/* packet-stcsig.c

 * Routines for dissecting Spirent Test Center Signatures

 * Copyright 2018 Joerg Mayer (see AUTHORS file)

 * Based on disassembly of Spirent's modified version of Wireshark 1.10.3

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

/* The logic is based on the disassembly of libwireshark.dll which was

 * part of wireshark-win64-1.10.3-spirent-2.exe, distributed by Spirent

 * to customers of their Spirent Test Center.

 * As the installer displays the normal GPLv2+ license the choice was

 * made to go with disassembly instead of finding out who to ask for

 * the source code.

 *

 * Please report errors or missing features when compared to the original.

 */

/* TODO:

 * - Find out the meaning of the unknown trailer (perhaps some fcs or

 *   some prbseq related stuff?)

 * - Find out meaning of prbseq

 * - Is there a (fixed) structure in the csp field?

 * - Find out what the TSLR really stands for - currently just a guess

 */

#include "config.h"

#include <epan/packet.h>

#include <tfs.h>

void proto_register_stcsig(void);

void proto_reg_handoff_stcsig(void);

static int proto_stcsig;

static int hf_stcsig_csp;

static int hf_stcsig_iv;

static int hf_stcsig_prbseq;

static int hf_stcsig_rawdata;

static int hf_stcsig_seqnum_complement;

static int hf_stcsig_seqnum_edm;

static int hf_stcsig_seqnum_sm;

static int hf_stcsig_streamid;

static int hf_stcsig_streamindex;

static int hf_stcsig_streamtype;

static int hf_stcsig_timestamp;

static int hf_stcsig_tslr;

static int hf_stcsig_unknown;

static int ett_stcsig;

static int ett_stcsig_streamid;

static const true_false_string tfs_end_start = { "EndOfFrame", "StartOfFrame" };

static const true_false_string tfs_hard_soft = { "Hard", "Soft" };

/*

 * For the last 20 bytes of the data section to be a Spirent Signature

 * the first byte (offset 0) plus the 11th byte (offset 10) of the decoded

 * signature must add up to 255

 */

static bool

is_signature(tvbuff_t *tvb, int sigoffset)

{

  /*

   * How to generate the table below:

   *

   * static uint8_t runit = 1;

   * for(int k=0; k<256; k++) {

   *  obfuscation_value = k;

   *  for(int i=1; i<=10; i++) {

   *    obfuscation_value = deobfuscate_this[obfuscation_value];

   *  }

   *  printf("0x%02x, ", obfuscation_value);

   *  if (k%8 == 7) printf("\n");

   * }

   */

  static const uint8_t deobfuscate_offset_10[256] = {

    0x00, 0x86, 0x0d, 0x8b, 0x9d, 0x1b, 0x90, 0x16,

    0xbc, 0x3a, 0xb1, 0x37, 0x21, 0xa7, 0x2c, 0xaa,

    0x78, 0xfe, 0x75, 0xf3, 0xe5, 0x63, 0xe8, 0x6e,

    0xc4, 0x42, 0xc9, 0x4f, 0x59, 0xdf, 0x54, 0xd2,

    0xf1, 0x77, 0xfc, 0x7a, 0x6c, 0xea, 0x61, 0xe7,

    0x4d, 0xcb, 0x40, 0xc6, 0xd0, 0x56, 0xdd, 0x5b,

    0x89, 0x0f, 0x84, 0x02, 0x14, 0x92, 0x19, 0x9f,

    0x35, 0xb3, 0x38, 0xbe, 0xa8, 0x2e, 0xa5, 0x23,

    0xe2, 0x64, 0xef, 0x69, 0x7f, 0xf9, 0x72, 0xf4,

    0x5e, 0xd8, 0x53, 0xd5, 0xc3, 0x45, 0xce, 0x48,

    0x9a, 0x1c, 0x97, 0x11, 0x07, 0x81, 0x0a, 0x8c,

    0x26, 0xa0, 0x2b, 0xad, 0xbb, 0x3d, 0xb6, 0x30,

    0x13, 0x95, 0x1e, 0x98, 0x8e, 0x08, 0x83, 0x05,

    0xaf, 0x29, 0xa2, 0x24, 0x32, 0xb4, 0x3f, 0xb9,

    0x6b, 0xed, 0x66, 0xe0, 0xf6, 0x70, 0xfb, 0x7d,

    0xd7, 0x51, 0xda, 0x5c, 0x4a, 0xcc, 0x47, 0xc1,

    0x43, 0xc5, 0x4e, 0xc8, 0xde, 0x58, 0xd3, 0x55,

    0xff, 0x79, 0xf2, 0x74, 0x62, 0xe4, 0x6f, 0xe9,

    0x3b, 0xbd, 0x36, 0xb0, 0xa6, 0x20, 0xab, 0x2d,

    0x87, 0x01, 0x8a, 0x0c, 0x1a, 0x9c, 0x17, 0x91,

    0xb2, 0x34, 0xbf, 0x39, 0x2f, 0xa9, 0x22, 0xa4,

    0x0e, 0x88, 0x03, 0x85, 0x93, 0x15, 0x9e, 0x18,

    0xca, 0x4c, 0xc7, 0x41, 0x57, 0xd1, 0x5a, 0xdc,

    0x76, 0xf0, 0x7b, 0xfd, 0xeb, 0x6d, 0xe6, 0x60,

    0xa1, 0x27, 0xac, 0x2a, 0x3c, 0xba, 0x31, 0xb7,

    0x1d, 0x9b, 0x10, 0x96, 0x80, 0x06, 0x8d, 0x0b,

    0xd9, 0x5f, 0xd4, 0x52, 0x44, 0xc2, 0x49, 0xcf,

    0x65, 0xe3, 0x68, 0xee, 0xf8, 0x7e, 0xf5, 0x73,

    0x50, 0xd6, 0x5d, 0xdb, 0xcd, 0x4b, 0xc0, 0x46,

    0xec, 0x6a, 0xe1, 0x67, 0x71, 0xf7, 0x7c, 0xfa,

    0x28, 0xae, 0x25, 0xa3, 0xb5, 0x33, 0xb8, 0x3e,

    0x94, 0x12, 0x99, 0x1f, 0x09, 0x8f, 0x04, 0x82

  };

  uint8_t byte0;

  uint8_t byte10;

  /* Byte 0 also is the initialization vector for the obfuscation of offsets 1 - 15 */

  byte0 = tvb_get_uint8(tvb, sigoffset);

  byte10 = tvb_get_uint8(tvb, sigoffset + 10);

  if (byte0 + (byte10 ^ deobfuscate_offset_10[byte0]) == 255) {

    return true;

  } else {

    return false;

  }

}

static void

decode_signature(uint8_t* decode_buffer)

{

  static const uint8_t deobfuscate_this[256] = {

    0x00, 0x71, 0xe3, 0x92, 0xb6, 0xc7, 0x55, 0x24,

    0x1c, 0x6d, 0xff, 0x8e, 0xaa, 0xdb, 0x49, 0x38,

    0x39, 0x48, 0xda, 0xab, 0x8f, 0xfe, 0x6c, 0x1d,

    0x25, 0x54, 0xc6, 0xb7, 0x93, 0xe2, 0x70, 0x01,

    0x72, 0x03, 0x91, 0xe0, 0xc4, 0xb5, 0x27, 0x56,

    0x6e, 0x1f, 0x8d, 0xfc, 0xd8, 0xa9, 0x3b, 0x4a,

    0x4b, 0x3a, 0xa8, 0xd9, 0xfd, 0x8c, 0x1e, 0x6f,

    0x57, 0x26, 0xb4, 0xc5, 0xe1, 0x90, 0x02, 0x73,

    0xe4, 0x95, 0x07, 0x76, 0x52, 0x23, 0xb1, 0xc0,

    0xf8, 0x89, 0x1b, 0x6a, 0x4e, 0x3f, 0xad, 0xdc,

    0xdd, 0xac, 0x3e, 0x4f, 0x6b, 0x1a, 0x88, 0xf9,

    0xc1, 0xb0, 0x22, 0x53, 0x77, 0x06, 0x94, 0xe5,

    0x96, 0xe7, 0x75, 0x04, 0x20, 0x51, 0xc3, 0xb2,

    0x8a, 0xfb, 0x69, 0x18, 0x3c, 0x4d, 0xdf, 0xae,

    0xaf, 0xde, 0x4c, 0x3d, 0x19, 0x68, 0xfa, 0x8b,

    0xb3, 0xc2, 0x50, 0x21, 0x05, 0x74, 0xe6, 0x97,

    0xb8, 0xc9, 0x5b, 0x2a, 0x0e, 0x7f, 0xed, 0x9c,

    0xa4, 0xd5, 0x47, 0x36, 0x12, 0x63, 0xf1, 0x80,

    0x81, 0xf0, 0x62, 0x13, 0x37, 0x46, 0xd4, 0xa5,

    0x9d, 0xec, 0x7e, 0x0f, 0x2b, 0x5a, 0xc8, 0xb9,

    0xca, 0xbb, 0x29, 0x58, 0x7c, 0x0d, 0x9f, 0xee,

    0xd6, 0xa7, 0x35, 0x44, 0x60, 0x11, 0x83, 0xf2,

    0xf3, 0x82, 0x10, 0x61, 0x45, 0x34, 0xa6, 0xd7,

    0xef, 0x9e, 0x0c, 0x7d, 0x59, 0x28, 0xba, 0xcb,

    0x5c, 0x2d, 0xbf, 0xce, 0xea, 0x9b, 0x09, 0x78,

    0x40, 0x31, 0xa3, 0xd2, 0xf6, 0x87, 0x15, 0x64,

    0x65, 0x14, 0x86, 0xf7, 0xd3, 0xa2, 0x30, 0x41,

    0x79, 0x08, 0x9a, 0xeb, 0xcf, 0xbe, 0x2c, 0x5d,

    0x2e, 0x5f, 0xcd, 0xbc, 0x98, 0xe9, 0x7b, 0x0a,

    0x32, 0x43, 0xd1, 0xa0, 0x84, 0xf5, 0x67, 0x16,

    0x17, 0x66, 0xf4, 0x85, 0xa1, 0xd0, 0x42, 0x33,

    0x0b, 0x7a, 0xe8, 0x99, 0xbd, 0xcc, 0x5e, 0x2f

  };

  uint8_t obfuscation_value;

  obfuscation_value = decode_buffer[0];

  for(int i=1; i<16; i++) {

    obfuscation_value = deobfuscate_this[obfuscation_value];

    decode_buffer[i] ^= obfuscation_value;

  }

  /* decode_buffer[16...19] is unobfuscated */

}

static int

dissect_stcsig(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)

{

  int        bytes, length;

  int        sig_offset;

  tvbuff_t   *stcsig_tvb;

  proto_item *ti;

  proto_tree *stcsig_tree;

  proto_tree *stcsig_streamid_tree;

  uint8_t    *real_stcsig;

  uint64_t   timestamp_2_5_ns;

  uint64_t   timestamp_ns;

  nstime_t   timestamp;

  length = tvb_captured_length(tvb);

  if (length >= 21 && tvb_get_uint8(tvb, length - 21) == 0 && is_signature(tvb, length - 20)) {

    bytes = 20;

  } else if (length >= 25 && tvb_get_uint8(tvb, length - 25) == 0 && is_signature(tvb, length - 24)) {

    /* Sigsize + 4 bytes FCS */

    bytes = 24;

  } else if (length >= 29 && tvb_get_uint8(tvb, length - 29) == 0 && is_signature(tvb, length - 28)) {

    /* Sigsize + 8 bytes FCS, i.e. FibreChannel */

    bytes = 28;

  } else if (length >= 20 && is_signature(tvb, length - 20)) {

    bytes = 20;

  } else if (length >= 24 && is_signature(tvb, length - 24)) {

    /* Sigsize + 4 bytes FCS */

    bytes = 24;

  } else if (length >= 28 && is_signature(tvb, length - 28)) {

    /* Sigsize + 8 bytes FCS, i.e. FibreChannel */

    bytes = 28;

  } else {

    return 0;

  }

  sig_offset = length - bytes;

#if 0

  /* Maybe make this a preference */

  col_set_str(pinfo->cinfo, COL_PROTOCOL, "STCSIG");

  col_set_str(pinfo->cinfo, COL_INFO, "Spirent Test Center Signature");

#endif

  real_stcsig = (uint8_t *)tvb_memdup(pinfo->pool, tvb, sig_offset, 20);

  decode_signature(real_stcsig);

  stcsig_tvb = tvb_new_child_real_data(tvb, real_stcsig, 20, 20);

  add_new_data_source(pinfo, stcsig_tvb, "Spirent Test Center Signature");

  ti = proto_tree_add_item(tree, proto_stcsig, tvb, sig_offset, 20, ENC_NA);

  stcsig_tree = proto_item_add_subtree(ti, ett_stcsig);

  proto_tree_add_item(stcsig_tree, hf_stcsig_rawdata, tvb, sig_offset, 20, ENC_NA);

  proto_tree_add_item(stcsig_tree, hf_stcsig_iv, stcsig_tvb, 0, 1, ENC_NA);

  ti = proto_tree_add_item(stcsig_tree, hf_stcsig_streamid, stcsig_tvb, 1, 4, ENC_BIG_ENDIAN);

  stcsig_streamid_tree = proto_item_add_subtree(ti, ett_stcsig_streamid);

  /* This subtree is mostly an optical hierarchy, auto expand it */

  tree_expanded_set(ett_stcsig_streamid, true);

  proto_tree_add_item(stcsig_streamid_tree, hf_stcsig_csp, stcsig_tvb, 1, 2, ENC_BIG_ENDIAN);

  proto_tree_add_item(stcsig_streamid_tree, hf_stcsig_streamtype, stcsig_tvb, 3, 1, ENC_NA);

  proto_tree_add_item(stcsig_streamid_tree, hf_stcsig_streamindex, stcsig_tvb, 3, 2, ENC_BIG_ENDIAN);

  if (tvb_get_ntohs(stcsig_tvb, 5) + tvb_get_ntohs(stcsig_tvb, 7) == 0xffff) {

    proto_tree_add_item(stcsig_tree, hf_stcsig_seqnum_complement, stcsig_tvb, 5, 2, ENC_BIG_ENDIAN);

    proto_tree_add_item(stcsig_tree, hf_stcsig_seqnum_edm, stcsig_tvb, 7, 4, ENC_BIG_ENDIAN);

  } else {

    proto_tree_add_item(stcsig_tree, hf_stcsig_seqnum_sm, stcsig_tvb, 5, 6, ENC_BIG_ENDIAN);

  }

  timestamp_2_5_ns = (uint64_t)(tvb_get_uint8(stcsig_tvb, 15) & 0xfc) << 30;

  timestamp_2_5_ns |= tvb_get_ntohl(stcsig_tvb, 11);

  /* Convert 2.5 ns ticks to nanoseconds */

  timestamp_ns = timestamp_2_5_ns * 25 / 10;

  timestamp.secs = (time_t)(timestamp_ns / 1000000000L);

  timestamp.nsecs = (int)(timestamp_ns % 1000000000L);

  proto_tree_add_time(stcsig_tree, hf_stcsig_timestamp, stcsig_tvb, 11, 5, &timestamp);

  proto_tree_add_item(stcsig_tree, hf_stcsig_prbseq, stcsig_tvb, 15, 1, ENC_NA);

  proto_tree_add_item(stcsig_tree, hf_stcsig_tslr, stcsig_tvb, 15, 1, ENC_NA);

  proto_tree_add_item(stcsig_tree, hf_stcsig_unknown, stcsig_tvb, 16, 4, ENC_NA);

  /* Ignored for post-dissectors but required by function type */

  return length;

}

void

proto_register_stcsig(void)

{

  static hf_register_info hf[] = {

    { &hf_stcsig_rawdata,

      { "Raw Data", "stcsig.rawdata",

        FT_BYTES, BASE_NONE, NULL, 0x0,

        NULL, HFILL }

    },

    { &hf_stcsig_iv,

      { "IV", "stcsig.iv",

        FT_UINT8, BASE_HEX, NULL, 0x0,

        "Deobfuscation Initialization Vector and Complement of Sequence Low Byte", HFILL }

    },

    { &hf_stcsig_streamid,

      { "StreamID", "stcsig.streamid",

        FT_INT32, BASE_DEC, NULL, 0x0,

        NULL, HFILL }

    },

    { &hf_stcsig_csp,

      { "ChassisSlotPort", "stcsig.csp",

        FT_UINT16, BASE_DEC, NULL, 0x0,

        NULL, HFILL }

    },

    { &hf_stcsig_seqnum_complement,

      { "Complement (EDM)", "stcsig.complement",

        FT_UINT16, BASE_DEC, NULL, 0x0,

        "Complement of high bytes of Sequence Number", HFILL }

    },

    { &hf_stcsig_seqnum_edm,

      { "Sequence Number (EDM)", "stcsig.seqnum",

        FT_UINT32, BASE_DEC, NULL, 0x0,

        "Sequence Number (Enhanced Detection Mode)", HFILL }

    },

    { &hf_stcsig_seqnum_sm,

      { "Sequence Number (SM)", "stcsig.seqnum.sm",

        FT_UINT48, BASE_DEC, NULL, 0x0,

        "Sequence Number (Sequence Mode)", HFILL }

    },

    { &hf_stcsig_streamindex,

      { "Stream Index", "stcsig.streamindex",

        FT_UINT16, BASE_DEC, NULL, 0x0,

        NULL, HFILL }

    },

    { &hf_stcsig_timestamp,

      { "Timestamp", "stcsig.timestamp",

        FT_RELATIVE_TIME, BASE_NONE, NULL, 0x0,

        NULL, HFILL }

    },

    { &hf_stcsig_prbseq,

      { "Pseudo-Random Binary Sequence", "stcsig.prbseq",

        FT_BOOLEAN, 8, NULL, 0x02,

        NULL, HFILL }

    },

    { &hf_stcsig_tslr,

      { "TSLR", "stcsig.tslr",

        FT_BOOLEAN, 8, TFS(&tfs_end_start), 0x01,

        "Time Stamp Location Reference", HFILL }

    },

    { &hf_stcsig_streamtype,

      { "StreamType", "stcsig.streamtype",

        FT_BOOLEAN, 8, TFS(&tfs_hard_soft), 0x80,

        NULL, HFILL }

    },

    { &hf_stcsig_unknown,

      { "Unknown", "stcsig.unknown",

        FT_BYTES, BASE_NONE, NULL, 0x0,

        "Unknown Trailer (not obfuscated)", HFILL }

    },

  };

  static int *ett[] = {

    &ett_stcsig,

    &ett_stcsig_streamid

  };

  dissector_handle_t stcsig_handle;

  proto_stcsig = proto_register_protocol("Spirent Test Center Signature", "STCSIG", "stcsig");

  proto_register_field_array(proto_stcsig, hf, array_length(hf));

  proto_register_subtree_array(ett, array_length(ett));

  stcsig_handle = register_dissector("stcsig", dissect_stcsig, proto_stcsig);

  register_postdissector(stcsig_handle);

  /* STCSIG is a rarely used case, disable it by default for performance reasons. */

  proto_disable_by_default(proto_stcsig);

}

/*

 * 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:

 */