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 "extract.h"
  33
  34 #define MACSEC_DEFAULT_ICV_LEN 16
  35
  36 /* Header format (SecTAG), following an Ethernet header
  37  * IEEE 802.1AE-2006 9.3
  38  *
  39  * +---------------------------------+----------------+----------------+
  40  * |        (MACsec ethertype)       |     TCI_AN     |       SL       |
  41  * +---------------------------------+----------------+----------------+
  42  * |                           Packet Number                           |
  43  * +-------------------------------------------------------------------+
  44  * |                     Secure Channel Identifier                     |
  45  * |                            (optional)                             |
  46  * +-------------------------------------------------------------------+
  47  *
  48  * MACsec ethertype = 0x88e5
  49  * TCI: Tag Control Information, set of flags
  50  * AN: association number, 2 bits
  51  * SL (short length): 6-bit length of the protected payload, if < 48
  52  * Packet Number: 32-bits packet identifier
  53  * Secure Channel Identifier: 64-bit unique identifier, usually
  54  *     composed of a MAC address + 16-bit port number
  55  */
  56 struct macsec_sectag {
  57         nd_uint8_t  tci_an;
  58         nd_uint8_t  short_length;
  59         nd_uint32_t packet_number;
  60         nd_uint8_t  secure_channel_id[8]; /* optional */
  61 };
  62
  63 /* IEEE 802.1AE-2006 9.5 */
  64 #define MACSEC_TCI_VERSION 0x80
  65 #define MACSEC_TCI_ES      0x40 /* end station */
  66 #define MACSEC_TCI_SC      0x20 /* SCI present */
  67 #define MACSEC_TCI_SCB     0x10 /* epon */
  68 #define MACSEC_TCI_E       0x08 /* encryption */
  69 #define MACSEC_TCI_C       0x04 /* changed text */
  70 #define MACSEC_AN_MASK     0x03 /* association number */
  71 #define MACSEC_TCI_FLAGS   (MACSEC_TCI_ES | MACSEC_TCI_SC | MACSEC_TCI_SCB | MACSEC_TCI_E | MACSEC_TCI_C)
  72 #define MACSEC_TCI_CONFID  (MACSEC_TCI_E | MACSEC_TCI_C)
  73 #define MACSEC_SL_MASK     0x3F /* short length */
  74
  75 #define MACSEC_SECTAG_LEN_NOSCI 6  /* length of MACsec header without SCI */
  76 #define MACSEC_SECTAG_LEN_SCI   14 /* length of MACsec header with SCI */
  77
  78 #define SCI_FMT "%016" PRIx64
  79
  80 static const struct tok macsec_flag_values[] = {
  81         { MACSEC_TCI_E,   "E" },
  82         { MACSEC_TCI_C,   "C" },
  83         { MACSEC_TCI_ES,  "S" },
  84         { MACSEC_TCI_SCB, "B" },
  85         { MACSEC_TCI_SC,  "I" },
  86         { 0, NULL }
  87 };
  88
  89 static void
  90 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
 111 macsec_print(netdissect_options *ndo, const u_char **bp,
 112              u_int *lengthp, u_int *caplenp, u_int *hdrlenp,
 113              const struct lladdr_info *src, const struct lladdr_info *dst)
 114 {
 115         const char *save_protocol;
 116         const u_char *p = *bp;
 117         u_int length = *lengthp;
 118         u_int caplen = *caplenp;
 119         u_int hdrlen = *hdrlenp;
 120         const struct macsec_sectag *sectag = (const struct macsec_sectag *)p;
 121         u_int sectag_len;
 122         u_int short_length;
 123
 124         save_protocol = ndo->ndo_protocol;
 125         ndo->ndo_protocol = "macsec";
 126
 127         /* we need the full MACsec header in the capture */
 128         if (caplen < MACSEC_SECTAG_LEN_NOSCI) {
 129                 nd_print_trunc(ndo);
 130                 ndo->ndo_protocol = save_protocol;
 131                 return hdrlen + caplen;
 132         }
 133         if (length < MACSEC_SECTAG_LEN_NOSCI) {
 134                 nd_print_trunc(ndo);
 135                 ndo->ndo_protocol = save_protocol;
 136                 return hdrlen + caplen;
 137         }
 138
 139         if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) {
 140                 sectag_len = MACSEC_SECTAG_LEN_SCI;
 141                 if (caplen < MACSEC_SECTAG_LEN_SCI) {
 142                         nd_print_trunc(ndo);
 143                         ndo->ndo_protocol = save_protocol;
 144                         return hdrlen + caplen;
 145                 }
 146                 if (length < MACSEC_SECTAG_LEN_SCI) {
 147                         nd_print_trunc(ndo);
 148                         ndo->ndo_protocol = save_protocol;
 149                         return hdrlen + caplen;
 150                 }
 151         } else
 152                 sectag_len = MACSEC_SECTAG_LEN_NOSCI;
 153
 154         if ((GET_U_1(sectag->short_length) & ~MACSEC_SL_MASK) != 0 ||
 155             GET_U_1(sectag->tci_an) & MACSEC_TCI_VERSION) {
 156                 nd_print_invalid(ndo);
 157                 ndo->ndo_protocol = save_protocol;
 158                 return hdrlen + caplen;
 159         }
 160
 161         short_length = GET_U_1(sectag->short_length) & MACSEC_SL_MASK;
 162         if (ndo->ndo_eflag)
 163                 macsec_print_header(ndo, sectag, short_length);
 164
 165         /* Skip the MACsec header. */
 166         *bp += sectag_len;
 167         *hdrlenp += sectag_len;
 168
 169         /* Remove it from the lengths, as it's been processed. */
 170         *lengthp -= sectag_len;
 171         *caplenp -= sectag_len;
 172
 173         if ((GET_U_1(sectag->tci_an) & MACSEC_TCI_CONFID)) {
 174                 /*
 175                  * The payload is encrypted.  Print link-layer
 176                  * information, if it hasn't already been printed.
 177                  */
 178                 if (!ndo->ndo_eflag) {
 179                         /*
 180                          * Nobody printed the link-layer addresses,
 181                          * so print them, if we have any.
 182                          */
 183                         if (src != NULL && dst != NULL) {
 184                                 ND_PRINT("%s > %s ",
 185                                         (src->addr_string)(ndo, src->addr),
 186                                         (dst->addr_string)(ndo, dst->addr));
 187                         }
 188
 189                         ND_PRINT("802.1AE MACsec, ");
 190
 191                         /*
 192                          * Print the MACsec header.
 193                          */
 194                         macsec_print_header(ndo, sectag, short_length);
 195                 }
 196
 197                 /*
 198                  * Tell our caller it can't be dissected.
 199                  */
 200                 ndo->ndo_protocol = save_protocol;
 201                 return 0;
 202         }
 203
 204         /*
 205          * The payload isn't encrypted; remove the
 206          * ICV length from the lengths, so our caller
 207          * doesn't treat it as payload.
 208          */
 209         if (*lengthp < MACSEC_DEFAULT_ICV_LEN) {
 210                 nd_print_trunc(ndo);
 211                 ndo->ndo_protocol = save_protocol;
 212                 return hdrlen + caplen;
 213         }
 214         if (*caplenp < MACSEC_DEFAULT_ICV_LEN) {
 215                 nd_print_trunc(ndo);
 216                 ndo->ndo_protocol = save_protocol;
 217                 return hdrlen + caplen;
 218         }
 219         *lengthp -= MACSEC_DEFAULT_ICV_LEN;
 220         *caplenp -= MACSEC_DEFAULT_ICV_LEN;
 221         /*
 222          * Update the snapend thus the ICV field is not in the payload for
 223          * the caller.
 224          * The ICV (Integrity Check Value) is at the end of the frame, after
 225          * the secure data.
 226          */
 227         ndo->ndo_snapend -= MACSEC_DEFAULT_ICV_LEN;
 228
 229         /*
 230          * If the SL field is non-zero, then it's the length of the
 231          * Secure Data; otherwise, the Secure Data is what's left
 232          * ver after the MACsec header and ICV are removed.
 233          */
 234         if (short_length != 0) {
 235                 /*
 236                  * If the short length is more than we *have*,
 237                  * that's an error.
 238                  */
 239                 if (short_length > *lengthp) {
 240                         nd_print_trunc(ndo);
 241                         ndo->ndo_protocol = save_protocol;
 242                         return hdrlen + caplen;
 243                 }
 244                 if (short_length > *caplenp) {
 245                         nd_print_trunc(ndo);
 246                         ndo->ndo_protocol = save_protocol;
 247                         return hdrlen + caplen;
 248                 }
 249                 if (*lengthp > short_length)
 250                         *lengthp = short_length;
 251                 if (*caplenp > short_length)
 252                         *caplenp = short_length;
 253         }
 254
 255         ndo->ndo_protocol = save_protocol;
 256         return -1;
 257 }