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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 <string.h>
#include "netdissect.h"
#include "addrtoname.h"
#include "ether.h"
#include "ethertype.h"
#include "extract.h"
static const char tstr[] = "[|MACsec]";
#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
#define MACSEC_SECTAG_LEN_SCI 14
static int
ieee8021ae_sectag_len(netdissect_options *ndo, const struct macsec_sectag *sectag)
{
return (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) ?
MACSEC_SECTAG_LEN_SCI :
MACSEC_SECTAG_LEN_NOSCI;
}
static int macsec_check_length(netdissect_options *ndo, cconst struct macsec_sectag *sectag, u_int length, u_int caplen)
{
u_int len;
/* we need the full MACsec header in the capture */
if (caplen < (MACSEC_SECTAG_LEN_NOSCI + 2))
return 0;
len = ieee8021ae_sectag_len(ndo, sectag);
if (caplen < (len + 2))
return 0;
if ((GET_U_1(sectag->short_length) & MACSEC_SL_MASK) != 0) {
/* original packet must have exact length */
u_int exact = ETHER_HDRLEN + len + 2 + (GET_U_1(sectag->short_length) & MACSEC_SL_MASK);
return exact == length;
} else {
/* original packet must not be short */
u_int minlen = ETHER_HDRLEN + len + 2 + 48;
return length >= minlen;
}
return 1;
}
#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 }
};
/* 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,
u_short *length_type)
{
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 len;
if (!macsec_check_length(sectag, length, caplen)) {
ND_PRINT((ndo, tstr));
return hdrlen + caplen;
}
if (sectag->unused || sectag->tci_an & MACSEC_TCI_VERSION) {
ND_PRINT((ndo, "%s", istr));
return hdrlen + caplen;
}
if (ndo->ndo_eflag) {
char buf[128];
int n = snprintf(buf, sizeof(buf), "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 (n < 0)
return hdrlen + caplen;
if ((GET_U_1(sectag->short_length) & MACSEC_SL_MASK) != 0 {
int r = snprintf(buf + n, sizeof(buf) - n, ", sl %u",
GET_U_1(sectag->short_length) & MACSEC_SL_MASK);
if (r < 0)
return hdrlen + caplen;
n += r;
}
if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) {
uint64_t sci;
int r;
sci = GET_BE_U_8(sectag->secure_channel_id);
r = snprintf(buf + n, sizeof(buf) - n, ", sci " SCI_FMT, sci);
if (r < 0)
return hdrlen + caplen;
n += r;
}
ND_PRINT((ndo, "%s, ", buf));
}
len = ieee8021ae_sectag_len(ndo, sectag);
*length_type = GET_BE_U_2(*bp + len);
if (ndo->ndo_eflag && *length_type > ETHERMTU && !(GET_U_1(sectag->tci_an) & MACSEC_TCI_E))
ND_PRINT((ndo, "ethertype %s, ", tok2str(ethertype_values,"0x%04x", *length_type)));
if ((GET_U_1(sectag->tci_an) & MACSEC_TCI_CONFID)) {
*bp += len;
*hdrlenp += len;
*lengthp -= len;
*caplenp -= len;
return 0;
} else {
len += 2;
*bp += len;
*hdrlenp += len;
len += MACSEC_DEFAULT_ICV_LEN;
*lengthp -= len;
*caplenp -= len;
return -1;
}
}
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