257 lines
7.6 KiB
C
257 lines
7.6 KiB
C
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/* Copyright (c) 2017, Sabrina Dubroca <sd@queasysnail.net>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. The names of the authors may not be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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/* \summary: MACsec printer */
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include "netdissect-stdinc.h"
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#include "netdissect.h"
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#include "addrtoname.h"
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#include "ethertype.h"
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#include "extract.h"
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#define MACSEC_DEFAULT_ICV_LEN 16
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/* Header format (SecTAG), following an Ethernet header
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* IEEE 802.1AE-2006 9.3
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*
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* +---------------------------------+----------------+----------------+
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* | (MACsec ethertype) | TCI_AN | SL |
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* +---------------------------------+----------------+----------------+
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* | Packet Number |
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* +-------------------------------------------------------------------+
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* | Secure Channel Identifier |
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* | (optional) |
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* +-------------------------------------------------------------------+
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*
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* MACsec ethertype = 0x88e5
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* TCI: Tag Control Information, set of flags
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* AN: association number, 2 bits
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* SL (short length): 6-bit length of the protected payload, if < 48
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* Packet Number: 32-bits packet identifier
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* Secure Channel Identifier: 64-bit unique identifier, usually
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* composed of a MAC address + 16-bit port number
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*/
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struct macsec_sectag {
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nd_uint8_t tci_an;
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nd_uint8_t short_length;
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nd_uint32_t packet_number;
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nd_uint8_t secure_channel_id[8]; /* optional */
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};
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/* IEEE 802.1AE-2006 9.5 */
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#define MACSEC_TCI_VERSION 0x80
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#define MACSEC_TCI_ES 0x40 /* end station */
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#define MACSEC_TCI_SC 0x20 /* SCI present */
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#define MACSEC_TCI_SCB 0x10 /* epon */
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#define MACSEC_TCI_E 0x08 /* encryption */
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#define MACSEC_TCI_C 0x04 /* changed text */
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#define MACSEC_AN_MASK 0x03 /* association number */
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#define MACSEC_TCI_FLAGS (MACSEC_TCI_ES | MACSEC_TCI_SC | MACSEC_TCI_SCB | MACSEC_TCI_E | MACSEC_TCI_C)
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#define MACSEC_TCI_CONFID (MACSEC_TCI_E | MACSEC_TCI_C)
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#define MACSEC_SL_MASK 0x3F /* short length */
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#define MACSEC_SECTAG_LEN_NOSCI 6 /* length of MACsec header without SCI */
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#define MACSEC_SECTAG_LEN_SCI 14 /* length of MACsec header with SCI */
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#define SCI_FMT "%016" PRIx64
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static const struct tok macsec_flag_values[] = {
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{ MACSEC_TCI_E, "E" },
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{ MACSEC_TCI_C, "C" },
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{ MACSEC_TCI_ES, "S" },
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{ MACSEC_TCI_SCB, "B" },
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{ MACSEC_TCI_SC, "I" },
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{ 0, NULL }
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};
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static void macsec_print_header(netdissect_options *ndo,
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const struct macsec_sectag *sectag,
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u_int short_length)
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{
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ND_PRINT("an %u, pn %u, flags %s",
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GET_U_1(sectag->tci_an) & MACSEC_AN_MASK,
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GET_BE_U_4(sectag->packet_number),
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bittok2str_nosep(macsec_flag_values, "none",
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GET_U_1(sectag->tci_an) & MACSEC_TCI_FLAGS));
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if (short_length != 0)
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ND_PRINT(", sl %u", short_length);
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if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC)
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ND_PRINT(", sci " SCI_FMT, GET_BE_U_8(sectag->secure_channel_id));
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ND_PRINT(", ");
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}
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/* returns < 0 iff the packet can be decoded completely */
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int macsec_print(netdissect_options *ndo, const u_char **bp,
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u_int *lengthp, u_int *caplenp, u_int *hdrlenp,
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const struct lladdr_info *src, const struct lladdr_info *dst)
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{
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const char *save_protocol;
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const u_char *p = *bp;
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u_int length = *lengthp;
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u_int caplen = *caplenp;
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u_int hdrlen = *hdrlenp;
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const struct macsec_sectag *sectag = (const struct macsec_sectag *)p;
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u_int sectag_len;
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u_int short_length;
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save_protocol = ndo->ndo_protocol;
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ndo->ndo_protocol = "macsec";
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/* we need the full MACsec header in the capture */
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if (caplen < MACSEC_SECTAG_LEN_NOSCI) {
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nd_print_trunc(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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if (length < MACSEC_SECTAG_LEN_NOSCI) {
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nd_print_trunc(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) {
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sectag_len = MACSEC_SECTAG_LEN_SCI;
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if (caplen < MACSEC_SECTAG_LEN_SCI) {
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nd_print_trunc(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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if (length < MACSEC_SECTAG_LEN_SCI) {
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nd_print_trunc(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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} else
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sectag_len = MACSEC_SECTAG_LEN_NOSCI;
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if ((GET_U_1(sectag->short_length) & ~MACSEC_SL_MASK) != 0 ||
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GET_U_1(sectag->tci_an) & MACSEC_TCI_VERSION) {
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nd_print_invalid(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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short_length = GET_U_1(sectag->short_length) & MACSEC_SL_MASK;
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if (ndo->ndo_eflag)
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macsec_print_header(ndo, sectag, short_length);
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/* Skip the MACsec header. */
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*bp += sectag_len;
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*hdrlenp += sectag_len;
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/* Remove it from the lengths, as it's been processed. */
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*lengthp -= sectag_len;
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*caplenp -= sectag_len;
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if ((GET_U_1(sectag->tci_an) & MACSEC_TCI_CONFID)) {
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/*
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* The payload is encrypted. Print link-layer
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* information, if it hasn't already been printed.
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*/
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if (!ndo->ndo_eflag) {
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/*
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* Nobody printed the link-layer addresses,
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* so print them, if we have any.
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*/
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if (src != NULL && dst != NULL) {
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ND_PRINT("%s > %s ",
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(src->addr_string)(ndo, src->addr),
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(dst->addr_string)(ndo, dst->addr));
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}
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ND_PRINT("802.1AE MACsec, ");
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/*
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* Print the MACsec header.
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*/
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macsec_print_header(ndo, sectag, short_length);
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}
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/*
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* Tell our caller it can't be dissected.
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*/
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ndo->ndo_protocol = save_protocol;
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return 0;
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}
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/*
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* The payload isn't encrypted; remove the
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* ICV length from the lengths, so our caller
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* doesn't treat it as payload.
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*/
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if (*lengthp < MACSEC_DEFAULT_ICV_LEN) {
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nd_print_trunc(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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if (*caplenp < MACSEC_DEFAULT_ICV_LEN) {
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nd_print_trunc(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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*lengthp -= MACSEC_DEFAULT_ICV_LEN;
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*caplenp -= MACSEC_DEFAULT_ICV_LEN;
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/*
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* Update the snapend thus the ICV field is not in the payload for
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* the caller.
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* The ICV (Integrity Check Value) is at the end of the frame, after
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* the secure data.
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*/
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ndo->ndo_snapend -= MACSEC_DEFAULT_ICV_LEN;
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/*
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* If the SL field is non-zero, then it's the length of the
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* Secure Data; otherwise, the Secure Data is what's left
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* ver after the MACsec header and ICV are removed.
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*/
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if (short_length != 0) {
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/*
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* If the short length is more than we *have*,
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* that's an error.
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*/
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if (short_length > *lengthp) {
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nd_print_trunc(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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if (short_length > *caplenp) {
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nd_print_trunc(ndo);
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ndo->ndo_protocol = save_protocol;
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return hdrlen + caplen;
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}
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if (*lengthp > short_length)
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*lengthp = short_length;
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if (*caplenp > short_length)
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*caplenp = short_length;
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}
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ndo->ndo_protocol = save_protocol;
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return -1;
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}
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