src); err != nil {
+		t.Fatal(err)
+	}
+	server := httptest.NewServer(g.Handler())
+	defer server.Close()
+	for _, tc := range []struct {
+		path, key string
+		status    int
+	}{
+		{"/api/plugins/http/relaydeny/expired/vnc.html", "", 401},
+		{"/api/plugins/http/relaydeny/expired/vnc.html", "sk-test", 404},
+		{"/api/plugins/http/relaydeny-not-a-child/expired/vnc.html", "sk-test", 404},
+	} {
+		req, _ := http.NewRequest("GET", server.URL+tc.path, nil)
+		if tc.key != "" {
+			req.Header.Set("Authorization", "Bearer "+tc.key)
+		}
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		b, _ := io.ReadAll(resp.Body)
+		resp.Body.Close()
+		if resp.StatusCode != tc.status {
+			t.Fatalf("%s got %d %s", tc.path, resp.StatusCode, b)
+		}
+		if tc.key != "" && strings.Contains(tc.path, "/expired/") && strings.Contains(tc.path, "/relaydeny/") && string(b) != "expired session" {
+			t.Fatalf("revocation response=%s", b)
+		}
+	}
+}

internal/gateway/plugin_proxy_test.go

@@ -0,0 +1,82 @@
+package gateway
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+// Drive the real authenticated plugin route, including the access-log wrapper.
+// A successful static request alone does not prove WebSocket can upgrade.
+func TestPluginPrefixProxyHTTPAndUpgrade(t *testing.T) {
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("Authorization") != "" || r.Header.Get("Cookie") != "" || r.URL.Query().Get("api_key") != "" {
+			t.Error("gateway credentials leaked to plugin backend")
+		}
+		if r.URL.Path == "/websockify" {
+			c, b, err := w.(http.Hijacker).Hijack()
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			defer c.Close()
+			fmt.Fprint(b, "HTTP/1.1 101 Switching Protocols\r\nConnection: Upgrade\r\nUpgrade: websocket\r\n\r\n")
+			b.Flush()
+			io.Copy(c, c)
+			return
+		}
+		fmt.Fprint(w, r.URL.Path+"?"+r.URL.RawQuery)
+	}))
+	defer backend.Close()
+	g, _ := gatewayWithSpy(t)
+	src := fmt.Sprintf(`local p={name="relay",http={{path="relay/:session",prefix=true,method="GET",roles={"admin"},handler="proxy"}}}
+ function p.proxy(req)
+ if req.params.session ~= "live" then return {status=404,body="expired"} end
+ return {proxy=%q}
+ end
+ return p`, backend.URL)
+	if err := g.core.Plugins().LoadSource("relay", src); err != nil {
+		t.Fatal(err)
+	}
+	server := httptest.NewServer(g.Handler())
+	defer server.Close()
+	req, _ := http.NewRequest("GET", server.URL+"/api/plugins/http/relay/live/app/main.js?x=1&api_key=sk-test", nil)
+	req.Header.Set("Authorization", "Bearer sk-test")
+	req.AddCookie(&http.Cookie{Name: "gw_key", Value: "sk-test"})
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, _ := io.ReadAll(resp.Body)
+	resp.Body.Close()
+	if resp.StatusCode != 200 || string(body) != "/app/main.js?x=1" {
+		t.Fatalf("HTTP proxy: %d %s", resp.StatusCode, body)
+	}
+	c, err := net.Dial("tcp", strings.TrimPrefix(server.URL, "http://"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+	fmt.Fprintf(c, "GET /api/plugins/http/relay/live/websockify HTTP/1.1\r\nHost: %s\r\nAuthorization: Bearer sk-test\r\nConnection: Upgrade\r\nUpgrade: websocket\r\n\r\n", strings.TrimPrefix(server.URL, "http://"))
+	b := bufio.NewReader(c)
+	reply, err := http.ReadResponse(b, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if reply.StatusCode != 101 {
+		t.Fatalf("upgrade failed: %s", reply.Status)
+	}
+	c.Write([]byte("ping"))
+	got := make([]byte, 4)
+	if _, err = io.ReadFull(b, got); err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "ping" {
+		t.Fatalf("tunnel payload=%q", got)
+	}
+}

internal/gateway/server.go

@@ -187,6 +187,10 @@ type statusRecorder struct {
 	code int
 }
 
+// Unwrap preserves optional writer capabilities (notably Hijack for WebSocket)
+// through the access-log middleware via http.ResponseController.
+func (s *statusRecorder) Unwrap() http.ResponseWriter { return s.ResponseWriter }
+
 func (s *statusRecorder) WriteHeader(code int) {
 	if s.code == 0 {
 		s.code = code