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 "netdissect.h"
  31 #include "addrtoname.h"
  32 #include "ethertype.h"
  33 #include "extract.h"
  34
  35 #define MACSEC_DEFAULT_ICV_LEN 16
  36
  37 /* Header format (SecTAG), following an Ethernet header
  38  * IEEE 802.1AE-2006 9.3
  39  *
  40  * +---------------------------------+----------------+----------------+
  41  * |        (MACsec ethertype)       |     TCI_AN     |       SL       |
  42  * +---------------------------------+----------------+----------------+
  43  * |                           Packet Number                           |
  44  * +-------------------------------------------------------------------+
  45  * |                     Secure Channel Identifier                     |
  46  * |                            (optional)                             |
  47  * +-------------------------------------------------------------------+
  48  *
  49  * MACsec ethertype = 0x88e5
  50  * TCI: Tag Control Information, set of flags
  51  * AN: association number, 2 bits
  52  * SL (short length): 6-bit length of the protected payload, if < 48
  53  * Packet Number: 32-bits packet identifier
  54  * Secure Channel Identifier: 64-bit unique identifier, usually
  55  *     composed of a MAC address + 16-bit port number
  56  */
  57 struct macsec_sectag {
  58         nd_uint8_t  tci_an;
  59         nd_uint8_t  short_length;
  60         nd_uint32_t packet_number;
  61         nd_uint8_t  secure_channel_id[8]; /* optional */
  62 };
  63
  64 /* IEEE 802.1AE-2006 9.5 */
  65 #define MACSEC_TCI_VERSION 0x80
  66 #define MACSEC_TCI_ES      0x40 /* end station */
  67 #define MACSEC_TCI_SC      0x20 /* SCI present */
  68 #define MACSEC_TCI_SCB     0x10 /* epon */
  69 #define MACSEC_TCI_E       0x08 /* encryption */
  70 #define MACSEC_TCI_C       0x04 /* changed text */
  71 #define MACSEC_AN_MASK     0x03 /* association number */
  72 #define MACSEC_TCI_FLAGS   (MACSEC_TCI_ES | MACSEC_TCI_SC | MACSEC_TCI_SCB | MACSEC_TCI_E | MACSEC_TCI_C)
  73 #define MACSEC_TCI_CONFID  (MACSEC_TCI_E | MACSEC_TCI_C)
  74 #define MACSEC_SL_MASK     0x3F /* short length */
  75
  76 #define MACSEC_SECTAG_LEN_NOSCI 6  /* length of MACsec header without SCI */
  77 #define MACSEC_SECTAG_LEN_SCI   14 /* length of MACsec header with SCI */
  78
  79 #define SCI_FMT "%016" PRIx64
  80
  81 static const struct tok macsec_flag_values[] = {
  82         { MACSEC_TCI_E,   "E" },
  83         { MACSEC_TCI_C,   "C" },
  84         { MACSEC_TCI_ES,  "S" },
  85         { MACSEC_TCI_SCB, "B" },
  86         { MACSEC_TCI_SC,  "I" },
  87         { 0, NULL }
  88 };
  89
  90 static void macsec_print_header(netdissect_options *ndo,
  91                                 const struct macsec_sectag *sectag,
  92                                 u_int short_length)
  93 {
  94         ND_PRINT("an %u, pn %u, flags %s",
  95                  GET_U_1(sectag->tci_an) & MACSEC_AN_MASK,
  96                  GET_BE_U_4(sectag->packet_number),
  97                  bittok2str_nosep(macsec_flag_values, "none",
  98                                   GET_U_1(sectag->tci_an) & MACSEC_TCI_FLAGS));
  99
 100         if (short_length != 0)
 101                 ND_PRINT(", sl %u", short_length);
 102
 103         if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC)
 104                 ND_PRINT(", sci " SCI_FMT, GET_BE_U_8(sectag->secure_channel_id));
 105
 106         ND_PRINT(", ");
 107 }
 108
 109 /* returns < 0 iff the packet can be decoded completely */
 110 int macsec_print(netdissect_options *ndo, const u_char **bp,
 111                  u_int *lengthp, u_int *caplenp, u_int *hdrlenp,
 112                  const struct lladdr_info *src, const struct lladdr_info *dst)
 113 {
 114         const char *save_protocol;
 115         const u_char *p = *bp;
 116         u_int length = *lengthp;
 117         u_int caplen = *caplenp;
 118         u_int hdrlen = *hdrlenp;
 119         const struct macsec_sectag *sectag = (const struct macsec_sectag *)p;
 120         u_int sectag_len;
 121         u_int short_length;
 122
 123         save_protocol = ndo->ndo_protocol;
 124         ndo->ndo_protocol = "macsec";
 125
 126         /* we need the full MACsec header in the capture */
 127         if (caplen < MACSEC_SECTAG_LEN_NOSCI) {
 128                 nd_print_trunc(ndo);
 129                 ndo->ndo_protocol = save_protocol;
 130                 return hdrlen + caplen;
 131         }
 132         if (length < MACSEC_SECTAG_LEN_NOSCI) {
 133                 nd_print_trunc(ndo);
 134                 ndo->ndo_protocol = save_protocol;
 135                 return hdrlen + caplen;
 136         }
 137
 138         if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) {
 139                 sectag_len = MACSEC_SECTAG_LEN_SCI;
 140                 if (caplen < MACSEC_SECTAG_LEN_SCI) {
 141                         nd_print_trunc(ndo);
 142                         ndo->ndo_protocol = save_protocol;
 143                         return hdrlen + caplen;
 144                 }
 145                 if (length < MACSEC_SECTAG_LEN_SCI) {
 146                         nd_print_trunc(ndo);
 147                         ndo->ndo_protocol = save_protocol;
 148                         return hdrlen + caplen;
 149                 }
 150         } else
 151                 sectag_len = MACSEC_SECTAG_LEN_NOSCI;
 152
 153         if ((GET_U_1(sectag->short_length) & ~MACSEC_SL_MASK) != 0 ||
 154             GET_U_1(sectag->tci_an) & MACSEC_TCI_VERSION) {
 155                 nd_print_invalid(ndo);
 156                 ndo->ndo_protocol = save_protocol;
 157                 return hdrlen + caplen;
 158         }
 159
 160         short_length = GET_U_1(sectag->short_length) & MACSEC_SL_MASK;
 161         if (ndo->ndo_eflag)
 162                 macsec_print_header(ndo, sectag, short_length);
 163
 164         /* Skip the MACsec header. */
 165         *bp += sectag_len;
 166         *hdrlenp += sectag_len;
 167
 168         /* Remove it from the lengths, as it's been processed. */
 169         *lengthp -= sectag_len;
 170         *caplenp -= sectag_len;
 171
 172         if ((GET_U_1(sectag->tci_an) & MACSEC_TCI_CONFID)) {
 173                 /*
 174                  * The payload is encrypted.  Print link-layer
 175                  * information, if it hasn't already been printed.
 176                  */
 177                 if (!ndo->ndo_eflag) {
 178                         /*
 179                          * Nobody printed the link-layer addresses,
 180                          * so print them, if we have any.
 181                          */
 182                         if (src != NULL && dst != NULL) {
 183                                 ND_PRINT("%s > %s ",
 184                                         (src->addr_string)(ndo, src->addr),
 185                                         (dst->addr_string)(ndo, dst->addr));
 186                         }
 187
 188                         ND_PRINT("802.1AE MACsec, ");
 189
 190                         /*
 191                          * Print the MACsec header.
 192                          */
 193                         macsec_print_header(ndo, sectag, short_length);
 194                 }
 195
 196                 /*
 197                  * Tell our caller it can't be dissected.
 198                  */
 199                 ndo->ndo_protocol = save_protocol;
 200                 return 0;
 201         }
 202
 203         /*
 204          * The payload isn't encrypted; remove the
 205          * ICV length from the lengths, so our caller
 206          * doesn't treat it as payload.
 207          */
 208         if (*lengthp < MACSEC_DEFAULT_ICV_LEN) {
 209                 nd_print_trunc(ndo);
 210                 ndo->ndo_protocol = save_protocol;
 211                 return hdrlen + caplen;
 212         }
 213         if (*caplenp < MACSEC_DEFAULT_ICV_LEN) {
 214                 nd_print_trunc(ndo);
 215                 ndo->ndo_protocol = save_protocol;
 216                 return hdrlen + caplen;
 217         }
 218         *lengthp -= MACSEC_DEFAULT_ICV_LEN;
 219         *caplenp -= MACSEC_DEFAULT_ICV_LEN;
 220
 221         /*
 222          * If the SL field is non-zero, then it's the length of the
 223          * Secure Data; otherwise, the Secure Data is what's left
 224          * ver after the MACsec header and ICV are removed.
 225          */
 226         if (short_length != 0) {
 227                 /*
 228                  * If the short length is more than we *have*,
 229                  * that's an error.
 230                  */
 231                 if (short_length > *lengthp) {
 232                         nd_print_trunc(ndo);
 233                         ndo->ndo_protocol = save_protocol;
 234                         return hdrlen + caplen;
 235                 }
 236                 if (short_length > *caplenp) {
 237                         nd_print_trunc(ndo);
 238                         ndo->ndo_protocol = save_protocol;
 239                         return hdrlen + caplen;
 240                 }
 241                 if (*lengthp > short_length)
 242                         *lengthp = short_length;
 243                 if (*caplenp > short_length)
 244                         *caplenp = short_length;
 245         }
 246
 247         ndo->ndo_protocol = save_protocol;
 248         return -1;
 249 }