Add proxy dialer support

cmd/grpcurl/grpcurl.go

@@ -553,6 +553,7 @@ func main() {
 			grpcurlUA = *userAgent + " " + grpcurlUA
 		}
 		opts = append(opts, grpc.WithUserAgent(grpcurlUA))
+		grpcurl.GrpcurlUA = grpcurlUA
 
 		blockingDialTiming := dialTiming.Child("BlockingDial")
 		defer blockingDialTiming.Done()

grpcurl.go

@@ -37,6 +37,8 @@ import (
 	"google.golang.org/protobuf/types/known/structpb"
 )
 
+var GrpcurlUA string
+
 // ListServices uses the given descriptor source to return a sorted list of fully-qualified
 // service names.
 func ListServices(source DescriptorSource) ([]string, error) {
@@ -653,7 +655,7 @@ func BlockingDial(ctx context.Context, network, address string, creds credential
 		// handshake). And that would mean that the library would send the
 		// wrong ":scheme" metaheader to servers: it would send "http" instead
 		// of "https" because it is unaware that TLS is actually in use.
-		conn, err := (&net.Dialer{}).DialContext(ctx, network, address)
+		conn, err := proxyDial(ctx, address, GrpcurlUA)
 		if err != nil {
 			writeResult(err)
 		}

proxy.go

@@ -0,0 +1,156 @@
+// NOTE: This source file contains the internal grpc-go proxy implementation
+// found in google.golang.org/grpc/internal/transport, with minor
+// modifications for use in grpcurl. Below is the original license:
+
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpcurl
+
+import (
+	"bufio"
+	"context"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	// "google.golang.org/grpc/internal"
+)
+
+const proxyAuthHeaderKey = "Proxy-Authorization"
+
+var (
+	// The following variable will be overwritten in the tests.
+	httpProxyFromEnvironment = http.ProxyFromEnvironment
+)
+
+func mapAddress(address string) (*url.URL, error) {
+	req := &http.Request{
+		URL: &url.URL{
+			Scheme: "https",
+			Host:   address,
+		},
+	}
+	url, err := httpProxyFromEnvironment(req)
+	if err != nil {
+		return nil, err
+	}
+	return url, nil
+}
+
+// To read a response from a net.Conn, http.ReadResponse() takes a bufio.Reader.
+// It's possible that this reader reads more than what's need for the response and stores
+// those bytes in the buffer.
+// bufConn wraps the original net.Conn and the bufio.Reader to make sure we don't lose the
+// bytes in the buffer.
+type bufConn struct {
+	net.Conn
+	r io.Reader
+}
+
+func (c *bufConn) Read(b []byte) (int, error) {
+	return c.r.Read(b)
+}
+
+func basicAuth(username, password string) string {
+	auth := username + ":" + password
+	return base64.StdEncoding.EncodeToString([]byte(auth))
+}
+
+func doHTTPConnectHandshake(ctx context.Context, conn net.Conn, backendAddr string, proxyURL *url.URL, grpcUA string) (_ net.Conn, err error) {
+	defer func() {
+		if err != nil {
+			conn.Close()
+		}
+	}()
+
+	req := &http.Request{
+		Method: http.MethodConnect,
+		URL:    &url.URL{Host: backendAddr},
+		Header: map[string][]string{"User-Agent": {grpcUA}},
+	}
+	if t := proxyURL.User; t != nil {
+		u := t.Username()
+		p, _ := t.Password()
+		req.Header.Add(proxyAuthHeaderKey, "Basic "+basicAuth(u, p))
+	}
+
+	if err := sendHTTPRequest(ctx, req, conn); err != nil {
+		return nil, fmt.Errorf("failed to write the HTTP request: %v", err)
+	}
+
+	r := bufio.NewReader(conn)
+	resp, err := http.ReadResponse(r, req)
+	if err != nil {
+		return nil, fmt.Errorf("reading server HTTP response: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		dump, err := httputil.DumpResponse(resp, true)
+		if err != nil {
+			return nil, fmt.Errorf("failed to do connect handshake, status code: %s", resp.Status)
+		}
+		return nil, fmt.Errorf("failed to do connect handshake, response: %q", dump)
+	}
+	// The buffer could contain extra bytes from the target server, so we can't
+	// discard it. However, in many cases where the server waits for the client
+	// to send the first message (e.g. when TLS is being used), the buffer will
+	// be empty, so we can avoid the overhead of reading through this buffer.
+	if r.Buffered() != 0 {
+		return &bufConn{Conn: conn, r: r}, nil
+	}
+	return conn, nil
+}
+
+// proxyDial dials, connecting to a proxy first if necessary. Checks if a proxy
+// is necessary, dials, does the HTTP CONNECT handshake, and returns the
+// connection.
+func proxyDial(ctx context.Context, addr string, grpcUA string) (net.Conn, error) {
+	newAddr := addr
+	proxyURL, err := mapAddress(addr)
+	if err != nil {
+		return nil, err
+	}
+	if proxyURL != nil {
+		newAddr = proxyURL.Host
+	}
+
+	// NOTE: Use net.Dialer to avoid dependency on grpc-go's internal package
+	// conn, err := internal.NetDialerWithTCPKeepalive().DialContext(ctx, "tcp", newAddr)
+
+	conn, err := (&net.Dialer{}).DialContext(ctx, "tcp", newAddr)
+	if err != nil {
+		return nil, err
+	}
+	if proxyURL == nil {
+		// proxy is disabled if proxyURL is nil.
+		return conn, err
+	}
+	return doHTTPConnectHandshake(ctx, conn, addr, proxyURL, grpcUA)
+}
+
+func sendHTTPRequest(ctx context.Context, req *http.Request, conn net.Conn) error {
+	req = req.WithContext(ctx)
+	if err := req.Write(conn); err != nil {
+		return fmt.Errorf("failed to write the HTTP request: %v", err)
+	}
+	return nil
+}