/* packet-osi.c

 * Routines for ISO/OSI network and transport protocol packet disassembly

 * Main entrance point and common functions

 *

 * Laurent Deniel <laurent.deniel@free.fr>

 * Ralf Schneider <Ralf.Schneider@t-online.de>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

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

 */

#include "config.h"

#include <epan/packet.h>

#include <epan/prefs.h>

#include <epan/llcsaps.h>

#include <epan/aftypes.h>

#include <epan/nlpid.h>

#include <epan/ppptypes.h>

#include <epan/chdlctypes.h>

#include <epan/ipproto.h>

#include "packet-osi.h"

#include "packet-tpkt.h"

#include "packet-juniper.h"

void proto_reg_handoff_osi(void);

void proto_register_osi(void);

int  proto_osi;

static int hf_osi_nlpid;

static dissector_handle_t osi_handle;

static dissector_handle_t osi_tpkt_handle;

static dissector_handle_t osi_juniper_handle;

/* Preferences for OSI over TPKT over TCP */

static bool tpkt_desegment;

bool

osi_calc_checksum( tvbuff_t *tvb, int offset, unsigned len, uint32_t* c0, uint32_t* c1) {

  unsigned      available_len;

  const uint8_t *p;

  unsigned      seglen;

  unsigned      i;

  available_len = tvb_captured_length_remaining( tvb, offset );

  if ( available_len < len )

    return false;

  p = tvb_get_ptr( tvb, offset, len );

  /*

   * The maximum values of c0 and c1 will occur if all bytes have the

   * value 255; if so, then c0 will be len*255 and c1 will be

   * (len*255 + (len-1)*255 + ... + 255), which is

   * (len + (len - 1) + ... + 1)*255, or 255*(len*(len + 1))/2.

   * This means it can overflow if "len" is 5804 or greater.

   *

   * (A+B) mod 255 = ((A mod 255) + (B mod 255) mod 255, so

   * we can solve this by taking c0 and c1 mod 255 every

   * 5803 bytes.

   */

  *c0 = 0;

  *c1 = 0;

  while (len != 0) {

    seglen = len;

    if (seglen > 5803)

      seglen = 5803;

    for (i = 0; i < seglen; i++) {

      (*c0) += *(p++);

      (*c1) += (*c0);

    }

    (*c0) = (*c0) % 255;

    (*c1) = (*c1) % 255;

    len -= seglen;

  }

  return true;

}

bool

osi_check_and_get_checksum( tvbuff_t *tvb, int offset, unsigned len, int offset_check, uint16_t* result) {

  const uint8_t *p;

  uint8_t       discard         = 0;

  uint32_t      c0, c1, factor;

  unsigned      seglen, initlen = len;

  unsigned      i;

  int           block, x, y;

  /* Make sure the checksum is part of the data being checksummed. */

  DISSECTOR_ASSERT(offset_check >= offset);

  DISSECTOR_ASSERT((unsigned)offset_check + 2 <= (unsigned)offset + len);

  /*

   * If we don't have all the data to be checksummed, report that and don't

   * try checksumming.

   */

  if (!tvb_bytes_exist(tvb, offset, len))

    return false;

  offset_check -= offset;

  p = tvb_get_ptr( tvb, offset, len );

  block  = offset_check / 5803;

  /*

   * The maximum values of c0 and c1 will occur if all bytes have the

   * value 255; if so, then c0 will be len*255 and c1 will be

   * (len*255 + (len-1)*255 + ... + 255), which is

   * (len + (len - 1) + ... + 1)*255, or 255*(len*(len + 1))/2.

   * This means it can overflow if "len" is 5804 or greater.

   *

   * (A+B) mod 255 = ((A mod 255) + (B mod 255) mod 255, so

   * we can solve this by taking c0 and c1 mod 255 every

   * 5803 bytes.

   */

  c0 = 0;

  c1 = 0;

  while (len != 0) {

    seglen = len;

    if ( block-- == 0 ) {

      seglen = offset_check % 5803;

      discard = 1;

    } else if ( seglen > 5803 )

      seglen = 5803;

    for (i = 0; i < seglen; i++) {

      c0 = c0 + *(p++);

      c1 += c0;

    }

    if ( discard ) {

      /*

       * This works even if (offset_check % 5803) == 5802

       */

      p += 2;

      c1 += 2*c0;

      len -= 2;

      discard = 0;

    }

    c0 = c0 % 255;

    c1 = c1 % 255;

    len -= seglen;

  }

  factor = ( initlen - offset_check ) * c0;

  x = factor - c0 - c1;

  y = c1 - factor - 1;

  /*

   * This algorithm uses the 8 bits one's complement arithmetic.

   * Therefore, we must correct an effect produced

   * by the "standard" arithmetic (two's complement)

   */

  if (x < 0 ) x--;

  if (y > 0 ) y++;

  x %= 255;

  y %= 255;

  if (x == 0) x = 0xFF;

  if (y == 0) y = 0x01;

  *result = ( x << 8 ) | ( y & 0xFF );

  return true;

}

/* 4 octet ATN extended checksum: ICAO doc 9705 Ed3 Volume V section 5.5.4.6.4 */

/* It is calculated over TP4 userdata (all checksums set to zero ) and a pseudo tailer */

/* of length SRC-NSAP, SRC-NSAP, length DST-NSAP, DST-NSAP and ATN extended checksum. */

/* In case of a CR TPDU, the value of the ISO 8073 16-bit fletcher checksum parameter shall */

/* be set to zero. */

uint32_t check_atn_ec_32(

  tvbuff_t *tvb, unsigned tpdu_len,

  unsigned offset_ec_32_val,   /* offset ATN extended checksum value, calculated at last as part of pseudo trailer */

  unsigned offset_iso8073_val, /* offset ISO 8073 fletcher checksum, CR only*/

  unsigned clnp_dst_len,       /* length of DST-NSAP */

  const uint8_t *clnp_dst,   /* DST-NSAP */

  unsigned clnp_src_len,       /* length of SRC-NSAP */

  const uint8_t *clnp_src)   /* SRC-NSAP */

{

  unsigned  i = 0;

  uint32_t c0 = 0;

  uint32_t c1 = 0;

  uint32_t c2 = 0;

  uint32_t c3 = 0;

  uint32_t sum = 0;

  /* sum across complete TPDU  */

  for ( i =0; i< tpdu_len; i++){

    c0 += tvb_get_uint8(tvb, i) ;

    if( ( i >= offset_ec_32_val ) &&  /* ignore 32 bit ATN extended checksum value */

        ( i < ( offset_ec_32_val + 4 ) ) ) {

      c0 -= tvb_get_uint8(tvb, i);

    }

    if( ( offset_iso8073_val ) && /* ignore 16 bit ISO 8073 checksum, if present*/

        ( i >= offset_iso8073_val ) &&

        ( i < ( offset_iso8073_val + 2 ) ) ) {

      c0 -= tvb_get_uint8(tvb, i);

    }

    if ( c0 >= 0x000000FF )

      c0 -= 0x00000FF;

    c1 += c0;

    if ( c1 >= 0x000000FF )

      c1 -= 0x000000FF;

    c2 += c1;

    if ( c2 >= 0x000000FF )

      c2 -= 0x000000FF;

    c3 += c2;

    if ( c3 >= 0x000000FF )

      c3 -= 0x000000FF;

  }

  /* add NSAP parts of pseudo trailer */

  c0 += clnp_dst_len;

  if ( c0 >= 0x000000FF )

    c0 -= 0x000000FF;

  c1 += c0;

  if ( c1 >= 0x000000FF )

    c1 -= 0x000000FF;

  c2 += c1;

  if ( c2 >= 0x000000FF )

    c2 -= 0x000000FF;

  c3 += c2;

  if ( c3 >= 0x000000FF )

    c3 -= 0x000000FF;

  for ( i =0; i< clnp_dst_len; i++){

    c0 += clnp_dst[i];

    if ( c0 >= 0x000000FF )

      c0 -= 0x000000FF;

    c1 += c0;

    if ( c1 >= 0x000000FF )

      c1 -= 0x000000FF;

    c2 += c1;

    if ( c2 >= 0x000000FF )

      c2 -= 0x000000FF;

    c3 += c2;

    if ( c3 >= 0x000000FF )

      c3 -= 0x000000FF;

  }

  c0 += clnp_src_len;

  if ( c0 >= 0x000000FF )

    c0 -= 0x000000FF;

  c1 += c0;

  if ( c1 >= 0x000000FF )

    c1 -= 0x000000FF;

  c2 += c1;

  if ( c2 >= 0x000000FF )

    c2 -= 0x000000FF;

  c3 += c2;

  if ( c3 >= 0x000000FF )

    c3 -= 0x000000FF;

  for ( i =0; i< clnp_src_len; i++){

    c0 += clnp_src[i];

    if ( c0 >= 0x000000FF )

      c0 -= 0x000000FF;

    c1 += c0;

    if ( c1 >= 0x000000FF )

      c1 -= 0x000000FF;

    c2 += c1;

    if ( c2 >= 0x000000FF )

      c2 -= 0x000000FF;

    c3 += c2;

    if ( c3 >= 0x000000FF )

      c3 -= 0x000000FF;

  }

  /* add extended checksum as last part of the pseudo trailer */

  for ( i = offset_ec_32_val; i< (offset_ec_32_val+4); i++){

    c0 += tvb_get_uint8(tvb, i) ;

    if ( c0 >= 0x000000FF )

      c0 -= 0x00000FF;

    c1 += c0;

    if ( c1 >= 0x000000FF )

      c1 -= 0x000000FF;

    c2 += c1;

    if ( c2 >= 0x000000FF )

      c2 -= 0x000000FF;

    c3 += c2;

    if ( c3 >= 0x000000FF )

      c3 -= 0x000000FF;

  }

  sum = (c3 << 24) + (c2 << 16 ) + (c1 << 8) + c0;

  return sum;

}

/* 2 octet ATN extended checksum: ICAO doc 9705 Ed3 Volume V section 5.5.4.6.4 */

/* It is calculated over TP4 userdata (all checksums set to zero ) and a pseudo tailer */

/* of length SRC-NSAP, SRC-NSAP, length DST-NSAP, DST-NSAP and ATN extended checksum. */

/* In case of a CR TPDU, the value of the ISO 8073 16-bit fletcher checksum parameter shall */

/* be set to zero. */

/* this routine is currently *untested* because of the unavailability of samples.*/

uint16_t check_atn_ec_16(

  tvbuff_t *tvb,

  unsigned tpdu_len,

  unsigned offset_ec_16_val,   /* offset ATN extended checksum value, calculated at last as part of pseudo trailer */

  unsigned offset_iso8073_val, /* offset ISO 8073 fletcher checksum, CR only*/

  unsigned clnp_dst_len,       /* length of DST-NSAP */

  const uint8_t *clnp_dst,   /* DST-NSAP */

  unsigned clnp_src_len,       /* length of SRC-NSAP */

  const uint8_t *clnp_src)   /* SRC-NSAP */

{

  unsigned i = 0;

  uint16_t c0 = 0;

  uint16_t c1 = 0;

  uint16_t sum;

  /* sum across complete TPDU */

  for ( i =0; i< tpdu_len; i++){

    c0 += tvb_get_uint8(tvb, i);

    if( (i >= offset_ec_16_val) && /* ignore 16 bit extended checksum */

        (i < (offset_ec_16_val + 2) ) ) {

      c0 -= tvb_get_uint8(tvb, i) ;

    }

    if( (i >= offset_iso8073_val) && /* ignore 16 bit ISO 8073 checksum, if present*/

        (i < (offset_iso8073_val + 2) ) ) {

      c0 -= tvb_get_uint8(tvb, i) ;

    }

    if ( c0 >= 0x00FF )

       c0 -= 0x00FF;

    c1 += c0;

    if ( c1 >= 0x00FF )

      c1 -= 0x00FF;

  }

  /* add NSAP parts of pseudo trailer */

  c0 += clnp_dst_len;

  if ( c0 >= 0x00FF )

    c0 -= 0x00FF;

  c1 += c0;

  if ( c1 >= 0x00FF )

    c1 -= 0x00FF;

  for ( i =0; i< clnp_dst_len; i++){

    c0 += clnp_dst[i];

    if ( c0 >= 0x00FF )

      c0 -= 0x00FF;

    c1 += c0;

    if ( c1 >= 0x00FF )

      c1 -= 0x00FF;

  }

  c0 += clnp_src_len;

  if ( c0 >= 0x00FF )

    c0 -= 0x00FF;

  c1 += c0;

  if ( c1 >= 0x00FF )

    c1 -= 0x00FF;

  for ( i =0; i< clnp_src_len; i++){

    c0 += clnp_src[i];

    if ( c0 >= 0x00FF )

      c0 -= 0x00FF;

    c1 += c0;

    if ( c1 >= 0x00FF )

      c1 -= 0x00FF;

  }

  /* add extended checksum as last part of the pseudo trailer */

  for ( i = offset_ec_16_val; i< (offset_ec_16_val+2); i++){

    c0 += tvb_get_uint8(tvb, i) ;

    if ( c0 >= 0x00FF )

      c0 -= 0x00FF;

    c1 += c0;

    if ( c1 >= 0x00FF )

      c1 -= 0x00FF;

  }

  sum =  (c1 << 8) + c0 ;

  return sum;

}

/* main entry point */

/*

 * These assume the NLPID is a secondary protocol identifier, not an

 * initial protocol identifier.

 *

 * This is an issue only if, in any packet where an NLPID appears, it's

 * an initial protocol identifier *AND* it can have the value 1, which

 * means T.70 for an IPI and X.29 for an SPI.

 */

const value_string nlpid_vals[] = {

  { NLPID_NULL,            "NULL" },

  { NLPID_SPI_X_29,        "X.29" },

  { NLPID_X_633,           "X.633" },

  { NLPID_Q_931,           "Q.931" },

  { NLPID_Q_2931,          "Q.2931" },

  { NLPID_Q_2119,          "Q.2119" },

  { NLPID_SNAP,            "SNAP" },

  { NLPID_ISO8473_CLNP,    "CLNP" },

  { NLPID_ISO9542_ESIS,    "ESIS" },

  { NLPID_ISO10589_ISIS,   "ISIS" },

  { NLPID_ISO10747_IDRP,   "IDRP" },

  { NLPID_AVAYA_IPVPN,     "Avaya SPBM Fabric IPVPN" },

  { NLPID_ISO9542X25_ESIS, "ESIS (X.25)" },

  { NLPID_ISO10030,        "ISO 10030" },

  { NLPID_ISO11577,        "ISO 11577" },

  { NLPID_COMPRESSED,      "Data compression protocol" },

  { NLPID_IP,              "IP" },

  { NLPID_TRILL,           "TRILL" },

  { NLPID_SNDCF,           "SubNetwork Dependent Convergence Function"},

  { NLPID_IP6,             "IPv6" },

  { NLPID_PPP,             "PPP" },

  { 0,                     NULL },

};

static dissector_table_t osinl_incl_subdissector_table;

static dissector_table_t osinl_excl_subdissector_table;

static dissector_handle_t ppp_handle;

/* Dissect OSI over TCP over TPKT */

static int

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

{

  dissect_tpkt_encap(tvb, pinfo, tree, tpkt_desegment, osi_handle);

  return tvb_captured_length(tvb);

}

static int dissect_osi_juniper(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)

{

  uint8_t    nlpid;

  tvbuff_t   *next_tvb;

  nlpid = tvb_get_uint8(tvb, 0);

  if(dissector_try_uint(osinl_incl_subdissector_table, nlpid, tvb, pinfo, tree))

    return tvb_captured_length(tvb);

  next_tvb = tvb_new_subset_remaining(tvb, 1);

  dissector_try_uint(osinl_excl_subdissector_table, nlpid, next_tvb, pinfo, tree);

  return tvb_captured_length(tvb);

}

static int dissect_osi(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)

{

  uint8_t   nlpid;

  tvbuff_t *new_tvb;

  nlpid = tvb_get_uint8(tvb, 0);

  /*

   * Try the subdissector table for protocols in which the NLPID is

   * considered part of the PDU; it should be handed a tvbuff that

   * includes the NLPID, and should put the NLPID into the protocol

   * tree itself.

   */

  if (dissector_try_uint(osinl_incl_subdissector_table, nlpid, tvb, pinfo, tree))

    return tvb_captured_length(tvb);

  /*

   * Try the subdissector table for protocols in which the NLPID is

   * *not* considered part of the PDU; it should be handed a tvbuff

   * that doesn't include the NLPID, and we should put the NLPID into

   * the protocol tree ourselves.

   */

  proto_tree_add_uint(tree, hf_osi_nlpid, tvb, 0, 1, nlpid);

  new_tvb = tvb_new_subset_remaining(tvb, 1);

  if (dissector_try_uint(osinl_excl_subdissector_table, nlpid, new_tvb, pinfo, tree))

    return tvb_captured_length(tvb);

  switch (nlpid) {

    /* ESIS (X.25) is not currently decoded */

    case NLPID_ISO9542X25_ESIS:

      col_set_str(pinfo->cinfo, COL_PROTOCOL, "ESIS (X.25)");

      call_data_dissector(tvb, pinfo, tree);

      break;

    case NLPID_ISO10747_IDRP:

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

      call_data_dissector(tvb, pinfo, tree);

      break;

    default:

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

      col_add_fstr(pinfo->cinfo, COL_INFO, "Unknown ISO protocol (%02x)", nlpid);

      call_data_dissector(tvb, pinfo, tree);

      break;

  }

  return tvb_captured_length(tvb);

} /* dissect_osi */

void

proto_reg_handoff_osi(void)

{

  dissector_add_uint("llc.dsap", SAP_OSINL1, osi_handle);

  dissector_add_uint("llc.dsap", SAP_OSINL2, osi_handle);

  dissector_add_uint("llc.dsap", SAP_OSINL3, osi_handle);

  dissector_add_uint("llc.dsap", SAP_OSINL4, osi_handle);

  dissector_add_uint("llc.dsap", SAP_OSINL5, osi_handle);

  dissector_add_uint("ppp.protocol", PPP_OSI, osi_handle);

  dissector_add_uint("chdlc.protocol", CHDLCTYPE_OSI, osi_handle);

  dissector_add_uint("null.type", BSD_AF_ISO, osi_handle);

  dissector_add_uint("gre.proto", SAP_OSINL5, osi_handle);

  dissector_add_uint("ip.proto", IP_PROTO_ISOIP, osi_handle); /* ISO network layer PDUs [RFC 1070] */

  dissector_add_uint("juniper.proto", JUNIPER_PROTO_ISO, osi_juniper_handle);

  dissector_add_uint("juniper.proto", JUNIPER_PROTO_CLNP, osi_juniper_handle);

  dissector_add_uint("juniper.proto", JUNIPER_PROTO_MPLS_CLNP, osi_juniper_handle);

  ppp_handle  = find_dissector("ppp");

  dissector_add_for_decode_as_with_preference("tcp.port", osi_tpkt_handle);

}

void

proto_register_osi(void)

{

  static hf_register_info hf[] = {

    { &hf_osi_nlpid,

      { "Network Layer Protocol Identifier", "osi.nlpid", FT_UINT8, BASE_HEX,

        VALS(nlpid_vals), 0x0, NULL, HFILL }},

  };

  module_t *osi_module;

  proto_osi = proto_register_protocol("OSI", "OSI", "osi");

  proto_register_field_array(proto_osi, hf, array_length(hf));

  /* There's no "OSI" protocol *per se*, but we do register a

     dissector table so various protocols running at the

     network layer can register themselves.

     all protocols that require inclusion of the NLPID

     should register here

  */

  osinl_incl_subdissector_table = register_dissector_table("osinl.incl",

                                                           "OSI incl NLPID", proto_osi, FT_UINT8, BASE_HEX);

  /* This dissector table is for those protocols whose PDUs

   * aren't* defined to begin with an NLPID.

   * (typically non OSI protocols like IP,IPv6,PPP */

  osinl_excl_subdissector_table = register_dissector_table("osinl.excl",

                                                           "OSI excl NLPID", proto_osi, FT_UINT8, BASE_HEX);

  /* Preferences how OSI protocols should be dissected */

  osi_module = prefs_register_protocol(proto_osi, NULL);

  prefs_register_bool_preference(osi_module, "tpkt_reassemble",

                                 "Reassemble segmented TPKT datagrams",

                                 "Whether segmented TPKT datagrams should be reassembled",

                                 &tpkt_desegment);

  /* Register the dissector handles */

  osi_handle = register_dissector("osi", dissect_osi, proto_osi);

  osi_juniper_handle = register_dissector("osi_juniper", dissect_osi_juniper, proto_osi);

  osi_tpkt_handle = register_dissector("osi_tpkt", dissect_osi_tpkt, proto_osi);

}

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local Variables:

 * c-basic-offset: 2

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * ex: set shiftwidth=2 tabstop=8 expandtab:

 * :indentSize=2:tabSize=8:noTabs=true:

 */