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