2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * Rhosts authentication. This file contains code to check whether to admit
6 * the login based on rhosts authentication. This file also processes
9 * 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".
17 RCSID("$OpenBSD: auth-rhosts.c,v 1.35 2006/02/20 17:19:53 stevesk Exp $");
19 #include <sys/types.h>
22 #ifdef HAVE_NETGROUP_H
23 # include <netgroup.h>
28 #include "pathnames.h"
35 extern ServerOptions options;
36 extern int use_privsep;
39 * This function processes an rhosts-style file (.rhosts, .shosts, or
40 * /etc/hosts.equiv). This returns true if authentication can be granted
41 * based on the file, and returns zero otherwise.
45 check_rhosts_file(const char *filename, const char *hostname,
46 const char *ipaddr, const char *client_user,
47 const char *server_user)
50 char buf[1024]; /* Must not be larger than host, user, dummy below. */
52 /* Open the .rhosts file, deny if unreadable */
53 f = fopen(filename, "r");
57 while (fgets(buf, sizeof(buf), f)) {
58 /* All three must be at least as big as buf to avoid overflows. */
59 char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
62 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
64 if (*cp == '#' || *cp == '\n' || !*cp)
68 * NO_PLUS is supported at least on OSF/1. We skip it (we
69 * don't ever support the plus syntax).
71 if (strncmp(cp, "NO_PLUS", 7) == 0)
75 * This should be safe because each buffer is as big as the
76 * whole string, and thus cannot be overwritten.
78 switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
81 auth_debug_add("Found empty line in %.100s.", filename);
85 strlcpy(userbuf, server_user, sizeof(userbuf));
88 /* Got both host and user name. */
91 auth_debug_add("Found garbage in %.100s.", filename);
102 /* Process negated host names, or positive netgroups. */
103 if (host[0] == '-') {
106 } else if (host[0] == '+')
109 if (user[0] == '-') {
112 } else if (user[0] == '+')
115 /* Check for empty host/user names (particularly '+'). */
116 if (!host[0] || !user[0]) {
117 /* We come here if either was '+' or '-'. */
118 auth_debug_add("Ignoring wild host/user names in %.100s.",
122 /* Verify that host name matches. */
123 if (host[0] == '@') {
124 if (!innetgr(host + 1, hostname, NULL, NULL) &&
125 !innetgr(host + 1, ipaddr, NULL, NULL))
127 } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
128 continue; /* Different hostname. */
130 /* Verify that user name matches. */
131 if (user[0] == '@') {
132 if (!innetgr(user + 1, NULL, client_user, NULL))
134 } else if (strcmp(user, client_user) != 0)
135 continue; /* Different username. */
137 /* Found the user and host. */
140 /* If the entry was negated, deny access. */
142 auth_debug_add("Matched negative entry in %.100s.",
146 /* Accept authentication. */
150 /* Authentication using this file denied. */
156 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
157 * true if authentication succeeds. If ignore_rhosts is true, only
158 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
162 auth_rhosts(struct passwd *pw, const char *client_user)
164 const char *hostname, *ipaddr;
166 hostname = get_canonical_hostname(options.use_dns);
167 ipaddr = get_remote_ipaddr();
168 return auth_rhosts2(pw, client_user, hostname, ipaddr);
172 auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
177 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
178 u_int rhosts_file_index;
180 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
181 client_user, hostname, ipaddr);
183 /* Switch to the user's uid. */
184 temporarily_use_uid(pw);
186 * Quick check: if the user has no .shosts or .rhosts files, return
187 * failure immediately without doing costly lookups from name
190 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
191 rhosts_file_index++) {
192 /* Check users .rhosts or .shosts. */
193 snprintf(buf, sizeof buf, "%.500s/%.100s",
194 pw->pw_dir, rhosts_files[rhosts_file_index]);
195 if (stat(buf, &st) >= 0)
198 /* Switch back to privileged uid. */
201 /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
202 if (!rhosts_files[rhosts_file_index] &&
203 stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
204 stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
207 /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
208 if (pw->pw_uid != 0) {
209 if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
210 client_user, pw->pw_name)) {
211 auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
215 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
216 client_user, pw->pw_name)) {
217 auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
218 hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
223 * Check that the home directory is owned by root or the user, and is
224 * not group or world writable.
226 if (stat(pw->pw_dir, &st) < 0) {
227 logit("Rhosts authentication refused for %.100s: "
228 "no home directory %.200s", pw->pw_name, pw->pw_dir);
229 auth_debug_add("Rhosts authentication refused for %.100s: "
230 "no home directory %.200s", pw->pw_name, pw->pw_dir);
233 if (options.strict_modes &&
234 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
235 (st.st_mode & 022) != 0)) {
236 logit("Rhosts authentication refused for %.100s: "
237 "bad ownership or modes for home directory.", pw->pw_name);
238 auth_debug_add("Rhosts authentication refused for %.100s: "
239 "bad ownership or modes for home directory.", pw->pw_name);
242 /* Temporarily use the user's uid. */
243 temporarily_use_uid(pw);
245 /* Check all .rhosts files (currently .shosts and .rhosts). */
246 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
247 rhosts_file_index++) {
248 /* Check users .rhosts or .shosts. */
249 snprintf(buf, sizeof buf, "%.500s/%.100s",
250 pw->pw_dir, rhosts_files[rhosts_file_index]);
251 if (stat(buf, &st) < 0)
255 * Make sure that the file is either owned by the user or by
256 * root, and make sure it is not writable by anyone but the
257 * owner. This is to help avoid novices accidentally
258 * allowing access to their account by anyone.
260 if (options.strict_modes &&
261 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
262 (st.st_mode & 022) != 0)) {
263 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
265 auth_debug_add("Bad file modes for %.200s", buf);
268 /* Check if we have been configured to ignore .rhosts and .shosts files. */
269 if (options.ignore_rhosts) {
270 auth_debug_add("Server has been configured to ignore %.100s.",
271 rhosts_files[rhosts_file_index]);
274 /* Check if authentication is permitted by the file. */
275 if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
276 auth_debug_add("Accepted by %.100s.",
277 rhosts_files[rhosts_file_index]);
278 /* Restore the privileged uid. */
280 auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
281 hostname, ipaddr, client_user, pw->pw_name);
286 /* Restore the privileged uid. */
292 auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
298 ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);