From 63a9f680a00f402a5abcdec27e66ae9221ab5868 Mon Sep 17 00:00:00 2001 From: Nick Wellnhofer Date: Wed, 31 Aug 2022 22:11:25 +0200 Subject: [PATCH] [CVE-2022-40304] Fix dict corruption caused by entity reference cycles When an entity reference cycle is detected, the entity content is cleared by setting its first byte to zero. But the entity content might be allocated from a dict. In this case, the dict entry becomes corrupted leading to all kinds of logic errors, including memory errors like double-frees. Stop storing entity content, orig, ExternalID and SystemID in a dict. These values are unlikely to occur multiple times in a document, so they shouldn't have been stored in a dict in the first place. Thanks to Ned Williamson and Nathan Wachholz working with Google Project Zero for the report! Change-Id: I885a9da0cce3dd3e8c62f5d9c309deb2ca5c1d85 Signed-off-by: DongHun Kwak --- entities.c | 55 ++++++++++++++++--------------------------------------- 1 file changed, 16 insertions(+), 39 deletions(-) diff --git a/entities.c b/entities.c index 7cdbc4d..e572a9a 100644 --- a/entities.c +++ b/entities.c @@ -112,36 +112,19 @@ xmlFreeEntity(xmlEntityPtr entity) if ((entity->children) && (entity->owner == 1) && (entity == (xmlEntityPtr) entity->children->parent)) xmlFreeNodeList(entity->children); - if (dict != NULL) { - if ((entity->name != NULL) && (!xmlDictOwns(dict, entity->name))) - xmlFree((char *) entity->name); - if ((entity->ExternalID != NULL) && - (!xmlDictOwns(dict, entity->ExternalID))) - xmlFree((char *) entity->ExternalID); - if ((entity->SystemID != NULL) && - (!xmlDictOwns(dict, entity->SystemID))) - xmlFree((char *) entity->SystemID); - if ((entity->URI != NULL) && (!xmlDictOwns(dict, entity->URI))) - xmlFree((char *) entity->URI); - if ((entity->content != NULL) - && (!xmlDictOwns(dict, entity->content))) - xmlFree((char *) entity->content); - if ((entity->orig != NULL) && (!xmlDictOwns(dict, entity->orig))) - xmlFree((char *) entity->orig); - } else { - if (entity->name != NULL) - xmlFree((char *) entity->name); - if (entity->ExternalID != NULL) - xmlFree((char *) entity->ExternalID); - if (entity->SystemID != NULL) - xmlFree((char *) entity->SystemID); - if (entity->URI != NULL) - xmlFree((char *) entity->URI); - if (entity->content != NULL) - xmlFree((char *) entity->content); - if (entity->orig != NULL) - xmlFree((char *) entity->orig); - } + if ((entity->name != NULL) && + ((dict == NULL) || (!xmlDictOwns(dict, entity->name)))) + xmlFree((char *) entity->name); + if (entity->ExternalID != NULL) + xmlFree((char *) entity->ExternalID); + if (entity->SystemID != NULL) + xmlFree((char *) entity->SystemID); + if (entity->URI != NULL) + xmlFree((char *) entity->URI); + if (entity->content != NULL) + xmlFree((char *) entity->content); + if (entity->orig != NULL) + xmlFree((char *) entity->orig); xmlFree(entity); } @@ -177,18 +160,12 @@ xmlCreateEntity(xmlDictPtr dict, const xmlChar *name, int type, ret->SystemID = xmlStrdup(SystemID); } else { ret->name = xmlDictLookup(dict, name, -1); - if (ExternalID != NULL) - ret->ExternalID = xmlDictLookup(dict, ExternalID, -1); - if (SystemID != NULL) - ret->SystemID = xmlDictLookup(dict, SystemID, -1); + ret->ExternalID = xmlStrdup(ExternalID); + ret->SystemID = xmlStrdup(SystemID); } if (content != NULL) { ret->length = xmlStrlen(content); - if ((dict != NULL) && (ret->length < 5)) - ret->content = (xmlChar *) - xmlDictLookup(dict, content, ret->length); - else - ret->content = xmlStrndup(content, ret->length); + ret->content = xmlStrndup(content, ret->length); } else { ret->length = 0; ret->content = NULL; -- 2.7.4