1 /* $OpenBSD: auth-rhosts.c,v 1.47 2016/03/07 19:02:43 djm Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Rhosts authentication. This file contains code to check whether to admit
7 * the login based on rhosts authentication. This file also processes
10 * As far as I am concerned, the code I have written for this software
11 * can be used freely for any purpose. Any derived versions of this
12 * software must be clearly marked as such, and if the derived work is
13 * incompatible with the protocol description in the RFC file, it must be
14 * called by a name other than "ssh" or "Secure Shell".
19 #include <sys/types.h>
22 #ifdef HAVE_NETGROUP_H
23 # include <netgroup.h>
34 #include "pathnames.h"
37 #include "buffer.h" /* XXX */
38 #include "key.h" /* XXX */
46 extern ServerOptions options
;
47 extern int use_privsep
;
50 * This function processes an rhosts-style file (.rhosts, .shosts, or
51 * /etc/hosts.equiv). This returns true if authentication can be granted
52 * based on the file, and returns zero otherwise.
56 check_rhosts_file(const char *filename
, const char *hostname
,
57 const char *ipaddr
, const char *client_user
,
58 const char *server_user
)
62 char buf
[RBUFLN
];/* Must not be larger than host, user, dummy below. */
66 /* Open the .rhosts file, deny if unreadable */
67 if ((fd
= open(filename
, O_RDONLY
|O_NONBLOCK
)) == -1)
69 if (fstat(fd
, &st
) == -1) {
73 if (!S_ISREG(st
.st_mode
)) {
74 logit("User %s hosts file %s is not a regular file",
75 server_user
, filename
);
80 if ((f
= fdopen(fd
, "r")) == NULL
) {
84 while (fgets(buf
, sizeof(buf
), f
)) {
85 /* All three must have length >= buf to avoid overflows. */
86 char hostbuf
[RBUFLN
], userbuf
[RBUFLN
], dummy
[RBUFLN
];
87 char *host
, *user
, *cp
;
90 for (cp
= buf
; *cp
== ' ' || *cp
== '\t'; cp
++)
92 if (*cp
== '#' || *cp
== '\n' || !*cp
)
96 * NO_PLUS is supported at least on OSF/1. We skip it (we
97 * don't ever support the plus syntax).
99 if (strncmp(cp
, "NO_PLUS", 7) == 0)
103 * This should be safe because each buffer is as big as the
104 * whole string, and thus cannot be overwritten.
106 switch (sscanf(buf
, "%1023s %1023s %1023s", hostbuf
, userbuf
,
109 auth_debug_add("Found empty line in %.100s.", filename
);
112 /* Host name only. */
113 strlcpy(userbuf
, server_user
, sizeof(userbuf
));
116 /* Got both host and user name. */
119 auth_debug_add("Found garbage in %.100s.", filename
);
130 /* Process negated host names, or positive netgroups. */
131 if (host
[0] == '-') {
134 } else if (host
[0] == '+')
137 if (user
[0] == '-') {
140 } else if (user
[0] == '+')
143 /* Check for empty host/user names (particularly '+'). */
144 if (!host
[0] || !user
[0]) {
145 /* We come here if either was '+' or '-'. */
146 auth_debug_add("Ignoring wild host/user names "
147 "in %.100s.", filename
);
150 /* Verify that host name matches. */
151 if (host
[0] == '@') {
152 if (!innetgr(host
+ 1, hostname
, NULL
, NULL
) &&
153 !innetgr(host
+ 1, ipaddr
, NULL
, NULL
))
155 } else if (strcasecmp(host
, hostname
) &&
156 strcmp(host
, ipaddr
) != 0)
157 continue; /* Different hostname. */
159 /* Verify that user name matches. */
160 if (user
[0] == '@') {
161 if (!innetgr(user
+ 1, NULL
, client_user
, NULL
))
163 } else if (strcmp(user
, client_user
) != 0)
164 continue; /* Different username. */
166 /* Found the user and host. */
169 /* If the entry was negated, deny access. */
171 auth_debug_add("Matched negative entry in %.100s.",
175 /* Accept authentication. */
179 /* Authentication using this file denied. */
185 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
186 * true if authentication succeeds. If ignore_rhosts is true, only
187 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
191 auth_rhosts(struct passwd
*pw
, const char *client_user
)
193 struct ssh
*ssh
= active_state
; /* XXX */
194 const char *hostname
, *ipaddr
;
196 hostname
= auth_get_canonical_hostname(ssh
, options
.use_dns
);
197 ipaddr
= ssh_remote_ipaddr(ssh
);
198 return auth_rhosts2(pw
, client_user
, hostname
, ipaddr
);
202 auth_rhosts2_raw(struct passwd
*pw
, const char *client_user
, const char *hostname
,
207 static const char *rhosts_files
[] = {".shosts", ".rhosts", NULL
};
208 u_int rhosts_file_index
;
210 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
211 client_user
, hostname
, ipaddr
);
213 /* Switch to the user's uid. */
214 temporarily_use_uid(pw
);
216 * Quick check: if the user has no .shosts or .rhosts files and
217 * no system hosts.equiv/shosts.equiv files exist then return
218 * failure immediately without doing costly lookups from name
221 for (rhosts_file_index
= 0; rhosts_files
[rhosts_file_index
];
222 rhosts_file_index
++) {
223 /* Check users .rhosts or .shosts. */
224 snprintf(buf
, sizeof buf
, "%.500s/%.100s",
225 pw
->pw_dir
, rhosts_files
[rhosts_file_index
]);
226 if (stat(buf
, &st
) >= 0)
229 /* Switch back to privileged uid. */
233 * Deny if The user has no .shosts or .rhosts file and there
234 * are no system-wide files.
236 if (!rhosts_files
[rhosts_file_index
] &&
237 stat(_PATH_RHOSTS_EQUIV
, &st
) < 0 &&
238 stat(_PATH_SSH_HOSTS_EQUIV
, &st
) < 0) {
239 debug3("%s: no hosts access files exist", __func__
);
244 * If not logging in as superuser, try /etc/hosts.equiv and
248 debug3("%s: root user, ignoring system hosts files", __func__
);
250 if (check_rhosts_file(_PATH_RHOSTS_EQUIV
, hostname
, ipaddr
,
251 client_user
, pw
->pw_name
)) {
252 auth_debug_add("Accepted for %.100s [%.100s] by "
253 "/etc/hosts.equiv.", hostname
, ipaddr
);
256 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV
, hostname
, ipaddr
,
257 client_user
, pw
->pw_name
)) {
258 auth_debug_add("Accepted for %.100s [%.100s] by "
259 "%.100s.", hostname
, ipaddr
, _PATH_SSH_HOSTS_EQUIV
);
265 * Check that the home directory is owned by root or the user, and is
266 * not group or world writable.
268 if (stat(pw
->pw_dir
, &st
) < 0) {
269 logit("Rhosts authentication refused for %.100s: "
270 "no home directory %.200s", pw
->pw_name
, pw
->pw_dir
);
271 auth_debug_add("Rhosts authentication refused for %.100s: "
272 "no home directory %.200s", pw
->pw_name
, pw
->pw_dir
);
275 if (options
.strict_modes
&&
276 ((st
.st_uid
!= 0 && st
.st_uid
!= pw
->pw_uid
) ||
277 (st
.st_mode
& 022) != 0)) {
278 logit("Rhosts authentication refused for %.100s: "
279 "bad ownership or modes for home directory.", pw
->pw_name
);
280 auth_debug_add("Rhosts authentication refused for %.100s: "
281 "bad ownership or modes for home directory.", pw
->pw_name
);
284 /* Temporarily use the user's uid. */
285 temporarily_use_uid(pw
);
287 /* Check all .rhosts files (currently .shosts and .rhosts). */
288 for (rhosts_file_index
= 0; rhosts_files
[rhosts_file_index
];
289 rhosts_file_index
++) {
290 /* Check users .rhosts or .shosts. */
291 snprintf(buf
, sizeof buf
, "%.500s/%.100s",
292 pw
->pw_dir
, rhosts_files
[rhosts_file_index
]);
293 if (stat(buf
, &st
) < 0)
297 * Make sure that the file is either owned by the user or by
298 * root, and make sure it is not writable by anyone but the
299 * owner. This is to help avoid novices accidentally
300 * allowing access to their account by anyone.
302 if (options
.strict_modes
&&
303 ((st
.st_uid
!= 0 && st
.st_uid
!= pw
->pw_uid
) ||
304 (st
.st_mode
& 022) != 0)) {
305 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
307 auth_debug_add("Bad file modes for %.200s", buf
);
311 * Check if we have been configured to ignore .rhosts
314 if (options
.ignore_rhosts
) {
315 auth_debug_add("Server has been configured to "
316 "ignore %.100s.", rhosts_files
[rhosts_file_index
]);
319 /* Check if authentication is permitted by the file. */
320 if (check_rhosts_file(buf
, hostname
, ipaddr
,
321 client_user
, pw
->pw_name
)) {
322 auth_debug_add("Accepted by %.100s.",
323 rhosts_files
[rhosts_file_index
]);
324 /* Restore the privileged uid. */
326 auth_debug_add("Accepted host %s ip %s client_user "
327 "%s server_user %s", hostname
, ipaddr
,
328 client_user
, pw
->pw_name
);
333 /* Restore the privileged uid. */
339 auth_rhosts2(struct passwd
*pw
, const char *client_user
, const char *hostname
,
342 return auth_rhosts2_raw(pw
, client_user
, hostname
, ipaddr
);