nexmon – Rev 1
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/* packet-skype.c
* Routines for the disassembly of Skype
*
* Copyright 2009 Joerg Mayer (see AUTHORS file)
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/*
* Documentation that formed the basis of the packet decoding:
* https://github.com/matthiasbock/OpenSkype/wiki/Skype's-UDP-Format
* For additional information see: https://wiki.wireshark.org/Skype
*
* TODO:
* - Authentication
* - TCP
* - Conversation stuff (to obtain external IPs for decryption)
* - Decryption (with given keys)
* - Test CRC check (requires working decryption)
* - Heuristics to reliably detect Skype traffic - most likely impossible
* to implement in Wireshark (see http://en.wikipedia.org/wiki/Skype)
* - Improve tests
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/conversation.h>
void proto_register_skype(void);
void proto_reg_handoff_skype(void);
/* Things we may want to remember for a whole conversation */
typedef struct _skype_udp_conv_info_t {
guint32 global_src_ip;
guint32 global_dst_ip;
} skype_udp_conv_info_t;
/* protocol handles */
static int proto_skype = -1;
/* ett handles */
static int ett_skype = -1;
#define SKYPE_SOM_UNK_MASK 0xF0
#define SKYPE_SOM_TYPE_MASK 0x0F
/* hf elements */
/* Start of Message */
static int hf_skype_som_id = -1;
static int hf_skype_som_unk = -1;
static int hf_skype_som_type = -1;
/* Message body */
/* Unknown_0 */
static int hf_skype_unknown_0_unk1 = -1;
/* Payload */
static int hf_skype_payload_iv = -1;
static int hf_skype_payload_crc = -1;
static int hf_skype_payload_enc_data = -1;
/* Resend */
static int hf_skype_ffr_num = -1;
static int hf_skype_ffr_unk1 = -1;
static int hf_skype_ffr_iv = -1;
static int hf_skype_ffr_crc = -1;
static int hf_skype_ffr_enc_data = -1;
/* Nat info */
static int hf_skype_natinfo_srcip = -1;
static int hf_skype_natinfo_dstip = -1;
/* Nat request */
static int hf_skype_natrequest_srcip = -1;
static int hf_skype_natrequest_dstip = -1;
/* Audio */
static int hf_skype_audio_unk1 = -1;
/* Unknown_f */
static int hf_skype_unknown_f_unk1 = -1;
/* Unknown packet type */
static int hf_skype_unknown_packet = -1;
#define PROTO_SHORT_NAME "SKYPE"
#define PROTO_LONG_NAME "SKYPE"
typedef enum {
SKYPE_TYPE_UNKNOWN_0 = 0,
SKYPE_TYPE_PAYLOAD = 2,
SKYPE_TYPE_FFR = 3,
SKYPE_TYPE_NAT_INFO = 5,
SKYPE_TYPE_NAT_REPEAT = 7,
SKYPE_TYPE_AUDIO = 0xd,
SKYPE_TYPE_UNKNOWN_F = 0xf
} skype_type_t;
static const value_string skype_type_vals[] = {
{ SKYPE_TYPE_UNKNOWN_0, "Unknown_0" },
{ SKYPE_TYPE_PAYLOAD, "Payload" },
{ SKYPE_TYPE_FFR, "Fragment/Forward/Resend" },
{ SKYPE_TYPE_NAT_INFO , "NAT info" },
{ SKYPE_TYPE_NAT_REPEAT,"NAT repeat" },
{ SKYPE_TYPE_AUDIO, "Audio" },
{ SKYPE_TYPE_UNKNOWN_F, "Unknown_F" },
{ 0, NULL }
};
static int
dissect_skype_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
proto_item *ti;
proto_tree *skype_tree = NULL;
guint32 offset = 0;
guint32 packet_length;
guint8 packet_type;
/* XXX: Just until we know how to decode skype over tcp */
packet_type = 255;
packet_length = tvb_captured_length(tvb);
col_set_str(pinfo->cinfo, COL_PROTOCOL, PROTO_SHORT_NAME);
col_add_str(pinfo->cinfo, COL_INFO, val_to_str(packet_type,
skype_type_vals, "Type 0x%1x"));
if (tree) {
/* Start of message dissection */
ti = proto_tree_add_item(tree, proto_skype, tvb, offset, -1,
ENC_NA);
skype_tree = proto_item_add_subtree(ti, ett_skype);
/* Body dissection */
switch (packet_type) {
default:
proto_tree_add_item(skype_tree, hf_skype_unknown_packet, tvb, offset, -1,
ENC_NA);
offset = packet_length;
break;
}
}
return offset;
}
static int
dissect_skype_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
proto_item *ti;
proto_tree *skype_tree = NULL;
guint32 offset = 0;
guint32 packet_length;
guint8 packet_type, packet_unk;
conversation_t *conversation = NULL;
skype_udp_conv_info_t *skype_udp_info;
/* look up the conversation */
conversation = find_or_create_conversation(pinfo);
/* if conversation found get the data pointer that you stored */
skype_udp_info = (skype_udp_conv_info_t *)conversation_get_proto_data(conversation, proto_skype);
if (!skype_udp_info) {
/* new conversation create local data structure */
skype_udp_info = wmem_new(wmem_file_scope(), skype_udp_conv_info_t);
skype_udp_info->global_src_ip = 0;
skype_udp_info->global_dst_ip = 0;
conversation_add_proto_data(conversation, proto_skype,
skype_udp_info);
}
/* at this point the conversation data is ready */
packet_type = tvb_get_guint8(tvb, 2) & SKYPE_SOM_TYPE_MASK;
packet_unk = (tvb_get_guint8(tvb, 2) & SKYPE_SOM_UNK_MASK) >> 4;
packet_length = tvb_captured_length(tvb);
col_set_str(pinfo->cinfo, COL_PROTOCOL, PROTO_SHORT_NAME);
col_add_str(pinfo->cinfo, COL_INFO, val_to_str(packet_type,
skype_type_vals, "Type 0x%1x"));
if (packet_unk) {
col_append_fstr(pinfo->cinfo, COL_INFO, " Unk: %1x", packet_unk);
}
if (tree) {
/* Start of message dissection */
ti = proto_tree_add_item(tree, proto_skype, tvb, offset, -1,
ENC_NA);
skype_tree = proto_item_add_subtree(ti, ett_skype);
proto_tree_add_item(skype_tree, hf_skype_som_id, tvb, offset, 2,
ENC_BIG_ENDIAN);
offset += 2;
proto_tree_add_item(skype_tree, hf_skype_som_unk, tvb, offset, 1,
ENC_BIG_ENDIAN);
proto_tree_add_item(skype_tree, hf_skype_som_type, tvb, offset, 1,
ENC_BIG_ENDIAN);
offset += 1;
/* Body dissection */
switch (packet_type) {
case SKYPE_TYPE_UNKNOWN_0:
proto_tree_add_item(skype_tree, hf_skype_unknown_0_unk1, tvb, offset, -1,
ENC_NA);
offset = packet_length;
break;
case SKYPE_TYPE_PAYLOAD:
proto_tree_add_item(skype_tree, hf_skype_payload_iv, tvb, offset, 4,
ENC_BIG_ENDIAN);
offset += 4;
proto_tree_add_item(skype_tree, hf_skype_payload_crc, tvb, offset, 4,
ENC_BIG_ENDIAN);
offset += 4;
proto_tree_add_item(skype_tree, hf_skype_payload_enc_data, tvb, offset, -1,
ENC_NA);
offset = packet_length;
break;
case SKYPE_TYPE_FFR:
proto_tree_add_item(skype_tree, hf_skype_ffr_num, tvb, offset, 1,
ENC_BIG_ENDIAN);
offset += 1;
proto_tree_add_item(skype_tree, hf_skype_ffr_unk1, tvb, offset, 4,
ENC_BIG_ENDIAN);
offset += 4;
proto_tree_add_item(skype_tree, hf_skype_ffr_iv, tvb, offset, 4,
ENC_BIG_ENDIAN);
offset += 4;
proto_tree_add_item(skype_tree, hf_skype_ffr_crc, tvb, offset, 4,
ENC_BIG_ENDIAN);
offset += 4;
proto_tree_add_item(skype_tree, hf_skype_ffr_enc_data, tvb, offset, -1,
ENC_NA);
offset = packet_length;
break;
case SKYPE_TYPE_NAT_INFO:
proto_tree_add_item(skype_tree, hf_skype_natinfo_srcip, tvb, offset, 4,
ENC_BIG_ENDIAN);
skype_udp_info->global_src_ip = tvb_get_ipv4(tvb, offset);
offset += 4;
proto_tree_add_item(skype_tree, hf_skype_natinfo_dstip, tvb, offset, 4,
ENC_BIG_ENDIAN);
skype_udp_info->global_dst_ip = tvb_get_ipv4(tvb, offset);
offset += 4;
break;
case SKYPE_TYPE_NAT_REPEAT:
proto_tree_add_item(skype_tree, hf_skype_natrequest_srcip, tvb, offset, 4,
ENC_BIG_ENDIAN);
skype_udp_info->global_src_ip = tvb_get_ipv4(tvb, offset);
offset += 4;
proto_tree_add_item(skype_tree, hf_skype_natrequest_dstip, tvb, offset, 4,
ENC_BIG_ENDIAN);
skype_udp_info->global_dst_ip = tvb_get_ipv4(tvb, offset);
offset += 4;
break;
case SKYPE_TYPE_AUDIO:
proto_tree_add_item(skype_tree, hf_skype_audio_unk1, tvb, offset, -1,
ENC_NA);
offset = packet_length;
break;
case SKYPE_TYPE_UNKNOWN_F:
proto_tree_add_item(skype_tree, hf_skype_unknown_f_unk1, tvb, offset, -1,
ENC_NA);
offset = packet_length;
break;
default:
proto_tree_add_item(skype_tree, hf_skype_unknown_packet, tvb, offset, -1,
ENC_NA);
offset = packet_length;
break;
}
}
return offset;
}
static gboolean
test_skype_udp(tvbuff_t *tvb)
{
/* Minimum of 3 bytes, check for valid message type */
if (tvb_captured_length(tvb) > 3)
{
guint8 type = tvb_get_guint8(tvb, 2) & 0xF;
if ( type == 0 ||
/* FIXME: Extend this by minimum or exact length per message type */
type == 2 ||
type == 3 ||
type == 5 ||
type == 7 ||
type == 0xd ||
type == 0xf
)
{
return TRUE;
}
}
return FALSE;
}
static gboolean
dissect_skype_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
if ( !test_skype_udp(tvb) ) {
return FALSE;
}
dissect_skype_udp(tvb, pinfo, tree);
return TRUE;
}
static int
dissect_skype_static(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
/*
* Don't test for valid packet - we only end here when
* the user did a decode-as.
*/
if (pinfo->ptype == PT_UDP) {
return dissect_skype_udp(tvb, pinfo, tree);
} else if (pinfo->ptype == PT_TCP) {
return dissect_skype_tcp(tvb, pinfo, tree);
}
return 0;
}
void
proto_register_skype(void)
{
static hf_register_info hf[] = {
/* Start of message fields */
{ &hf_skype_som_id,
{ "ID", "skype.som.id", FT_UINT16, BASE_HEX, NULL,
0x0, "Message ID", HFILL }},
{ &hf_skype_som_unk,
{ "Unknown", "skype.som.unk", FT_UINT8, BASE_HEX, NULL,
SKYPE_SOM_UNK_MASK, NULL, HFILL }},
{ &hf_skype_som_type,
{ "Type", "skype.som.type", FT_UINT8, BASE_HEX, VALS(skype_type_vals),
SKYPE_SOM_TYPE_MASK, "Message type", HFILL }},
/* Message body */
/* Unknown_0 */
{ &hf_skype_unknown_0_unk1,
{ "Unknown1", "skype.unknown_0.unk1", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
/* Payload */
{ &hf_skype_payload_iv,
{ "IV", "skype.payload.iv", FT_UINT32, BASE_HEX, NULL,
0x0, NULL, HFILL }},
{ &hf_skype_payload_crc,
{ "CRC", "skype.payload.crc", FT_UINT32, BASE_HEX, NULL,
0x0, NULL, HFILL }},
{ &hf_skype_payload_enc_data,
{ "Enc Data", "skype.payload.encdata", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
/* Resend */
{ &hf_skype_ffr_num,
{ "Num", "skype.ffr.num", FT_UINT8, BASE_HEX, NULL,
0x0, NULL, HFILL }},
{ &hf_skype_ffr_unk1,
{ "Unk1", "skype.ffr.unk1", FT_UINT32, BASE_HEX, NULL,
0x0, NULL, HFILL }},
{ &hf_skype_ffr_iv,
{ "IV", "skype.ffr.iv", FT_UINT32, BASE_HEX, NULL,
0x0, NULL, HFILL }},
{ &hf_skype_ffr_crc,
{ "CRC", "skype.ffr.crc", FT_UINT32, BASE_HEX, NULL,
0x0, NULL, HFILL }},
{ &hf_skype_ffr_enc_data,
{ "Enc Data", "skype.ffr.encdata", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
/* Nat info */
{ &hf_skype_natinfo_srcip,
{ "Src IP", "skype.natinfo.srcip", FT_IPv4, BASE_NONE, NULL,
0x0, "Global source IP", HFILL }},
{ &hf_skype_natinfo_dstip,
{ "Dst IP", "skype.natinfo.dstip", FT_UINT32, BASE_HEX, NULL,
0x0, "Global destination IP", HFILL }},
/* Nat request */
{ &hf_skype_natrequest_srcip,
{ "Src IP", "skype.natrequest.srcip", FT_IPv4, BASE_NONE, NULL,
0x0, "Global source IP", HFILL }},
{ &hf_skype_natrequest_dstip,
{ "Dst IP", "skype.natrequest.dstip", FT_UINT32, BASE_HEX, NULL,
0x0, NULL, HFILL }},
/* Audio */
{ &hf_skype_audio_unk1,
{ "Unknown1", "skype.audio.unk1", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
/* Unknown_F */
{ &hf_skype_unknown_f_unk1,
{ "Unknown1", "skype.unknown_f.unk1", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
/* Unknown packet */
{ &hf_skype_unknown_packet,
{ "Unknown Packet", "skype.unknown_packet", FT_BYTES, BASE_NONE, NULL,
0x0, NULL, HFILL }},
};
static gint *ett[] = {
&ett_skype,
};
proto_skype = proto_register_protocol(PROTO_LONG_NAME, PROTO_SHORT_NAME, "skype");
proto_register_field_array(proto_skype, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
}
void
proto_reg_handoff_skype(void)
{
dissector_handle_t skype_handle;
skype_handle = create_dissector_handle(dissect_skype_static, proto_skype);
dissector_add_for_decode_as("tcp.port", skype_handle);
dissector_add_for_decode_as("udp.port", skype_handle);
heur_dissector_add("udp", dissect_skype_heur, "Skype over UDP", "skype_udp", proto_skype, HEURISTIC_DISABLE);
}
/*
* Editor modelines - http://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:
*/