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
  88 macsec_print_header(netdissect_options *ndo,
  89                     const struct macsec_sectag *sectag,
  90                     u_int short_length)
  91 {
  92         ND_PRINT("an %u, pn %u, flags %s",
  93                  GET_U_1(sectag->tci_an) & MACSEC_AN_MASK,
  94                  GET_BE_U_4(sectag->packet_number),
  95                  bittok2str_nosep(macsec_flag_values, "none",
  96                                   GET_U_1(sectag->tci_an) & MACSEC_TCI_FLAGS));
  97
  98         if (short_length != 0)
  99                 ND_PRINT(", sl %u", short_length);
 100
 101         if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC)
 102                 ND_PRINT(", sci " SCI_FMT, GET_BE_U_8(sectag->secure_channel_id));
 103
 104         ND_PRINT(", ");
 105 }
 106
 107 /* returns < 0 iff the packet can be decoded completely */
 108 int
 109 macsec_print(netdissect_options *ndo, const u_char **bp,
 110              u_int *lengthp, u_int *caplenp, u_int *hdrlenp,
 111              const struct lladdr_info *src, const struct lladdr_info *dst)
 112 {
 113         const char *save_protocol;
 114         const u_char *p = *bp;
 115         u_int length = *lengthp;
 116         u_int caplen = *caplenp;
 117         u_int hdrlen = *hdrlenp;
 118         const struct macsec_sectag *sectag = (const struct macsec_sectag *)p;
 119         u_int sectag_len;
 120         u_int short_length;
 121
 122         save_protocol = ndo->ndo_protocol;
 123         ndo->ndo_protocol = "macsec";
 124
 125         /* we need the full MACsec header in the capture */
 126         if (caplen < MACSEC_SECTAG_LEN_NOSCI) {
 127                 nd_print_trunc(ndo);
 128                 ndo->ndo_protocol = save_protocol;
 129                 return hdrlen + caplen;
 130         }
 131         if (length < MACSEC_SECTAG_LEN_NOSCI) {
 132                 nd_print_trunc(ndo);
 133                 ndo->ndo_protocol = save_protocol;
 134                 return hdrlen + caplen;
 135         }
 136
 137         if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) {
 138                 sectag_len = MACSEC_SECTAG_LEN_SCI;
 139                 if (caplen < MACSEC_SECTAG_LEN_SCI) {
 140                         nd_print_trunc(ndo);
 141                         ndo->ndo_protocol = save_protocol;
 142                         return hdrlen + caplen;
 143                 }
 144                 if (length < MACSEC_SECTAG_LEN_SCI) {
 145                         nd_print_trunc(ndo);
 146                         ndo->ndo_protocol = save_protocol;
 147                         return hdrlen + caplen;
 148                 }
 149         } else
 150                 sectag_len = MACSEC_SECTAG_LEN_NOSCI;
 151
 152         if ((GET_U_1(sectag->short_length) & ~MACSEC_SL_MASK) != 0 ||
 153             GET_U_1(sectag->tci_an) & MACSEC_TCI_VERSION) {
 154                 nd_print_invalid(ndo);
 155                 ndo->ndo_protocol = save_protocol;
 156                 return hdrlen + caplen;
 157         }
 158
 159         short_length = GET_U_1(sectag->short_length) & MACSEC_SL_MASK;
 160         if (ndo->ndo_eflag)
 161                 macsec_print_header(ndo, sectag, short_length);
 162
 163         /* Skip the MACsec header. */
 164         *bp += sectag_len;
 165         *hdrlenp += sectag_len;
 166
 167         /* Remove it from the lengths, as it's been processed. */
 168         *lengthp -= sectag_len;
 169         *caplenp -= sectag_len;
 170
 171         if ((GET_U_1(sectag->tci_an) & MACSEC_TCI_CONFID)) {
 172                 /*
 173                  * The payload is encrypted.  Print link-layer
 174                  * information, if it hasn't already been printed.
 175                  */
 176                 if (!ndo->ndo_eflag) {
 177                         /*
 178                          * Nobody printed the link-layer addresses,
 179                          * so print them, if we have any.
 180                          */
 181                         if (src != NULL && dst != NULL) {
 182                                 ND_PRINT("%s > %s ",
 183                                         (src->addr_string)(ndo, src->addr),
 184                                         (dst->addr_string)(ndo, dst->addr));
 185                         }
 186
 187                         ND_PRINT("802.1AE MACsec, ");
 188
 189                         /*
 190                          * Print the MACsec header.
 191                          */
 192                         macsec_print_header(ndo, sectag, short_length);
 193                 }
 194
 195                 /*
 196                  * Tell our caller it can't be dissected.
 197                  */
 198                 ndo->ndo_protocol = save_protocol;
 199                 return 0;
 200         }
 201
 202         /*
 203          * The payload isn't encrypted; remove the
 204          * ICV length from the lengths, so our caller
 205          * doesn't treat it as payload.
 206          */
 207         if (*lengthp < MACSEC_DEFAULT_ICV_LEN) {
 208                 nd_print_trunc(ndo);
 209                 ndo->ndo_protocol = save_protocol;
 210                 return hdrlen + caplen;
 211         }
 212         if (*caplenp < MACSEC_DEFAULT_ICV_LEN) {
 213                 nd_print_trunc(ndo);
 214                 ndo->ndo_protocol = save_protocol;
 215                 return hdrlen + caplen;
 216         }
 217         *lengthp -= MACSEC_DEFAULT_ICV_LEN;
 218         *caplenp -= MACSEC_DEFAULT_ICV_LEN;
 219         /*
 220          * Update the snapend thus the ICV field is not in the payload for
 221          * the caller.
 222          * The ICV (Integrity Check Value) is at the end of the frame, after
 223          * the secure data.
 224          */
 225         ndo->ndo_snapend -= MACSEC_DEFAULT_ICV_LEN;
 226
 227         /*
 228          * If the SL field is non-zero, then it's the length of the
 229          * Secure Data; otherwise, the Secure Data is what's left
 230          * ver after the MACsec header and ICV are removed.
 231          */
 232         if (short_length != 0) {
 233                 /*
 234                  * If the short length is more than we *have*,
 235                  * that's an error.
 236                  */
 237                 if (short_length > *lengthp) {
 238                         nd_print_trunc(ndo);
 239                         ndo->ndo_protocol = save_protocol;
 240                         return hdrlen + caplen;
 241                 }
 242                 if (short_length > *caplenp) {
 243                         nd_print_trunc(ndo);
 244                         ndo->ndo_protocol = save_protocol;
 245                         return hdrlen + caplen;
 246                 }
 247                 if (*lengthp > short_length)
 248                         *lengthp = short_length;
 249                 if (*caplenp > short_length)
 250                         *caplenp = short_length;
 251         }
 252
 253         ndo->ndo_protocol = save_protocol;
 254         return -1;
 255 }