Skip uninteresting APPn markers when searching for EXIF block.

libexif rejects images where any APPn marker other than APP0 appears
before APP1.  The EXIF spec says that this is not allowed, but there are
a lot of images where it happens anyway (e.g., from Photoshop).
Patch from Google.

diff --git a/libexif/exif-data.c b/libexif/exif-data.c
index 002af86..23278f5 100644 (file)
--- a/libexif/exif-data.c
+++ b/libexif/exif-data.c
@@ -826,8 +826,16 @@ exif_data_load_data (ExifData *data, const unsigned char *d_orig,
                                continue;
                        }
 
-                       /* JPEG_MARKER_APP0 */
-                       if (ds >= 3 && d[0] == JPEG_MARKER_APP0) {
+                       /* JPEG_MARKER_APP1 */
+                       if (ds && d[0] == JPEG_MARKER_APP1)
+                               break;
+
+                       /* Skip irrelevant APP markers. The branch for APP1 must come before this,
+                          otherwise this code block will cause APP1 to be skipped. This code path
+                          is only relevant for files that are nonconformant to the EXIF
+                          specification. For conformant files, the APP1 code path above will be
+                          taken. */
+                       if (ds >= 3 && d[0] >= 0xe0 && d[0] <= 0xef) {  // JPEG_MARKER_APPn
                                d++;
                                ds--;
                                l = (d[0] << 8) | d[1];
@@ -838,10 +846,6 @@ exif_data_load_data (ExifData *data, const unsigned char *d_orig,
                                continue;
                        }
 
-                       /* JPEG_MARKER_APP1 */
-                       if (ds && d[0] == JPEG_MARKER_APP1)
-                               break;
-
                        /* Unknown marker or data. Give up. */
                        exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA,
                                  "ExifData", _("EXIF marker not found."));