print-ahcp.c revision 1.3 
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 1.3 2015/03/31 21:59:35 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{
110	time_t t;
111	struct tm *tm;
112	char buf[BUFSIZE];
113
114	if (cp + 4 != ep)
115		goto corrupt;
116	ND_TCHECK2(*cp, 4);
117	t = EXTRACT_32BITS(cp);
118	if (NULL == (tm = gmtime(&t)))
119		ND_PRINT((ndo, ": gmtime() error"));
120	else if (0 == strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", tm))
121		ND_PRINT((ndo, ": strftime() error"));
122	else
123		ND_PRINT((ndo, ": %s UTC", buf));
124	return 0;
125
126corrupt:
127	ND_PRINT((ndo, ": %s", cstr));
128	ND_TCHECK2(*cp, ep - cp);
129	return 0;
130trunc:
131	ND_PRINT((ndo, "%s", tstr));
132	return -1;
133}
134
135static int
136ahcp_seconds_print(netdissect_options *ndo, const u_char *cp, const u_char *ep)
137{
138	if (cp + 4 != ep)
139		goto corrupt;
140	ND_TCHECK2(*cp, 4);
141	ND_PRINT((ndo, ": %us", EXTRACT_32BITS(cp)));
142	return 0;
143
144corrupt:
145	ND_PRINT((ndo, ": %s", cstr));
146	ND_TCHECK2(*cp, ep - cp);
147	return 0;
148trunc:
149	ND_PRINT((ndo, "%s", tstr));
150	return -1;
151}
152
153static int
154ahcp_ipv6_addresses_print(netdissect_options *ndo, const u_char *cp, const u_char *ep)
155{
156	const char *sep = ": ";
157
158	while (cp < ep) {
159		if (cp + 16 > ep)
160			goto corrupt;
161		ND_TCHECK2(*cp, 16);
162#ifdef INET6
163		ND_PRINT((ndo, "%s%s", sep, ip6addr_string(ndo, cp)));
164#else
165		ND_PRINT((ndo, "%s(compiled w/o IPv6)", sep));
166#endif /* INET6 */
167		cp += 16;
168		sep = ", ";
169	}
170	return 0;
171
172corrupt:
173	ND_PRINT((ndo, ": %s", cstr));
174	ND_TCHECK2(*cp, ep - cp);
175	return 0;
176trunc:
177	ND_PRINT((ndo, "%s", tstr));
178	return -1;
179}
180
181static int
182ahcp_ipv4_addresses_print(netdissect_options *ndo, const u_char *cp, const u_char *ep)
183{
184	const char *sep = ": ";
185
186	while (cp < ep) {
187		if (cp + 4 > ep)
188			goto corrupt;
189		ND_TCHECK2(*cp, 4);
190		ND_PRINT((ndo, "%s%s", sep, ipaddr_string(ndo, cp)));
191		cp += 4;
192		sep = ", ";
193	}
194	return 0;
195
196corrupt:
197	ND_PRINT((ndo, ": %s", cstr));
198	ND_TCHECK2(*cp, ep - cp);
199	return 0;
200trunc:
201	ND_PRINT((ndo, "%s", tstr));
202	return -1;
203}
204
205static int
206ahcp_ipv6_prefixes_print(netdissect_options *ndo, const u_char *cp, const u_char *ep)
207{
208	const char *sep = ": ";
209
210	while (cp < ep) {
211		if (cp + 17 > ep)
212			goto corrupt;
213		ND_TCHECK2(*cp, 17);
214#ifdef INET6
215		ND_PRINT((ndo, "%s%s/%u", sep, ip6addr_string(ndo, cp), *(cp + 16)));
216#else
217		ND_PRINT((ndo, "%s(compiled w/o IPv6)/%u", sep, *(cp + 16)));
218#endif /* INET6 */
219		cp += 17;
220		sep = ", ";
221	}
222	return 0;
223
224corrupt:
225	ND_PRINT((ndo, ": %s", cstr));
226	ND_TCHECK2(*cp, ep - cp);
227	return 0;
228trunc:
229	ND_PRINT((ndo, "%s", tstr));
230	return -1;
231}
232
233static int
234ahcp_ipv4_prefixes_print(netdissect_options *ndo, const u_char *cp, const u_char *ep)
235{
236	const char *sep = ": ";
237
238	while (cp < ep) {
239		if (cp + 5 > ep)
240			goto corrupt;
241		ND_TCHECK2(*cp, 5);
242		ND_PRINT((ndo, "%s%s/%u", sep, ipaddr_string(ndo, cp), *(cp + 4)));
243		cp += 5;
244		sep = ", ";
245	}
246	return 0;
247
248corrupt:
249	ND_PRINT((ndo, ": %s", cstr));
250	ND_TCHECK2(*cp, ep - cp);
251	return 0;
252trunc:
253	ND_PRINT((ndo, "%s", tstr));
254	return -1;
255}
256
257/* Data decoders signal truncated data with -1. */
258static int
259(* const data_decoders[AHCP1_OPT_MAX + 1])(netdissect_options *, const u_char *, const u_char *) = {
260	/* [AHCP1_OPT_PAD]                    = */  NULL,
261	/* [AHCP1_OPT_MANDATORY]              = */  NULL,
262	/* [AHCP1_OPT_ORIGIN_TIME]            = */  ahcp_time_print,
263	/* [AHCP1_OPT_EXPIRES]                = */  ahcp_seconds_print,
264	/* [AHCP1_OPT_MY_IPV6_ADDRESS]        = */  ahcp_ipv6_addresses_print,
265	/* [AHCP1_OPT_MY_IPV4_ADDRESS]        = */  ahcp_ipv4_addresses_print,
266	/* [AHCP1_OPT_IPV6_PREFIX]            = */  ahcp_ipv6_prefixes_print,
267	/* [AHCP1_OPT_IPV4_PREFIX]            = */  NULL,
268	/* [AHCP1_OPT_IPV6_ADDRESS]           = */  ahcp_ipv6_addresses_print,
269	/* [AHCP1_OPT_IPV4_ADDRESS]           = */  ahcp_ipv4_addresses_print,
270	/* [AHCP1_OPT_IPV6_PREFIX_DELEGATION] = */  ahcp_ipv6_prefixes_print,
271	/* [AHCP1_OPT_IPV4_PREFIX_DELEGATION] = */  ahcp_ipv4_prefixes_print,
272	/* [AHCP1_OPT_NAME_SERVER]            = */  ahcp_ipv6_addresses_print,
273	/* [AHCP1_OPT_NTP_SERVER]             = */  ahcp_ipv6_addresses_print,
274};
275
276static void
277ahcp1_options_print(netdissect_options *ndo, const u_char *cp, const u_char *ep)
278{
279	uint8_t option_no, option_len;
280
281	while (cp < ep) {
282		/* Option no */
283		ND_TCHECK2(*cp, 1);
284		option_no = *cp;
285		cp += 1;
286		ND_PRINT((ndo, "\n\t %s", tok2str(ahcp1_opt_str, "Unknown-%u", option_no)));
287		if (option_no == AHCP1_OPT_PAD || option_no == AHCP1_OPT_MANDATORY)
288			continue;
289		/* Length */
290		if (cp + 1 > ep)
291			goto corrupt;
292		ND_TCHECK2(*cp, 1);
293		option_len = *cp;
294		cp += 1;
295		if (cp + option_len > ep)
296			goto corrupt;
297		/* Value */
298		if (option_no <= AHCP1_OPT_MAX && data_decoders[option_no] != NULL) {
299			if (data_decoders[option_no](ndo, cp, cp + option_len) < 0)
300				break; /* truncated and already marked up */
301		} else {
302			ND_PRINT((ndo, " (Length %u)", option_len));
303			ND_TCHECK2(*cp, option_len);
304		}
305		cp += option_len;
306	}
307	return;
308
309corrupt:
310	ND_PRINT((ndo, " %s", cstr));
311	ND_TCHECK2(*cp, ep - cp);
312	return;
313trunc:
314	ND_PRINT((ndo, "%s", tstr));
315}
316
317static void
318ahcp1_body_print(netdissect_options *ndo, const u_char *cp, const u_char *ep)
319{
320	uint8_t type, mbz;
321	uint16_t body_len;
322
323	if (cp + AHCP1_BODY_MIN_LEN > ep)
324		goto corrupt;
325	/* Type */
326	ND_TCHECK2(*cp, 1);
327	type = *cp;
328	cp += 1;
329	/* MBZ */
330	ND_TCHECK2(*cp, 1);
331	mbz = *cp;
332	cp += 1;
333	/* Length */
334	ND_TCHECK2(*cp, 2);
335	body_len = EXTRACT_16BITS(cp);
336	cp += 2;
337
338	if (ndo->ndo_vflag) {
339		ND_PRINT((ndo, "\n\t%s", tok2str(ahcp1_msg_str, "Unknown-%u", type)));
340		if (mbz != 0)
341			ND_PRINT((ndo, ", MBZ %u", mbz));
342		ND_PRINT((ndo, ", Length %u", body_len));
343	}
344	if (cp + body_len > ep)
345		goto corrupt;
346
347	/* Options */
348	if (ndo->ndo_vflag >= 2)
349		ahcp1_options_print(ndo, cp, cp + body_len); /* not ep (ignore extra data) */
350	else
351		ND_TCHECK2(*cp, body_len);
352	return;
353
354corrupt:
355	ND_PRINT((ndo, " %s", cstr));
356	ND_TCHECK2(*cp, ep - cp);
357	return;
358trunc:
359	ND_PRINT((ndo, "%s", tstr));
360}
361
362void
363ahcp_print(netdissect_options *ndo, const u_char *cp, const u_int len)
364{
365	const u_char *ep = cp + len;
366	uint8_t version;
367
368	ND_PRINT((ndo, "AHCP"));
369	if (len < 2)
370		goto corrupt;
371	/* Magic */
372	ND_TCHECK2(*cp, 1);
373	if (*cp != AHCP_MAGIC_NUMBER)
374		goto corrupt;
375	cp += 1;
376	/* Version */
377	ND_TCHECK2(*cp, 1);
378	version = *cp;
379	cp += 1;
380	switch (version) {
381		case AHCP_VERSION_1: {
382			ND_PRINT((ndo, " Version 1"));
383			if (len < AHCP1_HEADER_FIX_LEN)
384				goto corrupt;
385			if (!ndo->ndo_vflag) {
386				ND_TCHECK2(*cp, AHCP1_HEADER_FIX_LEN - 2);
387				cp += AHCP1_HEADER_FIX_LEN - 2;
388			} else {
389				/* Hopcount */
390				ND_TCHECK2(*cp, 1);
391				ND_PRINT((ndo, "\n\tHopcount %u", *cp));
392				cp += 1;
393				/* Original Hopcount */
394				ND_TCHECK2(*cp, 1);
395				ND_PRINT((ndo, ", Original Hopcount %u", *cp));
396				cp += 1;
397				/* Nonce */
398				ND_TCHECK2(*cp, 4);
399				ND_PRINT((ndo, ", Nonce 0x%08x", EXTRACT_32BITS(cp)));
400				cp += 4;
401				/* Source Id */
402				ND_TCHECK2(*cp, 8);
403				ND_PRINT((ndo, ", Source Id %s", linkaddr_string(ndo, cp, 0, 8)));
404				cp += 8;
405				/* Destination Id */
406				ND_TCHECK2(*cp, 8);
407				ND_PRINT((ndo, ", Destination Id %s", linkaddr_string(ndo, cp, 0, 8)));
408				cp += 8;
409			}
410			/* Body */
411			ahcp1_body_print(ndo, cp, ep);
412			break;
413		}
414		default:
415			ND_PRINT((ndo, " Version %u (unknown)", version));
416			break;
417	}
418	return;
419
420corrupt:
421	ND_PRINT((ndo, " %s", cstr));
422	ND_TCHECK2(*cp, ep - cp);
423	return;
424trunc:
425	ND_PRINT((ndo, "%s", tstr));
426}
427