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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"
Damien Miller3a961dc2003-06-03 10:25:48 +100017RCSID("$OpenBSD: auth-rhosts.c,v 1.31 2003/06/02 09:17:34 markus Exp $");
Damien Millerd4a8b7e1999-10-27 13:42:43 +100018
19#include "packet.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100020#include "uidswap.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000021#include "pathnames.h"
22#include "log.h"
Damien Miller6d7b2cd1999-11-12 15:19:27 +110023#include "servconf.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000024#include "canohost.h"
Ben Lindstrom31ca54a2001-02-09 02:11:24 +000025#include "auth.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100026
Ben Lindstrom5eabda32001-04-12 23:34:34 +000027/* import */
28extern ServerOptions options;
Ben Lindstrombdde3302002-05-15 16:19:37 +000029extern int use_privsep;
Ben Lindstrom5eabda32001-04-12 23:34:34 +000030
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
Ben Lindstrombba81212001-06-25 05:01:22 +000037static int
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 Millera9825782003-05-18 20:53:10 +100071 switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
72 dummy)) {
Damien Miller95def091999-11-25 00:26:21 +110073 case 0:
Ben Lindstrombdde3302002-05-15 16:19:37 +000074 auth_debug_add("Found empty line in %.100s.", filename);
Damien Miller95def091999-11-25 00:26:21 +110075 continue;
76 case 1:
77 /* Host name only. */
78 strlcpy(userbuf, server_user, sizeof(userbuf));
79 break;
80 case 2:
81 /* Got both host and user name. */
82 break;
83 case 3:
Ben Lindstrombdde3302002-05-15 16:19:37 +000084 auth_debug_add("Found garbage in %.100s.", filename);
Damien Miller95def091999-11-25 00:26:21 +110085 continue;
86 default:
87 /* Weird... */
88 continue;
89 }
90
91 host = hostbuf;
92 user = userbuf;
93 negated = 0;
94
95 /* Process negated host names, or positive netgroups. */
96 if (host[0] == '-') {
97 negated = 1;
98 host++;
99 } else if (host[0] == '+')
100 host++;
101
102 if (user[0] == '-') {
103 negated = 1;
104 user++;
105 } else if (user[0] == '+')
106 user++;
107
108 /* Check for empty host/user names (particularly '+'). */
109 if (!host[0] || !user[0]) {
110 /* We come here if either was '+' or '-'. */
Ben Lindstrombdde3302002-05-15 16:19:37 +0000111 auth_debug_add("Ignoring wild host/user names in %.100s.",
112 filename);
Damien Miller95def091999-11-25 00:26:21 +1100113 continue;
114 }
115 /* Verify that host name matches. */
116 if (host[0] == '@') {
117 if (!innetgr(host + 1, hostname, NULL, NULL) &&
118 !innetgr(host + 1, ipaddr, NULL, NULL))
119 continue;
120 } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
121 continue; /* Different hostname. */
122
123 /* Verify that user name matches. */
124 if (user[0] == '@') {
125 if (!innetgr(user + 1, NULL, client_user, NULL))
126 continue;
127 } else if (strcmp(user, client_user) != 0)
128 continue; /* Different username. */
129
130 /* Found the user and host. */
131 fclose(f);
132
133 /* If the entry was negated, deny access. */
134 if (negated) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000135 auth_debug_add("Matched negative entry in %.100s.",
136 filename);
Damien Miller95def091999-11-25 00:26:21 +1100137 return 0;
138 }
139 /* Accept authentication. */
140 return 1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000141 }
142
Damien Miller95def091999-11-25 00:26:21 +1100143 /* Authentication using this file denied. */
144 fclose(f);
145 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000146}
147
Damien Miller5428f641999-11-25 11:54:57 +1100148/*
149 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
150 * true if authentication succeeds. If ignore_rhosts is true, only
151 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
152 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000153
Damien Miller4af51302000-04-16 11:18:38 +1000154int
Damien Miller95def091999-11-25 00:26:21 +1100155auth_rhosts(struct passwd *pw, const char *client_user)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000156{
Damien Miller95def091999-11-25 00:26:21 +1100157 const char *hostname, *ipaddr;
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000158
Damien Miller3a961dc2003-06-03 10:25:48 +1000159 hostname = get_canonical_hostname(options.use_dns);
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000160 ipaddr = get_remote_ipaddr();
Ben Lindstrombdde3302002-05-15 16:19:37 +0000161 return auth_rhosts2(pw, client_user, hostname, ipaddr);
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000162}
163
Ben Lindstrombdde3302002-05-15 16:19:37 +0000164static int
165auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000166 const char *ipaddr)
167{
168 char buf[1024];
Damien Miller95def091999-11-25 00:26:21 +1100169 struct stat st;
170 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
Ben Lindstrom46c16222000-12-22 01:43:59 +0000171 u_int rhosts_file_index;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000172
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000173 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
174 client_user, hostname, ipaddr);
175
Damien Miller874d77b2000-10-14 16:23:11 +1100176 /* no user given */
177 if (pw == NULL)
178 return 0;
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000179
Damien Miller95def091999-11-25 00:26:21 +1100180 /* Switch to the user's uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000181 temporarily_use_uid(pw);
Damien Miller5428f641999-11-25 11:54:57 +1100182 /*
183 * Quick check: if the user has no .shosts or .rhosts files, return
184 * failure immediately without doing costly lookups from name
185 * servers.
186 */
Damien Miller95def091999-11-25 00:26:21 +1100187 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
Damien Miller9f0f5c62001-12-21 14:45:46 +1100188 rhosts_file_index++) {
Damien Miller95def091999-11-25 00:26:21 +1100189 /* Check users .rhosts or .shosts. */
190 snprintf(buf, sizeof buf, "%.500s/%.100s",
191 pw->pw_dir, rhosts_files[rhosts_file_index]);
192 if (stat(buf, &st) >= 0)
193 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000194 }
Damien Miller95def091999-11-25 00:26:21 +1100195 /* Switch back to privileged uid. */
196 restore_uid();
197
198 /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
199 if (!rhosts_files[rhosts_file_index] &&
Ben Lindstrom226cfa02001-01-22 05:34:40 +0000200 stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
201 stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
Damien Miller95def091999-11-25 00:26:21 +1100202 return 0;
203
Damien Miller95def091999-11-25 00:26:21 +1100204 /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
205 if (pw->pw_uid != 0) {
Damien Miller9f0f5c62001-12-21 14:45:46 +1100206 if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
207 client_user, pw->pw_name)) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000208 auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
Damien Miller9f0f5c62001-12-21 14:45:46 +1100209 hostname, ipaddr);
Damien Miller95def091999-11-25 00:26:21 +1100210 return 1;
211 }
Damien Miller9f0f5c62001-12-21 14:45:46 +1100212 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
213 client_user, pw->pw_name)) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000214 auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
Damien Miller9f0f5c62001-12-21 14:45:46 +1100215 hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
Damien Miller95def091999-11-25 00:26:21 +1100216 return 1;
217 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000218 }
Damien Miller5428f641999-11-25 11:54:57 +1100219 /*
220 * Check that the home directory is owned by root or the user, and is
221 * not group or world writable.
222 */
Damien Miller95def091999-11-25 00:26:21 +1100223 if (stat(pw->pw_dir, &st) < 0) {
Damien Miller996acd22003-04-09 20:59:48 +1000224 logit("Rhosts authentication refused for %.100s: "
Ben Lindstrombdde3302002-05-15 16:19:37 +0000225 "no home directory %.200s", pw->pw_name, pw->pw_dir);
226 auth_debug_add("Rhosts authentication refused for %.100s: "
227 "no home directory %.200s", pw->pw_name, pw->pw_dir);
Damien Miller95def091999-11-25 00:26:21 +1100228 return 0;
229 }
230 if (options.strict_modes &&
231 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
Damien Miller9f0f5c62001-12-21 14:45:46 +1100232 (st.st_mode & 022) != 0)) {
Damien Miller996acd22003-04-09 20:59:48 +1000233 logit("Rhosts authentication refused for %.100s: "
Ben Lindstrombdde3302002-05-15 16:19:37 +0000234 "bad ownership or modes for home directory.", pw->pw_name);
235 auth_debug_add("Rhosts authentication refused for %.100s: "
236 "bad ownership or modes for home directory.", pw->pw_name);
Damien Miller95def091999-11-25 00:26:21 +1100237 return 0;
238 }
239 /* Temporarily use the user's uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000240 temporarily_use_uid(pw);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000241
Damien Miller95def091999-11-25 00:26:21 +1100242 /* Check all .rhosts files (currently .shosts and .rhosts). */
243 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
Damien Miller9f0f5c62001-12-21 14:45:46 +1100244 rhosts_file_index++) {
Damien Miller95def091999-11-25 00:26:21 +1100245 /* Check users .rhosts or .shosts. */
246 snprintf(buf, sizeof buf, "%.500s/%.100s",
247 pw->pw_dir, rhosts_files[rhosts_file_index]);
248 if (stat(buf, &st) < 0)
249 continue;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000250
Damien Miller5428f641999-11-25 11:54:57 +1100251 /*
252 * Make sure that the file is either owned by the user or by
253 * root, and make sure it is not writable by anyone but the
254 * owner. This is to help avoid novices accidentally
255 * allowing access to their account by anyone.
256 */
Damien Miller95def091999-11-25 00:26:21 +1100257 if (options.strict_modes &&
258 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
Damien Miller9f0f5c62001-12-21 14:45:46 +1100259 (st.st_mode & 022) != 0)) {
Damien Miller996acd22003-04-09 20:59:48 +1000260 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
Damien Miller95def091999-11-25 00:26:21 +1100261 pw->pw_name, buf);
Ben Lindstrombdde3302002-05-15 16:19:37 +0000262 auth_debug_add("Bad file modes for %.200s", buf);
Damien Miller95def091999-11-25 00:26:21 +1100263 continue;
264 }
265 /* Check if we have been configured to ignore .rhosts and .shosts files. */
266 if (options.ignore_rhosts) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000267 auth_debug_add("Server has been configured to ignore %.100s.",
268 rhosts_files[rhosts_file_index]);
Damien Miller95def091999-11-25 00:26:21 +1100269 continue;
270 }
271 /* Check if authentication is permitted by the file. */
272 if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000273 auth_debug_add("Accepted by %.100s.",
274 rhosts_files[rhosts_file_index]);
Damien Miller95def091999-11-25 00:26:21 +1100275 /* Restore the privileged uid. */
276 restore_uid();
Ben Lindstrombdde3302002-05-15 16:19:37 +0000277 auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
278 hostname, ipaddr, client_user, pw->pw_name);
Damien Miller95def091999-11-25 00:26:21 +1100279 return 1;
280 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000281 }
282
Damien Miller95def091999-11-25 00:26:21 +1100283 /* Restore the privileged uid. */
284 restore_uid();
285 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000286}
Ben Lindstrombdde3302002-05-15 16:19:37 +0000287
288int
289auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
290 const char *ipaddr)
291{
292 int ret;
293
294 auth_debug_reset();
295 ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
296 if (!use_privsep)
297 auth_debug_send();
298 return ret;
299}