Ethereal-dev: Re: [Ethereal-dev] Ethereal patch for TLS Hello Extensions (RFC 3546)
On Sat, Dec 25, 2004 at 04:29:17PM -0800, Guy Harris wrote:
> Jouni Malinen wrote:
> >The attached patch adds parsing of TLS Extensions (RFC 3546) for
> >ClientHello and ServerHello.
>
> Checked in.
Oops.. I did some more testing and it became clear that using
tvb_length_remaining() was not exactly the best thing to do here. This
worked fine for frames that ending in the TLS extensions, but it seemed
to confuse parsing of things following ClientHello/ServerHello. The
attached patch changes this to use the length of the Client/ServerHello
explicitly to limit the area for TLS extensions parsing. Is this the
correct way of handling this in Ethereal or are there any better
mechanisms for getting remaining data area for a partial block of the
packet similarly to tvb_length_remaining()?
--
Jouni Malinen PGP id EFC895FA
Index: epan/dissectors/packet-ssl.c
===================================================================
--- epan/dissectors/packet-ssl.c (revision 12836)
+++ epan/dissectors/packet-ssl.c (working copy)
@@ -726,11 +726,11 @@
static void dissect_ssl3_hnd_cli_hello(tvbuff_t *tvb,
proto_tree *tree,
- guint32 offset);
+ guint32 offset, guint32 length);
static void dissect_ssl3_hnd_srv_hello(tvbuff_t *tvb,
proto_tree *tree,
- guint32 offset);
+ guint32 offset, guint32 length);
static void dissect_ssl3_hnd_cert(tvbuff_t *tvb,
proto_tree *tree, guint32 offset, packet_info *pinfo);
@@ -1439,11 +1439,11 @@
break;
case SSL_HND_CLIENT_HELLO:
- dissect_ssl3_hnd_cli_hello(tvb, ssl_hand_tree, offset);
+ dissect_ssl3_hnd_cli_hello(tvb, ssl_hand_tree, offset, length);
break;
case SSL_HND_SERVER_HELLO:
- dissect_ssl3_hnd_srv_hello(tvb, ssl_hand_tree, offset);
+ dissect_ssl3_hnd_srv_hello(tvb, ssl_hand_tree, offset, length);
break;
case SSL_HND_CERTIFICATE:
@@ -1530,7 +1530,7 @@
static int
dissect_ssl3_hnd_hello_ext(tvbuff_t *tvb,
- proto_tree *tree, guint32 offset)
+ proto_tree *tree, guint32 offset, guint32 left)
{
guint16 extension_length;
guint16 ext_type;
@@ -1538,15 +1538,16 @@
proto_item *pi;
proto_tree *ext_tree;
- if (tvb_length_remaining(tvb, offset) < 2)
+ if (left < 2)
return offset;
extension_length = tvb_get_ntohs(tvb, offset);
proto_tree_add_uint(tree, hf_ssl_handshake_extensions_len,
tvb, offset, 2, extension_length);
offset += 2;
+ left -= 2;
- while (tvb_length_remaining(tvb, offset) >= 4)
+ while (left >= 4)
{
ext_type = tvb_get_ntohs(tvb, offset);
ext_len = tvb_get_ntohs(tvb, offset + 2);
@@ -1574,6 +1575,7 @@
"Data (%u byte%s)",
ext_len, plurality(ext_len, "", "s"));
offset += ext_len;
+ left -= 2 + 2 + ext_len;
}
return offset;
@@ -1581,7 +1583,7 @@
static void
dissect_ssl3_hnd_cli_hello(tvbuff_t *tvb,
- proto_tree *tree, guint32 offset)
+ proto_tree *tree, guint32 offset, guint32 length)
{
/* struct {
* ProtocolVersion client_version;
@@ -1598,6 +1600,7 @@
guint16 cipher_suite_length = 0;
guint8 compression_methods_length = 0;
guint8 compression_method;
+ guint16 start_offset = offset;
if (tree)
{
@@ -1682,13 +1685,18 @@
}
}
- offset = dissect_ssl3_hnd_hello_ext(tvb, tree, offset);
+ if (length > offset - start_offset)
+ {
+ offset = dissect_ssl3_hnd_hello_ext(tvb, tree, offset,
+ length -
+ (offset - start_offset));
+ }
}
}
static void
dissect_ssl3_hnd_srv_hello(tvbuff_t *tvb,
- proto_tree *tree, guint32 offset)
+ proto_tree *tree, guint32 offset, guint32 length)
{
/* struct {
* ProtocolVersion server_version;
@@ -1699,6 +1707,7 @@
* Extension server_hello_extension_list<0..2^16-1>;
* } ServerHello;
*/
+ guint16 start_offset = offset;
if (tree)
{
@@ -1722,7 +1731,12 @@
tvb, offset, 1, FALSE);
offset++;
- offset = dissect_ssl3_hnd_hello_ext(tvb, tree, offset);
+ if (length > offset - start_offset)
+ {
+ offset = dissect_ssl3_hnd_hello_ext(tvb, tree, offset,
+ length -
+ (offset - start_offset));
+ }
}
}
