Wireshark-dev: Re: [Wireshark-dev] [libsmi] Re: Building libsmi from SVN as a .dll
On Wed, Apr 16, 2008 at 09:22:38AM +1000, Andrew Hood wrote:
> I think I have also tracked down one of the reasons wireshark crashes.
[...]
> At line 595 oids.c calls smiRenderOID to format the node. The implicit
> node is not completely filled in, and wireshark/tshark crashes in
> libsmi. This is not totally unreasonable since implicit nodes should
> never be seen.
A crash _inside_ libsmi is not really acceptable; smiRenderOID should
return NULL if it can't do what the caller wants. So I created a sample
MIB and a little program to test this (see attachment) and I found
where things go wrong.
Attached is a patch which causes smiRenderOID() to render the OID
as a sequence of numbers in case it is called with SMI_RENDER_NAME
or SMI_RENDER_QUALIFIED and the label of the node is not known. But
this might not be the right thing to do; it might be better to
fail by returning NULL so that the caller gets control of what
should happen. On the other hand, we always append numeric OIDs.
/js
--
Juergen Schoenwaelder Jacobs University Bremen gGmbH
Phone: +49 421 200 3587 Campus Ring 1, 28759 Bremen, Germany
Fax: +49 421 200 3103 <http://www.jacobs-university.de/>
FOO-MIB DEFINITIONS ::= BEGIN
IMPORTS mib-2 FROM SNMPv2-SMI;
foo OBJECT IDENTIFIER ::= { mib-2 88 1 }
END
#include <stdio.h>
#include <smi.h>
static SmiSubid oid[] = {1, 3, 6, 1, 2, 1, 88};
static void
render(int flags)
{
char *s;
s = smiRenderOID(sizeof(oid)/sizeof(SmiSubid), oid, flags);
printf(">%s<\n", s);
smiFree(s);
}
int
main(int argc, char **argv)
{
int i;
smiInit(NULL);
for (i = 1; i < argc; i++) {
smiLoadModule(argv[i]);
}
render(0);
render(SMI_RENDER_NAME);
render(SMI_RENDER_QUALIFIED);
return 0;
}
Index: smi.c
===================================================================
--- smi.c (revision 8023)
+++ smi.c (working copy)
@@ -1878,7 +1878,7 @@
if (flags & (SMI_RENDER_NAME | SMI_RENDER_QUALIFIED)) {
nodePtr = smiGetNodeByOID(oidlen, oid);
- if (nodePtr) {
+ if (nodePtr && nodePtr->name) {
i = nodePtr->oidlen;
if (flags & SMI_RENDER_QUALIFIED) {
modulePtr = smiGetNodeModule(nodePtr);
