sw HTML export: fix missing escaping for image links

Hyperlink URLs on images are currently written to the HTML output as-is,
without any any encoding.

Image links are written using HtmlWriter from svtools, which has the
advantage of not building the markup manually (similar to
sax_fastparser::FastSerializerHelper for XML), but that doesn't do any
escaping. Some other parts of the HTML export build the export markup
manually, but use HTMLOutFuncs::Out_String() to encode problematic
content.

Fix the problem by using HTMLOutFuncs::Out_String() in HtmlWriter for
attribute values: it seems reasonable to assume that users of HtmlWriter
would pass in unencoded strings, similar to how the sax serializer
works.

This could lead to double-encoding in case some user of
HtmlWriter::attribute() would encode its attribute value already, but
inspecting existing calls, none of the clients seem to do that at the
moment.

Change-Id: I5439e829b1b837cb9c51292b118f0b47e84197db
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/136399
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>

2 files changed, 23 insertions, 1 deletions

diff --git a/svtools/qa/unit/testHtmlWriter.cxx b/svtools/qa/unit/testHtmlWriter.cxx
index d4c8e24e4390..702bf64464ab 100644
--- a/svtools/qa/unit/testHtmlWriter.cxx
+++ b/svtools/qa/unit/testHtmlWriter.cxx
@@ -198,6 +198,27 @@ CPPUNIT_TEST_FIXTURE(Test, testExactElementEnd)
     CPPUNIT_ASSERT_EQUAL(OString("<start><a/><b/></start>"), aString);
 }
 
+CPPUNIT_TEST_FIXTURE(Test, testAttributeValueEncode)
+{
+    // Given a HTML writer:
+    SvMemoryStream aStream;
+    HtmlWriter aHtml(aStream);
+    aHtml.prettyPrint(false);
+
+    // When writing an attribute with a value that needs encoding:
+    aHtml.start("element");
+    aHtml.attribute("attribute", "a&b");
+    aHtml.end();
+
+    // Then make sure that the encoding is performed:
+    OString aString = extractFromStream(aStream);
+    // Without the accompanying fix in place, this test would have failed with:
+    // - Expected: <element attribute="a&amp;b"/>
+    // - Actual  : <element attribute="a&b"/>
+    // i.e. attribute value was not encoded in HTML, but it was in e.g. XML.
+    CPPUNIT_ASSERT_EQUAL(OString("<element attribute=\"a&amp;b\"/>"), aString);
+}
+
 CPPUNIT_PLUGIN_IMPLEMENT();
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/svtools/source/svhtml/HtmlWriter.cxx b/svtools/source/svhtml/HtmlWriter.cxx
index f7c35a644706..b813c7ee50e8 100644
--- a/svtools/source/svhtml/HtmlWriter.cxx
+++ b/svtools/source/svhtml/HtmlWriter.cxx
@@ -11,6 +11,7 @@
 #include <svtools/HtmlWriter.hxx>
 #include <tools/stream.hxx>
 #include <sal/log.hxx>
+#include <svtools/htmlout.hxx>
 
 HtmlWriter::HtmlWriter(SvStream& rStream, std::string_view rNamespace) :
     mrStream(rStream),
@@ -127,7 +128,7 @@ void HtmlWriter::writeAttribute(SvStream& rStream, std::string_view aAttribute,
     rStream.WriteOString(aAttribute);
     rStream.WriteChar('=');
     rStream.WriteChar('"');
-    rStream.WriteOString(aValue);
+    HTMLOutFuncs::Out_String(rStream, OStringToOUString(aValue, RTL_TEXTENCODING_UTF8));
     rStream.WriteChar('"');
 }