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 #include <config.h>
  25
  26 #include "netdissect-stdinc.h"
  27
  28 #include "netdissect.h"
  29 #include "addrtoname.h"
  30 #include "extract.h"
  31
  32 #define MACSEC_DEFAULT_ICV_LEN 16
  33
  34 /* Header format (SecTAG), following an Ethernet header
  35  * IEEE 802.1AE-2006 9.3
  36  *
  37  * +---------------------------------+----------------+----------------+
  38  * |        (MACsec ethertype)       |     TCI_AN     |       SL       |
  39  * +---------------------------------+----------------+----------------+
  40  * |                           Packet Number                           |
  41  * +-------------------------------------------------------------------+
  42  * |                     Secure Channel Identifier                     |
  43  * |                            (optional)                             |
  44  * +-------------------------------------------------------------------+
  45  *
  46  * MACsec ethertype = 0x88e5
  47  * TCI: Tag Control Information, set of flags
  48  * AN: association number, 2 bits
  49  * SL (short length): 6-bit length of the protected payload, if < 48
  50  * Packet Number: 32-bits packet identifier
  51  * Secure Channel Identifier: 64-bit unique identifier, usually
  52  *     composed of a MAC address + 16-bit port number
  53  */
  54 struct macsec_sectag {
  55         nd_uint8_t  tci_an;
  56         nd_uint8_t  short_length;
  57         nd_uint32_t packet_number;
  58         nd_uint8_t  secure_channel_id[8]; /* optional */
  59 };
  60
  61 /* IEEE 802.1AE-2006 9.5 */
  62 #define MACSEC_TCI_VERSION 0x80
  63 #define MACSEC_TCI_ES      0x40 /* end station */
  64 #define MACSEC_TCI_SC      0x20 /* SCI present */
  65 #define MACSEC_TCI_SCB     0x10 /* epon */
  66 #define MACSEC_TCI_E       0x08 /* encryption */
  67 #define MACSEC_TCI_C       0x04 /* changed text */
  68 #define MACSEC_AN_MASK     0x03 /* association number */
  69 #define MACSEC_TCI_FLAGS   (MACSEC_TCI_ES | MACSEC_TCI_SC | MACSEC_TCI_SCB | MACSEC_TCI_E | MACSEC_TCI_C)
  70 #define MACSEC_TCI_CONFID  (MACSEC_TCI_E | MACSEC_TCI_C)
  71 #define MACSEC_SL_MASK     0x3F /* short length */
  72
  73 #define MACSEC_SECTAG_LEN_NOSCI 6  /* length of MACsec header without SCI */
  74 #define MACSEC_SECTAG_LEN_SCI   14 /* length of MACsec header with SCI */
  75
  76 #define SCI_FMT "%016" PRIx64
  77
  78 static const struct tok macsec_flag_values[] = {
  79         { MACSEC_TCI_E,   "E" },
  80         { MACSEC_TCI_C,   "C" },
  81         { MACSEC_TCI_ES,  "S" },
  82         { MACSEC_TCI_SCB, "B" },
  83         { MACSEC_TCI_SC,  "I" },
  84         { 0, NULL }
  85 };
  86
  87 static void macsec_print_header(netdissect_options *ndo,
  88                                 const struct macsec_sectag *sectag,
  89                                 u_int short_length)
  90 {
  91         ND_PRINT("an %u, pn %u, flags %s",
  92                  GET_U_1(sectag->tci_an) & MACSEC_AN_MASK,
  93                  GET_BE_U_4(sectag->packet_number),
  94                  bittok2str_nosep(macsec_flag_values, "none",
  95                                   GET_U_1(sectag->tci_an) & MACSEC_TCI_FLAGS));
  96
  97         if (short_length != 0)
  98                 ND_PRINT(", sl %u", short_length);
  99
 100         if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC)
 101                 ND_PRINT(", sci " SCI_FMT, GET_BE_U_8(sectag->secure_channel_id));
 102
 103         ND_PRINT(", ");
 104 }
 105
 106 /* returns < 0 iff the packet can be decoded completely */
 107 int macsec_print(netdissect_options *ndo, const u_char **bp,
 108                  u_int *lengthp, u_int *caplenp, u_int *hdrlenp,
 109                  const struct lladdr_info *src, const struct lladdr_info *dst)
 110 {
 111         const char *save_protocol;
 112         const u_char *p = *bp;
 113         u_int length = *lengthp;
 114         u_int caplen = *caplenp;
 115         u_int hdrlen = *hdrlenp;
 116         const struct macsec_sectag *sectag = (const struct macsec_sectag *)p;
 117         u_int sectag_len;
 118         u_int short_length;
 119
 120         save_protocol = ndo->ndo_protocol;
 121         ndo->ndo_protocol = "macsec";
 122
 123         /* we need the full MACsec header in the capture */
 124         if (caplen < MACSEC_SECTAG_LEN_NOSCI) {
 125                 nd_print_trunc(ndo);
 126                 ndo->ndo_protocol = save_protocol;
 127                 return hdrlen + caplen;
 128         }
 129         if (length < MACSEC_SECTAG_LEN_NOSCI) {
 130                 nd_print_trunc(ndo);
 131                 ndo->ndo_protocol = save_protocol;
 132                 return hdrlen + caplen;
 133         }
 134
 135         if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) {
 136                 sectag_len = MACSEC_SECTAG_LEN_SCI;
 137                 if (caplen < MACSEC_SECTAG_LEN_SCI) {
 138                         nd_print_trunc(ndo);
 139                         ndo->ndo_protocol = save_protocol;
 140                         return hdrlen + caplen;
 141                 }
 142                 if (length < MACSEC_SECTAG_LEN_SCI) {
 143                         nd_print_trunc(ndo);
 144                         ndo->ndo_protocol = save_protocol;
 145                         return hdrlen + caplen;
 146                 }
 147         } else
 148                 sectag_len = MACSEC_SECTAG_LEN_NOSCI;
 149
 150         if ((GET_U_1(sectag->short_length) & ~MACSEC_SL_MASK) != 0 ||
 151             GET_U_1(sectag->tci_an) & MACSEC_TCI_VERSION) {
 152                 nd_print_invalid(ndo);
 153                 ndo->ndo_protocol = save_protocol;
 154                 return hdrlen + caplen;
 155         }
 156
 157         short_length = GET_U_1(sectag->short_length) & MACSEC_SL_MASK;
 158         if (ndo->ndo_eflag)
 159                 macsec_print_header(ndo, sectag, short_length);
 160
 161         /* Skip the MACsec header. */
 162         *bp += sectag_len;
 163         *hdrlenp += sectag_len;
 164
 165         /* Remove it from the lengths, as it's been processed. */
 166         *lengthp -= sectag_len;
 167         *caplenp -= sectag_len;
 168
 169         if ((GET_U_1(sectag->tci_an) & MACSEC_TCI_CONFID)) {
 170                 /*
 171                  * The payload is encrypted.  Print link-layer
 172                  * information, if it hasn't already been printed.
 173                  */
 174                 if (!ndo->ndo_eflag) {
 175                         /*
 176                          * Nobody printed the link-layer addresses,
 177                          * so print them, if we have any.
 178                          */
 179                         if (src != NULL && dst != NULL) {
 180                                 ND_PRINT("%s > %s ",
 181                                         (src->addr_string)(ndo, src->addr),
 182                                         (dst->addr_string)(ndo, dst->addr));
 183                         }
 184
 185                         ND_PRINT("802.1AE MACsec, ");
 186
 187                         /*
 188                          * Print the MACsec header.
 189                          */
 190                         macsec_print_header(ndo, sectag, short_length);
 191                 }
 192
 193                 /*
 194                  * Tell our caller it can't be dissected.
 195                  */
 196                 ndo->ndo_protocol = save_protocol;
 197                 return 0;
 198         }
 199
 200         /*
 201          * The payload isn't encrypted; remove the
 202          * ICV length from the lengths, so our caller
 203          * doesn't treat it as payload.
 204          */
 205         if (*lengthp < MACSEC_DEFAULT_ICV_LEN) {
 206                 nd_print_trunc(ndo);
 207                 ndo->ndo_protocol = save_protocol;
 208                 return hdrlen + caplen;
 209         }
 210         if (*caplenp < MACSEC_DEFAULT_ICV_LEN) {
 211                 nd_print_trunc(ndo);
 212                 ndo->ndo_protocol = save_protocol;
 213                 return hdrlen + caplen;
 214         }
 215         *lengthp -= MACSEC_DEFAULT_ICV_LEN;
 216         *caplenp -= MACSEC_DEFAULT_ICV_LEN;
 217         /*
 218          * Update the snapend thus the ICV field is not in the payload for
 219          * the caller.
 220          * The ICV (Integrity Check Value) is at the end of the frame, after
 221          * the secure data.
 222          */
 223         ndo->ndo_snapend -= MACSEC_DEFAULT_ICV_LEN;
 224
 225         /*
 226          * If the SL field is non-zero, then it's the length of the
 227          * Secure Data; otherwise, the Secure Data is what's left
 228          * ver after the MACsec header and ICV are removed.
 229          */
 230         if (short_length != 0) {
 231                 /*
 232                  * If the short length is more than we *have*,
 233                  * that's an error.
 234                  */
 235                 if (short_length > *lengthp) {
 236                         nd_print_trunc(ndo);
 237                         ndo->ndo_protocol = save_protocol;
 238                         return hdrlen + caplen;
 239                 }
 240                 if (short_length > *caplenp) {
 241                         nd_print_trunc(ndo);
 242                         ndo->ndo_protocol = save_protocol;
 243                         return hdrlen + caplen;
 244                 }
 245                 if (*lengthp > short_length)
 246                         *lengthp = short_length;
 247                 if (*caplenp > short_length)
 248                         *caplenp = short_length;
 249         }
 250
 251         ndo->ndo_protocol = save_protocol;
 252         return -1;
 253 }