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From f5048b3e71fc30ad096970b8df6e7af073bae4cb Mon Sep 17 00:00:00 2001
From: Daniel Veillard <veillard@redhat.com>
Date: Thu, 18 Aug 2011 09:10:13 +0000
Subject: Hardening of XPath evaluation
Add a mechanism of frame for XPath evaluation when entering a function
or a scoped evaluation, also fix a potential problem in predicate
evaluation.
---
diff --git a/include/libxml/xpath.h b/include/libxml/xpath.h
index 1a9e30e..ddd9dd8 100644
--- a/include/libxml/xpath.h
+++ b/include/libxml/xpath.h
@@ -68,7 +68,8 @@ typedef enum {
XPATH_UNDEF_PREFIX_ERROR,
XPATH_ENCODING_ERROR,
XPATH_INVALID_CHAR_ERROR,
- XPATH_INVALID_CTXT
+ XPATH_INVALID_CTXT,
+ XPATH_STACK_ERROR
} xmlXPathError;
/*
@@ -380,6 +381,8 @@ struct _xmlXPathParserContext {
xmlXPathCompExprPtr comp; /* the precompiled expression */
int xptr; /* it this an XPointer expression */
xmlNodePtr ancestor; /* used for walking preceding axis */
+
+ int valueFrame; /* used to limit Pop on the stack */
};
/************************************************************************
diff --git a/xpath.c b/xpath.c
index b59ac5a..bcee2ea 100644
--- a/xpath.c
+++ b/xpath.c
@@ -252,6 +252,7 @@ static const char *xmlXPathErrorMessages[] = {
"Encoding error\n",
"Char out of XML range\n",
"Invalid or incomplete context\n",
+ "Stack usage errror\n",
"?? Unknown error ??\n" /* Must be last in the list! */
};
#define MAXERRNO ((int)(sizeof(xmlXPathErrorMessages) / \
@@ -2398,6 +2399,42 @@ xmlXPathCacheConvertNumber(xmlXPathContextPtr ctxt, xmlXPathObjectPtr val) {
************************************************************************/
/**
+ * xmlXPathSetFrame:
+ * @ctxt: an XPath parser context
+ *
+ * Set the callee evaluation frame
+ *
+ * Returns the previous frame value to be restored once done
+ */
+static int
+xmlXPathSetFrame(xmlXPathParserContextPtr ctxt) {
+ int ret;
+
+ if (ctxt == NULL)
+ return(0);
+ ret = ctxt->valueFrame;
+ ctxt->valueFrame = ctxt->valueNr;
+ return(ret);
+}
+
+/**
+ * xmlXPathPopFrame:
+ * @ctxt: an XPath parser context
+ * @frame: the previous frame value
+ *
+ * Remove the callee evaluation frame
+ */
+static void
+xmlXPathPopFrame(xmlXPathParserContextPtr ctxt, int frame) {
+ if (ctxt == NULL)
+ return;
+ if (ctxt->valueNr < ctxt->valueFrame) {
+ xmlXPatherror(ctxt, __FILE__, __LINE__, XPATH_STACK_ERROR);
+ }
+ ctxt->valueFrame = frame;
+}
+
+/**
* valuePop:
* @ctxt: an XPath evaluation context
*
@@ -2412,6 +2449,12 @@ valuePop(xmlXPathParserContextPtr ctxt)
if ((ctxt == NULL) || (ctxt->valueNr <= 0))
return (NULL);
+
+ if (ctxt->valueNr <= ctxt->valueFrame) {
+ xmlXPatherror(ctxt, __FILE__, __LINE__, XPATH_STACK_ERROR);
+ return (NULL);
+ }
+
ctxt->valueNr--;
if (ctxt->valueNr > 0)
ctxt->value = ctxt->valueTab[ctxt->valueNr - 1];
@@ -6154,6 +6197,7 @@ xmlXPathCompParserContext(xmlXPathCompExprPtr comp, xmlXPathContextPtr ctxt) {
ret->valueNr = 0;
ret->valueMax = 10;
ret->value = NULL;
+ ret->valueFrame = 0;
ret->context = ctxt;
ret->comp = comp;
@@ -11711,6 +11755,7 @@ xmlXPathCompOpEvalPositionalPredicate(xmlXPathParserContextPtr ctxt,
xmlXPathObjectPtr contextObj = NULL, exprRes = NULL;
xmlNodePtr oldContextNode, contextNode = NULL;
xmlXPathContextPtr xpctxt = ctxt->context;
+ int frame;
#ifdef LIBXML_XPTR_ENABLED
/*
@@ -11730,6 +11775,8 @@ xmlXPathCompOpEvalPositionalPredicate(xmlXPathParserContextPtr ctxt,
*/
exprOp = &ctxt->comp->steps[op->ch2];
for (i = 0; i < set->nodeNr; i++) {
+ xmlXPathObjectPtr tmp;
+
if (set->nodeTab[i] == NULL)
continue;
@@ -11757,23 +11804,25 @@ xmlXPathCompOpEvalPositionalPredicate(xmlXPathParserContextPtr ctxt,
xmlXPathNodeSetAddUnique(contextObj->nodesetval,
contextNode);
+ frame = xmlXPathSetFrame(ctxt);
valuePush(ctxt, contextObj);
res = xmlXPathCompOpEvalToBoolean(ctxt, exprOp, 1);
+ tmp = valuePop(ctxt);
+ xmlXPathPopFrame(ctxt, frame);
if ((ctxt->error != XPATH_EXPRESSION_OK) || (res == -1)) {
- xmlXPathObjectPtr tmp;
- /* pop the result if any */
- tmp = valuePop(ctxt);
- if (tmp != contextObj) {
+ while (tmp != contextObj) {
/*
* Free up the result
* then pop off contextObj, which will be freed later
*/
xmlXPathReleaseObject(xpctxt, tmp);
- valuePop(ctxt);
+ tmp = valuePop(ctxt);
}
goto evaluation_error;
}
+ /* push the result back onto the stack */
+ valuePush(ctxt, tmp);
if (res)
pos++;
@@ -13377,7 +13426,9 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
xmlXPathFunction func;
const xmlChar *oldFunc, *oldFuncURI;
int i;
+ int frame;
+ frame = xmlXPathSetFrame(ctxt);
if (op->ch1 != -1)
total +=
xmlXPathCompOpEval(ctxt, &comp->steps[op->ch1]);
@@ -13385,15 +13436,18 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
xmlGenericError(xmlGenericErrorContext,
"xmlXPathCompOpEval: parameter error\n");
ctxt->error = XPATH_INVALID_OPERAND;
+ xmlXPathPopFrame(ctxt, frame);
return (total);
}
- for (i = 0; i < op->value; i++)
+ for (i = 0; i < op->value; i++) {
if (ctxt->valueTab[(ctxt->valueNr - 1) - i] == NULL) {
xmlGenericError(xmlGenericErrorContext,
"xmlXPathCompOpEval: parameter error\n");
ctxt->error = XPATH_INVALID_OPERAND;
+ xmlXPathPopFrame(ctxt, frame);
return (total);
}
+ }
if (op->cache != NULL)
XML_CAST_FPTR(func) = op->cache;
else {
@@ -13409,6 +13463,7 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
xmlGenericError(xmlGenericErrorContext,
"xmlXPathCompOpEval: function %s bound to undefined prefix %s\n",
(char *)op->value4, (char *)op->value5);
+ xmlXPathPopFrame(ctxt, frame);
return (total);
}
func = xmlXPathFunctionLookupNS(ctxt->context,
@@ -13430,6 +13485,7 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
func(ctxt, op->value);
ctxt->context->function = oldFunc;
ctxt->context->functionURI = oldFuncURI;
+ xmlXPathPopFrame(ctxt, frame);
return (total);
}
case XPATH_OP_ARG:
@@ -14333,6 +14389,7 @@ xmlXPathRunEval(xmlXPathParserContextPtr ctxt, int toBool)
ctxt->valueNr = 0;
ctxt->valueMax = 10;
ctxt->value = NULL;
+ ctxt->valueFrame = 0;
}
#ifdef XPATH_STREAMING
if (ctxt->comp->stream) {
diff --git a/xpointer.c b/xpointer.c
index 7a42d02..37afa3a 100644
--- a/xpointer.c
+++ b/xpointer.c
@@ -1269,6 +1269,7 @@ xmlXPtrEvalXPointer(xmlXPathParserContextPtr ctxt) {
ctxt->valueNr = 0;
ctxt->valueMax = 10;
ctxt->value = NULL;
+ ctxt->valueFrame = 0;
}
SKIP_BLANKS;
if (CUR == '/') {
--
cgit v0.9.0.2
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