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/* packet-dtcp-ip.c
* Routines for DTCP-IP dissection
* (Digital Transmission Content Protection over IP)
*
* Copyright 2012, Martin Kaiser <martin@kaiser.cx>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
/*
* quote from www.dtcp.com:
* "DTCP is a method of protecting audio and audiovisual entertainment
* content on home and personal networks over highbandwidth bidirectional
* digital interfaces"
*
* this dissector supports DTCP on top of TCP/IP
* for now, only the AKE (authentication and key exchange)
* messages are implemented
*
* the dissector is based on the publicly available (informative) specifications
* obtained from http://www.dtcp.com/specifications.aspx
* (complete specifications are available only to licensees)
*/
#include "config.h"
#include <epan/packet.h>
static int proto_dtcp_ip = -1;
void proto_register_dtcp_ip(void);
void proto_reg_handoff_dtcp_ip(void);
static dissector_handle_t dtcp_ip_handle;
static gint ett_dtcp_ip = -1;
static gint ett_dtcp_ip_ctrl = -1;
static gint ett_dtcp_ip_ake_procedure = -1;
static int hf_dtcp_ip_type = -1;
static int hf_dtcp_ip_length = -1;
static int hf_dtcp_ip_ctype = -1;
static int hf_dtcp_ip_category = -1;
static int hf_dtcp_ip_ake_id = -1;
static int hf_dtcp_ip_subfct = -1;
static int hf_dtcp_ip_ake_procedure = -1;
static int hf_dtcp_ip_ake_proc_full = -1;
static int hf_dtcp_ip_ake_proc_ex_full = -1;
static int hf_dtcp_ip_ake_xchg_key = -1;
static int hf_dtcp_ip_subfct_dep = -1;
static int hf_dtcp_ip_ake_label = -1;
static int hf_dtcp_ip_number = -1;
static int hf_dtcp_ip_status = -1;
static int hf_dtcp_ip_ake_info = -1;
#define CTRL_LEN 8 /* control block is 8 bytes long */
/* these definitions are taken from the public DTCP specification
it sounds like the private version defines more subfunctions */
static const value_string subfct[] = {
{ 0x01, "challenge" },
{ 0x02, "response" },
{ 0x03, "exchange_key" },
{ 0, NULL }
};
static int * const ake_procedure_fields[] = { /* must be int, not gint */
&hf_dtcp_ip_ake_proc_full,
&hf_dtcp_ip_ake_proc_ex_full,
NULL
};
/* only one bit may be set in exchange_key, we can use a value string */
static const value_string xchg_key[] = {
{ 0x00, "None" },
{ 0x08, "Exchange key (K_X) for AES-128" },
{ 0x20, "Session Exchange key (K_S) for AES-128" },
{ 0x40, "Remote Exchange key (K_R) for AES-128" },
{ 0, NULL }
};
static const value_string ctrl_status[] = {
{ 0x0, "No error" },
{ 0x1, "Support for no more authentication procedures is currently available" },
{ 0x7, "Any other error" },
{ 0xF, "No information" },
{ 0, NULL }
};
/* check if the packet is actually DTCP-IP */
static gboolean
dtcp_ip_check_packet(tvbuff_t *tvb)
{
guint offset = 0;
guint8 type;
guint16 length;
/* a minimum DTCP-IP AKE packet has Type (1 byte),
Length (2 bytes) and Control (8 bytes) */
if (tvb_reported_length(tvb) < 1+2+CTRL_LEN)
return FALSE;
type = tvb_get_guint8(tvb, offset);
/* all DTCP-IP AKE packets have type 1 */
if (type != 1)
return FALSE;
offset++;
/* length field is length of the control block +
length of ake_info */
length = tvb_get_ntohs(tvb, offset);
if (length < CTRL_LEN)
return FALSE;
return TRUE;
}
static int
dissect_dtcp_ip(tvbuff_t *tvb, packet_info *pinfo,
proto_tree *tree, void *data _U_)
{
guint offset = 0;
guint16 length;
proto_item *pi;
proto_tree *dtcp_ip_tree, *dtcp_ip_ctrl_tree;
guint8 subfct_val;
const gchar *subfct_str;
gint ake_info_len;
if (!dtcp_ip_check_packet(tvb))
return 0; /* not a DTCP-IP packet */
col_set_str(pinfo->cinfo, COL_PROTOCOL, "DTCP-IP");
col_clear(pinfo->cinfo, COL_INFO);
pi = proto_tree_add_protocol_format(tree, proto_dtcp_ip,
tvb, 0, -1, "DTCP-IP");
dtcp_ip_tree = proto_item_add_subtree(pi, ett_dtcp_ip);
proto_tree_add_item(dtcp_ip_tree, hf_dtcp_ip_type,
tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
length = tvb_get_ntohs(tvb, 1);
/* overall packet length is 1 byte for tag + 2 bytes for length field +
the value encoded in the length field */
proto_item_set_len(pi, 1+2+length);
proto_tree_add_item(dtcp_ip_tree, hf_dtcp_ip_length,
tvb, offset, 2, ENC_BIG_ENDIAN);
offset += 2;
dtcp_ip_ctrl_tree = proto_tree_add_subtree(dtcp_ip_tree,
tvb, offset, CTRL_LEN, ett_dtcp_ip_ctrl, NULL, "Control");
/* for now, we don't display the 4 reserved bits */
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_ctype,
tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_category,
tvb, offset, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_ake_id,
tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
subfct_val = tvb_get_guint8(tvb, offset);
subfct_str = val_to_str_const(subfct_val, subfct, "unknown");
col_append_sep_fstr(pinfo->cinfo, COL_INFO, NULL,
"%s (0x%x)", subfct_str, subfct_val);
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_subfct,
tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
proto_tree_add_bitmask(dtcp_ip_ctrl_tree, tvb, offset,
hf_dtcp_ip_ake_procedure, ett_dtcp_ip_ake_procedure,
ake_procedure_fields, ENC_BIG_ENDIAN);
offset++;
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_ake_xchg_key,
tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_subfct_dep,
tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_ake_label,
tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_number,
tvb, offset, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_status,
tvb, offset, 1, ENC_BIG_ENDIAN);
offset++;
ake_info_len = length-CTRL_LEN;
if (ake_info_len > 0) {
proto_tree_add_item(dtcp_ip_tree, hf_dtcp_ip_ake_info,
tvb, offset, ake_info_len, ENC_NA);
offset += (guint)ake_info_len;
}
return offset;
}
void
proto_register_dtcp_ip(void)
{
static hf_register_info hf[] = {
{ &hf_dtcp_ip_type,
{ "Type", "dtcp-ip.type", FT_UINT8, BASE_HEX,
NULL, 0, NULL, HFILL } },
{ &hf_dtcp_ip_length,
{ "Length", "dtcp-ip.length", FT_UINT16, BASE_DEC,
NULL, 0, NULL, HFILL } },
/* it seems that / is not allowed in a filter name ... */
{ &hf_dtcp_ip_ctype,
{ "ctype/response", "dtcp-ip.ctrl.ctype_response", FT_UINT8,
BASE_HEX, NULL, 0x0F, NULL, HFILL } },
{ &hf_dtcp_ip_category,
{ "Category", "dtcp-ip.ctrl.category", FT_UINT8, BASE_HEX,
NULL, 0xF0, NULL, HFILL } },
{ &hf_dtcp_ip_ake_id,
{ "AKE_ID", "dtcp-ip.ctrl.ake_id", FT_UINT8, BASE_HEX,
NULL, 0x0F, NULL, HFILL } },
{ &hf_dtcp_ip_subfct,
{ "Subfunction", "dtcp-ip.ctrl.subfunction", FT_UINT8, BASE_HEX,
VALS(subfct), 0, NULL, HFILL } },
{ &hf_dtcp_ip_ake_procedure,
{ "AKE_procedure", "dtcp-ip.ctrl.ake_procedure", FT_UINT8,
BASE_HEX, NULL, 0, NULL, HFILL } },
/* 8 is the bit witdh of the field */
{ &hf_dtcp_ip_ake_proc_full,
{ "Full Authentication procedure",
"dtcp-ip.ctrl.ake_procedure.full_auth", FT_BOOLEAN, 8,
NULL, 0x04, NULL, HFILL } },
{ &hf_dtcp_ip_ake_proc_ex_full,
{ "Extended Full Authentication procedure",
"dtcp-ip.ctrl.ake_procedure.ex_full_auth", FT_BOOLEAN, 8,
NULL, 0x08, NULL, HFILL } },
{ &hf_dtcp_ip_ake_xchg_key,
{ "exchange_key", "dtcp-ip.ctrl.exchange_key", FT_UINT8, BASE_HEX,
VALS(xchg_key), 0, NULL, HFILL } },
{ &hf_dtcp_ip_subfct_dep,
{ "subfunction_dependent", "dtcp-ip.ctrl.subfunction_dependent",
FT_UINT8, BASE_HEX, NULL, 0, NULL, HFILL } },
{ &hf_dtcp_ip_ake_label,
{ "AKE_label", "dtcp-ip.ctrl.ake_label", FT_UINT8, BASE_HEX,
NULL, 0, NULL, HFILL } },
{ &hf_dtcp_ip_number,
{ "number", "dtcp-ip.ctrl.number", FT_UINT8, BASE_HEX,
NULL, 0xF0, NULL, HFILL } },
{ &hf_dtcp_ip_status,
{ "Status", "dtcp-ip.ctrl.status", FT_UINT8, BASE_HEX,
VALS(ctrl_status), 0x0F, NULL, HFILL } },
{ &hf_dtcp_ip_ake_info,
{ "AKE_Info", "dtcp-ip.ake_info", FT_BYTES, BASE_NONE,
NULL, 0, NULL, HFILL } }
};
static gint *ett[] = {
&ett_dtcp_ip,
&ett_dtcp_ip_ctrl,
&ett_dtcp_ip_ake_procedure
};
proto_dtcp_ip = proto_register_protocol("Digital Transmission Content Protection over IP", "DTCP-IP", "dtcp-ip");
proto_register_field_array(proto_dtcp_ip, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
dtcp_ip_handle = register_dissector("dtcp-ip", dissect_dtcp_ip, proto_dtcp_ip);
}
void
proto_reg_handoff_dtcp_ip(void)
{
dissector_add_for_decode_as_with_preference("tcp.port", dtcp_ip_handle);
}
/*
* Editor modelines - https://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:
*/
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