The Tcpdump Group git mirrors - tcpdump/blob - print-macsec.c

   1 /* Copyright (c) 2017, Sabrina Dubroca <sd@queasysnail.net>
   2  *
   3  * Redistribution and use in source and binary forms, with or without
   4  * modification, are permitted provided that the following conditions
   5  * are met:
   6  *
   7  *   1. Redistributions of source code must retain the above copyright
   8  *      notice, this list of conditions and the following disclaimer.
   9  *   2. Redistributions in binary form must reproduce the above copyright
  10  *      notice, this list of conditions and the following disclaimer in
  11  *      the documentation and/or other materials provided with the
  12  *      distribution.
  13  *   3. The names of the authors may not be used to endorse or promote
  14  *      products derived from this software without specific prior
  15  *      written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  */
  21
  22 /* \summary: MACsec printer */
  23
  24 #ifdef HAVE_CONFIG_H
  25 #include "config.h"
  26 #endif
  27
  28 #include <netdissect-stdinc.h>
  29
  30 #include <string.h>
  31
  32 #include "netdissect.h"
  33 #include "addrtoname.h"
  34 #include "ether.h"
  35 #include "ethertype.h"
  36 #include "extract.h"
  37
  38 static const char tstr[] = "[|MACsec]";
  39
  40 #define MACSEC_DEFAULT_ICV_LEN 16
  41
  42 /* Header format (SecTAG), following an Ethernet header
  43  * IEEE 802.1AE-2006 9.3
  44  *
  45  * +---------------------------------+----------------+----------------+
  46  * |        (MACsec ethertype)       |     TCI_AN     |       SL       |
  47  * +---------------------------------+----------------+----------------+
  48  * |                           Packet Number                           |
  49  * +-------------------------------------------------------------------+
  50  * |                     Secure Channel Identifier                     |
  51  * |                            (optional)                             |
  52  * +-------------------------------------------------------------------+
  53  *
  54  * MACsec ethertype = 0x88e5
  55  * TCI: Tag Control Information, set of flags
  56  * AN: association number, 2 bits
  57  * SL (short length): 6-bit length of the protected payload, if < 48
  58  * Packet Number: 32-bits packet identifier
  59  * Secure Channel Identifier: 64-bit unique identifier, usually
  60  *     composed of a MAC address + 16-bit port number
  61  */
  62 struct macsec_sectag {
  63         nd_uint8_t  tci_an;
  64         nd_uint8_t  short_length;
  65         nd_uint32_t packet_number;
  66         nd_uint8_t  secure_channel_id[8]; /* optional */
  67 };
  68
  69 /* IEEE 802.1AE-2006 9.5 */
  70 #define MACSEC_TCI_VERSION 0x80
  71 #define MACSEC_TCI_ES      0x40 /* end station */
  72 #define MACSEC_TCI_SC      0x20 /* SCI present */
  73 #define MACSEC_TCI_SCB     0x10 /* epon */
  74 #define MACSEC_TCI_E       0x08 /* encryption */
  75 #define MACSEC_TCI_C       0x04 /* changed text */
  76 #define MACSEC_AN_MASK     0x03 /* association number */
  77 #define MACSEC_TCI_FLAGS   (MACSEC_TCI_ES | MACSEC_TCI_SC | MACSEC_TCI_SCB | MACSEC_TCI_E | MACSEC_TCI_C)
  78 #define MACSEC_TCI_CONFID  (MACSEC_TCI_E | MACSEC_TCI_C)
  79 #define MACSEC_SL_MASK     0x3F /* short length */
  80
  81 #define MACSEC_SECTAG_LEN_NOSCI 6
  82 #define MACSEC_SECTAG_LEN_SCI 14
  83 static int
  84 ieee8021ae_sectag_len(netdissect_options *ndo, const struct macsec_sectag *sectag)
  85 {
  86         return (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) ?
  87                MACSEC_SECTAG_LEN_SCI :
  88                MACSEC_SECTAG_LEN_NOSCI;
  89 }
  90
  91 static int macsec_check_length(netdissect_options *ndo, cconst struct macsec_sectag *sectag, u_int length, u_int caplen)
  92 {
  93         u_int len;
  94
  95         /* we need the full MACsec header in the capture */
  96         if (caplen < (MACSEC_SECTAG_LEN_NOSCI + 2))
  97                 return 0;
  98
  99         len = ieee8021ae_sectag_len(ndo, sectag);
 100         if (caplen < (len + 2))
 101                 return 0;
 102
 103         if ((GET_U_1(sectag->short_length) & MACSEC_SL_MASK) != 0) {
 104                 /* original packet must have exact length */
 105                 u_int exact = ETHER_HDRLEN + len + 2 + (GET_U_1(sectag->short_length) & MACSEC_SL_MASK);
 106                 return exact == length;
 107         } else {
 108                 /* original packet must not be short */
 109                 u_int minlen = ETHER_HDRLEN + len + 2 + 48;
 110                 return length >= minlen;
 111         }
 112
 113         return 1;
 114 }
 115
 116 #define SCI_FMT "%016" PRIx64
 117
 118 static const struct tok macsec_flag_values[] = {
 119         { MACSEC_TCI_E,   "E" },
 120         { MACSEC_TCI_C,   "C" },
 121         { MACSEC_TCI_ES,  "S" },
 122         { MACSEC_TCI_SCB, "B" },
 123         { MACSEC_TCI_SC,  "I" },
 124         { 0, NULL }
 125 };
 126
 127 /* returns < 0 iff the packet can be decoded completely */
 128 int macsec_print(netdissect_options *ndo, const u_char **bp,
 129                  u_int *lengthp, u_int *caplenp, u_int *hdrlenp,
 130                  u_short *length_type)
 131 {
 132         const u_char *p = *bp;
 133         u_int length = *lengthp;
 134         u_int caplen = *caplenp;
 135         u_int hdrlen = *hdrlenp;
 136         const struct macsec_sectag *sectag = (const struct macsec_sectag *)p;
 137         u_int len;
 138
 139         if (!macsec_check_length(sectag, length, caplen)) {
 140                 ND_PRINT((ndo, tstr));
 141                 return hdrlen + caplen;
 142         }
 143
 144         if (sectag->unused || sectag->tci_an & MACSEC_TCI_VERSION) {
 145                 ND_PRINT((ndo, "%s", istr));
 146                 return hdrlen + caplen;
 147         }
 148
 149         if (ndo->ndo_eflag) {
 150                 char buf[128];
 151                 int n = snprintf(buf, sizeof(buf), "an %u, pn %u, flags %s",
 152                                  GET_U_1(sectag->tci_an) & MACSEC_AN_MASK,
 153                                  GET_BE_U_4(sectag->packet_number),
 154                                  bittok2str_nosep(macsec_flag_values, "none",
 155                                                   GET_U_1(sectag->tci_an) & MACSEC_TCI_FLAGS));
 156                 if (n < 0)
 157                         return hdrlen + caplen;
 158
 159
 160                 if ((GET_U_1(sectag->short_length) & MACSEC_SL_MASK) != 0 {
 161                         int r = snprintf(buf + n, sizeof(buf) - n, ", sl %u",
 162                                          GET_U_1(sectag->short_length) & MACSEC_SL_MASK);
 163                         if (r < 0)
 164                                 return hdrlen + caplen;
 165                         n += r;
 166                 }
 167
 168                 if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) {
 169                         uint64_t sci;
 170                         int r;
 171                         sci = GET_BE_U_8(sectag->secure_channel_id);
 172                         r = snprintf(buf + n, sizeof(buf) - n, ", sci " SCI_FMT, sci);
 173                         if (r < 0)
 174                                 return hdrlen + caplen;
 175                         n += r;
 176                 }
 177
 178                 ND_PRINT((ndo, "%s, ", buf));
 179         }
 180
 181         len = ieee8021ae_sectag_len(ndo, sectag);
 182         *length_type = GET_BE_U_2(*bp + len);
 183         if (ndo->ndo_eflag && *length_type > ETHERMTU && !(GET_U_1(sectag->tci_an) & MACSEC_TCI_E))
 184                 ND_PRINT((ndo, "ethertype %s, ", tok2str(ethertype_values,"0x%04x", *length_type)));
 185
 186         if ((GET_U_1(sectag->tci_an) & MACSEC_TCI_CONFID)) {
 187                 *bp += len;
 188                 *hdrlenp += len;
 189
 190                 *lengthp -= len;
 191                 *caplenp -= len;
 192                 return 0;
 193         } else {
 194                 len += 2;
 195                 *bp += len;
 196                 *hdrlenp += len;
 197
 198                 len += MACSEC_DEFAULT_ICV_LEN;
 199                 *lengthp -= len;
 200                 *caplenp -= len;
 201                 return -1;
 202         }
 203 }