Branch data Line data Source code
1 : : /* $OpenBSD: auth-rhosts.c,v 1.44 2010/03/07 11:57:13 dtucker Exp $ */
2 : : /*
3 : : * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 : : * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 : : * All rights reserved
6 : : * Rhosts authentication. This file contains code to check whether to admit
7 : : * the login based on rhosts authentication. This file also processes
8 : : * /etc/hosts.equiv.
9 : : *
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".
15 : : */
16 : :
17 : : #include "includes.h"
18 : :
19 : : #include <sys/types.h>
20 : : #include <sys/stat.h>
21 : :
22 : : #ifdef HAVE_NETGROUP_H
23 : : # include <netgroup.h>
24 : : #endif
25 : : #include <pwd.h>
26 : : #include <stdio.h>
27 : : #include <string.h>
28 : : #include <stdarg.h>
29 : : #include <fcntl.h>
30 : : #include <unistd.h>
31 : :
32 : : #include "packet.h"
33 : : #include "buffer.h"
34 : : #include "uidswap.h"
35 : : #include "pathnames.h"
36 : : #include "log.h"
37 : : #include "servconf.h"
38 : : #include "canohost.h"
39 : : #include "key.h"
40 : : #include "hostfile.h"
41 : : #include "auth.h"
42 : : #include "misc.h"
43 : :
44 : : /* import */
45 : : extern ServerOptions options;
46 : : extern int use_privsep;
47 : :
48 : : /*
49 : : * This function processes an rhosts-style file (.rhosts, .shosts, or
50 : : * /etc/hosts.equiv). This returns true if authentication can be granted
51 : : * based on the file, and returns zero otherwise.
52 : : */
53 : :
54 : : static int
55 : 0 : check_rhosts_file(const char *filename, const char *hostname,
56 : : const char *ipaddr, const char *client_user,
57 : : const char *server_user)
58 : : {
59 : : FILE *f;
60 : : char buf[1024]; /* Must not be larger than host, user, dummy below. */
61 : : int fd;
62 : : struct stat st;
63 : :
64 : : /* Open the .rhosts file, deny if unreadable */
65 [ # # ]: 0 : if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1)
66 : : return 0;
67 [ # # ]: 0 : if (fstat(fd, &st) == -1) {
68 : 0 : close(fd);
69 : 0 : return 0;
70 : : }
71 [ # # ]: 0 : if (!S_ISREG(st.st_mode)) {
72 : 0 : logit("User %s hosts file %s is not a regular file",
73 : : server_user, filename);
74 : 0 : close(fd);
75 : 0 : return 0;
76 : : }
77 : 0 : unset_nonblock(fd);
78 [ # # ]: 0 : if ((f = fdopen(fd, "r")) == NULL) {
79 : 0 : close(fd);
80 : 0 : return 0;
81 : : }
82 [ # # ]: 0 : while (fgets(buf, sizeof(buf), f)) {
83 : : /* All three must be at least as big as buf to avoid overflows. */
84 : : char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
85 : : int negated;
86 : :
87 [ # # ]: 0 : for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
88 : : ;
89 [ # # ][ # # ]: 0 : if (*cp == '#' || *cp == '\n' || !*cp)
90 : 0 : continue;
91 : :
92 : : /*
93 : : * NO_PLUS is supported at least on OSF/1. We skip it (we
94 : : * don't ever support the plus syntax).
95 : : */
96 [ # # ]: 0 : if (strncmp(cp, "NO_PLUS", 7) == 0)
97 : 0 : continue;
98 : :
99 : : /*
100 : : * This should be safe because each buffer is as big as the
101 : : * whole string, and thus cannot be overwritten.
102 : : */
103 [ # # # # : 0 : switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
# ]
104 : : dummy)) {
105 : : case 0:
106 : 0 : auth_debug_add("Found empty line in %.100s.", filename);
107 : 0 : continue;
108 : : case 1:
109 : : /* Host name only. */
110 : 0 : strlcpy(userbuf, server_user, sizeof(userbuf));
111 : 0 : break;
112 : : case 2:
113 : : /* Got both host and user name. */
114 : : break;
115 : : case 3:
116 : 0 : auth_debug_add("Found garbage in %.100s.", filename);
117 : 0 : continue;
118 : : default:
119 : : /* Weird... */
120 : 0 : continue;
121 : : }
122 : :
123 : 0 : host = hostbuf;
124 : 0 : user = userbuf;
125 : 0 : negated = 0;
126 : :
127 : : /* Process negated host names, or positive netgroups. */
128 [ # # ]: 0 : if (host[0] == '-') {
129 : : negated = 1;
130 : : host++;
131 [ # # ]: 0 : } else if (host[0] == '+')
132 : 0 : host++;
133 : :
134 [ # # ]: 0 : if (user[0] == '-') {
135 : : negated = 1;
136 : : user++;
137 [ # # ]: 0 : } else if (user[0] == '+')
138 : 0 : user++;
139 : :
140 : : /* Check for empty host/user names (particularly '+'). */
141 [ # # ][ # # ]: 0 : if (!host[0] || !user[0]) {
142 : : /* We come here if either was '+' or '-'. */
143 : 0 : auth_debug_add("Ignoring wild host/user names in %.100s.",
144 : : filename);
145 : 0 : continue;
146 : : }
147 : : /* Verify that host name matches. */
148 [ # # ]: 0 : if (host[0] == '@') {
149 [ # # # # ]: 0 : if (!innetgr(host + 1, hostname, NULL, NULL) &&
150 : 0 : !innetgr(host + 1, ipaddr, NULL, NULL))
151 : 0 : continue;
152 [ # # ][ # # ]: 0 : } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
153 : 0 : continue; /* Different hostname. */
154 : :
155 : : /* Verify that user name matches. */
156 [ # # ]: 0 : if (user[0] == '@') {
157 [ # # ]: 0 : if (!innetgr(user + 1, NULL, client_user, NULL))
158 : 0 : continue;
159 [ # # ]: 0 : } else if (strcmp(user, client_user) != 0)
160 : 0 : continue; /* Different username. */
161 : :
162 : : /* Found the user and host. */
163 : 0 : fclose(f);
164 : :
165 : : /* If the entry was negated, deny access. */
166 [ # # ]: 0 : if (negated) {
167 : 0 : auth_debug_add("Matched negative entry in %.100s.",
168 : : filename);
169 : 0 : return 0;
170 : : }
171 : : /* Accept authentication. */
172 : : return 1;
173 : : }
174 : :
175 : : /* Authentication using this file denied. */
176 : 0 : fclose(f);
177 : 0 : return 0;
178 : : }
179 : :
180 : : /*
181 : : * Tries to authenticate the user using the .shosts or .rhosts file. Returns
182 : : * true if authentication succeeds. If ignore_rhosts is true, only
183 : : * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
184 : : */
185 : :
186 : : int
187 : 0 : auth_rhosts(struct passwd *pw, const char *client_user)
188 : : {
189 : : const char *hostname, *ipaddr;
190 : :
191 : 0 : hostname = get_canonical_hostname(options.use_dns);
192 : 0 : ipaddr = get_remote_ipaddr();
193 : 0 : return auth_rhosts2(pw, client_user, hostname, ipaddr);
194 : : }
195 : :
196 : : static int
197 : 0 : auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
198 : : const char *ipaddr)
199 : : {
200 : : char buf[1024];
201 : : struct stat st;
202 : : static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
203 : : u_int rhosts_file_index;
204 : :
205 : 0 : debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
206 : : client_user, hostname, ipaddr);
207 : :
208 : : /* Switch to the user's uid. */
209 : 0 : temporarily_use_uid(pw);
210 : : /*
211 : : * Quick check: if the user has no .shosts or .rhosts files, return
212 : : * failure immediately without doing costly lookups from name
213 : : * servers.
214 : : */
215 [ # # ]: 0 : for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
216 : 0 : rhosts_file_index++) {
217 : : /* Check users .rhosts or .shosts. */
218 : 0 : snprintf(buf, sizeof buf, "%.500s/%.100s",
219 : : pw->pw_dir, rhosts_files[rhosts_file_index]);
220 [ # # ]: 0 : if (stat(buf, &st) >= 0)
221 : : break;
222 : : }
223 : : /* Switch back to privileged uid. */
224 : 0 : restore_uid();
225 : :
226 : : /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
227 [ # # # # ]: 0 : if (!rhosts_files[rhosts_file_index] &&
228 [ # # ]: 0 : stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
229 : : stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
230 : : return 0;
231 : :
232 : : /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
233 [ # # ]: 0 : if (pw->pw_uid != 0) {
234 [ # # ]: 0 : if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
235 : 0 : client_user, pw->pw_name)) {
236 : 0 : auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
237 : : hostname, ipaddr);
238 : 0 : return 1;
239 : : }
240 [ # # ]: 0 : if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
241 : 0 : client_user, pw->pw_name)) {
242 : 0 : auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
243 : : hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
244 : 0 : return 1;
245 : : }
246 : : }
247 : : /*
248 : : * Check that the home directory is owned by root or the user, and is
249 : : * not group or world writable.
250 : : */
251 [ # # ]: 0 : if (stat(pw->pw_dir, &st) < 0) {
252 : 0 : logit("Rhosts authentication refused for %.100s: "
253 : : "no home directory %.200s", pw->pw_name, pw->pw_dir);
254 : 0 : auth_debug_add("Rhosts authentication refused for %.100s: "
255 : : "no home directory %.200s", pw->pw_name, pw->pw_dir);
256 : 0 : return 0;
257 : : }
258 [ # # ][ # # ]: 0 : if (options.strict_modes &&
259 [ # # ][ # # ]: 0 : ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
260 : 0 : (st.st_mode & 022) != 0)) {
261 : 0 : logit("Rhosts authentication refused for %.100s: "
262 : : "bad ownership or modes for home directory.", pw->pw_name);
263 : 0 : auth_debug_add("Rhosts authentication refused for %.100s: "
264 : : "bad ownership or modes for home directory.", pw->pw_name);
265 : 0 : return 0;
266 : : }
267 : : /* Temporarily use the user's uid. */
268 : 0 : temporarily_use_uid(pw);
269 : :
270 : : /* Check all .rhosts files (currently .shosts and .rhosts). */
271 [ # # ]: 0 : for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
272 : 0 : rhosts_file_index++) {
273 : : /* Check users .rhosts or .shosts. */
274 : 0 : snprintf(buf, sizeof buf, "%.500s/%.100s",
275 : : pw->pw_dir, rhosts_files[rhosts_file_index]);
276 [ # # ]: 0 : if (stat(buf, &st) < 0)
277 : 0 : continue;
278 : :
279 : : /*
280 : : * Make sure that the file is either owned by the user or by
281 : : * root, and make sure it is not writable by anyone but the
282 : : * owner. This is to help avoid novices accidentally
283 : : * allowing access to their account by anyone.
284 : : */
285 [ # # ][ # # ]: 0 : if (options.strict_modes &&
286 [ # # ][ # # ]: 0 : ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
287 : 0 : (st.st_mode & 022) != 0)) {
288 : 0 : logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
289 : : pw->pw_name, buf);
290 : 0 : auth_debug_add("Bad file modes for %.200s", buf);
291 : 0 : continue;
292 : : }
293 : : /* Check if we have been configured to ignore .rhosts and .shosts files. */
294 [ # # ]: 0 : if (options.ignore_rhosts) {
295 : 0 : auth_debug_add("Server has been configured to ignore %.100s.",
296 : : rhosts_files[rhosts_file_index]);
297 : 0 : continue;
298 : : }
299 : : /* Check if authentication is permitted by the file. */
300 [ # # ]: 0 : if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
301 : 0 : auth_debug_add("Accepted by %.100s.",
302 : : rhosts_files[rhosts_file_index]);
303 : : /* Restore the privileged uid. */
304 : 0 : restore_uid();
305 : 0 : auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
306 : : hostname, ipaddr, client_user, pw->pw_name);
307 : 0 : return 1;
308 : : }
309 : : }
310 : :
311 : : /* Restore the privileged uid. */
312 : 0 : restore_uid();
313 : 0 : return 0;
314 : : }
315 : :
316 : : int
317 : 0 : auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
318 : : const char *ipaddr)
319 : : {
320 : 0 : return auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
321 : : }
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