nexmon – Rev 1
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/*
* packet-mcpe.c
*
* Routines for Minecraft Pocket Edition protocol packet disassembly.
*
* Nick Carter <ncarter100@gmail.com>
* Copyright 2014 Nick Carter
*
* Using info found at:
* http://wiki.vg/Pocket_Minecraft_Protocol#Packet_Encapsulation
*
* 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.
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/prefs.h>
#define MCPE_UDP_PORT_DEFAULT 19132
static guint mcpe_udp_port_requested = MCPE_UDP_PORT_DEFAULT;
static int proto_mcpe = -1;
static gint ett_mcpe = -1; /* Should this node be expanded */
/*
* First byte gives us the packet id
*/
static int hf_mcpe_packet_id = -1;
/*
* Custom payload encoding header.
*/
static int hf_mcpe_payload_encoding = -1;
static int hf_mcpe_general_packet_number = -1;
static int hf_mcpe_general_packet_payload = -1;
static int hf_mcpe_general_packet_payload_length = -1;
static int hf_mcpe_general_packet_payload_count = -1;
/*
* Fields specific to a packet id type.
*/
static int hf_mcpe_0xC0_unknown = -1;
static int hf_mcpe_0xC0_single_packet = -1;
/*
* Forward declarations.
*/
void proto_register_mcpe(void);
void proto_reg_handoff_mcpe(void);
static void
mcpe_dissect_detail_0xA0(tvbuff_t *tvb, proto_tree *raknet_tree, gint offset)
{
gboolean single_packet;
gint item_size;
item_size = 2;
proto_tree_add_item(raknet_tree, hf_mcpe_0xC0_unknown, tvb, offset,
item_size, ENC_BIG_ENDIAN);
offset += item_size;
single_packet = (tvb_get_guint8(tvb, offset) != 0);
item_size = 1;
proto_tree_add_item(raknet_tree, hf_mcpe_0xC0_single_packet, tvb, offset,
item_size, ENC_BIG_ENDIAN);
offset += item_size;
item_size = 3;
proto_tree_add_item(raknet_tree, hf_mcpe_general_packet_number, tvb, offset,
item_size, ENC_BIG_ENDIAN);
offset += item_size;
if (!single_packet) {
item_size = 3;
proto_tree_add_item(raknet_tree, hf_mcpe_general_packet_number, tvb,
offset, item_size, ENC_BIG_ENDIAN);
/*offset += item_size;*/
}
}
/*
* offset is updated for use by the caller.
*/
static void
mcpe_dissect_detail_payload_0x00(tvbuff_t *tvb, proto_tree *mcpe_tree,
gint *offset)
{
gint item_size;
item_size = 2;
proto_tree_add_item(mcpe_tree, hf_mcpe_general_packet_payload_length, tvb,
*offset, item_size, ENC_BIG_ENDIAN);
*offset += item_size;
}
/*
* offset is updated for use by the caller.
*/
static void
mcpe_dissect_detail_payload_0x40(tvbuff_t *tvb, proto_tree *mcpe_tree,
gint *offset)
{
gint item_size;
item_size = 2;
proto_tree_add_item(mcpe_tree, hf_mcpe_general_packet_payload_length, tvb,
*offset, item_size, ENC_BIG_ENDIAN);
*offset += item_size;
item_size = 3;
proto_tree_add_item(mcpe_tree, hf_mcpe_general_packet_payload_count, tvb,
*offset, item_size, ENC_BIG_ENDIAN);
*offset += item_size;
}
static void
mcpe_dissect_detail_payload(tvbuff_t *tvb, proto_tree *mcpe_tree, gint offset)
{
gint payload_encoding;
gint item_size;
item_size = 3;
proto_tree_add_item(mcpe_tree, hf_mcpe_general_packet_number, tvb, offset,
item_size, ENC_BIG_ENDIAN);
offset += item_size;
payload_encoding = tvb_get_guint8(tvb, offset);
item_size = 1;
proto_tree_add_item(mcpe_tree, hf_mcpe_payload_encoding, tvb, offset,
item_size, ENC_BIG_ENDIAN);
offset += item_size;
switch (payload_encoding) {
case 0x00:
mcpe_dissect_detail_payload_0x00(tvb, mcpe_tree, &offset);
break;
case 0x40:
case 0x50:
case 0x60:
/*
* 0x50 and 0x60 contain extra fields before the payload. These fields
* are currently unknown, so just use 0x40 for a correct partial
* dissection.
*/
mcpe_dissect_detail_payload_0x40(tvb, mcpe_tree, &offset);
break;
default:
break;
}
item_size = -1; /* Read to end of buffer */
proto_tree_add_item(mcpe_tree, hf_mcpe_general_packet_payload, tvb, offset,
item_size, ENC_NA);
}
/*
* Common MCPE packet data
*/
static proto_tree *
mcpe_info(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gint *offset)
{
const char *packet_desc;
guint8 packet_id;
proto_tree *sub_tree;
proto_item *ti;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "MCPE");
col_clear(pinfo->cinfo, COL_INFO);
/*
* Take buffer start 0 to end -1 as single mcpe item.
*/
ti = proto_tree_add_item(tree, proto_mcpe, tvb, 0, -1, ENC_NA);
sub_tree = proto_item_add_subtree(ti, ett_mcpe);
packet_id = tvb_get_guint8(tvb, *offset);
proto_tree_add_item(sub_tree, hf_mcpe_packet_id, tvb, *offset,
1, ENC_BIG_ENDIAN);
*offset += 1;
switch (packet_id) {
case 0xA0:
packet_desc = " (NACK)";
break;
case 0xC0:
packet_desc = " (ACK)";
break;
default:
packet_desc = "";
break;
}
col_add_fstr(pinfo->cinfo, COL_INFO, "Type %#x%s", packet_id, packet_desc);
proto_item_append_text(ti, ", Packet id %#x", packet_id);
return sub_tree;
}
static int
mcpe_dissect(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
void *data _U_)
{
proto_tree *sub_tree;
gint offset;
offset = 0;
sub_tree = mcpe_info(tvb, pinfo, tree, &offset);
if (sub_tree != NULL) {
mcpe_dissect_detail_payload(tvb, sub_tree, offset);
}
return tvb_reported_length(tvb);
}
static int
mcpe_dissect_0xA0(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
void *data _U_)
{
proto_tree *sub_tree;
gint offset;
offset = 0;
sub_tree = mcpe_info(tvb, pinfo, tree, &offset);
if (sub_tree != NULL) {
mcpe_dissect_detail_0xA0(tvb, sub_tree, offset);
}
return tvb_reported_length(tvb);
}
static int
mcpe_dissect_0xC0(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
void *data _U_)
{
proto_tree *sub_tree;
gint offset;
offset = 0;
sub_tree = mcpe_info(tvb, pinfo, tree, &offset);
if (sub_tree != NULL) {
mcpe_dissect_detail_0xA0(tvb, sub_tree, offset); /* 0xA0 */
}
return tvb_reported_length(tvb);
}
void
proto_register_mcpe(void)
{
/*
* Arrays for detailed dissection, controls output formatting.
*/
static hf_register_info hf[] = {
{ &hf_mcpe_packet_id,
{ "MCPE Packet ID", "mcpe.type",
FT_UINT8, BASE_HEX,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_mcpe_payload_encoding,
{ "MCPE Payload encoding", "mcpe.payload_encoding",
FT_UINT8, BASE_HEX,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_mcpe_general_packet_number,
{ "MCPE Packet number", "mcpe.packet_number",
FT_UINT24, BASE_DEC,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_mcpe_general_packet_payload,
{ "MCPE Packet Payload", "mcpe.packet_payload",
FT_BYTES, BASE_NONE,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_mcpe_general_packet_payload_length,
{ "MCPE Payload length in *bits*", "mcpe.payload_length_bits",
FT_UINT16, BASE_DEC,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_mcpe_general_packet_payload_count,
{ "MCPE Packet payload count", "mcpe.payload_count",
FT_UINT24, BASE_DEC,
NULL, 0x0,
NULL, HFILL }
},
/*
* Packet ID 0xC0
*/
{ &hf_mcpe_0xC0_unknown,
{ "MCPE Unknown field", "mcpe.unknown",
FT_UINT8, BASE_DEC,
NULL, 0x0,
NULL, HFILL }
},
{ &hf_mcpe_0xC0_single_packet,
{ "MCPE single packet (boolean)", "mcpe.single_packet",
FT_UINT8, BASE_DEC,
NULL, 0x0,
NULL, HFILL }
}
};
/*
* Setup protocol subtree array
*/
static gint *ett[] = {
&ett_mcpe,
};
module_t *mcpe_module;
/*
* Register the protocol with wireshark.
*/
proto_mcpe = proto_register_protocol (
"Minecraft Pocket Edition", /* name */
"MCPE", /* short name */
"mcpe" /* abbrev */
);
/*
* Register detailed dissection arrays.
*/
proto_register_field_array(proto_mcpe, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
/* Register a configuration option for UDP port */
mcpe_module = prefs_register_protocol(proto_mcpe,
proto_reg_handoff_mcpe);
prefs_register_uint_preference(mcpe_module, "udp.port",
"MCPE Server UDP Port",
"Set the UDP port for the MCPE Server",
10, &mcpe_udp_port_requested);
}
void
proto_reg_handoff_mcpe(void)
{
static dissector_handle_t raknet_dissector = NULL;
static guint last_server_port;
static gboolean init_done = FALSE;
if (init_done) {
/*
* Just delete the dissector before the new add.
*/
dissector_delete_uint("udp.port", last_server_port, raknet_dissector);
} else {
/*
* First time, create dissector handle, and find raknet dissector.
*/
dissector_handle_t mcpe_gen_handle;
init_done = TRUE;
raknet_dissector = find_dissector("raknet");
mcpe_gen_handle = create_dissector_handle(mcpe_dissect, proto_mcpe);
dissector_add_uint("raknet.packet_id", 0x80, mcpe_gen_handle);
dissector_add_uint("raknet.packet_id", 0x84, mcpe_gen_handle);
dissector_add_uint("raknet.packet_id", 0x88, mcpe_gen_handle);
dissector_add_uint("raknet.packet_id", 0x8C, mcpe_gen_handle);
dissector_add_uint("raknet.packet_id", 0xA0,
create_dissector_handle(mcpe_dissect_0xA0,
proto_mcpe));
dissector_add_uint("raknet.packet_id", 0xC0,
create_dissector_handle(mcpe_dissect_0xC0,
proto_mcpe));
}
last_server_port = mcpe_udp_port_requested;
/* MCPE is the protocol that carries RakNet packets over UDP */
dissector_add_uint("udp.port", mcpe_udp_port_requested, raknet_dissector);
}
/*
* Editor modelines - http://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 4
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=4 tabstop=8 expandtab:
* :indentSize=4:tabSize=8:noTabs=true:
*/