From 4bee5743e965b8c1aaa58d1a428eccdddb776304 Mon Sep 17 00:00:00 2001
From: Niels Dossche <7771979+nielsdos@users.noreply.github.com>
Date: Tue, 25 Jul 2023 22:22:01 +0200
Subject: [PATCH] Fix GH-11792: LIBXML_NOXMLDECL is not implemented or broken

Fixes GH-11792.
Closes GH-11794.
---
 NEWS                                          |  4 +
 ext/dom/document.c                            | 74 ++++++++++++-------
 .../DOMDocument_saveXML_XML_SAVE_NO_DECL.phpt | 24 ++++++
 3 files changed, 74 insertions(+), 28 deletions(-)
 create mode 100644 ext/dom/tests/DOMDocument_saveXML_XML_SAVE_NO_DECL.phpt

diff --git a/NEWS b/NEWS
index 90283ae1539..982898615a3 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,10 @@ PHP                                                                        NEWS
 - Core:
   . Fixed oss-fuzz #60741 (Leak in open_basedir). (ilutov)
 
+- DOM:
+  . Fixed bug GH-11792 (LIBXML_NOXMLDECL is not implemented or broken).
+    (nielsdos)
+
 - FFI:
   . Fix leaking definitions when using FFI::cdef()->new(...). (ilutov)
 
diff --git a/ext/dom/document.c b/ext/dom/document.c
index ca136630ed3..2ee5435d8d2 100644
--- a/ext/dom/document.c
+++ b/ext/dom/document.c
@@ -23,6 +23,7 @@
 #if defined(HAVE_LIBXML) && defined(HAVE_DOM)
 #include "php_dom.h"
 #include <libxml/SAX.h>
+#include <libxml/xmlsave.h>
 #ifdef LIBXML_SCHEMAS_ENABLED
 #include <libxml/relaxng.h>
 #include <libxml/xmlschemas.h>
@@ -1462,9 +1463,9 @@ PHP_METHOD(DOMDocument, saveXML)
 	xmlDoc *docp;
 	xmlNode *node;
 	xmlBufferPtr buf;
-	xmlChar *mem;
+	const xmlChar *mem;
 	dom_object *intern, *nodeobj;
-	int size, format, saveempty = 0;
+	int size, format, old_xml_save_no_empty_tags;
 	zend_long options = 0;
 
 	id = ZEND_THIS;
@@ -1484,42 +1485,59 @@ PHP_METHOD(DOMDocument, saveXML)
 			php_dom_throw_error(WRONG_DOCUMENT_ERR, dom_get_strict_error(intern->document));
 			RETURN_FALSE;
 		}
+
 		buf = xmlBufferCreate();
 		if (!buf) {
 			php_error_docref(NULL, E_WARNING, "Could not fetch buffer");
 			RETURN_FALSE;
 		}
-		if (options & LIBXML_SAVE_NOEMPTYTAG) {
-			saveempty = xmlSaveNoEmptyTags;
-			xmlSaveNoEmptyTags = 1;
-		}
+		/* Save libxml2 global, override its vaule, and restore after saving. */
+		old_xml_save_no_empty_tags = xmlSaveNoEmptyTags;
+		xmlSaveNoEmptyTags = (options & LIBXML_SAVE_NOEMPTYTAG) ? 1 : 0;
 		xmlNodeDump(buf, docp, node, 0, format);
-		if (options & LIBXML_SAVE_NOEMPTYTAG) {
-			xmlSaveNoEmptyTags = saveempty;
-		}
-		mem = (xmlChar*) xmlBufferContent(buf);
-		if (!mem) {
-			xmlBufferFree(buf);
-			RETURN_FALSE;
-		}
-		RETVAL_STRING((char *) mem);
-		xmlBufferFree(buf);
+		xmlSaveNoEmptyTags = old_xml_save_no_empty_tags;
 	} else {
-		if (options & LIBXML_SAVE_NOEMPTYTAG) {
-			saveempty = xmlSaveNoEmptyTags;
-			xmlSaveNoEmptyTags = 1;
-		}
-		/* Encoding is handled from the encoding property set on the document */
-		xmlDocDumpFormatMemory(docp, &mem, &size, format);
-		if (options & LIBXML_SAVE_NOEMPTYTAG) {
-			xmlSaveNoEmptyTags = saveempty;
-		}
-		if (!size || !mem) {
+		buf = xmlBufferCreate();
+		if (!buf) {
+			php_error_docref(NULL, E_WARNING, "Could not fetch buffer");
 			RETURN_FALSE;
 		}
-		RETVAL_STRINGL((char *) mem, size);
-		xmlFree(mem);
+
+		int converted_options = XML_SAVE_AS_XML;
+		if (options & XML_SAVE_NO_DECL) {
+			converted_options |= XML_SAVE_NO_DECL;
+		}
+		if (format) {
+			converted_options |= XML_SAVE_FORMAT;
+		}
+		/* Save libxml2 global, override its vaule, and restore after saving. */
+		old_xml_save_no_empty_tags = xmlSaveNoEmptyTags;
+		xmlSaveNoEmptyTags = (options & LIBXML_SAVE_NOEMPTYTAG) ? 1 : 0;
+		/* Encoding is handled from the encoding property set on the document */
+		xmlSaveCtxtPtr ctxt = xmlSaveToBuffer(buf, (const char *) docp->encoding, converted_options);
+		xmlSaveNoEmptyTags = old_xml_save_no_empty_tags;
+		if (UNEXPECTED(!ctxt)) {
+			xmlBufferFree(buf);
+			php_error_docref(NULL, E_WARNING, "Could not create save context");
+			RETURN_FALSE;
+		}
+		if (UNEXPECTED(xmlSaveDoc(ctxt, docp) < 0)) {
+			(void) xmlSaveClose(ctxt);
+			xmlBufferFree(buf);
+			php_error_docref(NULL, E_WARNING, "Could not save document");
+			RETURN_FALSE;
+		}
+		(void) xmlSaveFlush(ctxt);
+		(void) xmlSaveClose(ctxt);
 	}
+	mem = xmlBufferContent(buf);
+	if (!mem) {
+		xmlBufferFree(buf);
+		RETURN_FALSE;
+	}
+	size = xmlBufferLength(buf);
+	RETVAL_STRINGL((const char *) mem, size);
+	xmlBufferFree(buf);
 }
 /* }}} end dom_document_savexml */
 
diff --git a/ext/dom/tests/DOMDocument_saveXML_XML_SAVE_NO_DECL.phpt b/ext/dom/tests/DOMDocument_saveXML_XML_SAVE_NO_DECL.phpt
new file mode 100644
index 00000000000..240e5d49848
--- /dev/null
+++ b/ext/dom/tests/DOMDocument_saveXML_XML_SAVE_NO_DECL.phpt
@@ -0,0 +1,24 @@
+--TEST--
+DOMDocument::saveXML(): XML_SAVE_NO_DECL
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+$doc = new DOMDocument();
+$doc->loadXML('<root>é</root>');
+
+echo $doc->saveXML(options: 0);
+echo $doc->saveXML(options: LIBXML_NOXMLDECL);
+$doc->encoding = "BIG5";
+echo $doc->saveXML(options: LIBXML_NOXMLDECL);
+
+// Edge case
+$doc = new DOMDocument();
+var_dump($doc->saveXML(options: LIBXML_NOXMLDECL));
+?>
+--EXPECT--
+<?xml version="1.0"?>
+<root>&#xE9;</root>
+<root>&#xE9;</root>
+<root>&#233;</root>
+string(0) ""