tcpdump  4.99.1
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print-macsec.c
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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 {
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 
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),
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 
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  * Update the snapend thus the ICV field is not in the payload for
222  * the caller.
223  * The ICV (Integrity Check Value) is at the end of the frame, after
224  * the secure data.
225  */
227 
228  /*
229  * If the SL field is non-zero, then it's the length of the
230  * Secure Data; otherwise, the Secure Data is what's left
231  * ver after the MACsec header and ICV are removed.
232  */
233  if (short_length != 0) {
234  /*
235  * If the short length is more than we *have*,
236  * that's an error.
237  */
238  if (short_length > *lengthp) {
239  nd_print_trunc(ndo);
240  ndo->ndo_protocol = save_protocol;
241  return hdrlen + caplen;
242  }
243  if (short_length > *caplenp) {
244  nd_print_trunc(ndo);
245  ndo->ndo_protocol = save_protocol;
246  return hdrlen + caplen;
247  }
248  if (*lengthp > short_length)
249  *lengthp = short_length;
250  if (*caplenp > short_length)
251  *caplenp = short_length;
252  }
253 
254  ndo->ndo_protocol = save_protocol;
255  return -1;
256 }
#define GET_BE_U_4(p)
Definition: extract.h:877
#define GET_BE_U_8(p)
Definition: extract.h:881
#define GET_U_1(p)
Definition: extract.h:872
void nd_print_invalid(netdissect_options *)
Definition: util-print.c:429
void nd_print_trunc(netdissect_options *)
Definition: util-print.c:409
char * bittok2str_nosep(const struct tok *, const char *, u_int)
Definition: util-print.c:547
#define ND_PRINT(...)
Definition: netdissect.h:385
unsigned char nd_uint32_t[4]
Definition: netdissect.h:49
unsigned char nd_uint8_t[1]
Definition: netdissect.h:46
#define SCI_FMT
Definition: print-macsec.c:79
int macsec_print(netdissect_options *ndo, const u_char **bp, u_int *lengthp, u_int *caplenp, u_int *hdrlenp, const struct lladdr_info *src, const struct lladdr_info *dst)
Definition: print-macsec.c:110
#define MACSEC_SECTAG_LEN_NOSCI
Definition: print-macsec.c:76
#define MACSEC_TCI_ES
Definition: print-macsec.c:66
#define MACSEC_TCI_C
Definition: print-macsec.c:70
#define MACSEC_TCI_VERSION
Definition: print-macsec.c:65
#define MACSEC_TCI_SCB
Definition: print-macsec.c:68
#define MACSEC_SECTAG_LEN_SCI
Definition: print-macsec.c:77
static const struct tok macsec_flag_values[]
Definition: print-macsec.c:81
#define MACSEC_AN_MASK
Definition: print-macsec.c:71
#define MACSEC_TCI_E
Definition: print-macsec.c:69
#define MACSEC_DEFAULT_ICV_LEN
Definition: print-macsec.c:35
static void macsec_print_header(netdissect_options *ndo, const struct macsec_sectag *sectag, u_int short_length)
Definition: print-macsec.c:90
#define MACSEC_TCI_SC
Definition: print-macsec.c:67
#define MACSEC_TCI_CONFID
Definition: print-macsec.c:73
#define MACSEC_TCI_FLAGS
Definition: print-macsec.c:72
#define MACSEC_SL_MASK
Definition: print-macsec.c:74
const u_char * addr
Definition: netdissect.h:545
const char *(* addr_string)(netdissect_options *, const u_char *)
Definition: netdissect.h:544
nd_uint8_t tci_an
Definition: print-macsec.c:58
nd_uint8_t short_length
Definition: print-macsec.c:59
nd_uint8_t secure_channel_id[8]
Definition: print-macsec.c:61
nd_uint32_t packet_number
Definition: print-macsec.c:60
const u_char * ndo_snapend
Definition: netdissect.h:239
const char * ndo_protocol
Definition: netdissect.h:218