Wireshark · Ethereal-dev: Re: [Ethereal-dev] tvb_strnlen problem

[Heikki Vatiainen <hessu@xxxxxxxxx>]

Guy Harris <guy@xxxxxxxxxx> wrote:

> Yes, the problem is that "tvb_strnlen()" is returning the offset of the
> '\0', not the length of the string.
> 
> The next problem is that "tvb_get_nstringz()" is assuming that it's
> returning the offset, rather than the length, so "tvb_get_nstringz()"
> should probably do
> 
> 	stringlen = tvb_strnlen(tvb, abs_offset, limit);
> 
> 	/* If NUL wasn't found, copy the data and return -1 */
> 	if (stringlen == -1) {
> 		tvb_memcpy(tvb, buffer, abs_offset, limit);
> 		return -1;
> 	}
> 
> 	/* Copy the string to buffer */
> 	tvb_memcpy(tvb, buffer, abs_offset, stringlen + 1);
> 	return stringlen;
> 
> So try changing "tvb_get_nstringz()" as per the above, and see if that
> works.

Thanks, it works now. The whole thing in patch format is below. The
first half of the patch changes tvb_strnlen() to return length, not
offset, and the second half does what was suggested above.


Index: tvbuff.c
===================================================================
RCS file: /cvsroot/ethereal/epan/tvbuff.c,v
retrieving revision 1.1
diff -u -r1.1 tvbuff.c
--- tvbuff.c	2000/09/27 04:54:53	1.1
+++ tvbuff.c	2000/10/16 10:52:08
@@ -1029,7 +1029,7 @@
 		return -1;
 	}
 	else {
-		return result_offset;
+		return result_offset - abs_offset;
 	}
 }
 
@@ -1090,7 +1090,7 @@
 gint
 tvb_get_nstringz(tvbuff_t *tvb, gint offset, guint maxlength, guint8* buffer)
 {
-	gint	stringlen, NUL_offset;
+	gint	stringlen;
 	guint	abs_offset, junk_length;
 	gint	limit;
 
@@ -1109,16 +1109,15 @@
 		limit = maxlength;
 	}
 
-	NUL_offset = tvb_strnlen(tvb, abs_offset, limit);
+	stringlen = tvb_strnlen(tvb, abs_offset, limit);
 
 	/* If NUL wasn't found, copy the data and return -1 */
-	if (NUL_offset == -1) {
+	if (stringlen == -1) {
 		tvb_memcpy(tvb, buffer, abs_offset, limit);
 		return -1;
 	}
 
 	/* Copy the string to buffer */
-	stringlen = NUL_offset - abs_offset;
 	tvb_memcpy(tvb, buffer, abs_offset, stringlen + 1);
 	return stringlen;
 }