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".
18 #include <sys/types.h>
21 #ifdef HAVE_NETGROUP_H
22 # include <netgroup.h>
27 #include "pathnames.h"
34 extern ServerOptions options;
35 extern int use_privsep;
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.
44 check_rhosts_file(const char *filename, const char *hostname,
45 const char *ipaddr, const char *client_user,
46 const char *server_user)
49 char buf[1024]; /* Must not be larger than host, user, dummy below. */
51 /* Open the .rhosts file, deny if unreadable */
52 f = fopen(filename, "r");
56 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;
61 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
63 if (*cp == '#' || *cp == '\n' || !*cp)
67 * NO_PLUS is supported at least on OSF/1. We skip it (we
68 * don't ever support the plus syntax).
70 if (strncmp(cp, "NO_PLUS", 7) == 0)
74 * This should be safe because each buffer is as big as the
75 * whole string, and thus cannot be overwritten.
77 switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
80 auth_debug_add("Found empty line in %.100s.", filename);
84 strlcpy(userbuf, server_user, sizeof(userbuf));
87 /* Got both host and user name. */
90 auth_debug_add("Found garbage in %.100s.", filename);
101 /* Process negated host names, or positive netgroups. */
102 if (host[0] == '-') {
105 } else if (host[0] == '+')
108 if (user[0] == '-') {
111 } else if (user[0] == '+')
114 /* Check for empty host/user names (particularly '+'). */
115 if (!host[0] || !user[0]) {
116 /* We come here if either was '+' or '-'. */
117 auth_debug_add("Ignoring wild host/user names in %.100s.",
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))
126 } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
127 continue; /* Different hostname. */
129 /* Verify that user name matches. */
130 if (user[0] == '@') {
131 if (!innetgr(user + 1, NULL, client_user, NULL))
133 } else if (strcmp(user, client_user) != 0)
134 continue; /* Different username. */
136 /* Found the user and host. */
139 /* If the entry was negated, deny access. */
141 auth_debug_add("Matched negative entry in %.100s.",
145 /* Accept authentication. */
149 /* Authentication using this file denied. */
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).
161 auth_rhosts(struct passwd *pw, const char *client_user)
163 const char *hostname, *ipaddr;
165 hostname = get_canonical_hostname(options.use_dns);
166 ipaddr = get_remote_ipaddr();
167 return auth_rhosts2(pw, client_user, hostname, ipaddr);
171 auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
176 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
177 u_int rhosts_file_index;
179 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
180 client_user, hostname, ipaddr);
182 /* Switch to the user's uid. */
183 temporarily_use_uid(pw);
185 * Quick check: if the user has no .shosts or .rhosts files, return
186 * failure immediately without doing costly lookups from name
189 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
190 rhosts_file_index++) {
191 /* 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)
197 /* Switch back to privileged uid. */
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] &&
202 stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
203 stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
206 /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
207 if (pw->pw_uid != 0) {
208 if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
209 client_user, pw->pw_name)) {
210 auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
214 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
215 client_user, pw->pw_name)) {
216 auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
217 hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
222 * Check that the home directory is owned by root or the user, and is
223 * not group or world writable.
225 if (stat(pw->pw_dir, &st) < 0) {
226 logit("Rhosts authentication refused for %.100s: "
227 "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);
232 if (options.strict_modes &&
233 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
234 (st.st_mode & 022) != 0)) {
235 logit("Rhosts authentication refused for %.100s: "
236 "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);
241 /* Temporarily use the user's uid. */
242 temporarily_use_uid(pw);
244 /* Check all .rhosts files (currently .shosts and .rhosts). */
245 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
246 rhosts_file_index++) {
247 /* 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)
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.
259 if (options.strict_modes &&
260 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
261 (st.st_mode & 022) != 0)) {
262 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
264 auth_debug_add("Bad file modes for %.200s", buf);
267 /* Check if we have been configured to ignore .rhosts and .shosts files. */
268 if (options.ignore_rhosts) {
269 auth_debug_add("Server has been configured to ignore %.100s.",
270 rhosts_files[rhosts_file_index]);
273 /* Check if authentication is permitted by the file. */
274 if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
275 auth_debug_add("Accepted by %.100s.",
276 rhosts_files[rhosts_file_index]);
277 /* Restore the privileged uid. */
279 auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
280 hostname, ipaddr, client_user, pw->pw_name);
285 /* Restore the privileged uid. */
291 auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
297 ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);