[libxml2] Disallow namespace nodes in XPointer ranges

[Nick Wellnhofer <nwellnhof src gnome org>]

commit c1d1f7121194036608bf555f08d3062a36fd344b
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Tue Jun 28 18:34:52 2016 +0200

    Disallow namespace nodes in XPointer ranges
    
    Namespace nodes must be copied to avoid use-after-free errors.
    But they don't necessarily have a physical representation in a
    document, so simply disallow them in XPointer ranges.
    
    Found with afl-fuzz.
    
    Fixes CVE-2016-4658.

 xpointer.c |  149 ++++++++++++++++++++++-------------------------------------
 1 files changed, 56 insertions(+), 93 deletions(-)
---
diff --git a/xpointer.c b/xpointer.c
index a7b03fb..694d120 100644
--- a/xpointer.c
+++ b/xpointer.c
@@ -320,6 +320,45 @@ xmlXPtrRangesEqual(xmlXPathObjectPtr range1, xmlXPathObjectPtr range2) {
 }
 
 /**
+ * xmlXPtrNewRangeInternal:
+ * @start:  the starting node
+ * @startindex:  the start index
+ * @end:  the ending point
+ * @endindex:  the ending index
+ *
+ * Internal function to create a new xmlXPathObjectPtr of type range
+ *
+ * Returns the newly created object.
+ */
+static xmlXPathObjectPtr
+xmlXPtrNewRangeInternal(xmlNodePtr start, int startindex,
+                        xmlNodePtr end, int endindex) {
+    xmlXPathObjectPtr ret;
+
+    /*
+     * Namespace nodes must be copied (see xmlXPathNodeSetDupNs).
+     * Disallow them for now.
+     */
+    if ((start != NULL) && (start->type == XML_NAMESPACE_DECL))
+       return(NULL);
+    if ((end != NULL) && (end->type == XML_NAMESPACE_DECL))
+       return(NULL);
+
+    ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
+    if (ret == NULL) {
+        xmlXPtrErrMemory("allocating range");
+       return(NULL);
+    }
+    memset(ret, 0, sizeof(xmlXPathObject));
+    ret->type = XPATH_RANGE;
+    ret->user = start;
+    ret->index = startindex;
+    ret->user2 = end;
+    ret->index2 = endindex;
+    return(ret);
+}
+
+/**
  * xmlXPtrNewRange:
  * @start:  the starting node
  * @startindex:  the start index
@@ -344,17 +383,7 @@ xmlXPtrNewRange(xmlNodePtr start, int startindex,
     if (endindex < 0)
        return(NULL);
 
-    ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
-    if (ret == NULL) {
-        xmlXPtrErrMemory("allocating range");
-       return(NULL);
-    }
-    memset(ret, 0 , (size_t) sizeof(xmlXPathObject));
-    ret->type = XPATH_RANGE;
-    ret->user = start;
-    ret->index = startindex;
-    ret->user2 = end;
-    ret->index2 = endindex;
+    ret = xmlXPtrNewRangeInternal(start, startindex, end, endindex);
     xmlXPtrRangeCheckOrder(ret);
     return(ret);
 }
@@ -381,17 +410,8 @@ xmlXPtrNewRangePoints(xmlXPathObjectPtr start, xmlXPathObjectPtr end) {
     if (end->type != XPATH_POINT)
        return(NULL);
 
-    ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
-    if (ret == NULL) {
-        xmlXPtrErrMemory("allocating range");
-       return(NULL);
-    }
-    memset(ret, 0 , (size_t) sizeof(xmlXPathObject));
-    ret->type = XPATH_RANGE;
-    ret->user = start->user;
-    ret->index = start->index;
-    ret->user2 = end->user;
-    ret->index2 = end->index;
+    ret = xmlXPtrNewRangeInternal(start->user, start->index, end->user,
+                                  end->index);
     xmlXPtrRangeCheckOrder(ret);
     return(ret);
 }
@@ -416,17 +436,7 @@ xmlXPtrNewRangePointNode(xmlXPathObjectPtr start, xmlNodePtr end) {
     if (start->type != XPATH_POINT)
        return(NULL);
 
-    ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
-    if (ret == NULL) {
-        xmlXPtrErrMemory("allocating range");
-       return(NULL);
-    }
-    memset(ret, 0 , (size_t) sizeof(xmlXPathObject));
-    ret->type = XPATH_RANGE;
-    ret->user = start->user;
-    ret->index = start->index;
-    ret->user2 = end;
-    ret->index2 = -1;
+    ret = xmlXPtrNewRangeInternal(start->user, start->index, end, -1);
     xmlXPtrRangeCheckOrder(ret);
     return(ret);
 }
@@ -453,17 +463,7 @@ xmlXPtrNewRangeNodePoint(xmlNodePtr start, xmlXPathObjectPtr end) {
     if (end->type != XPATH_POINT)
        return(NULL);
 
-    ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
-    if (ret == NULL) {
-        xmlXPtrErrMemory("allocating range");
-       return(NULL);
-    }
-    memset(ret, 0 , (size_t) sizeof(xmlXPathObject));
-    ret->type = XPATH_RANGE;
-    ret->user = start;
-    ret->index = -1;
-    ret->user2 = end->user;
-    ret->index2 = end->index;
+    ret = xmlXPtrNewRangeInternal(start, -1, end->user, end->index);
     xmlXPtrRangeCheckOrder(ret);
     return(ret);
 }
@@ -486,17 +486,7 @@ xmlXPtrNewRangeNodes(xmlNodePtr start, xmlNodePtr end) {
     if (end == NULL)
        return(NULL);
 
-    ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
-    if (ret == NULL) {
-        xmlXPtrErrMemory("allocating range");
-       return(NULL);
-    }
-    memset(ret, 0 , (size_t) sizeof(xmlXPathObject));
-    ret->type = XPATH_RANGE;
-    ret->user = start;
-    ret->index = -1;
-    ret->user2 = end;
-    ret->index2 = -1;
+    ret = xmlXPtrNewRangeInternal(start, -1, end, -1);
     xmlXPtrRangeCheckOrder(ret);
     return(ret);
 }
@@ -516,17 +506,7 @@ xmlXPtrNewCollapsedRange(xmlNodePtr start) {
     if (start == NULL)
        return(NULL);
 
-    ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
-    if (ret == NULL) {
-        xmlXPtrErrMemory("allocating range");
-       return(NULL);
-    }
-    memset(ret, 0 , (size_t) sizeof(xmlXPathObject));
-    ret->type = XPATH_RANGE;
-    ret->user = start;
-    ret->index = -1;
-    ret->user2 = NULL;
-    ret->index2 = -1;
+    ret = xmlXPtrNewRangeInternal(start, -1, NULL, -1);
     return(ret);
 }
 
@@ -541,6 +521,8 @@ xmlXPtrNewCollapsedRange(xmlNodePtr start) {
  */
 xmlXPathObjectPtr
 xmlXPtrNewRangeNodeObject(xmlNodePtr start, xmlXPathObjectPtr end) {
+    xmlNodePtr endNode;
+    int endIndex;
     xmlXPathObjectPtr ret;
 
     if (start == NULL)
@@ -549,7 +531,12 @@ xmlXPtrNewRangeNodeObject(xmlNodePtr start, xmlXPathObjectPtr end) {
        return(NULL);
     switch (end->type) {
        case XPATH_POINT:
+           endNode = end->user;
+           endIndex = end->index;
+           break;
        case XPATH_RANGE:
+           endNode = end->user2;
+           endIndex = end->index2;
            break;
        case XPATH_NODESET:
            /*
@@ -557,39 +544,15 @@ xmlXPtrNewRangeNodeObject(xmlNodePtr start, xmlXPathObjectPtr end) {
             */
            if (end->nodesetval->nodeNr <= 0)
                return(NULL);
+           endNode = end->nodesetval->nodeTab[end->nodesetval->nodeNr - 1];
+           endIndex = -1;
            break;
        default:
            /* TODO */
            return(NULL);
     }
 
-    ret = (xmlXPathObjectPtr) xmlMalloc(sizeof(xmlXPathObject));
-    if (ret == NULL) {
-        xmlXPtrErrMemory("allocating range");
-       return(NULL);
-    }
-    memset(ret, 0 , (size_t) sizeof(xmlXPathObject));
-    ret->type = XPATH_RANGE;
-    ret->user = start;
-    ret->index = -1;
-    switch (end->type) {
-       case XPATH_POINT:
-           ret->user2 = end->user;
-           ret->index2 = end->index;
-           break;
-       case XPATH_RANGE:
-           ret->user2 = end->user2;
-           ret->index2 = end->index2;
-           break;
-       case XPATH_NODESET: {
-           ret->user2 = end->nodesetval->nodeTab[end->nodesetval->nodeNr - 1];
-           ret->index2 = -1;
-           break;
-       }
-       default:
-           STRANGE
-           return(NULL);
-    }
+    ret = xmlXPtrNewRangeInternal(start, -1, endNode, endIndex);
     xmlXPtrRangeCheckOrder(ret);
     return(ret);
 }