diff options
Diffstat (limited to 'xml/apr_xml.c')
| -rw-r--r-- | xml/apr_xml.c | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/xml/apr_xml.c b/xml/apr_xml.c index 256223f44..b3ec87578 100644 --- a/xml/apr_xml.c +++ b/xml/apr_xml.c @@ -347,6 +347,25 @@ static apr_status_t cleanup_parser(void *ctx) return APR_SUCCESS; } +#if XML_MAJOR_VERSION > 1 +/* Stop the parser if an entity declaration is hit. */ +static void entity_declaration(void *userData, const XML_Char *entityName, + int is_parameter_entity, const XML_Char *value, + int value_length, const XML_Char *base, + const XML_Char *systemId, const XML_Char *publicId, + const XML_Char *notationName) +{ + apr_xml_parser *parser = userData; + + XML_StopParser(parser->xp, XML_FALSE); +} +#else +/* A noop default_handler. */ +static void default_handler(void *userData, const XML_Char *s, int len) +{ +} +#endif + APU_DECLARE(apr_xml_parser *) apr_xml_parser_create(apr_pool_t *pool) { apr_xml_parser *parser = apr_pcalloc(pool, sizeof(*parser)); @@ -372,6 +391,19 @@ APU_DECLARE(apr_xml_parser *) apr_xml_parser_create(apr_pool_t *pool) XML_SetElementHandler(parser->xp, start_handler, end_handler); XML_SetCharacterDataHandler(parser->xp, cdata_handler); + /* Prevent the "billion laughs" attack against expat by disabling + * internal entity expansion. With 2.x, forcibly stop the parser + * if an entity is declared - this is safer and a more obvious + * failure mode. With older versions, installing a noop + * DefaultHandler means that internal entities will be expanded as + * the empty string, which is also sufficient to prevent the + * attack. */ +#if XML_MAJOR_VERSION > 1 + XML_SetEntityDeclHandler(parser->xp, entity_declaration); +#else + XML_SetDefaultHandler(parser->xp, default_handler); +#endif + return parser; } |