1 /* $OpenBSD: auth-rhosts.c,v 1.48 2016/08/13 17:47:41 markus 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).
190 auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
195 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
196 u_int rhosts_file_index;
198 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
199 client_user, hostname, ipaddr);
201 /* Switch to the user's uid. */
202 temporarily_use_uid(pw);
204 * Quick check: if the user has no .shosts or .rhosts files and
205 * no system hosts.equiv/shosts.equiv files exist then return
206 * failure immediately without doing costly lookups from name
209 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
210 rhosts_file_index++) {
211 /* Check users .rhosts or .shosts. */
212 snprintf(buf, sizeof buf, "%.500s/%.100s",
213 pw->pw_dir, rhosts_files[rhosts_file_index]);
214 if (stat(buf, &st) >= 0)
217 /* Switch back to privileged uid. */
221 * Deny if The user has no .shosts or .rhosts file and there
222 * are no system-wide files.
224 if (!rhosts_files[rhosts_file_index] &&
225 stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
226 stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0) {
227 debug3("%s: no hosts access files exist", __func__);
232 * If not logging in as superuser, try /etc/hosts.equiv and
236 debug3("%s: root user, ignoring system hosts files", __func__);
238 if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
239 client_user, pw->pw_name)) {
240 auth_debug_add("Accepted for %.100s [%.100s] by "
241 "/etc/hosts.equiv.", hostname, ipaddr);
244 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
245 client_user, pw->pw_name)) {
246 auth_debug_add("Accepted for %.100s [%.100s] by "
247 "%.100s.", hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
253 * Check that the home directory is owned by root or the user, and is
254 * not group or world writable.
256 if (stat(pw->pw_dir, &st) < 0) {
257 logit("Rhosts authentication refused for %.100s: "
258 "no home directory %.200s", pw->pw_name, pw->pw_dir);
259 auth_debug_add("Rhosts authentication refused for %.100s: "
260 "no home directory %.200s", pw->pw_name, pw->pw_dir);
263 if (options.strict_modes &&
264 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
265 (st.st_mode & 022) != 0)) {
266 logit("Rhosts authentication refused for %.100s: "
267 "bad ownership or modes for home directory.", pw->pw_name);
268 auth_debug_add("Rhosts authentication refused for %.100s: "
269 "bad ownership or modes for home directory.", pw->pw_name);
272 /* Temporarily use the user's uid. */
273 temporarily_use_uid(pw);
275 /* Check all .rhosts files (currently .shosts and .rhosts). */
276 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
277 rhosts_file_index++) {
278 /* Check users .rhosts or .shosts. */
279 snprintf(buf, sizeof buf, "%.500s/%.100s",
280 pw->pw_dir, rhosts_files[rhosts_file_index]);
281 if (stat(buf, &st) < 0)
285 * Make sure that the file is either owned by the user or by
286 * root, and make sure it is not writable by anyone but the
287 * owner. This is to help avoid novices accidentally
288 * allowing access to their account by anyone.
290 if (options.strict_modes &&
291 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
292 (st.st_mode & 022) != 0)) {
293 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
295 auth_debug_add("Bad file modes for %.200s", buf);
299 * Check if we have been configured to ignore .rhosts
302 if (options.ignore_rhosts) {
303 auth_debug_add("Server has been configured to "
304 "ignore %.100s.", rhosts_files[rhosts_file_index]);
307 /* Check if authentication is permitted by the file. */
308 if (check_rhosts_file(buf, hostname, ipaddr,
309 client_user, pw->pw_name)) {
310 auth_debug_add("Accepted by %.100s.",
311 rhosts_files[rhosts_file_index]);
312 /* Restore the privileged uid. */
314 auth_debug_add("Accepted host %s ip %s client_user "
315 "%s server_user %s", hostname, ipaddr,
316 client_user, pw->pw_name);
321 /* Restore the privileged uid. */