add TLS integration test, update Client.DialContext docs

Turns out we already have the necessary hook (DialContext), which was
added in #158.

Updates #121

Signed-off-by: Brad Fitzpatrick <brad@danga.com>

memcache/fakecerts_test.go

@@ -0,0 +1,62 @@
+package memcache
+
+import "strings"
+
+// Copied from Go's net/http/internal/testcert package.
+
+// LocalhostCert is a PEM-encoded TLS cert with SAN IPs
+// "127.0.0.1" and "[::1]", expiring at Jan 29 16:00:00 2084 GMT.
+// generated from src/crypto/tls:
+// go run generate_cert.go  --rsa-bits 2048 --host 127.0.0.1,::1,example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
+var LocalhostCert = []byte(`-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`)
+
+// LocalhostKey is the private key for LocalhostCert.
+var LocalhostKey = []byte(testingKey(`-----BEGIN RSA TESTING KEY-----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+-----END RSA TESTING KEY-----`))
+
+func testingKey(s string) string { return strings.ReplaceAll(s, "TESTING KEY", "PRIVATE KEY") }

memcache/fakeserver_test.go

@@ -1,3 +1,19 @@
+/*
+Copyright 2023 The gomemcache 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 memcache
 
 import (

memcache/memcache.go

@@ -132,8 +132,12 @@ func NewFromSelector(ss ServerSelector) *Client {
 // Client is a memcache client.
 // It is safe for unlocked use by multiple concurrent goroutines.
 type Client struct {
-	// DialContext connects to the address on the named network
-	// using the provided context
+	// DialContext connects to the address on the named network using the
+	// provided context.
+	//
+	// To connect to servers using TLS (memcached running with "--enable-ssl"),
+	// use a DialContext func that uses tls.Dialer.DialContext. See this
+	// package's tests as an example.
 	DialContext func(ctx context.Context, network, address string) (net.Conn, error)
 
 	// Timeout specifies the socket read/write timeout.

memcache/memcache_test.go

@@ -19,17 +19,25 @@ package memcache
 
 import (
 	"bufio"
+	"bytes"
+	"context"
+	"crypto/tls"
+	"flag"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"net"
 	"os"
 	"os/exec"
+	"path/filepath"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
 )
 
+var debug = flag.Bool("debug", false, "be more verbose")
+
 const localhostTCPAddr = "localhost:11211"
 
 func TestLocalhost(t *testing.T) {
@@ -81,6 +89,77 @@ func TestFakeServer(t *testing.T) {
 	testWithClient(t, New(ln.Addr().String()))
 }
 
+func TestTLS(t *testing.T) {
+	t.Parallel()
+	td := t.TempDir()
+
+	// Test whether our memcached binary has TLS support. We --enable-ssl first,
+	// before --version, as memcached evaluates the flags in the order provided
+	// and we want it to fail if it's built without TLS support (as it is in
+	// Debian, but not Ubuntu or Homebrew).
+	out, err := exec.Command("memcached", "--enable-ssl", "--version").CombinedOutput()
+	if err != nil {
+		t.Skipf("skipping test; couldn't find memcached or no TLS support in binary: %v, %s", err, out)
+	}
+	t.Logf("version: %s", bytes.TrimSpace(out))
+
+	if err := os.WriteFile(filepath.Join(td, "/cert.pem"), LocalhostCert, 0644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(td, "/key.pem"), LocalhostKey, 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	// Find some unused port. This is racy but we hope for the best and hope the kernel
+	// doesn't reassign our ephemeral port to somebody in the tiny race window.
+	ln, err := net.Listen("tcp", "localhost:0")
+	if err != nil {
+		t.Fatalf("failed to listen: %v", err)
+	}
+	port := ln.Addr().(*net.TCPAddr).Port
+	ln.Close()
+
+	cmd := exec.Command("memcached",
+		"--port="+strconv.Itoa(port),
+		"--listen=127.0.0.1",
+		"--enable-ssl",
+		"-o", "ssl_chain_cert=cert.pem",
+		"-o", "ssl_key=key.pem")
+	cmd.Dir = td
+	if *debug {
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+	}
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("failed to start memcached: %v", err)
+	}
+	defer cmd.Wait()
+	defer cmd.Process.Kill()
+
+	// Wait a bit for the server to be running.
+	for i := 0; i < 10; i++ {
+		nc, err := net.Dial("tcp", "localhost:"+strconv.Itoa(port))
+		if err == nil {
+			t.Logf("localhost:%d is up.", port)
+			nc.Close()
+			break
+		}
+		t.Logf("waiting for localhost:%d to be up...", port)
+		time.Sleep(time.Duration(25*i) * time.Millisecond)
+	}
+
+	c := New(net.JoinHostPort("127.0.0.1", strconv.Itoa(port)))
+	c.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
+		var td tls.Dialer
+		td.Config = &tls.Config{
+			InsecureSkipVerify: true,
+		}
+		return td.DialContext(ctx, network, addr)
+
+	}
+	testWithClient(t, c)
+}
+
 func mustSetF(t *testing.T, c *Client) func(*Item) {
 	return func(it *Item) {
 		if err := c.Set(it); err != nil {