From 3338789c34d013baabae0b9a991ec019e1a40c18 Mon Sep 17 00:00:00 2001 From: Nick Wellnhofer Date: Tue, 8 Feb 2022 03:29:24 +0100 Subject: [PATCH] [CVE-2022-23308] Use-after-free of ID and IDREF attributes If a document is parsed with XML_PARSE_DTDVALID and without XML_PARSE_NOENT, the value of ID attributes has to be normalized after potentially expanding entities in xmlRemoveID. Otherwise, later calls to xmlGetID can return a pointer to previously freed memory. ID attributes which are empty or contain only whitespace after entity expansion are affected in a similar way. This is fixed by not storing such attributes in the ID table. The test to detect streaming mode when validating against a DTD was broken. In connection with the defects above, this could result in a use-after-free when using the xmlReader interface with validation. Fix detection of streaming mode to avoid similar issues. (This changes the expected result of a test case. But as far as I can tell, using the XML reader with XIncludes referencing the root document never worked properly, anyway.) All of these issues can result in denial of service. Using xmlReader with validation could result in disclosure of memory via the error channel, typically stderr. The security impact of xmlGetID returning a pointer to freed memory depends on the application. The typical use case of calling xmlGetID on an unmodified document is not affected. Change-Id: Iee3c796c5c163a35fe61fc449adf7182331be627 Signed-off-by: DongHun Kwak --- result/XInclude/ns1.xml.rdr | 2 +- valid.c | 88 ++++++++++++++++++++++++++++----------------- 2 files changed, 56 insertions(+), 34 deletions(-) diff --git a/result/XInclude/ns1.xml.rdr b/result/XInclude/ns1.xml.rdr index f23702f..9a3a5e7 100644 --- a/result/XInclude/ns1.xml.rdr +++ b/result/XInclude/ns1.xml.rdr @@ -1,7 +1,7 @@ 0 1 doc 0 0 1 14 #text 0 1 -1 1 ns:elem 1 0 +1 1 xi:include 1 0 1 14 #text 0 1 1 1 elem 0 0 diff --git a/valid.c b/valid.c index 5ee391c..8e596f1 100644 --- a/valid.c +++ b/valid.c @@ -479,6 +479,35 @@ nodeVPop(xmlValidCtxtPtr ctxt) return (ret); } +/** + * xmlValidNormalizeString: + * @str: a string + * + * Normalize a string in-place. + */ +static void +xmlValidNormalizeString(xmlChar *str) { + xmlChar *dst; + const xmlChar *src; + + if (str == NULL) + return; + src = str; + dst = str; + + while (*src == 0x20) src++; + while (*src != 0) { + if (*src == 0x20) { + while (*src == 0x20) src++; + if (*src != 0) + *dst++ = 0x20; + } else { + *dst++ = *src++; + } + } + *dst = 0; +} + #ifdef DEBUG_VALID_ALGO static void xmlValidPrintNode(xmlNodePtr cur) { @@ -2607,6 +2636,24 @@ xmlDumpNotationTable(xmlBufferPtr buf, xmlNotationTablePtr table) { (xmlDictOwns(dict, (const xmlChar *)(str)) == 0))) \ xmlFree((char *)(str)); +static int +xmlIsStreaming(xmlValidCtxtPtr ctxt) { + xmlParserCtxtPtr pctxt; + + if (ctxt == NULL) + return(0); + /* + * These magic values are also abused to detect whether we're validating + * while parsing a document. In this case, userData points to the parser + * context. + */ + if ((ctxt->finishDtd != XML_CTXT_FINISH_DTD_0) && + (ctxt->finishDtd != XML_CTXT_FINISH_DTD_1)) + return(0); + pctxt = ctxt->userData; + return(pctxt->parseMode == XML_PARSE_READER); +} + /** * xmlFreeID: * @not: A id @@ -2650,7 +2697,7 @@ xmlAddID(xmlValidCtxtPtr ctxt, xmlDocPtr doc, const xmlChar *value, if (doc == NULL) { return(NULL); } - if (value == NULL) { + if ((value == NULL) || (value[0] == 0)) { return(NULL); } if (attr == NULL) { @@ -2681,7 +2728,7 @@ xmlAddID(xmlValidCtxtPtr ctxt, xmlDocPtr doc, const xmlChar *value, */ ret->value = xmlStrdup(value); ret->doc = doc; - if ((ctxt != NULL) && (ctxt->vstateNr != 0)) { + if (xmlIsStreaming(ctxt)) { /* * Operating in streaming mode, attr is gonna disappear */ @@ -2820,6 +2867,7 @@ xmlRemoveID(xmlDocPtr doc, xmlAttrPtr attr) { ID = xmlNodeListGetString(doc, attr->children, 1); if (ID == NULL) return(-1); + xmlValidNormalizeString(ID); id = xmlHashLookup(table, ID); if (id == NULL || id->attr != attr) { @@ -3009,7 +3057,7 @@ xmlAddRef(xmlValidCtxtPtr ctxt, xmlDocPtr doc, const xmlChar *value, * fill the structure. */ ret->value = xmlStrdup(value); - if ((ctxt != NULL) && (ctxt->vstateNr != 0)) { + if (xmlIsStreaming(ctxt)) { /* * Operating in streaming mode, attr is gonna disappear */ @@ -4028,8 +4076,7 @@ xmlValidateAttributeValue2(xmlValidCtxtPtr ctxt, xmlDocPtr doc, xmlChar * xmlValidCtxtNormalizeAttributeValue(xmlValidCtxtPtr ctxt, xmlDocPtr doc, xmlNodePtr elem, const xmlChar *name, const xmlChar *value) { - xmlChar *ret, *dst; - const xmlChar *src; + xmlChar *ret; xmlAttributePtr attrDecl = NULL; int extsubset = 0; @@ -4070,19 +4117,7 @@ xmlValidCtxtNormalizeAttributeValue(xmlValidCtxtPtr ctxt, xmlDocPtr doc, ret = xmlStrdup(value); if (ret == NULL) return(NULL); - src = value; - dst = ret; - while (*src == 0x20) src++; - while (*src != 0) { - if (*src == 0x20) { - while (*src == 0x20) src++; - if (*src != 0) - *dst++ = 0x20; - } else { - *dst++ = *src++; - } - } - *dst = 0; + xmlValidNormalizeString(ret); if ((doc->standalone) && (extsubset == 1) && (!xmlStrEqual(value, ret))) { xmlErrValidNode(ctxt, elem, XML_DTD_NOT_STANDALONE, "standalone: %s on %s value had to be normalized based on external subset declaration\n", @@ -4114,8 +4149,7 @@ xmlValidCtxtNormalizeAttributeValue(xmlValidCtxtPtr ctxt, xmlDocPtr doc, xmlChar * xmlValidNormalizeAttributeValue(xmlDocPtr doc, xmlNodePtr elem, const xmlChar *name, const xmlChar *value) { - xmlChar *ret, *dst; - const xmlChar *src; + xmlChar *ret; xmlAttributePtr attrDecl = NULL; if (doc == NULL) return(NULL); @@ -4145,19 +4179,7 @@ xmlValidNormalizeAttributeValue(xmlDocPtr doc, xmlNodePtr elem, ret = xmlStrdup(value); if (ret == NULL) return(NULL); - src = value; - dst = ret; - while (*src == 0x20) src++; - while (*src != 0) { - if (*src == 0x20) { - while (*src == 0x20) src++; - if (*src != 0) - *dst++ = 0x20; - } else { - *dst++ = *src++; - } - } - *dst = 0; + xmlValidNormalizeString(ret); return(ret); } -- 2.7.4