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-rw-r--r--print-macsec.c256
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diff --git a/print-macsec.c b/print-macsec.c
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+/* Copyright (c) 2017, Sabrina Dubroca <sd@queasysnail.net>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ * 3. The names of the authors may not be used to endorse or promote
+ * products derived from this software without specific prior
+ * written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+/* \summary: MACsec printer */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "netdissect-stdinc.h"
+
+#include "netdissect.h"
+#include "addrtoname.h"
+#include "ethertype.h"
+#include "extract.h"
+
+#define MACSEC_DEFAULT_ICV_LEN 16
+
+/* Header format (SecTAG), following an Ethernet header
+ * IEEE 802.1AE-2006 9.3
+ *
+ * +---------------------------------+----------------+----------------+
+ * | (MACsec ethertype) | TCI_AN | SL |
+ * +---------------------------------+----------------+----------------+
+ * | Packet Number |
+ * +-------------------------------------------------------------------+
+ * | Secure Channel Identifier |
+ * | (optional) |
+ * +-------------------------------------------------------------------+
+ *
+ * MACsec ethertype = 0x88e5
+ * TCI: Tag Control Information, set of flags
+ * AN: association number, 2 bits
+ * SL (short length): 6-bit length of the protected payload, if < 48
+ * Packet Number: 32-bits packet identifier
+ * Secure Channel Identifier: 64-bit unique identifier, usually
+ * composed of a MAC address + 16-bit port number
+ */
+struct macsec_sectag {
+ nd_uint8_t tci_an;
+ nd_uint8_t short_length;
+ nd_uint32_t packet_number;
+ nd_uint8_t secure_channel_id[8]; /* optional */
+};
+
+/* IEEE 802.1AE-2006 9.5 */
+#define MACSEC_TCI_VERSION 0x80
+#define MACSEC_TCI_ES 0x40 /* end station */
+#define MACSEC_TCI_SC 0x20 /* SCI present */
+#define MACSEC_TCI_SCB 0x10 /* epon */
+#define MACSEC_TCI_E 0x08 /* encryption */
+#define MACSEC_TCI_C 0x04 /* changed text */
+#define MACSEC_AN_MASK 0x03 /* association number */
+#define MACSEC_TCI_FLAGS (MACSEC_TCI_ES | MACSEC_TCI_SC | MACSEC_TCI_SCB | MACSEC_TCI_E | MACSEC_TCI_C)
+#define MACSEC_TCI_CONFID (MACSEC_TCI_E | MACSEC_TCI_C)
+#define MACSEC_SL_MASK 0x3F /* short length */
+
+#define MACSEC_SECTAG_LEN_NOSCI 6 /* length of MACsec header without SCI */
+#define MACSEC_SECTAG_LEN_SCI 14 /* length of MACsec header with SCI */
+
+#define SCI_FMT "%016" PRIx64
+
+static const struct tok macsec_flag_values[] = {
+ { MACSEC_TCI_E, "E" },
+ { MACSEC_TCI_C, "C" },
+ { MACSEC_TCI_ES, "S" },
+ { MACSEC_TCI_SCB, "B" },
+ { MACSEC_TCI_SC, "I" },
+ { 0, NULL }
+};
+
+static void macsec_print_header(netdissect_options *ndo,
+ const struct macsec_sectag *sectag,
+ u_int short_length)
+{
+ ND_PRINT("an %u, pn %u, flags %s",
+ GET_U_1(sectag->tci_an) & MACSEC_AN_MASK,
+ GET_BE_U_4(sectag->packet_number),
+ bittok2str_nosep(macsec_flag_values, "none",
+ GET_U_1(sectag->tci_an) & MACSEC_TCI_FLAGS));
+
+ if (short_length != 0)
+ ND_PRINT(", sl %u", short_length);
+
+ if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC)
+ ND_PRINT(", sci " SCI_FMT, GET_BE_U_8(sectag->secure_channel_id));
+
+ ND_PRINT(", ");
+}
+
+/* returns < 0 iff the packet can be decoded completely */
+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)
+{
+ const char *save_protocol;
+ const u_char *p = *bp;
+ u_int length = *lengthp;
+ u_int caplen = *caplenp;
+ u_int hdrlen = *hdrlenp;
+ const struct macsec_sectag *sectag = (const struct macsec_sectag *)p;
+ u_int sectag_len;
+ u_int short_length;
+
+ save_protocol = ndo->ndo_protocol;
+ ndo->ndo_protocol = "macsec";
+
+ /* we need the full MACsec header in the capture */
+ if (caplen < MACSEC_SECTAG_LEN_NOSCI) {
+ nd_print_trunc(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+ if (length < MACSEC_SECTAG_LEN_NOSCI) {
+ nd_print_trunc(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+
+ if (GET_U_1(sectag->tci_an) & MACSEC_TCI_SC) {
+ sectag_len = MACSEC_SECTAG_LEN_SCI;
+ if (caplen < MACSEC_SECTAG_LEN_SCI) {
+ nd_print_trunc(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+ if (length < MACSEC_SECTAG_LEN_SCI) {
+ nd_print_trunc(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+ } else
+ sectag_len = MACSEC_SECTAG_LEN_NOSCI;
+
+ if ((GET_U_1(sectag->short_length) & ~MACSEC_SL_MASK) != 0 ||
+ GET_U_1(sectag->tci_an) & MACSEC_TCI_VERSION) {
+ nd_print_invalid(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+
+ short_length = GET_U_1(sectag->short_length) & MACSEC_SL_MASK;
+ if (ndo->ndo_eflag)
+ macsec_print_header(ndo, sectag, short_length);
+
+ /* Skip the MACsec header. */
+ *bp += sectag_len;
+ *hdrlenp += sectag_len;
+
+ /* Remove it from the lengths, as it's been processed. */
+ *lengthp -= sectag_len;
+ *caplenp -= sectag_len;
+
+ if ((GET_U_1(sectag->tci_an) & MACSEC_TCI_CONFID)) {
+ /*
+ * The payload is encrypted. Print link-layer
+ * information, if it hasn't already been printed.
+ */
+ if (!ndo->ndo_eflag) {
+ /*
+ * Nobody printed the link-layer addresses,
+ * so print them, if we have any.
+ */
+ if (src != NULL && dst != NULL) {
+ ND_PRINT("%s > %s ",
+ (src->addr_string)(ndo, src->addr),
+ (dst->addr_string)(ndo, dst->addr));
+ }
+
+ ND_PRINT("802.1AE MACsec, ");
+
+ /*
+ * Print the MACsec header.
+ */
+ macsec_print_header(ndo, sectag, short_length);
+ }
+
+ /*
+ * Tell our caller it can't be dissected.
+ */
+ ndo->ndo_protocol = save_protocol;
+ return 0;
+ }
+
+ /*
+ * The payload isn't encrypted; remove the
+ * ICV length from the lengths, so our caller
+ * doesn't treat it as payload.
+ */
+ if (*lengthp < MACSEC_DEFAULT_ICV_LEN) {
+ nd_print_trunc(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+ if (*caplenp < MACSEC_DEFAULT_ICV_LEN) {
+ nd_print_trunc(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+ *lengthp -= MACSEC_DEFAULT_ICV_LEN;
+ *caplenp -= MACSEC_DEFAULT_ICV_LEN;
+ /*
+ * Update the snapend thus the ICV field is not in the payload for
+ * the caller.
+ * The ICV (Integrity Check Value) is at the end of the frame, after
+ * the secure data.
+ */
+ ndo->ndo_snapend -= MACSEC_DEFAULT_ICV_LEN;
+
+ /*
+ * If the SL field is non-zero, then it's the length of the
+ * Secure Data; otherwise, the Secure Data is what's left
+ * ver after the MACsec header and ICV are removed.
+ */
+ if (short_length != 0) {
+ /*
+ * If the short length is more than we *have*,
+ * that's an error.
+ */
+ if (short_length > *lengthp) {
+ nd_print_trunc(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+ if (short_length > *caplenp) {
+ nd_print_trunc(ndo);
+ ndo->ndo_protocol = save_protocol;
+ return hdrlen + caplen;
+ }
+ if (*lengthp > short_length)
+ *lengthp = short_length;
+ if (*caplenp > short_length)
+ *caplenp = short_length;
+ }
+
+ ndo->ndo_protocol = save_protocol;
+ return -1;
+}
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