add ability to drop incoming headers #108

In some cases proxy should sanitize incoming headers. --drop-header and $DROP_HEADERS set list of headers (keys) and those headers removed from the request.

.github/workflows/ci.yml

@@ -11,10 +11,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - name: set up go 1.16
+      - name: set up go 1.17
         uses: actions/setup-go@v2
         with:
-          go-version: 1.16
+          go-version: 1.17
         id: go
 
       - name: checkout

README.md

@@ -18,7 +18,7 @@ Reproxy is a simple edge HTTP(s) server / reverse proxy supporting various provi
 - Docker container distribution
 - Built-in static assets server with optional "SPA friendly" mode
 - Support for redirect rules 
-- Optional limiter for the overall activity as well as for user's activity   
+- Optional limiter for the overall activity as well as for user's activity
 - Live health check and fail-over/load-balancing  
 - Management server with routes info and prometheus metrics
 - Plugins support via RPC to implement custom functionality
@@ -225,6 +225,7 @@ supported codes:
 - `--gzip`   enables gzip compression for responses.
 - `--max=N`  allows to set the maximum size of request (default 64k). Setting it to `0` disables the size check.
 - `--header` sets extra header(s) added to each proxied response. 
+- `--drop-header` drops headers from incoming request. 
   
 For example this is how it can be done with the docker compose:
 
@@ -324,7 +325,8 @@ This is the list of all options supporting multiple elements:
   -l, --listen=                     listen on host:port (default: 0.0.0.0:8080/8443 under docker, 127.0.0.1:80/443 without) [$LISTEN]
   -m, --max=                        max request size (default: 64K) [$MAX_SIZE]
   -g, --gzip                        enable gz compression [$GZIP]
-  -x, --header=                     proxy headers
+  -x, --header=                     outgoing proxy headers to add
+      --drop-header=                incoming headers to drop [$DROP_HEADERS]
       --lb-type=[random|failover]   load balancer type (default: random) [$LB_TYPE]
       --signature                   enable reproxy signature headers [$SIGNATURE]
       --dbg                         debug mode [$DEBUG]
@@ -407,6 +409,7 @@ plugin:
 
 Help Options:
   -h, --help                        Show this help message
+
 ```
 
 ## Status

app/main.go

@@ -33,7 +33,8 @@ var opts struct {
 	Listen       string   `short:"l" long:"listen" env:"LISTEN" description:"listen on host:port (default: 0.0.0.0:8080/8443 under docker, 127.0.0.1:80/443 without)"`
 	MaxSize      string   `short:"m" long:"max" env:"MAX_SIZE" default:"64K" description:"max request size"`
 	GzipEnabled  bool     `short:"g" long:"gzip" env:"GZIP" description:"enable gz compression"`
-	ProxyHeaders []string `short:"x" long:"header" description:"proxy headers"` // env HEADER split in code to allow , inside ""
+	ProxyHeaders []string `short:"x" long:"header" description:"outgoing proxy headers to add"` // env HEADER split in code to allow , inside ""
+	DropHeaders  []string `long:"drop-header" env:"DROP_HEADERS" description:"incoming headers to drop" env-delim:","`
 
 	LBType string `long:"lb-type" env:"LB_TYPE" description:"load balancer type" choice:"random" choice:"failover" default:"random"` //nolint
 
@@ -239,6 +240,7 @@ func run() error {
 		GzEnabled:      opts.GzipEnabled,
 		SSLConfig:      sslConfig,
 		ProxyHeaders:   proxyHeaders,
+		DropHeader:     opts.DropHeaders,
 		AccessLog:      accessLog,
 		StdOutEnabled:  opts.Logger.StdOut,
 		Signature:      opts.Signature,
@@ -258,7 +260,7 @@ func run() error {
 		Reporter:        errReporter,
 		PluginConductor: makePluginConductor(ctx),
 		ThrottleSystem:  opts.Throttle.System * 3,
-		ThottleUser:     opts.Throttle.User,
+		ThrottleUser:    opts.Throttle.User,
 	}
 
 	err = px.Run(ctx)

app/mgmt/metrics.go

@@ -45,7 +45,7 @@ func NewMetrics() *Metrics {
 		Buckets: []float64{0.01, 0.1, 0.5, 1, 2, 3, 5},
 	}, []string{"path"})
 
-	prometheus.Unregister(prometheus.NewGoCollector())
+	prometheus.Unregister(prometheus.NewGoCollector()) //nolint
 
 	if err := prometheus.Register(res.totalRequests); err != nil {
 		log.Printf("[WARN] can't register prometheus totalRequests, %v", err)

app/proxy/handlers.go

@@ -14,21 +14,28 @@ import (
 	"github.com/umputun/reproxy/app/discovery"
 )
 
-func headersHandler(headers []string) func(next http.Handler) http.Handler {
+func headersHandler(addHeaders, dropHeaders []string) func(next http.Handler) http.Handler {
 
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			if len(headers) == 0 {
+			if len(addHeaders) == 0 && len(dropHeaders) == 0 {
 				next.ServeHTTP(w, r)
 				return
 			}
-			for _, h := range headers {
+			// add headers to response
+			for _, h := range addHeaders {
 				elems := strings.Split(h, ":")
 				if len(elems) != 2 {
 					continue
 				}
 				w.Header().Set(strings.TrimSpace(elems[0]), strings.TrimSpace(elems[1]))
 			}
+
+			// drop headers from request
+			for _, h := range dropHeaders {
+				r.Header.Del(h)
+			}
+
 			next.ServeHTTP(w, r)
 		})
 	}

app/proxy/handlers_test.go

@@ -18,11 +18,17 @@ import (
 
 func Test_headersHandler(t *testing.T) {
 	wr := httptest.NewRecorder()
-	handler := headersHandler([]string{"k1:v1", "k2:v2"})(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	handler := headersHandler([]string{"k1:v1", "k2:v2"}, []string{"r1", "r2"})(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		t.Logf("req: %v", r)
+		assert.Equal(t, "", r.Header.Get("r1"), "r1 header dropped")
+		assert.Equal(t, "", r.Header.Get("r2"), "r2 header dropped")
+		assert.Equal(t, "rv3", r.Header.Get("r3"), "r3 kept")
 	}))
 	req, err := http.NewRequest("GET", "http://example.com", nil)
 	require.NoError(t, err)
+	req.Header.Set("r1", "rv1")
+	req.Header.Set("r2", "rv2")
+	req.Header.Set("r3", "rv3")
 	handler.ServeHTTP(wr, req)
 	assert.Equal(t, "v1", wr.Result().Header.Get("k1"))
 	assert.Equal(t, "v2", wr.Result().Header.Get("k2"))

app/proxy/proxy.go

@@ -32,6 +32,7 @@ type Http struct { // nolint golint
 	MaxBodySize     int64
 	GzEnabled       bool
 	ProxyHeaders    []string
+	DropHeader      []string
 	SSLConfig       SSLConfig
 	Version         string
 	AccessLog       io.Writer
@@ -45,7 +46,7 @@ type Http struct { // nolint golint
 	LBSelector      func(len int) int
 
 	ThrottleSystem int
-	ThottleUser    int
+	ThrottleUser   int
 }
 
 // Matcher source info (server and route) to the destination url
@@ -110,17 +111,17 @@ func (h *Http) Run(ctx context.Context) error {
 	}()
 
 	handler := R.Wrap(h.proxyHandler(),
-		R.Recoverer(log.Default()),               // recover on errors
-		signatureHandler(h.Signature, h.Version), // send app signature
-		h.pingHandler,                            // respond to /ping
-		h.healthMiddleware,                       // respond to /health
-		h.matchHandler,                           // set matched routes to context
-		limiterSystemHandler(h.ThrottleSystem),   // limit total requests/sec
-		limiterUserHandler(h.ThottleUser),        // req/seq per user/route match
-		h.mgmtHandler(),                          // handles /metrics and /routes for prometheus
-		h.pluginHandler(),                        // prc to external plugins
-		headersHandler(h.ProxyHeaders),           // set response headers
-		accessLogHandler(h.AccessLog),            // apache-format log file
+		R.Recoverer(log.Default()),                   // recover on errors
+		signatureHandler(h.Signature, h.Version),     // send app signature
+		h.pingHandler,                                // respond to /ping
+		h.healthMiddleware,                           // respond to /health
+		h.matchHandler,                               // set matched routes to context
+		limiterSystemHandler(h.ThrottleSystem),       // limit total requests/sec
+		limiterUserHandler(h.ThrottleUser),           // req/seq per user/route match
+		h.mgmtHandler(),                              // handles /metrics and /routes for prometheus
+		h.pluginHandler(),                            // prc to external plugins
+		headersHandler(h.ProxyHeaders, h.DropHeader), // add response headers and delete some request headers
+		accessLogHandler(h.AccessLog),                // apache-format log file
 		stdoutLogHandler(h.StdOutEnabled, logger.New(logger.Log(log.Default()), logger.Prefix("[INFO]")).Handler),
 		maxReqSizeHandler(h.MaxBodySize), // limit request max size
 		gzipHandler(h.GzEnabled),         // gzip response