[WiP] heifload: disable all security limits with unlimited

Also, increase the default maximum image size to 32768^2 to align
with libheif's defaults.

See:
strukturag/libheif#1389
strukturag/libheif#1359 (comment)

ChangeLog

@@ -2,6 +2,8 @@
 
 - add `keep_duplicate_frames` option to GIF save [dloebl]
 - add Magic Kernel support [akimon658]
+- heifload: increase maximum image size to 32768^2 [kleisauke]
+- heifload: "unlimited" flag disables all security limits [kleisauke]
 
 8.16.1
 

libvips/foreign/heifload.c

@@ -350,10 +350,14 @@ vips_foreign_load_heif_build(VipsObject *object)
 		struct heif_error error;
 
 		heif->ctx = heif_context_alloc();
-#ifdef HAVE_HEIF_SET_MAX_IMAGE_SIZE_LIMIT
+#ifdef HAVE_HEIF_CONTEXT_SET_SECURITY_LIMITS
+		if (heif->unlimited)
+			heif_context_set_security_limits(heif->ctx,
+				heif_get_disabled_security_limits());
+#elif defined(HAVE_HEIF_SET_MAX_IMAGE_SIZE_LIMIT)
 		heif_context_set_maximum_image_size_limit(heif->ctx,
-			heif->unlimited ? USHRT_MAX : 0x4000);
-#endif /* HAVE_HEIF_SET_MAX_IMAGE_SIZE_LIMIT */
+			heif->unlimited ? USHRT_MAX : 0x8000);
+#endif /* HAVE_HEIF_CONTEXT_SET_SECURITY_LIMITS */
 		error = heif_context_read_from_reader(heif->ctx,
 			heif->reader, heif, NULL);
 		if (error.code) {

meson.build

@@ -568,6 +568,10 @@ if libheif_dep.found()
     if libheif_dep.version().version_compare('>=1.17.0')
         cfg_var.set('HAVE_HEIF_ERROR_SUCCESS', '1')
     endif
+    # heif_context_set_security_limits added in 1.19.0
+    if libheif_dep.version().version_compare('>=1.19.0')
+        cfg_var.set('HAVE_HEIF_CONTEXT_SET_SECURITY_LIMITS', '1')
+    endif
 endif
 
 libjxl_dep = dependency('libjxl', version: '>=0.6', required: get_option('jpeg-xl'))