1 /* $OpenBSD: auth-rhosts.c,v 1.42 2008/06/13 04:40:22 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"
44 extern ServerOptions options;
45 extern int use_privsep;
48 * This function processes an rhosts-style file (.rhosts, .shosts, or
49 * /etc/hosts.equiv). This returns true if authentication can be granted
50 * based on the file, and returns zero otherwise.
54 check_rhosts_file(const char *filename, const char *hostname,
55 const char *ipaddr, const char *client_user,
56 const char *server_user)
59 char buf[1024]; /* Must not be larger than host, user, dummy below. */
63 /* Open the .rhosts file, deny if unreadable */
64 if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1)
66 if (fstat(fd, &st) == -1) {
70 if (!S_ISREG(st.st_mode)) {
71 logit("User %s hosts file %s is not a regular file",
72 server_user, filename);
77 if ((f = fdopen(fd, "r")) == NULL) {
81 while (fgets(buf, sizeof(buf), f)) {
82 /* All three must be at least as big as buf to avoid overflows. */
83 char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
86 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
88 if (*cp == '#' || *cp == '\n' || !*cp)
92 * NO_PLUS is supported at least on OSF/1. We skip it (we
93 * don't ever support the plus syntax).
95 if (strncmp(cp, "NO_PLUS", 7) == 0)
99 * This should be safe because each buffer is as big as the
100 * whole string, and thus cannot be overwritten.
102 switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
105 auth_debug_add("Found empty line in %.100s.", filename);
108 /* Host name only. */
109 strlcpy(userbuf, server_user, sizeof(userbuf));
112 /* Got both host and user name. */
115 auth_debug_add("Found garbage in %.100s.", filename);
126 /* Process negated host names, or positive netgroups. */
127 if (host[0] == '-') {
130 } else if (host[0] == '+')
133 if (user[0] == '-') {
136 } else if (user[0] == '+')
139 /* Check for empty host/user names (particularly '+'). */
140 if (!host[0] || !user[0]) {
141 /* We come here if either was '+' or '-'. */
142 auth_debug_add("Ignoring wild host/user names in %.100s.",
146 /* Verify that host name matches. */
147 if (host[0] == '@') {
148 if (!innetgr(host + 1, hostname, NULL, NULL) &&
149 !innetgr(host + 1, ipaddr, NULL, NULL))
151 } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
152 continue; /* Different hostname. */
154 /* Verify that user name matches. */
155 if (user[0] == '@') {
156 if (!innetgr(user + 1, NULL, client_user, NULL))
158 } else if (strcmp(user, client_user) != 0)
159 continue; /* Different username. */
161 /* Found the user and host. */
164 /* If the entry was negated, deny access. */
166 auth_debug_add("Matched negative entry in %.100s.",
170 /* Accept authentication. */
174 /* Authentication using this file denied. */
180 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
181 * true if authentication succeeds. If ignore_rhosts is true, only
182 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
186 auth_rhosts(struct passwd *pw, const char *client_user)
188 const char *hostname, *ipaddr;
190 hostname = get_canonical_hostname(options.use_dns);
191 ipaddr = get_remote_ipaddr();
192 return auth_rhosts2(pw, client_user, hostname, ipaddr);
196 auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
201 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
202 u_int rhosts_file_index;
204 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
205 client_user, hostname, ipaddr);
207 /* Switch to the user's uid. */
208 temporarily_use_uid(pw);
210 * Quick check: if the user has no .shosts or .rhosts files, return
211 * failure immediately without doing costly lookups from name
214 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
215 rhosts_file_index++) {
216 /* Check users .rhosts or .shosts. */
217 snprintf(buf, sizeof buf, "%.500s/%.100s",
218 pw->pw_dir, rhosts_files[rhosts_file_index]);
219 if (stat(buf, &st) >= 0)
222 /* Switch back to privileged uid. */
225 /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
226 if (!rhosts_files[rhosts_file_index] &&
227 stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
228 stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
231 /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
232 if (pw->pw_uid != 0) {
233 if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
234 client_user, pw->pw_name)) {
235 auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
239 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
240 client_user, pw->pw_name)) {
241 auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
242 hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
247 * Check that the home directory is owned by root or the user, and is
248 * not group or world writable.
250 if (stat(pw->pw_dir, &st) < 0) {
251 logit("Rhosts authentication refused for %.100s: "
252 "no home directory %.200s", pw->pw_name, pw->pw_dir);
253 auth_debug_add("Rhosts authentication refused for %.100s: "
254 "no home directory %.200s", pw->pw_name, pw->pw_dir);
257 if (options.strict_modes &&
258 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
259 (st.st_mode & 022) != 0)) {
260 logit("Rhosts authentication refused for %.100s: "
261 "bad ownership or modes for home directory.", pw->pw_name);
262 auth_debug_add("Rhosts authentication refused for %.100s: "
263 "bad ownership or modes for home directory.", pw->pw_name);
266 /* Temporarily use the user's uid. */
267 temporarily_use_uid(pw);
269 /* Check all .rhosts files (currently .shosts and .rhosts). */
270 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
271 rhosts_file_index++) {
272 /* Check users .rhosts or .shosts. */
273 snprintf(buf, sizeof buf, "%.500s/%.100s",
274 pw->pw_dir, rhosts_files[rhosts_file_index]);
275 if (stat(buf, &st) < 0)
279 * Make sure that the file is either owned by the user or by
280 * root, and make sure it is not writable by anyone but the
281 * owner. This is to help avoid novices accidentally
282 * allowing access to their account by anyone.
284 if (options.strict_modes &&
285 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
286 (st.st_mode & 022) != 0)) {
287 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
289 auth_debug_add("Bad file modes for %.200s", buf);
292 /* Check if we have been configured to ignore .rhosts and .shosts files. */
293 if (options.ignore_rhosts) {
294 auth_debug_add("Server has been configured to ignore %.100s.",
295 rhosts_files[rhosts_file_index]);
298 /* Check if authentication is permitted by the file. */
299 if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
300 auth_debug_add("Accepted by %.100s.",
301 rhosts_files[rhosts_file_index]);
302 /* Restore the privileged uid. */
304 auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
305 hostname, ipaddr, client_user, pw->pw_name);
310 /* Restore the privileged uid. */
316 auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
322 ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);