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wireshark/epan/dissectors/packet-macsec.c

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/* packet-macsec.c
* Routines for IEEE 802.1AE MACsec dissection
* Copyright 2013, Allan W. Nielsen <anielsen@vitesse.com>
*
* 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/etypes.h>
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, &ethertype_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:
*/
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