summaryrefslogtreecommitdiff
path: root/canohost.c
blob: 8e81b5193790e3012fd0b67fb248ef47ce558e92 (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
/* $OpenBSD: canohost.c,v 1.74 2019/06/28 13:35:04 deraadt Exp $ */
/*
 * 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"

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>

#include <netinet/in.h>
#include <arpa/inet.h>

#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>

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

/*
 * Returns the remote DNS hostname as a string. The returned string must not
 * be freed. NB. this will usually trigger a DNS query the first time it is
 * called.
 * This function does additional checks on the hostname to mitigate some
 * attacks on legacy rhosts-style authentication.
 * XXX is RhostsRSAAuthentication vulnerable to these?
 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
 */

char *
remote_hostname(struct ssh *ssh)
{
	struct sockaddr_storage from;
	socklen_t fromlen;
	struct addrinfo hints, *ai, *aitop;
	char name[NI_MAXHOST], ntop2[NI_MAXHOST];
	const char *ntop = ssh_remote_ipaddr(ssh);

	/* Get IP address of client. */
	fromlen = sizeof(from);
	memset(&from, 0, sizeof(from));
	if (getpeername(ssh_packet_get_connection_in(ssh),
	    (struct sockaddr *)&from, &fromlen) == -1) {
		debug("getpeername failed: %.100s", strerror(errno));
		return xstrdup(ntop);
	}

	ipv64_normalise_mapped(&from, &fromlen);
	if (from.ss_family == AF_INET6)
		fromlen = sizeof(struct sockaddr_in6);

	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, NULL, &hints, &ai) == 0) {
		logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
		    name, ntop);
		freeaddrinfo(ai);
		return xstrdup(ntop);
	}

	/* Names are stored in lowercase. */
	lowercase(name);

	/*
	 * 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.", 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 == NULL) {
		/* Address not found for the host name. */
		logit("Address %.100s maps to %.600s, but this does not "
		    "map back to the address.", ntop, name);
		return xstrdup(ntop);
	}
	return xstrdup(name);
}

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

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

/*
 * 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);
	}

	switch (addr.ss_family) {
	case AF_INET:
	case AF_INET6:
		/* Get the address in ascii. */
		if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
		    sizeof(ntop), NULL, 0, flags)) != 0) {
			error("%s: getnameinfo %d failed: %s", __func__,
			    flags, ssh_gai_strerror(r));
			return NULL;
		}
		return xstrdup(ntop);
	case AF_UNIX:
		/* Get the Unix domain socket path. */
		return xstrdup(((struct sockaddr_un *)&addr)->sun_path);
	default:
		/* We can't look up remote Unix domain sockets. */
		return NULL;
	}
}

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 fd)
{
	char *host, myname[NI_MAXHOST];

	/* Assume we were passed a socket */
	if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL)
		return host;

	/* Handle the case where we were passed a pipe */
	if (gethostname(myname, sizeof(myname)) == -1) {
		verbose("%s: gethostname: %s", __func__, strerror(errno));
		host = xstrdup("UNKNOWN");
	} else {
		host = xstrdup(myname);
	}

	return host;
}

/* 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) == -1) {
			error("getsockname failed: %.100s", strerror(errno));
			return 0;
		}
	} else {
		if (getpeername(sock, (struct sockaddr *)&from, &fromlen) == -1) {
			debug("getpeername failed: %.100s", strerror(errno));
			return -1;
		}
	}

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

	/* Non-inet sockets don't have a port number. */
	if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
		return 0;

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

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

int
get_local_port(int sock)
{
	return get_sock_port(sock, 1);
}