lib: added uds capability to http challenge server (#1485)

Co-authored-by: Fernandez Ludovic <ldez@users.noreply.github.com>

challenge/http01/http_challenge_server.go

@@ -2,9 +2,11 @@ package http01
 
 import (
 	"fmt"
+	"io/fs"
 	"net"
 	"net/http"
 	"net/textproto"
+	"os"
 	"strings"
 
 	"github.com/go-acme/lego/v4/log"
@@ -14,8 +16,11 @@ import (
 // It may be instantiated without using the NewProviderServer function if
 // you want only to use the default values.
 type ProviderServer struct {
-	iface    string
-	port     string
+	address string
+	network string // must be valid argument to net.Listen
+
+	socketMode fs.FileMode
+
 	matcher  domainMatcher
 	done     chan bool
 	listener net.Listener
@@ -29,24 +34,34 @@ func NewProviderServer(iface, port string) *ProviderServer {
 		port = "80"
 	}
 
-	return &ProviderServer{iface: iface, port: port, matcher: &hostMatcher{}}
+	return &ProviderServer{network: "tcp", address: net.JoinHostPort(iface, port), matcher: &hostMatcher{}}
+}
+
+func NewUnixProviderServer(socketPath string, mode fs.FileMode) *ProviderServer {
+	return &ProviderServer{network: "unix", address: socketPath, socketMode: mode, matcher: &hostMatcher{}}
 }
 
 // Present starts a web server and makes the token available at `ChallengePath(token)` for web requests.
 func (s *ProviderServer) Present(domain, token, keyAuth string) error {
 	var err error
-	s.listener, err = net.Listen("tcp", s.GetAddress())
+	s.listener, err = net.Listen(s.network, s.GetAddress())
 	if err != nil {
 		return fmt.Errorf("could not start HTTP server for challenge: %w", err)
 	}
 
+	if s.network == "unix" {
+		if err = os.Chmod(s.address, s.socketMode); err != nil {
+			return fmt.Errorf("chmod %s: %w", s.address, err)
+		}
+	}
+
 	s.done = make(chan bool)
 	go s.serve(domain, token, keyAuth)
 	return nil
 }
 
 func (s *ProviderServer) GetAddress() string {
-	return net.JoinHostPort(s.iface, s.port)
+	return s.address
 }
 
 // CleanUp closes the HTTP server and removes the token from `ChallengePath(token)`.
@@ -85,7 +100,7 @@ func (s *ProviderServer) SetProxyHeader(headerName string) {
 func (s *ProviderServer) serve(domain, token, keyAuth string) {
 	path := ChallengePath(token)
 
-	// The incoming request must will be validated to prevent DNS rebind attacks.
+	// The incoming request will be validated to prevent DNS rebind attacks.
 	// We only respond with the keyAuth, when we're receiving a GET requests with
 	// the "Host" header matching the domain (the latter is configurable though SetProxyHeader).
 	mux := http.NewServeMux()
@@ -99,7 +114,7 @@ func (s *ProviderServer) serve(domain, token, keyAuth string) {
 			}
 			log.Infof("[%s] Served key authentication", domain)
 		} else {
-			log.Warnf("Received request for domain %s with method %s but the domain did not match any challenge. Please ensure your are passing the %s header properly.", r.Host, r.Method, s.matcher.name())
+			log.Warnf("Received request for domain %s with method %s but the domain did not match any challenge. Please ensure you are passing the %s header properly.", r.Host, r.Method, s.matcher.name())
 			_, err := w.Write([]byte("TEST"))
 			if err != nil {
 				http.Error(w, err.Error(), http.StatusInternalServerError)

challenge/http01/http_challenge_test.go

@@ -1,12 +1,18 @@
 package http01
 
 import (
+	"context"
 	"crypto/rand"
 	"crypto/rsa"
 	"fmt"
 	"io"
+	"io/fs"
+	"net"
 	"net/http"
 	"net/textproto"
+	"os"
+	"path/filepath"
+	"runtime"
 	"testing"
 
 	"github.com/go-acme/lego/v4/acme"
@@ -17,6 +23,50 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestProviderServer_GetAddress(t *testing.T) {
+	dir := t.TempDir()
+	t.Cleanup(func() { _ = os.RemoveAll(dir) })
+
+	sock := filepath.Join(dir, "var", "run", "test")
+
+	testCases := []struct {
+		desc     string
+		server   *ProviderServer
+		expected string
+	}{
+		{
+			desc:     "TCP default address",
+			server:   NewProviderServer("", ""),
+			expected: ":80",
+		},
+		{
+			desc:     "TCP with explicit port",
+			server:   NewProviderServer("", "8080"),
+			expected: ":8080",
+		},
+		{
+			desc:     "TCP with host and port",
+			server:   NewProviderServer("localhost", "8080"),
+			expected: "localhost:8080",
+		},
+		{
+			desc:     "UDS socket",
+			server:   NewUnixProviderServer(sock, fs.ModeSocket|0o666),
+			expected: sock,
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			address := test.server.GetAddress()
+			assert.Equal(t, test.expected, address)
+		})
+	}
+}
+
 func TestChallenge(t *testing.T) {
 	_, apiURL := tester.SetupFakeAPI(t)
 
@@ -69,6 +119,75 @@ func TestChallenge(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestChallengeUnix(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Skip("only for UNIX systems")
+	}
+
+	_, apiURL := tester.SetupFakeAPI(t)
+
+	dir := t.TempDir()
+	t.Cleanup(func() { _ = os.RemoveAll(dir) })
+
+	socket := filepath.Join(dir, "lego-challenge-test.sock")
+
+	providerServer := NewUnixProviderServer(socket, fs.ModeSocket|0o666)
+
+	validate := func(_ *api.Core, _ string, chlng acme.Challenge) error {
+		// any uri will do, as we hijack the dial
+		uri := "http://localhost" + ChallengePath(chlng.Token)
+
+		client := &http.Client{Transport: &http.Transport{
+			DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+				return net.Dial("unix", socket)
+			},
+		}}
+
+		resp, err := client.Get(uri)
+		if err != nil {
+			return err
+		}
+
+		defer resp.Body.Close()
+
+		if want := "text/plain"; resp.Header.Get("Content-Type") != want {
+			t.Errorf("Get(%q) Content-Type: got %q, want %q", uri, resp.Header.Get("Content-Type"), want)
+		}
+
+		body, err := io.ReadAll(resp.Body)
+		if err != nil {
+			return err
+		}
+		bodyStr := string(body)
+
+		if bodyStr != chlng.KeyAuthorization {
+			t.Errorf("Get(%q) Body: got %q, want %q", uri, bodyStr, chlng.KeyAuthorization)
+		}
+
+		return nil
+	}
+
+	privateKey, err := rsa.GenerateKey(rand.Reader, 512)
+	require.NoError(t, err, "Could not generate test key")
+
+	core, err := api.New(http.DefaultClient, "lego-test", apiURL+"/dir", "", privateKey)
+	require.NoError(t, err)
+
+	solver := NewChallenge(core, validate, providerServer)
+
+	authz := acme.Authorization{
+		Identifier: acme.Identifier{
+			Value: "localhost",
+		},
+		Challenges: []acme.Challenge{
+			{Type: challenge.HTTP01.String(), Token: "http1"},
+		},
+	}
+
+	err = solver.Solve(authz)
+	require.NoError(t, err)
+}
+
 func TestChallengeInvalidPort(t *testing.T) {
 	_, apiURL := tester.SetupFakeAPI(t)