fix: basic auth invalid base64 string (#2191)

* fix: basic auth returns 400 on invalid base64 string

middleware/basic_auth.go

@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"strconv"
 	"strings"
+	"net/http"
 
 	"github.com/labstack/echo/v4"
 )
@@ -74,10 +75,13 @@ func BasicAuthWithConfig(config BasicAuthConfig) echo.MiddlewareFunc {
 			l := len(basic)
 
 			if len(auth) > l+1 && strings.EqualFold(auth[:l], basic) {
+				// Invalid base64 shouldn't be treated as error
+				// instead should be treated as invalid client input
 				b, err := base64.StdEncoding.DecodeString(auth[l+1:])
 				if err != nil {
-					return err
+					return echo.NewHTTPError(http.StatusBadRequest).SetInternal(err)
 				}
+
 				cred := string(b)
 				for i := 0; i < len(cred); i++ {
 					if cred[i] == ':' {

middleware/basic_auth_test.go

@@ -58,6 +58,12 @@ func TestBasicAuth(t *testing.T) {
 	assert.Equal(http.StatusUnauthorized, he.Code)
 	assert.Equal(basic+` realm="someRealm"`, res.Header().Get(echo.HeaderWWWAuthenticate))
 
+	// Invalid base64 string
+	auth = basic + " invalidString"
+	req.Header.Set(echo.HeaderAuthorization, auth)
+	he = h(c).(*echo.HTTPError)
+	assert.Equal(http.StatusBadRequest, he.Code)
+
 	// Missing Authorization header
 	req.Header.Del(echo.HeaderAuthorization)
 	he = h(c).(*echo.HTTPError)