fix CSRF middleware not being able to extract token from multipart/form-data form

middleware/extractor.go

@@ -168,8 +168,8 @@ func valuesFromCookie(name string) ValuesExtractor {
 // valuesFromForm returns a function that extracts values from the form field.
 func valuesFromForm(name string) ValuesExtractor {
 	return func(c echo.Context) ([]string, error) {
-		if parseErr := c.Request().ParseForm(); parseErr != nil {
-			return nil, fmt.Errorf("valuesFromForm parse form failed: %w", parseErr)
+		if c.Request().Form == nil {
+			_ = c.Request().ParseMultipartForm(32 << 20) // same what `c.Request().FormValue(name)` does
 		}
 		values := c.Request().Form[name]
 		if len(values) == 0 {

middleware/extractor_test.go

@@ -1,9 +1,11 @@
 package middleware
 
 import (
+	"bytes"
 	"fmt"
 	"github.com/labstack/echo/v4"
 	"github.com/stretchr/testify/assert"
+	"mime/multipart"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -499,6 +501,25 @@ func TestValuesFromForm(t *testing.T) {
 		return req
 	}
 
+	exampleMultiPartFormRequest := func(mod func(w *multipart.Writer)) *http.Request {
+		var b bytes.Buffer
+		w := multipart.NewWriter(&b)
+		w.WriteField("name", "Jon Snow")
+		w.WriteField("emails[]", "[email protected]")
+		if mod != nil {
+			mod(w)
+		}
+
+		fw, _ := w.CreateFormFile("upload", "my.file")
+		fw.Write([]byte(`<div>hi</div>`))
+		w.Close()
+
+		req := httptest.NewRequest(http.MethodPost, "/", strings.NewReader(b.String()))
+		req.Header.Add(echo.HeaderContentType, w.FormDataContentType())
+
+		return req
+	}
+
 	var testCases = []struct {
 		name         string
 		givenRequest *http.Request
@@ -520,6 +541,14 @@ func TestValuesFromForm(t *testing.T) {
 			whenName:     "emails[]",
 			expectValues: []string{"[email protected]", "[email protected]"},
 		},
+		{
+			name: "ok, POST multipart/form, multiple value",
+			givenRequest: exampleMultiPartFormRequest(func(w *multipart.Writer) {
+				w.WriteField("emails[]", "[email protected]")
+			}),
+			whenName:     "emails[]",
+			expectValues: []string{"[email protected]", "[email protected]"},
+		},
 		{
 			name:         "ok, GET form, single value",
 			givenRequest: exampleGetFormRequest(nil),
@@ -540,16 +569,6 @@ func TestValuesFromForm(t *testing.T) {
 			whenName:     "nope",
 			expectError:  errFormExtractorValueMissing.Error(),
 		},
-		{
-			name: "nok, POST form, form parsing error",
-			givenRequest: func() *http.Request {
-				req := httptest.NewRequest(http.MethodPost, "/", nil)
-				req.Body = nil
-				return req
-			}(),
-			whenName:    "name",
-			expectError: "valuesFromForm parse form failed: missing form body",
-		},
 		{
 			name: "ok, cut values over extractorLimit",
 			givenRequest: examplePostFormRequest(func(v *url.Values) {