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Damien Millerd4a8b7e1999-10-27 13:42:43 +10001/*
Damien Miller95def091999-11-25 00:26:21 +11002 * Author: Tatu Ylonen <ylo@cs.hut.fi>
Damien Miller95def091999-11-25 00:26:21 +11003 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 * All rights reserved
Damien Miller95def091999-11-25 00:26:21 +11005 * Rhosts authentication. This file contains code to check whether to admit
6 * the login based on rhosts authentication. This file also processes
7 * /etc/hosts.equiv.
Damien Miller4af51302000-04-16 11:18:38 +10008 *
Damien Millere4340be2000-09-16 13:29:08 +11009 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose. Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
Damien Miller95def091999-11-25 00:26:21 +110014 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100015
16#include "includes.h"
Ben Lindstrom5eabda32001-04-12 23:34:34 +000017RCSID("$OpenBSD: auth-rhosts.c,v 1.23 2001/04/12 19:15:24 markus Exp $");
Damien Millerd4a8b7e1999-10-27 13:42:43 +100018
19#include "packet.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100020#include "xmalloc.h"
21#include "uidswap.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000022#include "pathnames.h"
23#include "log.h"
Damien Miller6d7b2cd1999-11-12 15:19:27 +110024#include "servconf.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000025#include "canohost.h"
Ben Lindstrom31ca54a2001-02-09 02:11:24 +000026#include "auth.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100027
Ben Lindstrom5eabda32001-04-12 23:34:34 +000028/* import */
29extern ServerOptions options;
30
Damien Miller5428f641999-11-25 11:54:57 +110031/*
32 * This function processes an rhosts-style file (.rhosts, .shosts, or
33 * /etc/hosts.equiv). This returns true if authentication can be granted
34 * based on the file, and returns zero otherwise.
35 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100036
Damien Miller4af51302000-04-16 11:18:38 +100037int
Damien Miller95def091999-11-25 00:26:21 +110038check_rhosts_file(const char *filename, const char *hostname,
39 const char *ipaddr, const char *client_user,
40 const char *server_user)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100041{
Damien Miller95def091999-11-25 00:26:21 +110042 FILE *f;
43 char buf[1024]; /* Must not be larger than host, user, dummy below. */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100044
Damien Miller95def091999-11-25 00:26:21 +110045 /* Open the .rhosts file, deny if unreadable */
46 f = fopen(filename, "r");
47 if (!f)
48 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100049
Damien Miller95def091999-11-25 00:26:21 +110050 while (fgets(buf, sizeof(buf), f)) {
51 /* All three must be at least as big as buf to avoid overflows. */
52 char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
53 int negated;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100054
Damien Miller95def091999-11-25 00:26:21 +110055 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
56 ;
57 if (*cp == '#' || *cp == '\n' || !*cp)
58 continue;
59
Damien Miller5428f641999-11-25 11:54:57 +110060 /*
61 * NO_PLUS is supported at least on OSF/1. We skip it (we
62 * don't ever support the plus syntax).
63 */
Damien Miller95def091999-11-25 00:26:21 +110064 if (strncmp(cp, "NO_PLUS", 7) == 0)
65 continue;
66
Damien Miller5428f641999-11-25 11:54:57 +110067 /*
68 * This should be safe because each buffer is as big as the
69 * whole string, and thus cannot be overwritten.
70 */
Damien Miller95def091999-11-25 00:26:21 +110071 switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) {
72 case 0:
73 packet_send_debug("Found empty line in %.100s.", filename);
74 continue;
75 case 1:
76 /* Host name only. */
77 strlcpy(userbuf, server_user, sizeof(userbuf));
78 break;
79 case 2:
80 /* Got both host and user name. */
81 break;
82 case 3:
83 packet_send_debug("Found garbage in %.100s.", filename);
84 continue;
85 default:
86 /* Weird... */
87 continue;
88 }
89
90 host = hostbuf;
91 user = userbuf;
92 negated = 0;
93
94 /* Process negated host names, or positive netgroups. */
95 if (host[0] == '-') {
96 negated = 1;
97 host++;
98 } else if (host[0] == '+')
99 host++;
100
101 if (user[0] == '-') {
102 negated = 1;
103 user++;
104 } else if (user[0] == '+')
105 user++;
106
107 /* Check for empty host/user names (particularly '+'). */
108 if (!host[0] || !user[0]) {
109 /* We come here if either was '+' or '-'. */
110 packet_send_debug("Ignoring wild host/user names in %.100s.",
111 filename);
112 continue;
113 }
114 /* Verify that host name matches. */
115 if (host[0] == '@') {
116 if (!innetgr(host + 1, hostname, NULL, NULL) &&
117 !innetgr(host + 1, ipaddr, NULL, NULL))
118 continue;
119 } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
120 continue; /* Different hostname. */
121
122 /* Verify that user name matches. */
123 if (user[0] == '@') {
124 if (!innetgr(user + 1, NULL, client_user, NULL))
125 continue;
126 } else if (strcmp(user, client_user) != 0)
127 continue; /* Different username. */
128
129 /* Found the user and host. */
130 fclose(f);
131
132 /* If the entry was negated, deny access. */
133 if (negated) {
134 packet_send_debug("Matched negative entry in %.100s.",
135 filename);
136 return 0;
137 }
138 /* Accept authentication. */
139 return 1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000140 }
141
Damien Miller95def091999-11-25 00:26:21 +1100142 /* Authentication using this file denied. */
143 fclose(f);
144 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000145}
146
Damien Miller5428f641999-11-25 11:54:57 +1100147/*
148 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
149 * true if authentication succeeds. If ignore_rhosts is true, only
150 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
151 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000152
Damien Miller4af51302000-04-16 11:18:38 +1000153int
Damien Miller95def091999-11-25 00:26:21 +1100154auth_rhosts(struct passwd *pw, const char *client_user)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000155{
Damien Miller95def091999-11-25 00:26:21 +1100156 const char *hostname, *ipaddr;
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000157 int ret;
158
159 hostname = get_canonical_hostname(options.reverse_mapping_check);
160 ipaddr = get_remote_ipaddr();
161 ret = auth_rhosts2(pw, client_user, hostname, ipaddr);
162 return ret;
163}
164
165int
166auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
167 const char *ipaddr)
168{
169 char buf[1024];
Damien Miller95def091999-11-25 00:26:21 +1100170 struct stat st;
171 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
Ben Lindstrom46c16222000-12-22 01:43:59 +0000172 u_int rhosts_file_index;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000173
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000174 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
175 client_user, hostname, ipaddr);
176
Damien Miller874d77b2000-10-14 16:23:11 +1100177 /* no user given */
178 if (pw == NULL)
179 return 0;
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000180
Damien Miller95def091999-11-25 00:26:21 +1100181 /* Switch to the user's uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000182 temporarily_use_uid(pw);
Damien Miller5428f641999-11-25 11:54:57 +1100183 /*
184 * Quick check: if the user has no .shosts or .rhosts files, return
185 * failure immediately without doing costly lookups from name
186 * servers.
187 */
Damien Miller95def091999-11-25 00:26:21 +1100188 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
189 rhosts_file_index++) {
190 /* Check users .rhosts or .shosts. */
191 snprintf(buf, sizeof buf, "%.500s/%.100s",
192 pw->pw_dir, rhosts_files[rhosts_file_index]);
193 if (stat(buf, &st) >= 0)
194 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000195 }
Damien Miller95def091999-11-25 00:26:21 +1100196 /* Switch back to privileged uid. */
197 restore_uid();
198
199 /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
200 if (!rhosts_files[rhosts_file_index] &&
Ben Lindstrom226cfa02001-01-22 05:34:40 +0000201 stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
202 stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
Damien Miller95def091999-11-25 00:26:21 +1100203 return 0;
204
Damien Miller95def091999-11-25 00:26:21 +1100205 /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
206 if (pw->pw_uid != 0) {
Ben Lindstrom31ca54a2001-02-09 02:11:24 +0000207 if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, client_user,
Damien Miller95def091999-11-25 00:26:21 +1100208 pw->pw_name)) {
209 packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
210 hostname, ipaddr);
211 return 1;
212 }
Ben Lindstrom226cfa02001-01-22 05:34:40 +0000213 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, client_user,
Damien Miller95def091999-11-25 00:26:21 +1100214 pw->pw_name)) {
215 packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
Ben Lindstrom226cfa02001-01-22 05:34:40 +0000216 hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
Damien Miller95def091999-11-25 00:26:21 +1100217 return 1;
218 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000219 }
Damien Miller5428f641999-11-25 11:54:57 +1100220 /*
221 * Check that the home directory is owned by root or the user, and is
222 * not group or world writable.
223 */
Damien Miller95def091999-11-25 00:26:21 +1100224 if (stat(pw->pw_dir, &st) < 0) {
225 log("Rhosts authentication refused for %.100s: no home directory %.200s",
226 pw->pw_name, pw->pw_dir);
Damien Miller68e45de1999-12-27 23:54:55 +1100227 packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s",
Damien Miller95def091999-11-25 00:26:21 +1100228 pw->pw_name, pw->pw_dir);
229 return 0;
230 }
231 if (options.strict_modes &&
232 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
233 (st.st_mode & 022) != 0)) {
234 log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
235 pw->pw_name);
236 packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
237 pw->pw_name);
238 return 0;
239 }
240 /* Temporarily use the user's uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000241 temporarily_use_uid(pw);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000242
Damien Miller95def091999-11-25 00:26:21 +1100243 /* Check all .rhosts files (currently .shosts and .rhosts). */
244 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
245 rhosts_file_index++) {
246 /* Check users .rhosts or .shosts. */
247 snprintf(buf, sizeof buf, "%.500s/%.100s",
248 pw->pw_dir, rhosts_files[rhosts_file_index]);
249 if (stat(buf, &st) < 0)
250 continue;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000251
Damien Miller5428f641999-11-25 11:54:57 +1100252 /*
253 * Make sure that the file is either owned by the user or by
254 * root, and make sure it is not writable by anyone but the
255 * owner. This is to help avoid novices accidentally
256 * allowing access to their account by anyone.
257 */
Damien Miller95def091999-11-25 00:26:21 +1100258 if (options.strict_modes &&
259 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
260 (st.st_mode & 022) != 0)) {
261 log("Rhosts authentication refused for %.100s: bad modes for %.200s",
262 pw->pw_name, buf);
263 packet_send_debug("Bad file modes for %.200s", buf);
264 continue;
265 }
266 /* Check if we have been configured to ignore .rhosts and .shosts files. */
267 if (options.ignore_rhosts) {
268 packet_send_debug("Server has been configured to ignore %.100s.",
269 rhosts_files[rhosts_file_index]);
270 continue;
271 }
272 /* Check if authentication is permitted by the file. */
273 if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
274 packet_send_debug("Accepted by %.100s.",
275 rhosts_files[rhosts_file_index]);
276 /* Restore the privileged uid. */
277 restore_uid();
278 return 1;
279 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000280 }
281
Damien Miller95def091999-11-25 00:26:21 +1100282 /* Restore the privileged uid. */
283 restore_uid();
284 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000285}