vmproxy support for custom Host header

fixes #3626

vmproxy/main.go

@@ -38,6 +38,7 @@ type flags struct {
 	ListenPort    int      `default:"1280" help:"Listen port for proxy"`
 	ListenAddress string   `default:"127.0.0.1" help:"Listen address for proxy"`
 	HeaderName    string   `default:"X-Proxy-Filter" help:"Header name to read filter configuration from. The content of the header shall be a base64 encoded JSON array with strings. Each string is a filter. Multiple filters are joined with a logical OR."` //nolint:lll
+	HostHeader    string   `default:"" help:"Optional Host header value to set in the request, overrides existing"`
 }
 
 func main() {
@@ -67,6 +68,7 @@ func runProxy(opts flags, proxyFn func(cfg proxy.Config) error) error {
 		HeaderName:    opts.HeaderName,
 		ListenAddress: net.JoinHostPort(opts.ListenAddress, strconv.Itoa(opts.ListenPort)),
 		TargetURL:     opts.TargetURL,
+		HostHeader:    opts.HostHeader,
 	})
 
 	if !errors.Is(err, http.ErrServerClosed) {

vmproxy/proxy/proxy.go

@@ -39,6 +39,8 @@ type Config struct {
 	ListenAddress string
 	// Target URL to forward requests to
 	TargetURL *url.URL
+	// Optional Host header value to set in the request
+	HostHeader string
 }
 
 // RunProxy starts proxy which adds extra filters based on configuration.
@@ -51,7 +53,7 @@ func RunProxy(cfg Config) error {
 
 func getHandler(cfg Config) http.HandlerFunc {
 	rProxy := &httputil.ReverseProxy{
-		Director: director(cfg.TargetURL, cfg.HeaderName),
+		Director: director(cfg.TargetURL, cfg.HeaderName, strings.TrimSpace(cfg.HostHeader)),
 	}
 
 	return func(rw http.ResponseWriter, req *http.Request) {
@@ -78,47 +80,57 @@ func failOnInvalidHeader(rw http.ResponseWriter, req *http.Request, headerName s
 	return false
 }
 
-func director(target *url.URL, headerName string) func(*http.Request) {
-	return func(req *http.Request) {
-		now := time.Now()
+func prepareRequest(req *http.Request, target *url.URL, headerName string, hostHeader string) {
+	now := time.Now()
+
+	req.URL.Scheme = target.Scheme
+	req.URL.Host = target.Host
+
+	// Update or add Host header if hostHeader is provided
+	if hostHeader != "" {
+		req.Host = hostHeader
+		req.Header.Set("Host", hostHeader)
+	}
 
-		req.URL.Scheme = target.Scheme
-		req.URL.Host = target.Host
+	rp, err := target.Parse(strings.TrimPrefix(req.URL.Path, "/"))
+	if err != nil {
+		logrus.Error(err)
+	}
+	req.URL.Path = rp.Path
+
+	// Replace extra filters if present
+	if filters := req.Header.Get(headerName); filters != "" {
+		q := req.URL.Query()
+		q.Del("extra_filters[]")
 
-		rp, err := target.Parse(strings.TrimPrefix(req.URL.Path, "/"))
+		parsed, err := parseFilters(filters)
 		if err != nil {
 			logrus.Error(err)
 		}
-		req.URL.Path = rp.Path
 
-		// Replace extra filters if present
-		if filters := req.Header.Get(headerName); filters != "" {
-			q := req.URL.Query()
-			q.Del("extra_filters[]")
-
-			parsed, err := parseFilters(filters)
-			if err != nil {
-				logrus.Error(err)
-			}
+		for _, f := range parsed {
+			q.Add("extra_filters[]", f)
+		}
 
-			for _, f := range parsed {
-				q.Add("extra_filters[]", f)
-			}
+		req.URL.RawQuery = q.Encode()
 
-			req.URL.RawQuery = q.Encode()
+		logrus.Debugf(
+			"Received filters: %s, Parsed filters: %#v, Query: %s, Target URL: %s, Time spent: %s",
+			filters, parsed, req.URL.RawQuery, req.URL, time.Since(now))
+	}
 
-			logrus.Debugf(
-				"Received filters: %s, Parsed filters: %#v, Query: %s, Target URL: %s, Time spent: %s",
-				filters, parsed, req.URL.RawQuery, req.URL, time.Since(now))
-		}
+	// Do not trust the client
+	req.Header.Del("X-Forwarded-For")
 
-		// Do not trust the client
-		req.Header.Del("X-Forwarded-For")
+	if _, ok := req.Header["User-Agent"]; !ok {
+		// explicitly disable User-Agent so it's not set to default value
+		req.Header.Set("User-Agent", "")
+	}
+}
 
-		if _, ok := req.Header["User-Agent"]; !ok {
-			// explicitly disable User-Agent so it's not set to default value
-			req.Header.Set("User-Agent", "")
-		}
+func director(target *url.URL, headerName string, hostHeader string) func(*http.Request) {
+	return func(req *http.Request) {
+		prepareRequest(req, target, headerName, hostHeader)
 	}
 }
 

vmproxy/proxy/proxy_test.go

@@ -33,7 +33,7 @@ const (
 func TestProxy(t *testing.T) {
 	t.Parallel()
 
-	setup := func(t *testing.T, filters []string) http.HandlerFunc {
+	setup := func(t *testing.T, filters []string, hostHeader string) http.HandlerFunc {
 		t.Helper()
 		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			if filters != nil {
@@ -50,18 +50,23 @@ func TestProxy(t *testing.T) {
 		handler := getHandler(Config{
 			HeaderName: headerName,
 			TargetURL:  testURL,
+			HostHeader: hostHeader,
 		})
 
 		return handler
 	}
 
-	handler := setup(t, nil)
+	handler := setup(t, nil, "")
 
 	t.Run("shall proxy request", func(t *testing.T) {
 		t.Parallel()
 
 		rec := httptest.NewRecorder()
 		req := httptest.NewRequest(http.MethodGet, targetURL, nil)
+		hostHeader := ""
+		url, err := url.Parse(targetURL)
+		require.NoError(t, err)
+		prepareRequest(req, url, headerName, hostHeader)
 
 		handler.ServeHTTP(rec, req)
 		resp := rec.Result()
@@ -125,15 +130,20 @@ func TestProxy(t *testing.T) {
 			t.Run(tc.name, func(t *testing.T) {
 				t.Parallel()
 
-				url := targetURL
+				url, err := url.Parse(targetURL)
+				require.NoError(t, err)
+
 				if tc.targetURL != "" {
-					url = tc.targetURL
+					url, err = url.Parse(tc.targetURL)
+					require.NoError(t, err)
 				}
 
-				handler := setup(t, tc.expectedFilters)
+				handler := setup(t, tc.expectedFilters, "")
 
 				rec := httptest.NewRecorder()
-				req := httptest.NewRequest(http.MethodGet, url, nil)
+				req := httptest.NewRequest(http.MethodGet, targetURL, nil)
+				hostHeader := ""
+				prepareRequest(req, url, headerName, hostHeader)
 				req.Header.Set(headerName, tc.headerContent)
 
 				handler.ServeHTTP(rec, req)
@@ -144,4 +154,17 @@ func TestProxy(t *testing.T) {
 			})
 		}
 	})
+
+	t.Run("prepareRequest: set manual Host header", func(t *testing.T) {
+		t.Parallel()
+
+		hostHeader := "test.example.org"
+		req := httptest.NewRequest(http.MethodGet, targetURL, nil)
+		url, err := url.Parse(targetURL)
+		require.NoError(t, err)
+
+		prepareRequest(req, url, headerName, hostHeader)
+
+		require.Equal(t, hostHeader, req.Header["Host"][0])
+	})
 }