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/*
* Routines for the disassembly of the proprietary Cisco IPSEC in
* TCP encapsulation protocol
*
* Copyright 2007 Joerg Mayer (see AUTHORS file)
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
/* TODO:
* - Find out the meaning of the (unknown) trailer
* - UDP checksum is wrong
* - Currently doesn't handle AH (lack of sample trace)
*/
#include "config.h"
#include <epan/packet.h>
#include "packet-ndmp.h"
void proto_register_tcpencap(void);
void proto_reg_handoff_tcpencap(void);
static dissector_handle_t tcpencap_handle;
static int hf_tcpencap_unknown = -1;
static int hf_tcpencap_zero = -1;
static int hf_tcpencap_seq = -1;
static int hf_tcpencap_ike_direction = -1;
static int hf_tcpencap_esp_zero = -1;
static int hf_tcpencap_magic = -1;
static int hf_tcpencap_proto = -1;
static int hf_tcpencap_magic2 = -1;
static int proto_tcpencap = -1;
static gint ett_tcpencap = -1;
static gint ett_tcpencap_unknown = -1;
static const value_string tcpencap_ikedir_vals[] = {
{ 0x0000, "Server to client" },
{ 0x4000, "Client to server" },
{ 0, NULL }
};
static const value_string tcpencap_proto_vals[] = {
{ 0x11, "ISAKMP" },
{ 0x32, "ESP" },
{ 0, NULL }
};
#define TRAILERLENGTH 16
#define TCP_CISCO_IPSEC 10000
static dissector_handle_t esp_handle;
static dissector_handle_t udp_handle;
#define TCP_ENCAP_P_ESP 1
#define TCP_ENCAP_P_UDP 2
static int
packet_is_tcpencap(tvbuff_t *tvb, packet_info *pinfo, guint32 offset)
{
if ( /* Must be zero */
tvb_get_ntohl(tvb, offset + 0) != 0 ||
/* Lower 12 bits must be zero */
(tvb_get_ntohs(tvb, offset + 6) & 0xfff) != 0 ||
/* Protocol must be UDP or ESP */
(tvb_get_guint8(tvb, offset + 13) != 17 &&
tvb_get_guint8(tvb, offset + 13) != 50)
) {
return FALSE;
}
if(check_if_ndmp(tvb, pinfo)){
return FALSE;
}
return TRUE;
}
/*
* TCP Encapsulation of IPsec Packets
* as supported by the cisco vpn3000 concentrator series
*/
static int
dissect_tcpencap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
proto_tree *tcpencap_tree = NULL;
proto_tree *tcpencap_unknown_tree = NULL;
proto_item *tree_item = NULL;
proto_item *unknown_item = NULL;
tvbuff_t *next_tvb;
guint32 reported_length = tvb_reported_length(tvb);
guint32 offset;
guint8 protocol;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "TCPENCAP");
col_clear(pinfo->cinfo, COL_INFO);
/* If the first 4 bytes are 0x01f401f4 (udp src and dst port = 500)
we most likely have UDP (isakmp) traffic */
if (tvb_get_ntohl(tvb, 0) == 0x01f401f4) { /* UDP means ISAKMP */
protocol = TCP_ENCAP_P_UDP;
} else { /* Hopefully ESP */
protocol = TCP_ENCAP_P_ESP;
}
if (tree) {
tree_item = proto_tree_add_item(tree, proto_tcpencap, tvb, 0, -1, ENC_NA);
tcpencap_tree = proto_item_add_subtree(tree_item, ett_tcpencap);
/* Dissect the trailer following the encapsulated IPSEC/ISAKMP packet */
offset = reported_length - TRAILERLENGTH;
unknown_item = proto_tree_add_item(tcpencap_tree, hf_tcpencap_unknown, tvb,
offset, TRAILERLENGTH, ENC_NA);
/* Try to guess the contents of the trailer */
tcpencap_unknown_tree = proto_item_add_subtree(unknown_item, ett_tcpencap_unknown);
proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_zero, tvb, offset + 0, 4, ENC_NA);
proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_seq, tvb, offset + 4, 2, ENC_BIG_ENDIAN);
if (protocol == TCP_ENCAP_P_UDP) {
proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_ike_direction, tvb, offset + 6, 2, ENC_BIG_ENDIAN);
} else {
proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_esp_zero, tvb, offset + 6, 2, ENC_BIG_ENDIAN);
}
proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_magic, tvb, offset + 8, 5, ENC_NA);
proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_proto, tvb, offset + 13, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(tcpencap_unknown_tree, hf_tcpencap_magic2, tvb, offset + 14, 2, ENC_NA);
}
/* Create the tvbuffer for the next dissector */
next_tvb = tvb_new_subset_length_caplen(tvb, 0, reported_length - TRAILERLENGTH , -1);
if (protocol == TCP_ENCAP_P_UDP) {
call_dissector(udp_handle, next_tvb, pinfo, tree);
} else { /* Hopefully ESP */
call_dissector(esp_handle, next_tvb, pinfo, tree);
}
return tvb_captured_length(tvb);
}
static gboolean
dissect_tcpencap_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{
guint32 reported_length = tvb_reported_length(tvb);
guint32 captured_length = tvb_captured_length(tvb);
if (reported_length <= TRAILERLENGTH + 8 ||
/* Ensure we have enough bytes for packet_is_tcpencap analysis */
(reported_length - captured_length) > (TRAILERLENGTH - 13) ||
!packet_is_tcpencap(tvb, pinfo, reported_length - TRAILERLENGTH) ) {
return FALSE;
}
dissect_tcpencap(tvb, pinfo, tree, data);
return TRUE;
}
void
proto_register_tcpencap(void)
{
static hf_register_info hf[] = {
{ &hf_tcpencap_unknown,
{ "Unknown trailer", "tcpencap.unknown", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
{ &hf_tcpencap_zero,
{ "All zero", "tcpencap.zero", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
{ &hf_tcpencap_seq,
{ "Sequence number", "tcpencap.seq", FT_UINT16, BASE_HEX, NULL,
0x0, NULL, HFILL }},
{ &hf_tcpencap_esp_zero,
{ "ESP zero", "tcpencap.espzero", FT_UINT16, BASE_HEX, NULL,
0x0, NULL, HFILL }},
{ &hf_tcpencap_ike_direction,
{ "ISAKMP traffic direction", "tcpencap.ikedirection", FT_UINT16, BASE_HEX, VALS(tcpencap_ikedir_vals),
0x0, NULL, HFILL }},
{ &hf_tcpencap_magic,
{ "Magic number", "tcpencap.magic", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
{ &hf_tcpencap_proto,
{ "Protocol", "tcpencap.proto", FT_UINT8, BASE_HEX, VALS(tcpencap_proto_vals),
0x0, NULL, HFILL }},
{ &hf_tcpencap_magic2,
{ "Magic 2", "tcpencap.magic2", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
};
static gint *ett[] = {
&ett_tcpencap,
&ett_tcpencap_unknown,
};
proto_tcpencap = proto_register_protocol("TCP Encapsulation of IPsec Packets", "TCPENCAP", "tcpencap");
proto_register_field_array(proto_tcpencap, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
tcpencap_handle = register_dissector("tcpencap", dissect_tcpencap, proto_tcpencap);
}
void
proto_reg_handoff_tcpencap(void)
{
esp_handle = find_dissector_add_dependency("esp", proto_tcpencap);
udp_handle = find_dissector_add_dependency("udp", proto_tcpencap);
heur_dissector_add("tcp", dissect_tcpencap_heur, "TCP Encapsulation of IPsec Packets", "ipsec_tcp", proto_tcpencap, HEURISTIC_ENABLE);
/* Register TCP port for dissection */
dissector_add_for_decode_as_with_preference("tcp.port", tcpencap_handle);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 8
* tab-width: 8
* indent-tabs-mode: t
* End:
*
* vi: set shiftwidth=8 tabstop=8 noexpandtab:
* :indentSize=8:tabSize=8:noTabs=false:
*/
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