/* packet-osi.c * Routines for ISO/OSI network and transport protocol packet disassembly * Main entrance point and common functions * * Laurent Deniel * Ralf Schneider * * Wireshark - Network traffic analyzer * By Gerald Combs * Copyright 1998 Gerald Combs * * SPDX-License-Identifier: GPL-2.0-or-later */ #include "config.h" #include #include #include #include #include #include #include #include #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: */