libxml2: Backport buffer overflow fixes

Issue: https://gitlab.gnome.org/GNOME/libxml2/-/issues/535

Backported patches:
https://gitlab.gnome.org/GNOME/libxml2/-/commit/d0c3f01e110d54415611c5fa0040cdf4a56053f9
https://gitlab.gnome.org/GNOME/libxml2/-/commit/235b15a590eecf97b09e87bdb7e4f8333e9de129

gvsbuild/patches/libxml2/0001-parser-fix-old-SAX1-parser-with-custom-callbacks.patch

@@ -0,0 +1,32 @@
+From d0c3f01e110d54415611c5fa0040cdf4a56053f9 Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Sat, 6 May 2023 17:47:37 +0200
+Subject: [PATCH] parser: Fix old SAX1 parser with custom callbacks
+
+For some reason, xmlCtxtUseOptionsInternal set the start and end element
+SAX handlers to the internal DOM builder functions when XML_PARSE_SAX1
+was specified. This means that custom SAX handlers could never work with
+that flag because these functions would receive the wrong user data
+argument and crash immediately.
+
+Fixes #535.
+---
+ parser.c | 2 --
+ 1 file changed, 2 deletions(-)
+
+diff --git a/parser.c b/parser.c
+index bb05791d3..0c8bed129 100644
+--- a/parser.c
++++ b/parser.c
+@@ -14479,8 +14479,6 @@ xmlCtxtUseOptionsInternal(xmlParserCtxtPtr ctxt, int options, const char *encodi
+ }
+ #ifdef LIBXML_SAX1_ENABLED
+ if (options & XML_PARSE_SAX1) {
+- ctxt->sax->startElement = xmlSAX2StartElement;
+- ctxt->sax->endElement = xmlSAX2EndElement;
+ ctxt->sax->startElementNs = NULL;
+ ctxt->sax->endElementNs = NULL;
+ ctxt->sax->initialized = 1;
+-- 
+GitLab
+

gvsbuild/patches/libxml2/0002-sax-always-initialize-SAX1-element-handlers.patch

@@ -0,0 +1,67 @@
+From 235b15a590eecf97b09e87bdb7e4f8333e9de129 Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Mon, 8 May 2023 17:58:02 +0200
+Subject: [PATCH] SAX: Always initialize SAX1 element handlers
+
+Follow-up to commit d0c3f01e. A parser context will be initialized to
+SAX version 2, but this can be overridden with XML_PARSE_SAX1 later,
+so we must initialize the SAX1 element handlers as well.
+
+Change the check in xmlDetectSAX2 to only look for XML_SAX2_MAGIC, so
+we don't switch to SAX1 if the SAX2 element handlers are NULL.
+---
+ SAX2.c | 11 +++++++----
+ parser.c | 5 +----
+ 2 files changed, 8 insertions(+), 8 deletions(-)
+
+diff --git a/SAX2.c b/SAX2.c
+index b6be1a6c4..910193892 100644
+--- a/SAX2.c
++++ b/SAX2.c
+@@ -2874,20 +2874,23 @@ xmlSAXVersion(xmlSAXHandler *hdlr, int version)
+ {
+ if (hdlr == NULL) return(-1);
+ if (version == 2) {
+- hdlr->startElement = NULL;
+- hdlr->endElement = NULL;
+ hdlr->startElementNs = xmlSAX2StartElementNs;
+ hdlr->endElementNs = xmlSAX2EndElementNs;
+ hdlr->serror = NULL;
+ hdlr->initialized = XML_SAX2_MAGIC;
+ #ifdef LIBXML_SAX1_ENABLED
+ } else if (version == 1) {
+- hdlr->startElement = xmlSAX2StartElement;
+- hdlr->endElement = xmlSAX2EndElement;
+ hdlr->initialized = 1;
+ #endif /* LIBXML_SAX1_ENABLED */
+ } else
+ return(-1);
++#ifdef LIBXML_SAX1_ENABLED
++ hdlr->startElement = xmlSAX2StartElement;
++ hdlr->endElement = xmlSAX2EndElement;
++#else
++ hdlr->startElement = NULL;
++ hdlr->endElement = NULL;
++#endif /* LIBXML_SAX1_ENABLED */
+ hdlr->internalSubset = xmlSAX2InternalSubset;
+ hdlr->externalSubset = xmlSAX2ExternalSubset;
+ hdlr->isStandalone = xmlSAX2IsStandalone;
+diff --git a/parser.c b/parser.c
+index 0c8bed129..e133fe0a6 100644
+--- a/parser.c
++++ b/parser.c
+@@ -842,10 +842,7 @@ xmlDetectSAX2(xmlParserCtxtPtr ctxt) {
+ if (ctxt == NULL) return;
+ sax = ctxt->sax;
+ #ifdef LIBXML_SAX1_ENABLED
+- if ((sax) && (sax->initialized == XML_SAX2_MAGIC) &&
+- ((sax->startElementNs != NULL) ||
+- (sax->endElementNs != NULL) ||
+- ((sax->startElement == NULL) && (sax->endElement == NULL))))
++ if ((sax) && (sax->initialized == XML_SAX2_MAGIC))
+ ctxt->sax2 = 1;
+ #else
+ ctxt->sax2 = 1;
+-- 
+GitLab
+

gvsbuild/projects/libxml2.py

@@ -32,6 +32,10 @@ def __init__(self):
  archive_url="https://download.gnome.org/sources/libxml2/{major}.{minor}/libxml2-{version}.tar.xz",
  hash="3727b078c360ec69fa869de14bd6f75d7ee8d36987b071e6928d4720a28df3a6",
  dependencies=["win-iconv", "meson", "ninja"],
+ patches=[
+ "0001-parser-fix-old-SAX1-parser-with-custom-callbacks.patch",
+ "0002-sax-always-initialize-SAX1-element-handlers.patch",
+ ],
  )
 
  def build(self):