From 3d0adda7560137309be8b10c63ff41e41dfb1516 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
Date: Tue, 28 Jan 2020 17:05:32 +0100
Subject: [PATCH] Parse an ampersand entity in SAX interface
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After disabling parsing external entities in XML-LibXML-2.0202,
XML::LibXML::SAX interface stopped expanding & and & entities
in attribute values (often found in href XHTML attributes) and
returned "&" instead. This was discovered by a RDF-Trine test
suite failure <
https://github.com/kasei/perlrdf/issues/167>.
First, I suspected XML-LibXML
<
https://rt.cpan.org/Ticket/Display.html?id=131498>, but it turned out
that the unexpanded entity comes from libxml2 C library itself. And
that it's not just an ommitted expansion, but that it's actually an
escape sequence for "&" characters. Other XML metacharacters (like
"<") are not affeced. Also text nodes are also not affected. My
finding was confirmed by an old libxml2 bug report
<
https://bugzilla.gnome.org/show_bug.cgi?id=316487>.
This patch "fixes" this discepancy by replacing all "&"
subtstrings with a literal "&" in SAX interface of start_element()
callbacks.
Signed-off-by: Petr PÃsaÅ <ppisar@redhat.com>
---
MANIFEST | 1 +
perl-libxml-sax.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
t/52_sax_intent.t | 40 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 83 insertions(+), 2 deletions(-)
create mode 100755 t/52_sax_intent.t
diff --git a/MANIFEST b/MANIFEST
index 5248ea5..ccc3410 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -174,6 +174,7 @@ t/49callbacks_returning_undef.t
t/49global_extent.t
t/50devel.t
t/51_parse_html_string_rt87089.t
+t/52_sax_intent.t
t/60error_prev_chain.t
t/60struct_error.t
t/61error.t
diff --git a/perl-libxml-sax.c b/perl-libxml-sax.c
index b949d3c..232a879 100644
--- a/perl-libxml-sax.c
+++ b/perl-libxml-sax.c
@@ -20,6 +20,7 @@ extern "C" {
#include "ppport.h"
#include <stdlib.h>
+#include <string.h>
#include <libxml/xmlmemory.h>
#include <libxml/parser.h>
#include <libxml/parserInternals.h>
@@ -639,6 +640,34 @@ PmmGenNsName( const xmlChar * name, const xmlChar * nsURI )
return retval;
}
+/* If a value argument does not contain "&", the value pointer is returned.
+ * Otherwise a new xmlChar * string is allocated, the value copied there and
+ * "&" occurences replaced with "&". Then the caller must free it. */
+static
+xmlChar *
+_expandAmp( const xmlChar *value )
+{
+ xmlChar *expanded = NULL;
+ const xmlChar *entity;
+ int length;
+
+ if (value == NULL ||
+ (NULL == (entity = (const xmlChar *)strstr((const char *)value, "&")))) {
+ return (xmlChar *)value;
+ }
+
+ do {
+ length = entity - value;
+ expanded = xmlStrncat(expanded, value, length);
+ expanded = xmlStrncat(expanded, (const xmlChar *)"&", 1);
+ value += length + 5; /* "&" */
+ } while (NULL != (entity = (const xmlChar*)strstr((const char *)value, "&")));
+
+ expanded = xmlStrcat(expanded, value);
+
+ return expanded;
+}
+
HV *
PmmGenAttributeHashSV( pTHX_ PmmSAXVectorPtr sax,
const xmlChar **attr, SV * handler )
@@ -653,8 +682,8 @@ PmmGenAttributeHashSV( pTHX_ PmmSAXVectorPtr sax,
const xmlChar * nsURI = NULL;
const xmlChar **ta = attr;
const xmlChar * name = NULL;
- const xmlChar * value = NULL;
+ xmlChar * value = NULL;
xmlChar * keyname = NULL;
xmlChar * localname = NULL;
xmlChar * prefix = NULL;
@@ -665,7 +694,13 @@ PmmGenAttributeHashSV( pTHX_ PmmSAXVectorPtr sax,
while ( *ta != NULL ) {
atV = newHV();
name = *ta; ta++;
- value = *ta; ta++;
+ /* XXX: libxml2 SAX2 interface does not expand &
+ * entity in the attribute values
+ * <
https://bugzilla.gnome.org/show_bug.cgi?id=316487>
+ * resulting in stray "&" sequences after disabling
+ * external entity expansion
+ * <
https://rt.cpan.org/Ticket/Display.html?id=131498>. */
+ value = _expandAmp(*ta);
if ( name != NULL && XML_STR_NOT_EMPTY( name ) ) {
localname = xmlSplitQName(NULL, name, &prefix);
@@ -754,6 +789,11 @@ PmmGenAttributeHashSV( pTHX_ PmmSAXVectorPtr sax,
prefix = NULL;
}
+
+ if (value != *ta) {
+ xmlFree(value);
+ }
+ ta++;
}
}
diff --git a/t/52_sax_intent.t b/t/52_sax_intent.t
new file mode 100755
index 0000000..a45b4d1
--- /dev/null
+++ b/t/52_sax_intent.t
@@ -0,0 +1,40 @@
+use strict;
+use warnings;
+use Test::More;
+
+my %tests = (
+ # attribte name raw attrib. value expected parsed value
+ predefined => ['"', '"'], # alawys worked
+ numeric => ['A', 'A'], # always worked
+ numericampersand => ['&', '&'], # a regression
+ ampA => ['&A', '&A'], # a corner case
+ Aamp => ['A&', 'A&'], # a corner case
+ AampBampC => ['A&B&C', 'A&B&C'], # a corner case
+);
+plan tests => scalar (keys %tests);
+
+my $input = '<?xml version="1.0"?><root';
+for my $test (sort keys %tests) {
+ $input .= sprintf(" %s='%s'", $test, $tests{$test}->[0]);
+}
+$input .= '/>';
+
+diag("Parsing $input");
+use XML::LibXML::SAX;
+
+XML::LibXML::SAX->new(Handler => 'Handler')->parse_string($input);
+
+
+package Handler;
+sub start_element {
+ my ($self, $node) = @_;
+ for my $attribute (sort keys %{$node->{Attributes}}) {
+ my $name = $node->{Attributes}->{$attribute}->{Name};
+ Test::More::is(
+ $node->{Attributes}->{$attribute}->{Value},
+ $tests{$name}->[1],
+ sprintf("%s='%s' attribute", $name, $tests{$name}->[0])
+ );
+ }
+}
+
--
2.21.1
