Allow automatically resolved non root resources (#454)

* Allow non root resources

* code review

* code review

* code review

* code review

* add non root resource test

* add non root resource test

* add non root resource test

* code review

* code review

go/grpcweb/helpers.go

@@ -7,10 +7,14 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"regexp"
+	"strings"
 
 	"google.golang.org/grpc"
 )
 
+var pathMatcher = regexp.MustCompile(`/[^/]*/[^/]*$`)
+
 // ListGRPCResources is a helper function that lists all URLs that are registered on gRPC server.
 //
 // This makes it easy to register all the relevant routes in your HTTP router of choice.
@@ -35,3 +39,12 @@ func WebsocketRequestOrigin(req *http.Request) (string, error) {
 	}
 	return parsed.Host, nil
 }
+
+func getGRPCEndpoint(req *http.Request) string {
+	endpoint := pathMatcher.FindString(strings.TrimRight(req.URL.Path, "/"))
+	if len(endpoint) == 0 {
+		return req.URL.Path
+	}
+
+	return endpoint
+}

go/grpcweb/helpers_internal_test.go

@@ -0,0 +1,29 @@
+package grpcweb
+
+import (
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetGRPCEndpoint(t *testing.T) {
+	cases := []struct {
+		input  string
+		output string
+	}{
+		{input: "/", output: "/"},
+		{input: "/resource", output: "/resource"},
+		{input: "/improbable.grpcweb.test.TestService/PingEmpty", output: "/improbable.grpcweb.test.TestService/PingEmpty"},
+		{input: "/improbable.grpcweb.test.TestService/PingEmpty/", output: "/improbable.grpcweb.test.TestService/PingEmpty"},
+		{input: "/a/b/c/improbable.grpcweb.test.TestService/PingEmpty", output: "/improbable.grpcweb.test.TestService/PingEmpty"},
+		{input: "/a/b/c/improbable.grpcweb.test.TestService/PingEmpty/", output: "/improbable.grpcweb.test.TestService/PingEmpty"},
+	}
+
+	for _, c := range cases {
+		req := httptest.NewRequest("GET", c.input, nil)
+		result := getGRPCEndpoint(req)
+
+		assert.Equal(t, c.output, result)
+	}
+}

go/grpcweb/options.go

@@ -10,6 +10,7 @@ var (
 		allowedRequestHeaders:          []string{"*"},
 		corsForRegisteredEndpointsOnly: true,
 		originFunc:                     func(origin string) bool { return false },
+		allowNonRootResources:          false,
 	}
 )
 
@@ -19,6 +20,7 @@ type options struct {
 	originFunc                     func(origin string) bool
 	enableWebsockets               bool
 	websocketOriginFunc            func(req *http.Request) bool
+	allowNonRootResources          bool
 }
 
 func evaluateOptions(opts []Option) *options {
@@ -99,3 +101,16 @@ func WithWebsocketOriginFunc(websocketOriginFunc func(req *http.Request) bool) O
 		o.websocketOriginFunc = websocketOriginFunc
 	}
 }
+
+// WithAllowNonRootResource enables the gRPC wrapper to serve requests that have a path prefix
+// added to the URL, before the service name and method placeholders.
+//
+// This should be set to false when exposing the endpoint as the root resource, to avoid
+// the performance cost of path processing for every request.
+//
+// The default behaviour is `false`, i.e. always serves requests assuming there is no prefix to the gRPC endpoint.
+func WithAllowNonRootResource(allowNonRootResources bool) Option {
+	return func(o *options) {
+		o.allowNonRootResources = allowNonRootResources
+	}
+}

go/grpcweb/wrapper.go

@@ -35,6 +35,7 @@ type WrappedGrpcServer struct {
 	originFunc          func(origin string) bool
 	enableWebsockets    bool
 	websocketOriginFunc func(req *http.Request) bool
+	endpointFunc        func(req *http.Request) string
 }
 
 // WrapServer takes a gRPC Server in Go and returns a WrappedGrpcServer that provides gRPC-Web Compatibility.
@@ -56,13 +57,23 @@ func WrapServer(server *grpc.Server, options ...Option) *WrappedGrpcServer {
 	if websocketOriginFunc == nil {
 		websocketOriginFunc = defaultWebsocketOriginFunc
 	}
+
+	endpointFunc := func(req *http.Request) string {
+		return req.URL.Path
+	}
+
+	if opts.allowNonRootResources {
+		endpointFunc = getGRPCEndpoint
+	}
+
 	return &WrappedGrpcServer{
 		server:              server,
 		opts:                opts,
 		corsWrapper:         corsWrapper,
 		originFunc:          opts.originFunc,
 		enableWebsockets:    opts.enableWebsockets,
 		websocketOriginFunc: websocketOriginFunc,
+		endpointFunc:        endpointFunc,
 	}
 }
 
@@ -105,6 +116,7 @@ func (w *WrappedGrpcServer) IsGrpcWebSocketRequest(req *http.Request) bool {
 func (w *WrappedGrpcServer) HandleGrpcWebRequest(resp http.ResponseWriter, req *http.Request) {
 	intReq, isTextFormat := hackIntoNormalGrpcRequest(req)
 	intResp := newGrpcWebResponse(resp, isTextFormat)
+	req.URL.Path = w.endpointFunc(req)
 	w.server.ServeHTTP(intResp, intReq)
 	intResp.finishRequest(req)
 }
@@ -161,6 +173,7 @@ func (w *WrappedGrpcServer) handleWebSocket(wsConn *websocket.Conn, req *http.Re
 		grpclog.Errorf("web socket text format requests not yet supported")
 		return
 	}
+	req.URL.Path = w.endpointFunc(req)
 	w.server.ServeHTTP(respWriter, interceptedRequest)
 }
 
@@ -187,7 +200,7 @@ func (w *WrappedGrpcServer) IsAcceptableGrpcCorsRequest(req *http.Request) bool
 
 func (w *WrappedGrpcServer) isRequestForRegisteredEndpoint(req *http.Request) bool {
 	registeredEndpoints := ListGRPCResources(w.server)
-	requestedEndpoint := req.URL.Path
+	requestedEndpoint := w.endpointFunc(req)
 	for _, v := range registeredEndpoints {
 		if v == requestedEndpoint {
 			return true

go/grpcweb/wrapper_test.go

@@ -15,6 +15,7 @@ import (
 	"log"
 	"net"
 	"net/http"
+	"net/http/httptest"
 	"net/textproto"
 	"os"
 	"strconv"
@@ -67,6 +68,26 @@ func TestHttp1GrpcWebWrapperTestSuite(t *testing.T) {
 	suite.Run(t, &GrpcWebWrapperTestSuite{httpMajorVersion: 1})
 }
 
+func TestNonRootResource(t *testing.T) {
+	grpcServer := grpc.NewServer()
+	testproto.RegisterTestServiceServer(grpcServer, &testServiceImpl{})
+	wrappedServer := grpcweb.WrapServer(grpcServer,
+		grpcweb.WithAllowNonRootResource(true),
+		grpcweb.WithOriginFunc(func(origin string) bool {
+			return true
+		}))
+
+	headers := http.Header{}
+	headers.Add("Access-Control-Request-Method", "POST")
+	headers.Add("Access-Control-Request-Headers", "origin, x-something-custom, x-grpc-web, accept")
+	req := httptest.NewRequest("OPTIONS", "http://host/grpc/improbable.grpcweb.test.TestService/Echo", nil)
+	req.Header = headers
+	resp := httptest.NewRecorder()
+	wrappedServer.ServeHTTP(resp, req)
+
+	assert.Equal(t, http.StatusOK, resp.Code)
+}
+
 func (s *GrpcWebWrapperTestSuite) SetupTest() {
 	var err error
 	s.grpcServer = grpc.NewServer()