Cleanup properly after hijacking a request

The logging handler hijacks the HTTP request, but does
not properly clean up the files left behind by multipart
forms.

The HTTP library normally does this, but if the connection is hijacked,
all responsibility to clean up is on the hijacker.

logging.go

@@ -43,6 +43,9 @@ func (h loggingHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	url := *req.URL
 
 	h.handler.ServeHTTP(logger, req)
+	if req.MultipartForm != nil {
+		req.MultipartForm.RemoveAll()
+	}
 
 	params := LogFormatterParams{
 		Request:    req,

logging_test.go

@@ -6,9 +6,16 @@ package handlers
 
 import (
 	"bytes"
+	"encoding/base64"
+	"fmt"
+	"io/ioutil"
+	"math/rand"
+	"mime/multipart"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 	"time"
@@ -38,6 +45,72 @@ func TestMakeLogger(t *testing.T) {
 	}
 }
 
+func TestLoggerCleanup(t *testing.T) {
+	rand.Seed(time.Now().UnixNano())
+
+	rbuf := make([]byte, 128)
+	if _, err := rand.Read(rbuf); err != nil {
+		t.Fatalf("Failed to generate random content: %v", err)
+	}
+	contents := base64.StdEncoding.EncodeToString(rbuf)
+
+	var body bytes.Buffer
+	body.WriteString(fmt.Sprintf(`
+--boundary
+Content-Disposition: form-data; name="buzz"; filename="example.txt"
+
+%s
+--boundary--
+`, contents))
+	r := multipart.NewReader(&body, "boundary")
+	form, err := r.ReadForm(0) // small max memory to force flush to disk
+	if err != nil {
+		t.Fatalf("Failed to read multipart form: %v", err)
+	}
+
+	tmpFiles, err := ioutil.ReadDir(os.TempDir())
+	if err != nil {
+		t.Fatalf("Failed to list %s: %v", os.TempDir(), err)
+	}
+
+	var tmpFile string
+	for _, f := range tmpFiles {
+		if !strings.HasPrefix(f.Name(), "multipart-") {
+			continue
+		}
+
+		path := filepath.Join(os.TempDir(), f.Name())
+		switch b, err := ioutil.ReadFile(path); {
+		case err != nil:
+			t.Fatalf("Failed to read %s: %v", path, err)
+		case string(b) != contents:
+			continue
+		default:
+			tmpFile = path
+			break
+		}
+	}
+
+	if tmpFile == "" {
+		t.Fatal("Could not find multipart form tmp file")
+	}
+
+	req := newRequest("GET", "/subdir/asdf")
+	req.MultipartForm = form
+
+	var buf bytes.Buffer
+	handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		req.URL.Path = "/" // simulate http.StripPrefix and friends
+		w.WriteHeader(200)
+	})
+	logger := LoggingHandler(&buf, handler)
+	logger.ServeHTTP(httptest.NewRecorder(), req)
+
+	if _, err := os.Stat(tmpFile); err == nil || !os.IsNotExist(err) {
+		t.Fatalf("Expected %s to not exist, got %v", tmpFile, err)
+	}
+}
+
 func TestLogPathRewrites(t *testing.T) {
 	var buf bytes.Buffer