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         u_char  tci_an;
  64 #if __BYTE_ORDER == __LITTLE_ENDIAN
  65         u_char short_length:6,
  66                      unused:2;
  67 #else /* __BYTE_ORDER == __BIG_ENDIAN */
  68         u_char        unused:2,
  69                 short_length:6;
  70 #endif
  71         uint32_t packet_number;
  72         u_char secure_channel_id[8]; /* optional */
  73 } __attribute__((packed));
  74
  75 /* IEEE 802.1AE-2006 9.5 */
  76 #define MACSEC_TCI_VERSION 0x80
  77 #define MACSEC_TCI_ES      0x40 /* end station */
  78 #define MACSEC_TCI_SC      0x20 /* SCI present */
  79 #define MACSEC_TCI_SCB     0x10 /* epon */
  80 #define MACSEC_TCI_E       0x08 /* encryption */
  81 #define MACSEC_TCI_C       0x04 /* changed text */
  82 #define MACSEC_AN_MASK     0x03 /* association number */
  83 #define MACSEC_TCI_FLAGS   (MACSEC_TCI_ES | MACSEC_TCI_SC | MACSEC_TCI_SCB | MACSEC_TCI_E | MACSEC_TCI_C)
  84 #define MACSEC_TCI_CONFID  (MACSEC_TCI_E | MACSEC_TCI_C)
  85
  86 #define MACSEC_SECTAG_LEN_NOSCI 6
  87 #define MACSEC_SECTAG_LEN_SCI 14
  88 static int
  89 ieee8021ae_sectag_len(const struct macsec_sectag *sectag)
  90 {
  91         return (sectag->tci_an & MACSEC_TCI_SC) ?
  92                MACSEC_SECTAG_LEN_SCI :
  93                MACSEC_SECTAG_LEN_NOSCI;
  94 }
  95
  96 static int macsec_check_length(const struct macsec_sectag *sectag, u_int length, u_int caplen)
  97 {
  98         u_int len;
  99
 100         /* we need the full MACsec header in the capture */
 101         if (caplen < (MACSEC_SECTAG_LEN_NOSCI + 2))
 102                 return 0;
 103
 104         len = ieee8021ae_sectag_len(sectag);
 105         if (caplen < (len + 2))
 106                 return 0;
 107
 108         if (sectag->short_length != 0) {
 109                 /* original packet must have exact length */
 110                 u_int exact = ETHER_HDRLEN + len + 2 + sectag->short_length;
 111                 return exact == length;
 112         } else {
 113                 /* original packet must not be short */
 114                 u_int minlen = ETHER_HDRLEN + len + 2 + 48;
 115                 return length >= minlen;
 116         }
 117
 118         return 1;
 119 }
 120
 121 #define SCI_FMT "%016" PRIx64
 122
 123 static const struct tok macsec_flag_values[] = {
 124         { MACSEC_TCI_E,   "E" },
 125         { MACSEC_TCI_C,   "C" },
 126         { MACSEC_TCI_ES,  "S" },
 127         { MACSEC_TCI_SCB, "B" },
 128         { MACSEC_TCI_SC,  "I" },
 129         { 0, NULL }
 130 };
 131
 132 /* returns < 0 iff the packet can be decoded completely */
 133 int macsec_print(netdissect_options *ndo, const u_char **bp,
 134                  u_int *lengthp, u_int *caplenp, u_int *hdrlenp,
 135                  u_short *length_type)
 136 {
 137         const u_char *p = *bp;
 138         u_int length = *lengthp;
 139         u_int caplen = *caplenp;
 140         u_int hdrlen = *hdrlenp;
 141         const struct macsec_sectag *sectag = (const struct macsec_sectag *)p;
 142         u_int len;
 143
 144         if (!macsec_check_length(sectag, length, caplen)) {
 145                 ND_PRINT((ndo, tstr));
 146                 return hdrlen + caplen;
 147         }
 148
 149         if (sectag->unused || sectag->tci_an & MACSEC_TCI_VERSION) {
 150                 ND_PRINT((ndo, "%s", istr));
 151                 return hdrlen + caplen;
 152         }
 153
 154         if (ndo->ndo_eflag) {
 155                 char buf[128];
 156                 int n = snprintf(buf, sizeof(buf), "an %d, pn %d, flags %s",
 157                                  sectag->tci_an & MACSEC_AN_MASK,
 158                                  EXTRACT_32BITS(&sectag->packet_number),
 159                                  bittok2str_nosep(macsec_flag_values, "none",
 160                                                   sectag->tci_an & MACSEC_TCI_FLAGS));
 161                 if (n < 0)
 162                         return hdrlen + caplen;
 163
 164
 165                 if (sectag->short_length) {
 166                         int r = snprintf(buf + n, sizeof(buf) - n, ", sl %d",
 167                                          sectag->short_length);
 168                         if (r < 0)
 169                                 return hdrlen + caplen;
 170                         n += r;
 171                 }
 172
 173                 if (sectag->tci_an & MACSEC_TCI_SC) {
 174                         uint64_t sci;
 175                         int r;
 176                         sci = EXTRACT_64BITS(sectag->secure_channel_id);
 177                         r = snprintf(buf + n, sizeof(buf) - n, ", sci " SCI_FMT, sci);
 178                         if (r < 0)
 179                                 return hdrlen + caplen;
 180                         n += r;
 181                 }
 182
 183                 ND_PRINT((ndo, "%s, ", buf));
 184         }
 185
 186         len = ieee8021ae_sectag_len(sectag);
 187         *length_type = EXTRACT_16BITS(*bp + len);
 188         if (ndo->ndo_eflag && *length_type > ETHERMTU && !(sectag->tci_an & MACSEC_TCI_E))
 189                 ND_PRINT((ndo, "ethertype %s, ", tok2str(ethertype_values,"0x%04x", *length_type)));
 190
 191         if ((sectag->tci_an & MACSEC_TCI_CONFID)) {
 192                 *bp += len;
 193                 *hdrlenp += len;
 194
 195                 *lengthp -= len;
 196                 *caplenp -= len;
 197                 return 0;
 198         } else {
 199                 len += 2;
 200                 *bp += len;
 201                 *hdrlenp += len;
 202
 203                 len += MACSEC_DEFAULT_ICV_LEN;
 204                 *lengthp -= len;
 205                 *caplenp -= len;
 206                 return -1;
 207         }
 208 }