summaryrefslogtreecommitdiff
path: root/canohost.c
blob: f15aecb621641da3f5c5bcc7f7437b3bea1ea039 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Functions for returning the canonical host name of the remote site.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

#include "includes.h"
RCSID("$OpenBSD: canohost.c,v 1.50 2006/03/14 00:15:39 djm Exp $");

#include <ctype.h>

#include "packet.h"
#include "xmalloc.h"
#include "log.h"
#include "canohost.h"

static void check_ip_options(int, char *);

/*
 * Return the canonical name of the host at the other end of the socket. The
 * caller should free the returned string with xfree.
 */

static char *
get_remote_hostname(int sock, int use_dns)
{
	struct sockaddr_storage from;
	int i;
	socklen_t fromlen;
	struct addrinfo hints, *ai, *aitop;
	char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];

	/* Get IP address of client. */
	fromlen = sizeof(from);
	memset(&from, 0, sizeof(from));
	if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
		debug("getpeername failed: %.100s", strerror(errno));
		cleanup_exit(255);
	}

	ipv64_normalise_mapped(&from, &fromlen);

	if (from.ss_family == AF_INET6)
		fromlen = sizeof(struct sockaddr_in6);

	if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
	    NULL, 0, NI_NUMERICHOST) != 0)
		fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");

	if (from.ss_family == AF_INET)
		check_ip_options(sock, ntop);

	if (!use_dns)
		return xstrdup(ntop);

	debug3("Trying to reverse map address %.100s.", ntop);
	/* Map the IP address to a host name. */
	if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
	    NULL, 0, NI_NAMEREQD) != 0) {
		/* Host name not found.  Use ip address. */
		return xstrdup(ntop);
	}

	/*
	 * if reverse lookup result looks like a numeric hostname,
	 * someone is trying to trick us by PTR record like following:
	 *	1.1.1.10.in-addr.arpa.	IN PTR	2.3.4.5
	 */
	memset(&hints, 0, sizeof(hints));
	hints.ai_socktype = SOCK_DGRAM;	/*dummy*/
	hints.ai_flags = AI_NUMERICHOST;
	if (getaddrinfo(name, "0", &hints, &ai) == 0) {
		logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
		    name, ntop);
		freeaddrinfo(ai);
		return xstrdup(ntop);
	}

	/*
	 * Convert it to all lowercase (which is expected by the rest
	 * of this software).
	 */
	for (i = 0; name[i]; i++)
		if (isupper(name[i]))
			name[i] = tolower(name[i]);
	/*
	 * Map it back to an IP address and check that the given
	 * address actually is an address of this host.  This is
	 * necessary because anyone with access to a name server can
	 * define arbitrary names for an IP address. Mapping from
	 * name to IP address can be trusted better (but can still be
	 * fooled if the intruder has access to the name server of
	 * the domain).
	 */
	memset(&hints, 0, sizeof(hints));
	hints.ai_family = from.ss_family;
	hints.ai_socktype = SOCK_STREAM;
	if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
		logit("reverse mapping checking getaddrinfo for %.700s "
		    "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
		return xstrdup(ntop);
	}
	/* Look for the address from the list of addresses. */
	for (ai = aitop; ai; ai = ai->ai_next) {
		if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
		    sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
		    (strcmp(ntop, ntop2) == 0))
				break;
	}
	freeaddrinfo(aitop);
	/* If we reached the end of the list, the address was not there. */
	if (!ai) {
		/* Address not found for the host name. */
		logit("Address %.100s maps to %.600s, but this does not "
		    "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
		    ntop, name);
		return xstrdup(ntop);
	}
	return xstrdup(name);
}

/*
 * If IP options are supported, make sure there are none (log and
 * disconnect them if any are found).  Basically we are worried about
 * source routing; it can be used to pretend you are somebody
 * (ip-address) you are not. That itself may be "almost acceptable"
 * under certain circumstances, but rhosts autentication is useless
 * if source routing is accepted. Notice also that if we just dropped
 * source routing here, the other side could use IP spoofing to do
 * rest of the interaction and could still bypass security.  So we
 * exit here if we detect any IP options.
 */
/* IPv4 only */
static void
check_ip_options(int sock, char *ipaddr)
{
#ifdef IP_OPTIONS
	u_char options[200];
	char text[sizeof(options) * 3 + 1];
	socklen_t option_size;
	u_int i;
	int ipproto;
	struct protoent *ip;

	if ((ip = getprotobyname("ip")) != NULL)
		ipproto = ip->p_proto;
	else
		ipproto = IPPROTO_IP;
	option_size = sizeof(options);
	if (getsockopt(sock, ipproto, IP_OPTIONS, options,
	    &option_size) >= 0 && option_size != 0) {
		text[0] = '\0';
		for (i = 0; i < option_size; i++)
			snprintf(text + i*3, sizeof(text) - i*3,
			    " %2.2x", options[i]);
		fatal("Connection from %.100s with IP options:%.800s",
		    ipaddr, text);
	}
#endif /* IP_OPTIONS */
}

void
ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
{
	struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
	struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
	struct in_addr inaddr;
	u_int16_t port;

	if (addr->ss_family != AF_INET6 ||
	    !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
		return;

	debug3("Normalising mapped IPv4 in IPv6 address");

	memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
	port = a6->sin6_port;

	memset(addr, 0, sizeof(*a4));

	a4->sin_family = AF_INET;
	*len = sizeof(*a4);
	memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
	a4->sin_port = port;
}

/*
 * Return the canonical name of the host in the other side of the current
 * connection.  The host name is cached, so it is efficient to call this
 * several times.
 */

const char *
get_canonical_hostname(int use_dns)
{
	char *host;
	static char *canonical_host_name = NULL;
	static char *remote_ip = NULL;

	/* Check if we have previously retrieved name with same option. */
	if (use_dns && canonical_host_name != NULL)
		return canonical_host_name;
	if (!use_dns && remote_ip != NULL)
		return remote_ip;

	/* Get the real hostname if socket; otherwise return UNKNOWN. */
	if (packet_connection_is_on_socket())
		host = get_remote_hostname(packet_get_connection_in(), use_dns);
	else
		host = "UNKNOWN";

	if (use_dns)
		canonical_host_name = host;
	else
		remote_ip = host;
	return host;
}

/*
 * Returns the local/remote IP-address/hostname of socket as a string.
 * The returned string must be freed.
 */
static char *
get_socket_address(int sock, int remote, int flags)
{
	struct sockaddr_storage addr;
	socklen_t addrlen;
	char ntop[NI_MAXHOST];
	int r;

	/* Get IP address of client. */
	addrlen = sizeof(addr);
	memset(&addr, 0, sizeof(addr));

	if (remote) {
		if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
		    < 0)
			return NULL;
	} else {
		if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
		    < 0)
			return NULL;
	}

	/* Work around Linux IPv6 weirdness */
	if (addr.ss_family == AF_INET6)
		addrlen = sizeof(struct sockaddr_in6);

	ipv64_normalise_mapped(&addr, &addrlen);

	/* Get the address in ascii. */
	if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
	    sizeof(ntop), NULL, 0, flags)) != 0) {
		error("get_socket_address: getnameinfo %d failed: %s", flags,
		    r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
		return NULL;
	}
	return xstrdup(ntop);
}

char *
get_peer_ipaddr(int sock)
{
	char *p;

	if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
		return p;
	return xstrdup("UNKNOWN");
}

char *
get_local_ipaddr(int sock)
{
	char *p;

	if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
		return p;
	return xstrdup("UNKNOWN");
}

char *
get_local_name(int sock)
{
	return get_socket_address(sock, 0, NI_NAMEREQD);
}

/*
 * Returns the IP-address of the remote host as a string.  The returned
 * string must not be freed.
 */

const char *
get_remote_ipaddr(void)
{
	static char *canonical_host_ip = NULL;

	/* Check whether we have cached the ipaddr. */
	if (canonical_host_ip == NULL) {
		if (packet_connection_is_on_socket()) {
			canonical_host_ip =
			    get_peer_ipaddr(packet_get_connection_in());
			if (canonical_host_ip == NULL)
				cleanup_exit(255);
		} else {
			/* If not on socket, return UNKNOWN. */
			canonical_host_ip = xstrdup("UNKNOWN");
		}
	}
	return canonical_host_ip;
}

const char *
get_remote_name_or_ip(u_int utmp_len, int use_dns)
{
	static const char *remote = "";
	if (utmp_len > 0)
		remote = get_canonical_hostname(use_dns);
	if (utmp_len == 0 || strlen(remote) > utmp_len)
		remote = get_remote_ipaddr();
	return remote;
}

/* Returns the local/remote port for the socket. */

static int
get_sock_port(int sock, int local)
{
	struct sockaddr_storage from;
	socklen_t fromlen;
	char strport[NI_MAXSERV];
	int r;

	/* Get IP address of client. */
	fromlen = sizeof(from);
	memset(&from, 0, sizeof(from));
	if (local) {
		if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
			error("getsockname failed: %.100s", strerror(errno));
			return 0;
		}
	} else {
		if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
			debug("getpeername failed: %.100s", strerror(errno));
			return -1;
		}
	}

	/* Work around Linux IPv6 weirdness */
	if (from.ss_family == AF_INET6)
		fromlen = sizeof(struct sockaddr_in6);

	/* Return port number. */
	if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
	    strport, sizeof(strport), NI_NUMERICSERV)) != 0)
		fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
		    r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
	return atoi(strport);
}

/* Returns remote/local port number for the current connection. */

static int
get_port(int local)
{
	/*
	 * If the connection is not a socket, return 65535.  This is
	 * intentionally chosen to be an unprivileged port number.
	 */
	if (!packet_connection_is_on_socket())
		return 65535;

	/* Get socket and return the port number. */
	return get_sock_port(packet_get_connection_in(), local);
}

int
get_peer_port(int sock)
{
	return get_sock_port(sock, 0);
}

int
get_remote_port(void)
{
	static int port = -1;

	/* Cache to avoid getpeername() on a dead connection */
	if (port == -1)
		port = get_port(0);

	return port;
}

int
get_local_port(void)
{
	return get_port(1);
}