File 0002-Avoid-crash-on-spine-itemref-without-idref.patch of Package ebook-tools

From 37ccdd11e30ea60225276cbfaba4cdd483f9f6fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Br=C3=BCns?= <stefan.bruens@rwth-aachen.de>
Date: Sun, 23 Apr 2023 05:16:20 +0200
Subject: [PATCH 2/2] Avoid crash on spine itemref without idref

Although the idref attribute is required, it may be missing in a
malformed epub file.

Warn during parsing, and skip the node when linearizing.

Return a non-null empty string in case the iterator points to an
invalid element but not the last one, otherwise the iteration is stopped.
---
 src/libepub/epub.c | 9 ++++++++-
 src/libepub/opf.c  | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/libepub/epub.c b/src/libepub/epub.c
index a259d9d..956c7c5 100644
--- a/src/libepub/epub.c
+++ b/src/libepub/epub.c
@@ -255,6 +255,12 @@ char *_get_spine_it_url(struct eiterator *it) {
 	  return NULL;
   
   data = GetNodeData(it->curr);
+  if (!((struct spine *)data)->idref) {
+	  _epub_print_debug(it->epub, DEBUG_INFO,
+						"skipping spine itemref without idref");
+	  return NULL;
+  }
+
   tmp = _opf_manifest_get_by_id(it->epub->opf, 
                                 ((struct spine *)data)->idref);
   if (!tmp) {
@@ -375,7 +381,8 @@ char *epub_it_get_next(struct eiterator *it) {
     break;
   }
   
-  return epub_it_get_curr(it);
+  epub_it_get_curr(it);
+  return it->cache ? it->cache : it->curr ? "" : NULL;
 }
 
 int epub_close(struct epub *epub) {
diff --git a/src/libepub/opf.c b/src/libepub/opf.c
index ae41184..3eba55c 100644
--- a/src/libepub/opf.c
+++ b/src/libepub/opf.c
@@ -701,6 +701,10 @@ void _opf_parse_spine(struct opf *opf, xmlTextReaderPtr reader) {
 	memset(item, 0, sizeof(struct spine));
 
     item->idref = xmlTextReaderGetAttribute(reader, (xmlChar *)"idref");
+    if (!item->idref) {
+      _epub_print_debug(opf->epub, DEBUG_WARNING,
+                        "- missing idref in spine itemref");
+    }
     linear = xmlTextReaderGetAttribute(reader, (xmlChar *)"linear");
     if (linear && xmlStrcasecmp(linear, (xmlChar *)"no") == 0) {
       item->linear = 0;
-- 
2.40.0