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Damien Millerd4a8b7e1999-10-27 13:42:43 +10001/*
Damien Miller4af51302000-04-16 11:18:38 +10002 *
Damien Miller95def091999-11-25 00:26:21 +11003 * auth-rhosts.c
Damien Miller4af51302000-04-16 11:18:38 +10004 *
Damien Miller95def091999-11-25 00:26:21 +11005 * Author: Tatu Ylonen <ylo@cs.hut.fi>
Damien Miller4af51302000-04-16 11:18:38 +10006 *
Damien Miller95def091999-11-25 00:26:21 +11007 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8 * All rights reserved
Damien Miller4af51302000-04-16 11:18:38 +10009 *
Damien Miller95def091999-11-25 00:26:21 +110010 * Created: Fri Mar 17 05:12:18 1995 ylo
Damien Miller4af51302000-04-16 11:18:38 +100011 *
Damien Miller95def091999-11-25 00:26:21 +110012 * Rhosts authentication. This file contains code to check whether to admit
13 * the login based on rhosts authentication. This file also processes
14 * /etc/hosts.equiv.
Damien Miller4af51302000-04-16 11:18:38 +100015 *
Damien Miller95def091999-11-25 00:26:21 +110016 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100017
18#include "includes.h"
Damien Miller4af51302000-04-16 11:18:38 +100019RCSID("$Id: auth-rhosts.c,v 1.8 2000/04/16 01:18:39 damien Exp $");
Damien Millerd4a8b7e1999-10-27 13:42:43 +100020
21#include "packet.h"
22#include "ssh.h"
23#include "xmalloc.h"
24#include "uidswap.h"
Damien Miller6d7b2cd1999-11-12 15:19:27 +110025#include "servconf.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100026
Damien Miller5428f641999-11-25 11:54:57 +110027/*
28 * This function processes an rhosts-style file (.rhosts, .shosts, or
29 * /etc/hosts.equiv). This returns true if authentication can be granted
30 * based on the file, and returns zero otherwise.
31 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100032
Damien Miller4af51302000-04-16 11:18:38 +100033int
Damien Miller95def091999-11-25 00:26:21 +110034check_rhosts_file(const char *filename, const char *hostname,
35 const char *ipaddr, const char *client_user,
36 const char *server_user)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100037{
Damien Miller95def091999-11-25 00:26:21 +110038 FILE *f;
39 char buf[1024]; /* Must not be larger than host, user, dummy below. */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100040
Damien Miller95def091999-11-25 00:26:21 +110041 /* Open the .rhosts file, deny if unreadable */
42 f = fopen(filename, "r");
43 if (!f)
44 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100045
Damien Miller95def091999-11-25 00:26:21 +110046 while (fgets(buf, sizeof(buf), f)) {
47 /* All three must be at least as big as buf to avoid overflows. */
48 char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
49 int negated;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100050
Damien Miller95def091999-11-25 00:26:21 +110051 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
52 ;
53 if (*cp == '#' || *cp == '\n' || !*cp)
54 continue;
55
Damien Miller5428f641999-11-25 11:54:57 +110056 /*
57 * NO_PLUS is supported at least on OSF/1. We skip it (we
58 * don't ever support the plus syntax).
59 */
Damien Miller95def091999-11-25 00:26:21 +110060 if (strncmp(cp, "NO_PLUS", 7) == 0)
61 continue;
62
Damien Miller5428f641999-11-25 11:54:57 +110063 /*
64 * This should be safe because each buffer is as big as the
65 * whole string, and thus cannot be overwritten.
66 */
Damien Miller95def091999-11-25 00:26:21 +110067 switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) {
68 case 0:
69 packet_send_debug("Found empty line in %.100s.", filename);
70 continue;
71 case 1:
72 /* Host name only. */
73 strlcpy(userbuf, server_user, sizeof(userbuf));
74 break;
75 case 2:
76 /* Got both host and user name. */
77 break;
78 case 3:
79 packet_send_debug("Found garbage in %.100s.", filename);
80 continue;
81 default:
82 /* Weird... */
83 continue;
84 }
85
86 host = hostbuf;
87 user = userbuf;
88 negated = 0;
89
90 /* Process negated host names, or positive netgroups. */
91 if (host[0] == '-') {
92 negated = 1;
93 host++;
94 } else if (host[0] == '+')
95 host++;
96
97 if (user[0] == '-') {
98 negated = 1;
99 user++;
100 } else if (user[0] == '+')
101 user++;
102
103 /* Check for empty host/user names (particularly '+'). */
104 if (!host[0] || !user[0]) {
105 /* We come here if either was '+' or '-'. */
106 packet_send_debug("Ignoring wild host/user names in %.100s.",
107 filename);
108 continue;
109 }
110 /* Verify that host name matches. */
111 if (host[0] == '@') {
112 if (!innetgr(host + 1, hostname, NULL, NULL) &&
113 !innetgr(host + 1, ipaddr, NULL, NULL))
114 continue;
115 } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
116 continue; /* Different hostname. */
117
118 /* Verify that user name matches. */
119 if (user[0] == '@') {
120 if (!innetgr(user + 1, NULL, client_user, NULL))
121 continue;
122 } else if (strcmp(user, client_user) != 0)
123 continue; /* Different username. */
124
125 /* Found the user and host. */
126 fclose(f);
127
128 /* If the entry was negated, deny access. */
129 if (negated) {
130 packet_send_debug("Matched negative entry in %.100s.",
131 filename);
132 return 0;
133 }
134 /* Accept authentication. */
135 return 1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000136 }
137
Damien Miller95def091999-11-25 00:26:21 +1100138 /* Authentication using this file denied. */
139 fclose(f);
140 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000141}
142
Damien Miller5428f641999-11-25 11:54:57 +1100143/*
144 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
145 * true if authentication succeeds. If ignore_rhosts is true, only
146 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
147 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000148
Damien Miller4af51302000-04-16 11:18:38 +1000149int
Damien Miller95def091999-11-25 00:26:21 +1100150auth_rhosts(struct passwd *pw, const char *client_user)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000151{
Damien Miller95def091999-11-25 00:26:21 +1100152 extern ServerOptions options;
153 char buf[1024];
154 const char *hostname, *ipaddr;
155 struct stat st;
156 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
157 unsigned int rhosts_file_index;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000158
Damien Miller95def091999-11-25 00:26:21 +1100159 /* Switch to the user's uid. */
160 temporarily_use_uid(pw->pw_uid);
Damien Miller5428f641999-11-25 11:54:57 +1100161 /*
162 * Quick check: if the user has no .shosts or .rhosts files, return
163 * failure immediately without doing costly lookups from name
164 * servers.
165 */
Damien Miller95def091999-11-25 00:26:21 +1100166 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
167 rhosts_file_index++) {
168 /* Check users .rhosts or .shosts. */
169 snprintf(buf, sizeof buf, "%.500s/%.100s",
170 pw->pw_dir, rhosts_files[rhosts_file_index]);
171 if (stat(buf, &st) >= 0)
172 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000173 }
Damien Miller95def091999-11-25 00:26:21 +1100174 /* Switch back to privileged uid. */
175 restore_uid();
176
177 /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
178 if (!rhosts_files[rhosts_file_index] &&
179 stat("/etc/hosts.equiv", &st) < 0 &&
180 stat(SSH_HOSTS_EQUIV, &st) < 0)
181 return 0;
182
Damien Miller95def091999-11-25 00:26:21 +1100183 hostname = get_canonical_hostname();
184 ipaddr = get_remote_ipaddr();
185
186 /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
187 if (pw->pw_uid != 0) {
188 if (check_rhosts_file("/etc/hosts.equiv", hostname, ipaddr, client_user,
189 pw->pw_name)) {
190 packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
191 hostname, ipaddr);
192 return 1;
193 }
194 if (check_rhosts_file(SSH_HOSTS_EQUIV, hostname, ipaddr, client_user,
195 pw->pw_name)) {
196 packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
197 hostname, ipaddr, SSH_HOSTS_EQUIV);
198 return 1;
199 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000200 }
Damien Miller5428f641999-11-25 11:54:57 +1100201 /*
202 * Check that the home directory is owned by root or the user, and is
203 * not group or world writable.
204 */
Damien Miller95def091999-11-25 00:26:21 +1100205 if (stat(pw->pw_dir, &st) < 0) {
206 log("Rhosts authentication refused for %.100s: no home directory %.200s",
207 pw->pw_name, pw->pw_dir);
Damien Miller68e45de1999-12-27 23:54:55 +1100208 packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s",
Damien Miller95def091999-11-25 00:26:21 +1100209 pw->pw_name, pw->pw_dir);
210 return 0;
211 }
212 if (options.strict_modes &&
213 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
214 (st.st_mode & 022) != 0)) {
215 log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
216 pw->pw_name);
217 packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
218 pw->pw_name);
219 return 0;
220 }
221 /* Temporarily use the user's uid. */
222 temporarily_use_uid(pw->pw_uid);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000223
Damien Miller95def091999-11-25 00:26:21 +1100224 /* Check all .rhosts files (currently .shosts and .rhosts). */
225 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
226 rhosts_file_index++) {
227 /* Check users .rhosts or .shosts. */
228 snprintf(buf, sizeof buf, "%.500s/%.100s",
229 pw->pw_dir, rhosts_files[rhosts_file_index]);
230 if (stat(buf, &st) < 0)
231 continue;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000232
Damien Miller5428f641999-11-25 11:54:57 +1100233 /*
234 * Make sure that the file is either owned by the user or by
235 * root, and make sure it is not writable by anyone but the
236 * owner. This is to help avoid novices accidentally
237 * allowing access to their account by anyone.
238 */
Damien Miller95def091999-11-25 00:26:21 +1100239 if (options.strict_modes &&
240 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
241 (st.st_mode & 022) != 0)) {
242 log("Rhosts authentication refused for %.100s: bad modes for %.200s",
243 pw->pw_name, buf);
244 packet_send_debug("Bad file modes for %.200s", buf);
245 continue;
246 }
247 /* Check if we have been configured to ignore .rhosts and .shosts files. */
248 if (options.ignore_rhosts) {
249 packet_send_debug("Server has been configured to ignore %.100s.",
250 rhosts_files[rhosts_file_index]);
251 continue;
252 }
253 /* Check if authentication is permitted by the file. */
254 if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
255 packet_send_debug("Accepted by %.100s.",
256 rhosts_files[rhosts_file_index]);
257 /* Restore the privileged uid. */
258 restore_uid();
259 return 1;
260 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000261 }
262
Damien Miller95def091999-11-25 00:26:21 +1100263 /* Restore the privileged uid. */
264 restore_uid();
265 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000266}