Function xmlParserEntityCheck

ThirdParty/libxml2/vtklibxml2/parser.c:455–501

* xmlParserEntityCheck: * @ctxt: parser context * @extra: sum of unexpanded entity sizes * * Check for non-linear entity expansion behaviour. * * In some cases like xmlExpandEntityInAttValue, this function is called * for each, possibly nested entity and its unexpanded content length. * * In other cases like xmlParseReference, it's only called for each * top-level entity with its unexp

 * Returns 1 on error, 0 on success.
 */
static int
xmlParserEntityCheck(xmlParserCtxtPtr ctxt, unsigned long extra)
{
    unsigned long consumed;
    unsigned long *expandedSize;
    xmlParserInputPtr input = ctxt->input;
    xmlEntityPtr entity = input->entity;

    if ((entity) && (entity->flags & XML_ENT_CHECKED))
        return(0);

    /*
     * Compute total consumed bytes so far, including input streams of
     * external entities.
     */
    consumed = input->consumed;
    xmlSaturatedAddSizeT(&consumed, input->cur - input->base);
    xmlSaturatedAdd(&consumed, ctxt->sizeentities);

    if (entity)
        expandedSize = &entity->expandedSize;
    else
        expandedSize = &ctxt->sizeentcopy;

    /*
     * Add extra cost and some fixed cost.
     */
    xmlSaturatedAdd(expandedSize, extra);
    xmlSaturatedAdd(expandedSize, XML_ENT_FIXED_COST);

    /*
     * It's important to always use saturation arithmetic when tracking
     * entity sizes to make the size checks reliable. If "sizeentcopy"
     * overflows, we have to abort.
     */
    if ((*expandedSize > XML_PARSER_ALLOWED_EXPANSION) &&
        ((*expandedSize >= ULONG_MAX) ||
         (*expandedSize / ctxt->maxAmpl > consumed))) {
        xmlFatalErrMsg(ctxt, XML_ERR_RESOURCE_LIMIT,
                       "Maximum entity amplification factor exceeded, see "
                       "xmlCtxtSetMaxAmplification.\n");
        xmlHaltParser(ctxt);
        return(1);
    }

    return(0);
}

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