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Fix GH-21544: Dom\XMLDocument::C14N() drops namespace declarations on… #21561

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Fix GH-21544: Dom\XMLDocument::C14N() drops namespace declarations on… #21561

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6c4c5e3
Fix GH-21544: Dom\XMLDocument::C14N() drops namespace declarations on…
devnexen Mar 28, 2026
6ef3863
Factor out nsDef allocation into dom_alloc_ns_decl helper.
devnexen Apr 1, 2026
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89 changes: 69 additions & 20 deletions ext/dom/node.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2103,33 +2103,71 @@ PHP_METHOD(DOMNode, lookupNamespaceURI)
}
/* }}} end dom_node_lookup_namespace_uri */

/* Allocate, track and prepend a temporary nsDef entry for C14N.
* Returns the new xmlNsPtr for the caller to fill in href/prefix/_private,
* or NULL on allocation failure. */
static xmlNsPtr dom_alloc_ns_decl(HashTable *links, xmlNodePtr node)
{
xmlNsPtr ns = xmlMalloc(sizeof(*ns));
if (!ns) {
return NULL;
}

zval *zv = zend_hash_index_lookup(links, (zend_ulong) node);
if (Z_ISNULL_P(zv)) {
ZVAL_LONG(zv, 1);
} else {
Z_LVAL_P(zv)++;
}

memset(ns, 0, sizeof(*ns));
ns->type = XML_LOCAL_NAMESPACE;
ns->next = node->nsDef;
node->nsDef = ns;

return ns;
}

/* For DOM-built documents (e.g. createElementNS), namespaces live on node->ns
* without corresponding xmlns attributes. C14N expects nsDef entries, so create
* temporary ones. The _private field stays NULL to distinguish from attr-based
* entries during cleanup. */
static void dom_add_synthetic_ns_decl(HashTable *links, xmlNodePtr node, xmlNsPtr src_ns)
{
/* Pre-existing nsDef entries are never filled in for Dom\XMLDocument.
* This loop guards against duplicates from our own synthetic additions
* within the same C14N pass (e.g. when an element and its attributes
* share the same namespace prefix). */
for (xmlNsPtr existing = node->nsDef; existing; existing = existing->next) {
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@ndossche ndossche Mar 31, 2026

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Do we need this loop? I believe that for Dom\XMLDocument this is normally never filled in.

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@devnexen devnexen Apr 1, 2026

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The loop checks existing nsDef entries to avoid duplicates. While pre-existing nsDef is indeed empty for Dom\XMLDocument, the loop is still needed:
dom_add_synthetic_ns_decl is called multiple times per node (once for node->ns, once per attr->ns), and if the element and an attribute share the same namespace
prefix, the loop prevents adding a duplicate synthetic entry.

if (xmlStrEqual(existing->prefix, src_ns->prefix)) {
return;
}
}

xmlNsPtr ns = dom_alloc_ns_decl(links, node);
if (!ns) {
return;
}

ns->href = xmlStrdup(src_ns->href);
ns->prefix = src_ns->prefix ? xmlStrdup(src_ns->prefix) : NULL;
}

static void dom_relink_ns_decls_element(HashTable *links, xmlNodePtr node)
{
if (node->type == XML_ELEMENT_NODE) {
for (xmlAttrPtr attr = node->properties; attr; attr = attr->next) {
if (php_dom_ns_is_fast((const xmlNode *) attr, php_dom_ns_is_xmlns_magic_token)) {
xmlNsPtr ns = xmlMalloc(sizeof(*ns));
xmlNsPtr ns = dom_alloc_ns_decl(links, node);
if (!ns) {
return;
}

zval *zv = zend_hash_index_lookup(links, (zend_ulong) node);
if (Z_ISNULL_P(zv)) {
ZVAL_LONG(zv, 1);
} else {
Z_LVAL_P(zv)++;
}

bool should_free;
xmlChar *attr_value = php_libxml_attr_value(attr, &should_free);

memset(ns, 0, sizeof(*ns));
ns->type = XML_LOCAL_NAMESPACE;
ns->href = should_free ? attr_value : xmlStrdup(attr_value);
ns->prefix = attr->ns->prefix ? xmlStrdup(attr->name) : NULL;
ns->next = node->nsDef;
node->nsDef = ns;

ns->_private = attr;
if (attr->prev) {
attr->prev = attr->next;
Expand All @@ -2142,6 +2180,15 @@ static void dom_relink_ns_decls_element(HashTable *links, xmlNodePtr node)
}
}

if (node->ns) {
dom_add_synthetic_ns_decl(links, node, node->ns);
}
for (xmlAttrPtr attr = node->properties; attr; attr = attr->next) {
if (attr->ns && !php_dom_ns_is_fast((const xmlNode *) attr, php_dom_ns_is_xmlns_magic_token)) {
dom_add_synthetic_ns_decl(links, node, attr->ns);
}
}

/* The default namespace is handled separately from the other namespaces in C14N.
* The default namespace is explicitly looked up while the other namespaces are
* deduplicated and compared to a list of visible namespaces. */
Expand Down Expand Up @@ -2179,13 +2226,15 @@ static void dom_unlink_ns_decls(HashTable *links)
node->nsDef = ns->next;

xmlAttrPtr attr = ns->_private;
if (attr->prev) {
attr->prev->next = attr;
} else {
node->properties = attr;
}
if (attr->next) {
attr->next->prev = attr;
if (attr) {
if (attr->prev) {
attr->prev->next = attr;
} else {
node->properties = attr;
}
if (attr->next) {
attr->next->prev = attr;
}
}

xmlFreeNs(ns);
Expand Down
28 changes: 28 additions & 0 deletions ext/dom/tests/modern/xml/gh21544.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
--TEST--
GH-21544 (Dom\XMLDocument::C14N() drops namespace declarations on DOM-built documents)
--CREDITS--
Toon Verwerft (veewee)
--EXTENSIONS--
dom
--FILE--
<?php

$doc = Dom\XMLDocument::createEmpty();
$root = $doc->createElementNS("urn:envelope", "env:Root");
$doc->appendChild($root);
$child = $doc->createElementNS("urn:child", "x:Child");
$root->appendChild($child);

$parsed = Dom\XMLDocument::createFromString(
'<env:Root xmlns:env="urn:envelope"><x:Child xmlns:x="urn:child"/></env:Root>'
);

echo "DOM-built C14N: " . $doc->C14N() . PHP_EOL;
echo "Parsed C14N: " . $parsed->C14N() . PHP_EOL;
var_dump($doc->C14N() === $parsed->C14N());

?>
--EXPECT--
DOM-built C14N: <env:Root xmlns:env="urn:envelope"><x:Child xmlns:x="urn:child"></x:Child></env:Root>
Parsed C14N: <env:Root xmlns:env="urn:envelope"><x:Child xmlns:x="urn:child"></x:Child></env:Root>
bool(true)
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