blob: 0988935636b88033d8c68289c702cf4ab518abef [file] [log] [blame]
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 Millerf17883e2006-03-15 11:45:54 +110017
18#include <sys/types.h>
19#include <sys/stat.h>
Damien Miller015cd792006-03-15 11:08:02 +110020
21#ifdef HAVE_NETGROUP_H
22# include <netgroup.h>
23#endif
Damien Millerd4a8b7e1999-10-27 13:42:43 +100024
25#include "packet.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100026#include "uidswap.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000027#include "pathnames.h"
28#include "log.h"
Damien Miller6d7b2cd1999-11-12 15:19:27 +110029#include "servconf.h"
Ben Lindstrom226cfa02001-01-22 05:34:40 +000030#include "canohost.h"
Ben Lindstrom31ca54a2001-02-09 02:11:24 +000031#include "auth.h"
Damien Millerd4a8b7e1999-10-27 13:42:43 +100032
Ben Lindstrom5eabda32001-04-12 23:34:34 +000033/* import */
34extern ServerOptions options;
Ben Lindstrombdde3302002-05-15 16:19:37 +000035extern int use_privsep;
Ben Lindstrom5eabda32001-04-12 23:34:34 +000036
Damien Miller5428f641999-11-25 11:54:57 +110037/*
38 * This function processes an rhosts-style file (.rhosts, .shosts, or
39 * /etc/hosts.equiv). This returns true if authentication can be granted
40 * based on the file, and returns zero otherwise.
41 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100042
Ben Lindstrombba81212001-06-25 05:01:22 +000043static int
Damien Miller95def091999-11-25 00:26:21 +110044check_rhosts_file(const char *filename, const char *hostname,
45 const char *ipaddr, const char *client_user,
46 const char *server_user)
Damien Millerd4a8b7e1999-10-27 13:42:43 +100047{
Damien Miller95def091999-11-25 00:26:21 +110048 FILE *f;
49 char buf[1024]; /* Must not be larger than host, user, dummy below. */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100050
Damien Miller95def091999-11-25 00:26:21 +110051 /* Open the .rhosts file, deny if unreadable */
52 f = fopen(filename, "r");
53 if (!f)
54 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100055
Damien Miller95def091999-11-25 00:26:21 +110056 while (fgets(buf, sizeof(buf), f)) {
57 /* All three must be at least as big as buf to avoid overflows. */
58 char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
59 int negated;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100060
Damien Miller95def091999-11-25 00:26:21 +110061 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
62 ;
63 if (*cp == '#' || *cp == '\n' || !*cp)
64 continue;
65
Damien Miller5428f641999-11-25 11:54:57 +110066 /*
67 * NO_PLUS is supported at least on OSF/1. We skip it (we
68 * don't ever support the plus syntax).
69 */
Damien Miller95def091999-11-25 00:26:21 +110070 if (strncmp(cp, "NO_PLUS", 7) == 0)
71 continue;
72
Damien Miller5428f641999-11-25 11:54:57 +110073 /*
74 * This should be safe because each buffer is as big as the
75 * whole string, and thus cannot be overwritten.
76 */
Damien Millera9825782003-05-18 20:53:10 +100077 switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
78 dummy)) {
Damien Miller95def091999-11-25 00:26:21 +110079 case 0:
Ben Lindstrombdde3302002-05-15 16:19:37 +000080 auth_debug_add("Found empty line in %.100s.", filename);
Damien Miller95def091999-11-25 00:26:21 +110081 continue;
82 case 1:
83 /* Host name only. */
84 strlcpy(userbuf, server_user, sizeof(userbuf));
85 break;
86 case 2:
87 /* Got both host and user name. */
88 break;
89 case 3:
Ben Lindstrombdde3302002-05-15 16:19:37 +000090 auth_debug_add("Found garbage in %.100s.", filename);
Damien Miller95def091999-11-25 00:26:21 +110091 continue;
92 default:
93 /* Weird... */
94 continue;
95 }
96
97 host = hostbuf;
98 user = userbuf;
99 negated = 0;
100
101 /* Process negated host names, or positive netgroups. */
102 if (host[0] == '-') {
103 negated = 1;
104 host++;
105 } else if (host[0] == '+')
106 host++;
107
108 if (user[0] == '-') {
109 negated = 1;
110 user++;
111 } else if (user[0] == '+')
112 user++;
113
114 /* Check for empty host/user names (particularly '+'). */
115 if (!host[0] || !user[0]) {
116 /* We come here if either was '+' or '-'. */
Ben Lindstrombdde3302002-05-15 16:19:37 +0000117 auth_debug_add("Ignoring wild host/user names in %.100s.",
118 filename);
Damien Miller95def091999-11-25 00:26:21 +1100119 continue;
120 }
121 /* Verify that host name matches. */
122 if (host[0] == '@') {
123 if (!innetgr(host + 1, hostname, NULL, NULL) &&
124 !innetgr(host + 1, ipaddr, NULL, NULL))
125 continue;
126 } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
127 continue; /* Different hostname. */
128
129 /* Verify that user name matches. */
130 if (user[0] == '@') {
131 if (!innetgr(user + 1, NULL, client_user, NULL))
132 continue;
133 } else if (strcmp(user, client_user) != 0)
134 continue; /* Different username. */
135
136 /* Found the user and host. */
137 fclose(f);
138
139 /* If the entry was negated, deny access. */
140 if (negated) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000141 auth_debug_add("Matched negative entry in %.100s.",
Damien Miller0dc1bef2005-07-17 17:22:45 +1000142 filename);
Damien Miller95def091999-11-25 00:26:21 +1100143 return 0;
144 }
145 /* Accept authentication. */
146 return 1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000147 }
148
Damien Miller95def091999-11-25 00:26:21 +1100149 /* Authentication using this file denied. */
150 fclose(f);
151 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000152}
153
Damien Miller5428f641999-11-25 11:54:57 +1100154/*
155 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
156 * true if authentication succeeds. If ignore_rhosts is true, only
157 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
158 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000159
Damien Miller4af51302000-04-16 11:18:38 +1000160int
Damien Miller95def091999-11-25 00:26:21 +1100161auth_rhosts(struct passwd *pw, const char *client_user)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000162{
Damien Miller95def091999-11-25 00:26:21 +1100163 const char *hostname, *ipaddr;
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000164
Damien Miller3a961dc2003-06-03 10:25:48 +1000165 hostname = get_canonical_hostname(options.use_dns);
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000166 ipaddr = get_remote_ipaddr();
Ben Lindstrombdde3302002-05-15 16:19:37 +0000167 return auth_rhosts2(pw, client_user, hostname, ipaddr);
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000168}
169
Ben Lindstrombdde3302002-05-15 16:19:37 +0000170static int
171auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000172 const char *ipaddr)
173{
174 char buf[1024];
Damien Miller95def091999-11-25 00:26:21 +1100175 struct stat st;
176 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
Ben Lindstrom46c16222000-12-22 01:43:59 +0000177 u_int rhosts_file_index;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000178
Ben Lindstrom5eabda32001-04-12 23:34:34 +0000179 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
180 client_user, hostname, ipaddr);
181
Damien Miller95def091999-11-25 00:26:21 +1100182 /* Switch to the user's uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000183 temporarily_use_uid(pw);
Damien Miller5428f641999-11-25 11:54:57 +1100184 /*
185 * Quick check: if the user has no .shosts or .rhosts files, return
186 * failure immediately without doing costly lookups from name
187 * servers.
188 */
Damien Miller95def091999-11-25 00:26:21 +1100189 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
Damien Miller9f0f5c62001-12-21 14:45:46 +1100190 rhosts_file_index++) {
Damien Miller95def091999-11-25 00:26:21 +1100191 /* Check users .rhosts or .shosts. */
192 snprintf(buf, sizeof buf, "%.500s/%.100s",
193 pw->pw_dir, rhosts_files[rhosts_file_index]);
194 if (stat(buf, &st) >= 0)
195 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000196 }
Damien Miller95def091999-11-25 00:26:21 +1100197 /* Switch back to privileged uid. */
198 restore_uid();
199
200 /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
201 if (!rhosts_files[rhosts_file_index] &&
Ben Lindstrom226cfa02001-01-22 05:34:40 +0000202 stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
203 stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
Damien Miller95def091999-11-25 00:26:21 +1100204 return 0;
205
Damien Miller95def091999-11-25 00:26:21 +1100206 /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
207 if (pw->pw_uid != 0) {
Damien Miller9f0f5c62001-12-21 14:45:46 +1100208 if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
209 client_user, pw->pw_name)) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000210 auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
Damien Miller9f0f5c62001-12-21 14:45:46 +1100211 hostname, ipaddr);
Damien Miller95def091999-11-25 00:26:21 +1100212 return 1;
213 }
Damien Miller9f0f5c62001-12-21 14:45:46 +1100214 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
215 client_user, pw->pw_name)) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000216 auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
Damien Miller9f0f5c62001-12-21 14:45:46 +1100217 hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
Damien Miller95def091999-11-25 00:26:21 +1100218 return 1;
219 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000220 }
Damien Miller5428f641999-11-25 11:54:57 +1100221 /*
222 * Check that the home directory is owned by root or the user, and is
223 * not group or world writable.
224 */
Damien Miller95def091999-11-25 00:26:21 +1100225 if (stat(pw->pw_dir, &st) < 0) {
Damien Miller996acd22003-04-09 20:59:48 +1000226 logit("Rhosts authentication refused for %.100s: "
Ben Lindstrombdde3302002-05-15 16:19:37 +0000227 "no home directory %.200s", pw->pw_name, pw->pw_dir);
228 auth_debug_add("Rhosts authentication refused for %.100s: "
229 "no home directory %.200s", pw->pw_name, pw->pw_dir);
Damien Miller95def091999-11-25 00:26:21 +1100230 return 0;
231 }
232 if (options.strict_modes &&
233 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
Damien Miller9f0f5c62001-12-21 14:45:46 +1100234 (st.st_mode & 022) != 0)) {
Damien Miller996acd22003-04-09 20:59:48 +1000235 logit("Rhosts authentication refused for %.100s: "
Ben Lindstrombdde3302002-05-15 16:19:37 +0000236 "bad ownership or modes for home directory.", pw->pw_name);
237 auth_debug_add("Rhosts authentication refused for %.100s: "
238 "bad ownership or modes for home directory.", pw->pw_name);
Damien Miller95def091999-11-25 00:26:21 +1100239 return 0;
240 }
241 /* Temporarily use the user's uid. */
Ben Lindstrom3fcf1a22001-04-08 18:26:59 +0000242 temporarily_use_uid(pw);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000243
Damien Miller95def091999-11-25 00:26:21 +1100244 /* Check all .rhosts files (currently .shosts and .rhosts). */
245 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
Damien Miller9f0f5c62001-12-21 14:45:46 +1100246 rhosts_file_index++) {
Damien Miller95def091999-11-25 00:26:21 +1100247 /* Check users .rhosts or .shosts. */
248 snprintf(buf, sizeof buf, "%.500s/%.100s",
249 pw->pw_dir, rhosts_files[rhosts_file_index]);
250 if (stat(buf, &st) < 0)
251 continue;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000252
Damien Miller5428f641999-11-25 11:54:57 +1100253 /*
254 * Make sure that the file is either owned by the user or by
255 * root, and make sure it is not writable by anyone but the
256 * owner. This is to help avoid novices accidentally
257 * allowing access to their account by anyone.
258 */
Damien Miller95def091999-11-25 00:26:21 +1100259 if (options.strict_modes &&
260 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
Damien Miller9f0f5c62001-12-21 14:45:46 +1100261 (st.st_mode & 022) != 0)) {
Damien Miller996acd22003-04-09 20:59:48 +1000262 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
Damien Miller95def091999-11-25 00:26:21 +1100263 pw->pw_name, buf);
Ben Lindstrombdde3302002-05-15 16:19:37 +0000264 auth_debug_add("Bad file modes for %.200s", buf);
Damien Miller95def091999-11-25 00:26:21 +1100265 continue;
266 }
267 /* Check if we have been configured to ignore .rhosts and .shosts files. */
268 if (options.ignore_rhosts) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000269 auth_debug_add("Server has been configured to ignore %.100s.",
270 rhosts_files[rhosts_file_index]);
Damien Miller95def091999-11-25 00:26:21 +1100271 continue;
272 }
273 /* Check if authentication is permitted by the file. */
274 if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
Ben Lindstrombdde3302002-05-15 16:19:37 +0000275 auth_debug_add("Accepted by %.100s.",
276 rhosts_files[rhosts_file_index]);
Damien Miller95def091999-11-25 00:26:21 +1100277 /* Restore the privileged uid. */
278 restore_uid();
Ben Lindstrombdde3302002-05-15 16:19:37 +0000279 auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
280 hostname, ipaddr, client_user, pw->pw_name);
Damien Miller95def091999-11-25 00:26:21 +1100281 return 1;
282 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000283 }
284
Damien Miller95def091999-11-25 00:26:21 +1100285 /* Restore the privileged uid. */
286 restore_uid();
287 return 0;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000288}
Ben Lindstrombdde3302002-05-15 16:19:37 +0000289
290int
291auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
292 const char *ipaddr)
293{
294 int ret;
295
296 auth_debug_reset();
297 ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
298 if (!use_privsep)
299 auth_debug_send();
300 return ret;
301}