print-ahcp.c revision 1.2 
1/*
2 * This module implements decoding of AHCP (Ad Hoc Configuration Protocol) based
3 * on draft-chroboczek-ahcp-00 and source code of ahcpd-0.53.
4 *
5 *
6 * Copyright (c) 2013 The TCPDUMP project
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
21 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
22 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
24 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
25 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
26 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
28 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#include <sys/cdefs.h>
33#ifndef lint
34__RCSID("$NetBSD: print-ahcp.c,v 1.2 2014/11/20 03:05:03 christos Exp $");
35#endif
36
37#define NETDISSECT_REWORKED
38#ifdef HAVE_CONFIG_H
39#include "config.h"
40#endif
41
42#include <tcpdump-stdinc.h>
43
44#include "interface.h"
45#include "extract.h"
46#include "addrtoname.h"
47
48static const char tstr[] = " [|ahcp]";
49static const char cstr[] = "(corrupt)";
50
51#define AHCP_MAGIC_NUMBER 43
52#define AHCP_VERSION_1 1
53#define AHCP1_HEADER_FIX_LEN 24
54#define AHCP1_BODY_MIN_LEN 4
55
56#define AHCP1_MSG_DISCOVER 0
57#define AHCP1_MSG_OFFER    1
58#define AHCP1_MSG_REQUEST  2
59#define AHCP1_MSG_ACK      3
60#define AHCP1_MSG_NACK     4
61#define AHCP1_MSG_RELEASE  5
62
63static const struct tok ahcp1_msg_str[] = {
64	{ AHCP1_MSG_DISCOVER, "Discover" },
65	{ AHCP1_MSG_OFFER,    "Offer"    },
66	{ AHCP1_MSG_REQUEST,  "Request"  },
67	{ AHCP1_MSG_ACK,      "Ack"      },
68	{ AHCP1_MSG_NACK,     "Nack"     },
69	{ AHCP1_MSG_RELEASE,  "Release"  },
70	{ 0, NULL }
71};
72
73#define AHCP1_OPT_PAD                     0
74#define AHCP1_OPT_MANDATORY               1
75#define AHCP1_OPT_ORIGIN_TIME             2
76#define AHCP1_OPT_EXPIRES                 3
77#define AHCP1_OPT_MY_IPV6_ADDRESS         4
78#define AHCP1_OPT_MY_IPV4_ADDRESS         5
79#define AHCP1_OPT_IPV6_PREFIX             6
80#define AHCP1_OPT_IPV4_PREFIX             7
81#define AHCP1_OPT_IPV6_ADDRESS            8
82#define AHCP1_OPT_IPV4_ADDRESS            9
83#define AHCP1_OPT_IPV6_PREFIX_DELEGATION 10
84#define AHCP1_OPT_IPV4_PREFIX_DELEGATION 11
85#define AHCP1_OPT_NAME_SERVER            12
86#define AHCP1_OPT_NTP_SERVER             13
87#define AHCP1_OPT_MAX                    13
88
89static const struct tok ahcp1_opt_str[] = {
90	{ AHCP1_OPT_PAD,                    "Pad"                    },
91	{ AHCP1_OPT_MANDATORY,              "Mandatory"              },
92	{ AHCP1_OPT_ORIGIN_TIME,            "Origin Time"            },
93	{ AHCP1_OPT_EXPIRES,                "Expires"                },
94	{ AHCP1_OPT_MY_IPV6_ADDRESS,        "My-IPv6-Address"        },
95	{ AHCP1_OPT_MY_IPV4_ADDRESS,        "My-IPv4-Address"        },
96	{ AHCP1_OPT_IPV6_PREFIX,            "IPv6 Prefix"            },
97	{ AHCP1_OPT_IPV4_PREFIX,            "IPv4 Prefix"            },
98	{ AHCP1_OPT_IPV6_ADDRESS,           "IPv6 Address"           },
99	{ AHCP1_OPT_IPV4_ADDRESS,           "IPv4 Address"           },
100	{ AHCP1_OPT_IPV6_PREFIX_DELEGATION, "IPv6 Prefix Delegation" },
101	{ AHCP1_OPT_IPV4_PREFIX_DELEGATION, "IPv4 Prefix Delegation" },
102	{ AHCP1_OPT_NAME_SERVER,            "Name Server"            },
103	{ AHCP1_OPT_NTP_SERVER,             "NTP Server"             },
104	{ 0, NULL }
105};
106
107static int
108ahcp_time_print(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
109	time_t t;
110	struct tm *tm;
111	char buf[BUFSIZE];
112
113	if (cp + 4 != ep)
114		goto corrupt;
115	ND_TCHECK2(*cp, 4);
116	t = EXTRACT_32BITS(cp);
117	if (NULL == (tm = gmtime(&t)))
118		ND_PRINT((ndo, ": gmtime() error"));
119	else if (0 == strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", tm))
120		ND_PRINT((ndo, ": strftime() error"));
121	else
122		ND_PRINT((ndo, ": %s UTC", buf));
123	return 0;
124
125corrupt:
126	ND_PRINT((ndo, ": %s", cstr));
127	ND_TCHECK2(*cp, ep - cp);
128	return 0;
129trunc:
130	ND_PRINT((ndo, "%s", tstr));
131	return -1;
132}
133
134static int
135ahcp_seconds_print(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
136	if (cp + 4 != ep)
137		goto corrupt;
138	ND_TCHECK2(*cp, 4);
139	ND_PRINT((ndo, ": %us", EXTRACT_32BITS(cp)));
140	return 0;
141
142corrupt:
143	ND_PRINT((ndo, ": %s", cstr));
144	ND_TCHECK2(*cp, ep - cp);
145	return 0;
146trunc:
147	ND_PRINT((ndo, "%s", tstr));
148	return -1;
149}
150
151static int
152ahcp_ipv6_addresses_print(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
153	const char *sep = ": ";
154
155	while (cp < ep) {
156		if (cp + 16 > ep)
157			goto corrupt;
158		ND_TCHECK2(*cp, 16);
159#ifdef INET6
160		ND_PRINT((ndo, "%s%s", sep, ip6addr_string(ndo, cp)));
161#else
162		ND_PRINT((ndo, "%s(compiled w/o IPv6)", sep));
163#endif /* INET6 */
164		cp += 16;
165		sep = ", ";
166	}
167	return 0;
168
169corrupt:
170	ND_PRINT((ndo, ": %s", cstr));
171	ND_TCHECK2(*cp, ep - cp);
172	return 0;
173trunc:
174	ND_PRINT((ndo, "%s", tstr));
175	return -1;
176}
177
178static int
179ahcp_ipv4_addresses_print(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
180	const char *sep = ": ";
181
182	while (cp < ep) {
183		if (cp + 4 > ep)
184			goto corrupt;
185		ND_TCHECK2(*cp, 4);
186		ND_PRINT((ndo, "%s%s", sep, ipaddr_string(ndo, cp)));
187		cp += 4;
188		sep = ", ";
189	}
190	return 0;
191
192corrupt:
193	ND_PRINT((ndo, ": %s", cstr));
194	ND_TCHECK2(*cp, ep - cp);
195	return 0;
196trunc:
197	ND_PRINT((ndo, "%s", tstr));
198	return -1;
199}
200
201static int
202ahcp_ipv6_prefixes_print(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
203	const char *sep = ": ";
204
205	while (cp < ep) {
206		if (cp + 17 > ep)
207			goto corrupt;
208		ND_TCHECK2(*cp, 17);
209#ifdef INET6
210		ND_PRINT((ndo, "%s%s/%u", sep, ip6addr_string(ndo, cp), *(cp + 16)));
211#else
212		ND_PRINT((ndo, "%s(compiled w/o IPv6)/%u", sep, *(cp + 16)));
213#endif /* INET6 */
214		cp += 17;
215		sep = ", ";
216	}
217	return 0;
218
219corrupt:
220	ND_PRINT((ndo, ": %s", cstr));
221	ND_TCHECK2(*cp, ep - cp);
222	return 0;
223trunc:
224	ND_PRINT((ndo, "%s", tstr));
225	return -1;
226}
227
228static int
229ahcp_ipv4_prefixes_print(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
230	const char *sep = ": ";
231
232	while (cp < ep) {
233		if (cp + 5 > ep)
234			goto corrupt;
235		ND_TCHECK2(*cp, 5);
236		ND_PRINT((ndo, "%s%s/%u", sep, ipaddr_string(ndo, cp), *(cp + 4)));
237		cp += 5;
238		sep = ", ";
239	}
240	return 0;
241
242corrupt:
243	ND_PRINT((ndo, ": %s", cstr));
244	ND_TCHECK2(*cp, ep - cp);
245	return 0;
246trunc:
247	ND_PRINT((ndo, "%s", tstr));
248	return -1;
249}
250
251/* Data decoders signal truncated data with -1. */
252static int
253(* const data_decoders[AHCP1_OPT_MAX + 1])(netdissect_options *, const u_char *, const u_char *) = {
254	/* [AHCP1_OPT_PAD]                    = */  NULL,
255	/* [AHCP1_OPT_MANDATORY]              = */  NULL,
256	/* [AHCP1_OPT_ORIGIN_TIME]            = */  ahcp_time_print,
257	/* [AHCP1_OPT_EXPIRES]                = */  ahcp_seconds_print,
258	/* [AHCP1_OPT_MY_IPV6_ADDRESS]        = */  ahcp_ipv6_addresses_print,
259	/* [AHCP1_OPT_MY_IPV4_ADDRESS]        = */  ahcp_ipv4_addresses_print,
260	/* [AHCP1_OPT_IPV6_PREFIX]            = */  ahcp_ipv6_prefixes_print,
261	/* [AHCP1_OPT_IPV4_PREFIX]            = */  NULL,
262	/* [AHCP1_OPT_IPV6_ADDRESS]           = */  ahcp_ipv6_addresses_print,
263	/* [AHCP1_OPT_IPV4_ADDRESS]           = */  ahcp_ipv4_addresses_print,
264	/* [AHCP1_OPT_IPV6_PREFIX_DELEGATION] = */  ahcp_ipv6_prefixes_print,
265	/* [AHCP1_OPT_IPV4_PREFIX_DELEGATION] = */  ahcp_ipv4_prefixes_print,
266	/* [AHCP1_OPT_NAME_SERVER]            = */  ahcp_ipv6_addresses_print,
267	/* [AHCP1_OPT_NTP_SERVER]             = */  ahcp_ipv6_addresses_print,
268};
269
270static void
271ahcp1_options_print(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
272	uint8_t option_no, option_len;
273
274	while (cp < ep) {
275		/* Option no */
276		ND_TCHECK2(*cp, 1);
277		option_no = *cp;
278		cp += 1;
279		ND_PRINT((ndo, "\n\t %s", tok2str(ahcp1_opt_str, "Unknown-%u", option_no)));
280		if (option_no == AHCP1_OPT_PAD || option_no == AHCP1_OPT_MANDATORY)
281			continue;
282		/* Length */
283		if (cp + 1 > ep)
284			goto corrupt;
285		ND_TCHECK2(*cp, 1);
286		option_len = *cp;
287		cp += 1;
288		if (cp + option_len > ep)
289			goto corrupt;
290		/* Value */
291		if (option_no <= AHCP1_OPT_MAX && data_decoders[option_no] != NULL) {
292			if (data_decoders[option_no](ndo, cp, cp + option_len) < 0)
293				break; /* truncated and already marked up */
294		} else {
295			ND_PRINT((ndo, " (Length %u)", option_len));
296			ND_TCHECK2(*cp, option_len);
297		}
298		cp += option_len;
299	}
300	return;
301
302corrupt:
303	ND_PRINT((ndo, " %s", cstr));
304	ND_TCHECK2(*cp, ep - cp);
305	return;
306trunc:
307	ND_PRINT((ndo, "%s", tstr));
308}
309
310static void
311ahcp1_body_print(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
312	uint8_t type, mbz;
313	uint16_t body_len;
314
315	if (cp + AHCP1_BODY_MIN_LEN > ep)
316		goto corrupt;
317	/* Type */
318	ND_TCHECK2(*cp, 1);
319	type = *cp;
320	cp += 1;
321	/* MBZ */
322	ND_TCHECK2(*cp, 1);
323	mbz = *cp;
324	cp += 1;
325	/* Length */
326	ND_TCHECK2(*cp, 2);
327	body_len = EXTRACT_16BITS(cp);
328	cp += 2;
329
330	if (ndo->ndo_vflag) {
331		ND_PRINT((ndo, "\n\t%s", tok2str(ahcp1_msg_str, "Unknown-%u", type)));
332		if (mbz != 0)
333			ND_PRINT((ndo, ", MBZ %u", mbz));
334		ND_PRINT((ndo, ", Length %u", body_len));
335	}
336	if (cp + body_len > ep)
337		goto corrupt;
338
339	/* Options */
340	if (ndo->ndo_vflag >= 2)
341		ahcp1_options_print(ndo, cp, cp + body_len); /* not ep (ignore extra data) */
342	else
343		ND_TCHECK2(*cp, body_len);
344	return;
345
346corrupt:
347	ND_PRINT((ndo, " %s", cstr));
348	ND_TCHECK2(*cp, ep - cp);
349	return;
350trunc:
351	ND_PRINT((ndo, "%s", tstr));
352}
353
354void
355ahcp_print(netdissect_options *ndo, const u_char *cp, const u_int len) {
356	const u_char *ep = cp + len;
357	uint8_t version;
358
359	ND_PRINT((ndo, "AHCP"));
360	if (len < 2)
361		goto corrupt;
362	/* Magic */
363	ND_TCHECK2(*cp, 1);
364	if (*cp != AHCP_MAGIC_NUMBER)
365		goto corrupt;
366	cp += 1;
367	/* Version */
368	ND_TCHECK2(*cp, 1);
369	version = *cp;
370	cp += 1;
371	switch (version) {
372		case AHCP_VERSION_1: {
373			ND_PRINT((ndo, " Version 1"));
374			if (len < AHCP1_HEADER_FIX_LEN)
375				goto corrupt;
376			if (!ndo->ndo_vflag) {
377				ND_TCHECK2(*cp, AHCP1_HEADER_FIX_LEN - 2);
378				cp += AHCP1_HEADER_FIX_LEN - 2;
379			} else {
380				/* Hopcount */
381				ND_TCHECK2(*cp, 1);
382				ND_PRINT((ndo, "\n\tHopcount %u", *cp));
383				cp += 1;
384				/* Original Hopcount */
385				ND_TCHECK2(*cp, 1);
386				ND_PRINT((ndo, ", Original Hopcount %u", *cp));
387				cp += 1;
388				/* Nonce */
389				ND_TCHECK2(*cp, 4);
390				ND_PRINT((ndo, ", Nonce 0x%08x", EXTRACT_32BITS(cp)));
391				cp += 4;
392				/* Source Id */
393				ND_TCHECK2(*cp, 8);
394				ND_PRINT((ndo, ", Source Id %s", linkaddr_string(ndo, cp, 0, 8)));
395				cp += 8;
396				/* Destination Id */
397				ND_TCHECK2(*cp, 8);
398				ND_PRINT((ndo, ", Destination Id %s", linkaddr_string(ndo, cp, 0, 8)));
399				cp += 8;
400			}
401			/* Body */
402			ahcp1_body_print(ndo, cp, ep);
403			break;
404		}
405		default:
406			ND_PRINT((ndo, " Version %u (unknown)", version));
407			break;
408	}
409	return;
410
411corrupt:
412	ND_PRINT((ndo, " %s", cstr));
413	ND_TCHECK2(*cp, ep - cp);
414	return;
415trunc:
416	ND_PRINT((ndo, "%s", tstr));
417}
418
419