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Registry/safer parser functions #675

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merged 2 commits into from
Mar 11, 2025
Merged

Registry/safer parser functions #675

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dc1284f
meson: Fix libxml2 header test
wismill Mar 10, 2025
fe7f56b
registry: Use safer contextual libxml2 functions
wismill Mar 10, 2025
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13 changes: 11 additions & 2 deletions meson.build
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Original file line number Diff line number Diff line change
Expand Up @@ -381,13 +381,22 @@ endif
# libxkbregistry
if get_option('enable-xkbregistry')
dep_libxml = dependency('libxml-2.0')
# Since libxml-2.13
if cc.has_header_symbol(
'libxml/xmlerror.h',
'libxml/parser.h',
'xmlCtxtSetErrorHandler',
prefix: system_ext_define
prefix: system_ext_define,
)
configh_data.set10('HAVE_XML_CTXT_SET_ERRORHANDLER', true)
endif
# Since libxml-2.14
if cc.has_header_symbol(
'libxml/parser.h',
'xmlCtxtParseDtd',
prefix: system_ext_define,
)
configh_data.set10('HAVE_XML_CTXT_PARSE_DTD', true)
endif
deps_libxkbregistry = [dep_libxml]
libxkbregistry_sources = [
'src/registry.c',
Expand Down
71 changes: 48 additions & 23 deletions src/registry.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1142,13 +1142,16 @@ xml_structured_error_func(void *userData, const xmlError * error)
}
#endif

#ifdef XML_PARSE_NO_XXE
#define _XML_OPTIONS (XML_PARSE_NONET | XML_PARSE_NOENT | XML_PARSE_NO_XXE)
#else
#define _XML_OPTIONS (XML_PARSE_NONET)
#endif

static bool
validate(struct rxkb_context *ctx, xmlDoc *doc)
{
bool success = false;
xmlValidCtxt *dtdvalid = NULL;
xmlDtd *dtd = NULL;
xmlParserInputBufferPtr buf = NULL;
/* This is a modified version of the xkeyboard-config xkb.dtd:
* • xkeyboard-config requires modelList, layoutList and optionList,
* but we allow for any of those to be missing.
Expand Down Expand Up @@ -1183,34 +1186,53 @@ validate(struct rxkb_context *ctx, xmlDoc *doc)
"<!ELEMENT hwList (hwId+)>\n"
"<!ELEMENT hwId (#PCDATA)>\n";

#ifdef HAVE_XML_CTXT_PARSE_DTD
/* Use safer function with context if available, and set
* the contextual error handler. */
xmlParserCtxtPtr xmlCtxt = xmlNewParserCtxt();
if (!xmlCtxt)
return false;
xmlCtxtSetErrorHandler(xmlCtxt, xml_structured_error_func, ctx);
xmlCtxtSetOptions(xmlCtxt, _XML_OPTIONS | XML_PARSE_DTDLOAD);

xmlParserInputPtr pinput =
xmlNewInputFromMemory(NULL, dtdstr, sizeof(dtdstr),
XML_INPUT_BUF_STATIC);
if (!pinput)
goto dtd_error;

xmlDtd *dtd = xmlCtxtParseDtd(xmlCtxt, pinput, NULL, NULL);
#else
/* Note: do not use xmlParserInputBufferCreateStatic, it generates random
* DTD validity errors for unknown reasons */
buf = xmlParserInputBufferCreateMem(dtdstr, sizeof(dtdstr),
XML_CHAR_ENCODING_NONE);
xmlParserInputBufferPtr buf =
xmlParserInputBufferCreateMem(dtdstr, sizeof(dtdstr),
XML_CHAR_ENCODING_NONE);
if (!buf)
return false;
goto dtd_error;
xmlDtd *dtd = dtd = xmlIOParseDTD(NULL, buf, XML_CHAR_ENCODING_UTF8);
#endif

/* TODO: use safer function with context, once published, and set
* the contextual error handler.
* See: https://gitlab.gnome.org/GNOME/libxml2/-/issues/808 */
dtd = xmlIOParseDTD(NULL, buf, XML_CHAR_ENCODING_UTF8);
if (!dtd) {
log_err(ctx, XKB_LOG_MESSAGE_NO_ID, "Failed to load DTD\n");
return false;
goto dtd_error;
}

dtdvalid = xmlNewValidCtxt();
/* TODO: use safer function with context, once published, then set
* the contextual error handler.
* See: https://gitlab.gnome.org/GNOME/libxml2/-/issues/808 */
if (xmlValidateDtd(dtdvalid, doc, dtd))
success = true;

if (dtd)
xmlFreeDtd(dtd);
#ifdef HAVE_XML_CTXT_PARSE_DTD
success = xmlCtxtValidateDtd(xmlCtxt, doc, dtd);
#else
xmlValidCtxt *dtdvalid = xmlNewValidCtxt();
success = xmlValidateDtd(dtdvalid, doc, dtd);
if (dtdvalid)
xmlFreeValidCtxt(dtdvalid);
#endif

xmlFreeDtd(dtd);

dtd_error:
#ifdef HAVE_XML_CTXT_PARSE_DTD
xmlFreeParserCtxt(xmlCtxt);
#endif
return success;
}

Expand Down Expand Up @@ -1243,8 +1265,10 @@ parse(struct rxkb_context *ctx, const char *path,
* the global generic handler. */
xmlCtxtSetErrorHandler(xmlCtxt, xml_structured_error_func, ctx);
#endif
/* This is still unconditionnally needed for the DTD validation (for now) */
#ifndef HAVE_XML_CTXT_PARSE_DTD
/* This is needed for the DTD validation */
xmlSetGenericErrorFunc(ctx, xml_error_func);
#endif

doc = xmlCtxtReadFile(xmlCtxt, path, NULL, 0);
if (!doc)
Expand All @@ -1263,6 +1287,8 @@ parse(struct rxkb_context *ctx, const char *path,
validate_error:
xmlFreeDoc(doc);
parse_error:

#ifndef HAVE_XML_CTXT_PARSE_DTD
/*
* Reset the default libxml2 error handler to default, because this handler
* is global and may be used on an invalid rxkb_context, e.g. *after* the
Expand All @@ -1272,9 +1298,8 @@ parse(struct rxkb_context *ctx, const char *path,
* rxkb_context_parse();
* rxkb_context_unref();
*/
/* TODO: remove once safer variants of xmlIOParseDTD and xmlValidateDtd are
* published. See: https://gitlab.gnome.org/GNOME/libxml2/-/issues/808 */
xmlSetGenericErrorFunc(NULL, NULL);
#endif
#ifdef HAVE_XML_CTXT_SET_ERRORHANDLER
xmlCtxtSetErrorHandler(xmlCtxt, NULL, NULL);
#endif
Expand Down
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