/* packet-macsec.c * Routines for IEEE 802.1AE MACsec dissection * Copyright 2013, Allan W. Nielsen * * Wireshark - Network traffic analyzer * By Gerald Combs * Copyright 1998 Gerald Combs * * SPDX-License-Identifier: GPL-2.0-or-later */ #include "config.h" #include #include void proto_register_macsec(void); void proto_reg_handoff_macsec(void); static dissector_handle_t ethertype_handle; /* TCI/AN field masks */ #define TCI_MASK 0xFC #define TCI_V_MASK 0x80 #define TCI_ES_MASK 0x40 #define TCI_SC_MASK 0x20 #define TCI_SCB_MASK 0x10 #define TCI_E_MASK 0x08 #define TCI_C_MASK 0x04 #define AN_MASK 0x03 static int proto_macsec = -1; static int hf_macsec_TCI = -1; static int hf_macsec_TCI_V = -1; static int hf_macsec_TCI_ES = -1; static int hf_macsec_TCI_SC = -1; static int hf_macsec_TCI_SCB = -1; static int hf_macsec_TCI_E = -1; static int hf_macsec_TCI_C = -1; static int hf_macsec_AN = -1; static int hf_macsec_SL = -1; static int hf_macsec_PN = -1; static int hf_macsec_SCI_system_identifier = -1; static int hf_macsec_SCI_port_identifier = -1; static int hf_macsec_etype = -1; static int hf_macsec_eth_padding = -1; static int hf_macsec_ICV = -1; /* Initialize the subtree pointers */ static gint ett_macsec = -1; static gint ett_macsec_tci = -1; /* Code to actually dissect the packets */ static int dissect_macsec(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) { unsigned sectag_length, data_length, short_length, icv_length; unsigned fcs_length = 0; unsigned data_offset, icv_offset; guint8 tci_an_field; proto_item *macsec_item; proto_tree *macsec_tree = NULL; tvbuff_t *next_tvb; tci_an_field = tvb_get_guint8(tvb, 0); if ((tci_an_field & TCI_V_MASK) != 0) { /* version must be zero */ return 0; } icv_length = 16; /* Fixed size for version 0 */ if (tci_an_field & TCI_SC_MASK) { sectag_length = 14; /* optional SCI present */ } else { sectag_length = 6; } /* Check for length too short */ if (tvb_captured_length(tvb) <= (sectag_length + icv_length)) { return 0; } /* short length field: 1..47 bytes, 0 means 48 bytes or more */ short_length = (guint32)tvb_get_guint8(tvb, 1); /* Get the payload section */ if (short_length != 0) { data_length = short_length; fcs_length = tvb_captured_length(tvb) - sectag_length - icv_length - short_length; } else { /* * This assumes that no FCS is present after the ICV, which might not be true! * Workaround: turn Ethernet "Assume packets have FCS" = Always, when FCS present. * TODO: Find better heuristic to detect presence of FCS. */ data_length = tvb_captured_length(tvb) - sectag_length - icv_length; } data_offset = sectag_length; icv_offset = data_length + data_offset; col_set_str(pinfo->cinfo, COL_PROTOCOL, "MACSEC"); col_set_str(pinfo->cinfo, COL_INFO, "MACsec frame"); if (tree) { if (((tci_an_field & TCI_E_MASK) == TCI_E_MASK) || ((tci_an_field & TCI_C_MASK) == TCI_C_MASK)) { macsec_item = proto_tree_add_item(tree, proto_macsec, tvb, 0, sectag_length, ENC_NA); } else { /* Add the EtherType too since this is authentication only. */ macsec_item = proto_tree_add_item(tree, proto_macsec, tvb, 0, sectag_length + 2, ENC_NA); } macsec_tree = proto_item_add_subtree(macsec_item, ett_macsec); static int * const flags[] = { &hf_macsec_TCI_V, &hf_macsec_TCI_ES, &hf_macsec_TCI_SC, &hf_macsec_TCI_SCB, &hf_macsec_TCI_E, &hf_macsec_TCI_C, NULL }; proto_tree_add_bitmask_with_flags(macsec_tree, tvb, 0, hf_macsec_TCI, ett_macsec_tci, flags, ENC_NA, BMT_NO_TFS); proto_tree_add_item(macsec_tree, hf_macsec_AN, tvb, 0, 1, ENC_NA); proto_tree_add_item(macsec_tree, hf_macsec_SL, tvb, 1, 1, ENC_NA); proto_tree_add_item(macsec_tree, hf_macsec_PN, tvb, 2, 4, ENC_BIG_ENDIAN); if (sectag_length == 14) { proto_tree_add_item(macsec_tree, hf_macsec_SCI_system_identifier, tvb, 6, 6, ENC_NA); proto_tree_add_item(macsec_tree, hf_macsec_SCI_port_identifier, tvb, 12, 2, ENC_BIG_ENDIAN); } if (((tci_an_field & TCI_E_MASK) == TCI_E_MASK) || ((tci_an_field & TCI_C_MASK) == TCI_C_MASK)) { proto_tree_add_item(macsec_tree, hf_macsec_ICV, tvb, icv_offset, icv_length, ENC_NA); } else { proto_tree_add_item(macsec_tree, hf_macsec_etype, tvb, data_offset, 2, ENC_BIG_ENDIAN); } } /* if encrypted or changed, we can only display data */ if (((tci_an_field & TCI_E_MASK) == TCI_E_MASK) || ((tci_an_field & TCI_C_MASK) == TCI_C_MASK)) { next_tvb = tvb_new_subset_length(tvb, data_offset, data_length); call_data_dissector(next_tvb, pinfo, tree); } else { ethertype_data_t ethertype_data; ethertype_data.etype = tvb_get_ntohs(tvb, data_offset); ethertype_data.payload_offset = 0; ethertype_data.fh_tree = macsec_tree; /* fallback, if ethernet dissector does not identify padding correctly */ ethertype_data.trailer_id = hf_macsec_eth_padding; ethertype_data.fcs_len = 0; /* lets hand over a buffer without ICV to limit effect of wrong padding calculation */ next_tvb = tvb_new_subset_length(tvb, data_offset + 2, data_length - 2); /* help eth padding calculation by substracting length of the sectag, ethertype, icv, and fcs */ gint pkt_len_saved = pinfo->fd->pkt_len; pinfo->fd->pkt_len -= (sectag_length + 2 + icv_length + fcs_length); call_dissector_with_data(ethertype_handle, next_tvb, pinfo, tree, ðertype_data); /* restore original value */ pinfo->fd->pkt_len = pkt_len_saved; proto_tree_add_item(macsec_tree, hf_macsec_ICV, tvb, icv_offset, icv_length, ENC_NA); } return tvb_captured_length(tvb) - fcs_length; } void proto_register_macsec(void) { static hf_register_info hf[] = { { &hf_macsec_TCI, { "TCI", "macsec.TCI", FT_UINT8, BASE_HEX, NULL, TCI_MASK, "TAG Control Information", HFILL } }, { &hf_macsec_TCI_V, { "VER", "macsec.TCI.V", FT_UINT8, BASE_HEX, NULL, TCI_V_MASK, "Version", HFILL } }, { &hf_macsec_TCI_ES, { "ES", "macsec.TCI.ES", FT_BOOLEAN, 8, TFS(&tfs_set_notset), TCI_ES_MASK, "End Station", HFILL } }, { &hf_macsec_TCI_SC, { "SC", "macsec.TCI.SC", FT_BOOLEAN, 8, TFS(&tfs_set_notset), TCI_SC_MASK, "Secure Channel", HFILL } }, { &hf_macsec_TCI_SCB, { "SCB", "macsec.TCI.SCB", FT_BOOLEAN, 8, TFS(&tfs_set_notset), TCI_SCB_MASK, "Single Copy Broadcast", HFILL } }, { &hf_macsec_TCI_E, { "E", "macsec.TCI.E", FT_BOOLEAN, 8, TFS(&tfs_set_notset), TCI_E_MASK, "Encryption", HFILL } }, { &hf_macsec_TCI_C, { "C", "macsec.TCI.C", FT_BOOLEAN, 8, TFS(&tfs_set_notset), TCI_C_MASK, "Changed Text", HFILL } }, { &hf_macsec_AN, { "AN", "macsec.AN", FT_UINT8, BASE_HEX, NULL, AN_MASK, "Association Number", HFILL } }, { &hf_macsec_SL, { "Short length", "macsec.SL", FT_UINT8, BASE_DEC, NULL, 0, NULL, HFILL } }, { &hf_macsec_PN, { "Packet number", "macsec.PN", FT_UINT32, BASE_DEC, NULL, 0, NULL, HFILL } }, { &hf_macsec_SCI_system_identifier, { "System Identifier", "macsec.SCI.system_identifier", FT_ETHER, BASE_NONE, NULL, 0, NULL, HFILL } }, { &hf_macsec_SCI_port_identifier, { "Port Identifier", "macsec.SCI.port_identifier", FT_UINT16, BASE_DEC, NULL, 0, NULL, HFILL } }, { &hf_macsec_etype, { "Ethertype", "macsec.etype", FT_UINT16, BASE_HEX, NULL, 0, NULL, HFILL } }, { &hf_macsec_eth_padding, { "Padding", "macsec.eth_padding", FT_BYTES, BASE_NONE, NULL, 0, NULL, HFILL } }, { &hf_macsec_ICV, { "ICV", "macsec.ICV", FT_BYTES, BASE_NONE, NULL, 0, NULL, HFILL } } }; /* Setup protocol subtree array */ static gint *ett[] = { &ett_macsec, &ett_macsec_tci }; /* Register the protocol name and description */ proto_macsec = proto_register_protocol("802.1AE Security tag", "MACsec", "macsec"); /* Required function calls to register the header fields and subtrees used */ proto_register_field_array(proto_macsec, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); } void proto_reg_handoff_macsec(void) { dissector_handle_t macsec_handle; macsec_handle = create_dissector_handle(dissect_macsec, proto_macsec); dissector_add_uint("ethertype", ETHERTYPE_MACSEC, macsec_handle); ethertype_handle = find_dissector("ethertype"); } /* * 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: */