Handle subset tvbuffs where the length goes past the end of the parent.

Add a "contained length" to tvbuffs.  For non-subset tvbuffs, that's the
same as the reported length.  For a subset tvbuff, that's the amount of
the reported data that was actually present in the "contained data" of
the parent tvbuff.

This is unaffected by the *captured* length of any tvbuff; that differs
from the contained length only if the capture was cut short by a
snapshot length.

If a reference is within the reported data, but not within the contained
data, a ContainedBoundsError exception is thrown.  This exception
represents a protocol error, rather than a reference past the captured
data in the packet; we treat it as such.

Change-Id: Ide87f81238eaeb89b3093f54a87bf7f715485af5
Reviewed-on: https://code.wireshark.org/review/27039
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 2 insertions, 0 deletions

diff --git a/epan/tvbuff_composite.c b/epan/tvbuff_composite.c
index 5832477f81..f77aace029 100644
--- a/epan/tvbuff_composite.c
+++ b/epan/tvbuff_composite.c
@@ -259,6 +259,7 @@ tvb_composite_finalize(tvbuff_t *tvb)
 	DISSECTOR_ASSERT(tvb->ops == &tvb_composite_ops);
 	DISSECTOR_ASSERT(tvb->length == 0);
 	DISSECTOR_ASSERT(tvb->reported_length == 0);
+	DISSECTOR_ASSERT(tvb->contained_length == 0);
 
 	composite   = &composite_tvb->composite;
 	num_members = g_slist_length(composite->tvbs);
@@ -278,6 +279,7 @@ tvb_composite_finalize(tvbuff_t *tvb)
 		composite->start_offsets[i] = tvb->length;
 		tvb->length += member_tvb->length;
 		tvb->reported_length += member_tvb->reported_length;
+		tvb->contained_length += member_tvb->contained_length;
 		composite->end_offsets[i] = tvb->length - 1;
 		i++;
 	}