Merge pull request #27 from stripe/harold/mitmMutateRequestHook

Add a mitmMutateRequest hook and add ConnectAction to ProxyCtx

ctx.go

@@ -25,8 +25,9 @@ type ProxyCtx struct {
 	// call of RespHandler
 	UserData interface{}
 	// Will connect a request to a response
-	Session int64
-	proxy   *ProxyHttpServer
+	Session       int64
+	proxy         *ProxyHttpServer
+	ConnectAction ConnectActionLiteral
 }
 
 type RoundTripper interface {

https.go

@@ -43,9 +43,10 @@ var (
 )
 
 type ConnectAction struct {
-	Action    ConnectActionLiteral
-	Hijack    func(req *http.Request, client net.Conn, ctx *ProxyCtx)
-	TLSConfig func(host string, ctx *ProxyCtx) (*tls.Config, error)
+	Action            ConnectActionLiteral
+	Hijack            func(req *http.Request, client net.Conn, ctx *ProxyCtx)
+	TLSConfig         func(host string, ctx *ProxyCtx) (*tls.Config, error)
+	MitmMutateRequest func(req *http.Request, ctx *ProxyCtx)
 }
 
 func stripPort(s string) string {
@@ -114,6 +115,7 @@ func (proxy *ProxyHttpServer) handleHttps(w http.ResponseWriter, r *http.Request
 			break
 		}
 	}
+	ctx.ConnectAction = todo.Action
 	switch todo.Action {
 	case ConnectAccept:
 		if !hasPort.MatchString(host) {
@@ -264,7 +266,7 @@ func (proxy *ProxyHttpServer) handleHttps(w http.ResponseWriter, r *http.Request
 				req, err := http.ReadRequest(clientTlsReader)
 				// Set the RoundTripper on the ProxyCtx within the `HandleConnect` action of goproxy, then
 				// inject the roundtripper here in order to use a custom round tripper while mitm.
-				var ctx = &ProxyCtx{Req: req, Session: atomic.AddInt64(&proxy.sess, 1), proxy: proxy, UserData: ctx.UserData, RoundTripper: ctx.RoundTripper}
+				var ctx = &ProxyCtx{Req: req, Session: atomic.AddInt64(&proxy.sess, 1), proxy: proxy, UserData: ctx.UserData, RoundTripper: ctx.RoundTripper, ConnectAction: ctx.ConnectAction}
 				if err != nil && err != io.EOF {
 					return
 				}
@@ -273,6 +275,9 @@ func (proxy *ProxyHttpServer) handleHttps(w http.ResponseWriter, r *http.Request
 					return
 				}
 				req.RemoteAddr = r.RemoteAddr // since we're converting the request, need to carry over the original connecting IP as well
+				if todo.MitmMutateRequest != nil {
+					todo.MitmMutateRequest(req, ctx)
+				}
 				ctx.Logf("req %v", r.Host)
 
 				if !httpsRegexp.MatchString(req.URL.String()) {

proxy_test.go

@@ -41,9 +41,26 @@ func (QueryHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	io.WriteString(w, req.Form.Get("result"))
 }
 
+type HeadersHandler struct{}
+
+// This handlers returns a body with a string containing all the request headers it received.
+func (HeadersHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	var sb strings.Builder
+	for name, values := range req.Header {
+		for _, value := range values {
+			sb.WriteString(name)
+			sb.WriteString(": ")
+			sb.WriteString(value)
+			sb.WriteString(";")
+		}
+	}
+	io.WriteString(w, sb.String())
+}
+
 func init() {
 	http.DefaultServeMux.Handle("/bobo", ConstantHanlder("bobo"))
 	http.DefaultServeMux.Handle("/query", QueryHandler{})
+	http.DefaultServeMux.Handle("/headers", HeadersHandler{})
 }
 
 type ConstantHanlder string
@@ -436,6 +453,33 @@ func TestSimpleMitm(t *testing.T) {
 	}
 }
 
+func TestMitmMutateRequest(t *testing.T) {
+	mitmMutateRequest := func(req *http.Request, ctx *goproxy.ProxyCtx) {
+		// We inject a header in the request
+		req.Header.Set("Mitm-Header-Inject", "true")
+	}
+	mitmConnect := &goproxy.ConnectAction{
+		Action:            goproxy.ConnectMitm,
+		TLSConfig:         goproxy.TLSConfigFromCA(&goproxy.GoproxyCa),
+		MitmMutateRequest: mitmMutateRequest,
+	}
+	var mitm goproxy.FuncHttpsHandler = func(host string, ctx *goproxy.ProxyCtx) (*goproxy.ConnectAction, string) {
+		return mitmConnect, host
+	}
+
+	proxy := goproxy.NewProxyHttpServer()
+	proxy.OnRequest().HandleConnect(mitm)
+
+	client, l := oneShotProxy(proxy, t)
+	defer l.Close()
+
+	r := string(getOrFail(https.URL+"/headers", client, t))
+	if !strings.Contains(r, "Mitm-Header-Inject: true") {
+		t.Error("Expected response body to contain the MITM injected header. Got instead: ", r)
+	}
+
+}
+
 func TestConnectHandler(t *testing.T) {
 	proxy := goproxy.NewProxyHttpServer()
 	althttps := httptest.NewTLSServer(ConstantHanlder("althttps"))