epan/dissectors/packet-dtcp-ip.c

   1 /* packet-dtcp-ip.c
   2  * Routines for DTCP-IP dissection
   3  *  (Digital Transmission Content Protection over IP)
   4  *
   5  * Copyright 2012, Martin Kaiser <martin@kaiser.cx>
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998 Gerald Combs
  10  *
  11  * SPDX-License-Identifier: GPL-2.0-or-later
  12  */
  13
  14 /*
  15  * quote from www.dtcp.com:
  16  * "DTCP is a method of protecting audio and audiovisual entertainment
  17  *  content on home and personal networks over highbandwidth bidirectional
  18  *  digital interfaces"
  19  *
  20  * this dissector supports DTCP on top of TCP/IP
  21  * for now, only the AKE (authentication and key exchange)
  22  *  messages are implemented
  23  *
  24  * the dissector is based on the publicly available (informative) specifications
  25  * obtained from http://www.dtcp.com/specifications.aspx
  26  * (complete specifications are available only to licensees)
  27  */
  28
  29 #include "config.h"
  30
  31 #include <epan/packet.h>
  32
  33 static int proto_dtcp_ip;
  34
  35 void proto_register_dtcp_ip(void);
  36 void proto_reg_handoff_dtcp_ip(void);
  37
  38 static dissector_handle_t dtcp_ip_handle;
  39
  40 static int ett_dtcp_ip;
  41 static int ett_dtcp_ip_ctrl;
  42 static int ett_dtcp_ip_ake_procedure;
  43
  44 static int hf_dtcp_ip_type;
  45 static int hf_dtcp_ip_length;
  46 static int hf_dtcp_ip_ctype;
  47 static int hf_dtcp_ip_category;
  48 static int hf_dtcp_ip_ake_id;
  49 static int hf_dtcp_ip_subfct;
  50 static int hf_dtcp_ip_ake_procedure;
  51 static int hf_dtcp_ip_ake_proc_full;
  52 static int hf_dtcp_ip_ake_proc_ex_full;
  53 static int hf_dtcp_ip_ake_xchg_key;
  54 static int hf_dtcp_ip_subfct_dep;
  55 static int hf_dtcp_ip_ake_label;
  56 static int hf_dtcp_ip_number;
  57 static int hf_dtcp_ip_status;
  58 static int hf_dtcp_ip_ake_info;
  59
  60 #define CTRL_LEN 8 /* control block is 8 bytes long */
  61
  62 /* these definitions are taken from the public DTCP specification
  63    it sounds like the private version defines more subfunctions */
  64 static const value_string subfct[] = {
  65     { 0x01, "challenge" },
  66     { 0x02, "response" },
  67     { 0x03, "exchange_key" },
  68     { 0, NULL }
  69 };
  70
  71 static int * const ake_procedure_fields[] = {
  72     &hf_dtcp_ip_ake_proc_full,
  73     &hf_dtcp_ip_ake_proc_ex_full,
  74     NULL
  75 };
  76
  77 /* only one bit may be set in exchange_key, we can use a value string */
  78 static const value_string xchg_key[] = {
  79     { 0x00, "None" },
  80     { 0x08, "Exchange key (K_X) for AES-128" },
  81     { 0x20, "Session Exchange key (K_S) for AES-128" },
  82     { 0x40, "Remote Exchange key (K_R) for AES-128" },
  83     { 0, NULL }
  84 };
  85
  86 static const value_string ctrl_status[] = {
  87     { 0x0, "No error" },
  88     { 0x1, "Support for no more authentication procedures is currently available" },
  89     { 0x7, "Any other error" },
  90     { 0xF, "No information" },
  91     { 0, NULL }
  92 };
  93
  94
  95 /* check if the packet is actually DTCP-IP */
  96 static bool
  97 dtcp_ip_check_packet(tvbuff_t *tvb)
  98 {
  99     unsigned  offset = 0;
 100     uint8_t  type;
 101     uint16_t length;
 102
 103     /* a minimum DTCP-IP AKE packet has Type (1 byte),
 104        Length (2 bytes) and Control (8 bytes) */
 105     if (tvb_reported_length(tvb) < 1+2+CTRL_LEN)
 106         return false;
 107
 108     type = tvb_get_uint8(tvb, offset);
 109     /* all DTCP-IP AKE packets have type 1 */
 110     if (type != 1)
 111         return false;
 112     offset++;
 113
 114     /* length field is length of the control block +
 115        length of ake_info */
 116     length = tvb_get_ntohs(tvb, offset);
 117     if (length < CTRL_LEN)
 118         return false;
 119
 120     return true;
 121 }
 122
 123 static int
 124 dissect_dtcp_ip(tvbuff_t *tvb, packet_info *pinfo,
 125         proto_tree *tree, void *data _U_)
 126 {
 127     unsigned     offset = 0;
 128     uint16_t     length;
 129     proto_item  *pi;
 130     proto_tree  *dtcp_ip_tree, *dtcp_ip_ctrl_tree;
 131     uint8_t      subfct_val;
 132     const char *subfct_str;
 133     int          ake_info_len;
 134
 135
 136     if (!dtcp_ip_check_packet(tvb))
 137         return 0; /* not a DTCP-IP packet */
 138
 139     col_set_str(pinfo->cinfo, COL_PROTOCOL, "DTCP-IP");
 140     col_clear(pinfo->cinfo, COL_INFO);
 141
 142     pi = proto_tree_add_protocol_format(tree, proto_dtcp_ip,
 143                 tvb, 0, -1, "DTCP-IP");
 144     dtcp_ip_tree = proto_item_add_subtree(pi, ett_dtcp_ip);
 145
 146     proto_tree_add_item(dtcp_ip_tree, hf_dtcp_ip_type,
 147         tvb, offset, 1, ENC_BIG_ENDIAN);
 148     offset++;
 149
 150     length = tvb_get_ntohs(tvb, 1);
 151     /* overall packet length is 1 byte for tag + 2 bytes for length field +
 152        the value encoded in the length field */
 153     proto_item_set_len(pi, 1+2+length);
 154     proto_tree_add_item(dtcp_ip_tree, hf_dtcp_ip_length,
 155         tvb, offset, 2, ENC_BIG_ENDIAN);
 156     offset += 2;
 157
 158     dtcp_ip_ctrl_tree = proto_tree_add_subtree(dtcp_ip_tree,
 159             tvb, offset, CTRL_LEN, ett_dtcp_ip_ctrl, NULL, "Control");
 160
 161     /* for now, we don't display the 4 reserved bits */
 162     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_ctype,
 163             tvb, offset, 1, ENC_BIG_ENDIAN);
 164     offset++;
 165
 166     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_category,
 167             tvb, offset, 1, ENC_BIG_ENDIAN);
 168     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_ake_id,
 169             tvb, offset, 1, ENC_BIG_ENDIAN);
 170     offset++;
 171
 172     subfct_val = tvb_get_uint8(tvb, offset);
 173     subfct_str = val_to_str_const(subfct_val, subfct, "unknown");
 174     col_append_sep_fstr(pinfo->cinfo, COL_INFO, NULL,
 175             "%s (0x%x)", subfct_str, subfct_val);
 176     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_subfct,
 177             tvb, offset, 1, ENC_BIG_ENDIAN);
 178     offset++;
 179
 180     proto_tree_add_bitmask(dtcp_ip_ctrl_tree, tvb, offset,
 181             hf_dtcp_ip_ake_procedure, ett_dtcp_ip_ake_procedure,
 182             ake_procedure_fields, ENC_BIG_ENDIAN);
 183     offset++;
 184
 185     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_ake_xchg_key,
 186             tvb, offset, 1, ENC_BIG_ENDIAN);
 187     offset++;
 188
 189     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_subfct_dep,
 190             tvb, offset, 1, ENC_BIG_ENDIAN);
 191     offset++;
 192
 193     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_ake_label,
 194             tvb, offset, 1, ENC_BIG_ENDIAN);
 195     offset++;
 196
 197     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_number,
 198             tvb, offset, 1, ENC_BIG_ENDIAN);
 199     proto_tree_add_item(dtcp_ip_ctrl_tree, hf_dtcp_ip_status,
 200             tvb, offset, 1, ENC_BIG_ENDIAN);
 201     offset++;
 202
 203     ake_info_len = length-CTRL_LEN;
 204     if (ake_info_len > 0) {
 205         proto_tree_add_item(dtcp_ip_tree, hf_dtcp_ip_ake_info,
 206                 tvb, offset, ake_info_len, ENC_NA);
 207         offset += (unsigned)ake_info_len;
 208     }
 209
 210     return offset;
 211 }
 212
 213
 214 void
 215 proto_register_dtcp_ip(void)
 216 {
 217     static hf_register_info hf[] = {
 218         { &hf_dtcp_ip_type,
 219             { "Type", "dtcp-ip.type", FT_UINT8, BASE_HEX,
 220                 NULL, 0, NULL, HFILL } },
 221         { &hf_dtcp_ip_length,
 222             { "Length", "dtcp-ip.length", FT_UINT16, BASE_DEC,
 223                 NULL, 0, NULL, HFILL } },
 224         /* it seems that / is not allowed in a filter name ... */
 225         { &hf_dtcp_ip_ctype,
 226             { "ctype/response", "dtcp-ip.ctrl.ctype_response", FT_UINT8,
 227                 BASE_HEX, NULL, 0x0F, NULL, HFILL } },
 228         { &hf_dtcp_ip_category,
 229             { "Category", "dtcp-ip.ctrl.category", FT_UINT8, BASE_HEX,
 230                 NULL, 0xF0, NULL, HFILL } },
 231         { &hf_dtcp_ip_ake_id,
 232             { "AKE_ID", "dtcp-ip.ctrl.ake_id", FT_UINT8, BASE_HEX,
 233                 NULL, 0x0F, NULL, HFILL } },
 234         { &hf_dtcp_ip_subfct,
 235             { "Subfunction", "dtcp-ip.ctrl.subfunction", FT_UINT8, BASE_HEX,
 236                 VALS(subfct), 0, NULL, HFILL } },
 237         { &hf_dtcp_ip_ake_procedure,
 238             { "AKE_procedure", "dtcp-ip.ctrl.ake_procedure", FT_UINT8,
 239                 BASE_HEX, NULL, 0, NULL, HFILL } },
 240         /* 8 is the bit witdh of the field */
 241         { &hf_dtcp_ip_ake_proc_full,
 242             { "Full Authentication procedure",
 243                 "dtcp-ip.ctrl.ake_procedure.full_auth", FT_BOOLEAN, 8,
 244                 NULL, 0x04, NULL, HFILL } },
 245         { &hf_dtcp_ip_ake_proc_ex_full,
 246             { "Extended Full Authentication procedure",
 247                 "dtcp-ip.ctrl.ake_procedure.ex_full_auth", FT_BOOLEAN, 8,
 248                 NULL, 0x08, NULL, HFILL } },
 249         { &hf_dtcp_ip_ake_xchg_key,
 250             { "exchange_key", "dtcp-ip.ctrl.exchange_key", FT_UINT8, BASE_HEX,
 251                 VALS(xchg_key), 0, NULL, HFILL } },
 252         { &hf_dtcp_ip_subfct_dep,
 253             { "subfunction_dependent", "dtcp-ip.ctrl.subfunction_dependent",
 254                 FT_UINT8, BASE_HEX, NULL, 0, NULL, HFILL } },
 255         { &hf_dtcp_ip_ake_label,
 256             { "AKE_label", "dtcp-ip.ctrl.ake_label", FT_UINT8, BASE_HEX,
 257                 NULL, 0, NULL, HFILL } },
 258         { &hf_dtcp_ip_number,
 259             { "number", "dtcp-ip.ctrl.number", FT_UINT8, BASE_HEX,
 260                 NULL, 0xF0, NULL, HFILL } },
 261         { &hf_dtcp_ip_status,
 262             { "Status", "dtcp-ip.ctrl.status", FT_UINT8, BASE_HEX,
 263                 VALS(ctrl_status), 0x0F, NULL, HFILL } },
 264         { &hf_dtcp_ip_ake_info,
 265             { "AKE_Info", "dtcp-ip.ake_info", FT_BYTES, BASE_NONE,
 266                 NULL, 0, NULL, HFILL } }
 267     };
 268
 269     static int *ett[] = {
 270         &ett_dtcp_ip,
 271         &ett_dtcp_ip_ctrl,
 272         &ett_dtcp_ip_ake_procedure
 273     };
 274
 275     proto_dtcp_ip = proto_register_protocol("Digital Transmission Content Protection over IP", "DTCP-IP", "dtcp-ip");
 276
 277     proto_register_field_array(proto_dtcp_ip, hf, array_length(hf));
 278     proto_register_subtree_array(ett, array_length(ett));
 279
 280     dtcp_ip_handle = register_dissector("dtcp-ip", dissect_dtcp_ip, proto_dtcp_ip);
 281 }
 282
 283 void
 284 proto_reg_handoff_dtcp_ip(void)
 285 {
 286     dissector_add_for_decode_as_with_preference("tcp.port", dtcp_ip_handle);
 287 }
 288
 289 /*
 290  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 291  *
 292  * Local variables:
 293  * c-basic-offset: 4
 294  * tab-width: 8
 295  * indent-tabs-mode: nil
 296  * End:
 297  *
 298  * vi: set shiftwidth=4 tabstop=8 expandtab:
 299  * :indentSize=4:tabSize=8:noTabs=true:
 300  */