Media: Improve ReadUrl() implementation and tests #5330

Signed-off-by: Michael Mayer <michael@photoprism.app>

pkg/media/data_url.go

@@ -100,7 +100,14 @@ func ReadUrl(fileUrl string, schemes []string) (data []byte, err error) {
 			return DecodeBase64String(binaryData)
 		}
 	case scheme.File:
-		if data, err = os.ReadFile(fileUrl); err != nil { //nolint:gosec // fileUrl validated earlier
+		path := u.Path
+		if path == "" {
+			path = u.Opaque
+		}
+		if path == "" {
+			return data, fmt.Errorf("invalid %s url (empty path)", u.Scheme)
+		}
+		if data, err = os.ReadFile(path); err != nil { //nolint:gosec // file path validated earlier
 			return data, fmt.Errorf("invalid %s url (%s)", u.Scheme, err)
 		}
 	default:

pkg/media/data_url_test.go

@@ -5,6 +5,8 @@ import (
 	"io"
 	"net/http"
 	"net/http/httptest"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -75,6 +77,16 @@ func TestReadUrl(t *testing.T) {
 		_, err := ReadUrl("file:///this/does/not/exist", []string{"file"})
 		assert.Error(t, err)
 	})
+	t.Run("FileSchemeValidPng", func(t *testing.T) {
+		tmp := t.TempDir()
+		fn := filepath.Join(tmp, "pic.png")
+		payload := append([]byte{0x89, 'P', 'N', 'G', '\r', '\n', 0x1A, '\n'}, bytes.Repeat([]byte{0}, 16)...)
+		assert.NoError(t, os.WriteFile(fn, payload, 0o600))
+
+		data, err := ReadUrl("file://"+fn, []string{"file"})
+		assert.NoError(t, err)
+		assert.Equal(t, payload, data)
+	})
 }
 
 func TestDataUrl_LargeBinary(t *testing.T) {