[xml] C14N issue with digital signature due to pointer comparison

[Frank Gross <fg 4js com>]

Hi,

  I'm getting some trouble to verify a XML signature because the 
xmlC14NProcessNamespacesAxis() function does a xmlNsPtr pointer 
comparison to decide whether a sub node belongs to the same default 
namespace as an ancestor. But if the sub node has been manipulated by 
program (in my case) to point to another xmlNsPtr with same values, the 
canonicalization process breaks. Wouldn't it be better to check the 
namespace href values instead as in following patch ?

diff --git a/lib-xmlsoft-libxml2/src/c14n.c b/lib-xmlsoft-libxml2/src/c14n.c
index 9c3cad2..f73e709 100644
--- a/lib-xmlsoft-libxml2/src/c14n.c
+++ b/lib-xmlsoft-libxml2/src/c14n.c
@@ -623,7 +623,7 @@ xmlC14NProcessNamespacesAxis(xmlC14NCtxPtr ctx, 
xmlNodePtr cur, int visible)
     for(ns = n->nsDef; ns != NULL; ns = ns->next) {
         tmp = xmlSearchNs(cur->doc, cur, ns->prefix);

-        if((tmp == ns) && !xmlC14NIsXmlNs(ns) && xmlC14NIsVisible(ctx, 
ns, cur)) {
+        if((xmlStrEqual(tmp->href,ns->href)) && 
(xmlStrEqual(tmp->prefix,ns->prefix)) && !xmlC14NIsXmlNs(ns) && 
xmlC14NIsVisible(ctx, ns, cur)) {
         already_rendered = xmlC14NVisibleNsStackFind(ctx->ns_rendered, 
ns);
         if(visible) {
                 xmlC14NVisibleNsStackAdd(ctx->ns_rendered, ns, cur);

Regards,
Frank

--
Frank GROSS
Software Engineer - Web Services
Four J's Development Tools - http://www.4js.com