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3c0ef626 | 1 | /* |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5 | * Rhosts authentication. This file contains code to check whether to admit | |
6 | * the login based on rhosts authentication. This file also processes | |
7 | * /etc/hosts.equiv. | |
8 | * | |
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". | |
14 | */ | |
15 | ||
16 | #include "includes.h" | |
665a873d | 17 | RCSID("$OpenBSD: auth-rhosts.c,v 1.33 2005/07/17 07:17:54 djm Exp $"); |
3c0ef626 | 18 | |
19 | #include "packet.h" | |
3c0ef626 | 20 | #include "uidswap.h" |
21 | #include "pathnames.h" | |
22 | #include "log.h" | |
23 | #include "servconf.h" | |
24 | #include "canohost.h" | |
25 | #include "auth.h" | |
26 | ||
27 | /* import */ | |
28 | extern ServerOptions options; | |
700318f3 | 29 | extern int use_privsep; |
3c0ef626 | 30 | |
31 | /* | |
32 | * This function processes an rhosts-style file (.rhosts, .shosts, or | |
33 | * /etc/hosts.equiv). This returns true if authentication can be granted | |
34 | * based on the file, and returns zero otherwise. | |
35 | */ | |
36 | ||
37 | static int | |
38 | check_rhosts_file(const char *filename, const char *hostname, | |
39 | const char *ipaddr, const char *client_user, | |
40 | const char *server_user) | |
41 | { | |
42 | FILE *f; | |
43 | char buf[1024]; /* Must not be larger than host, user, dummy below. */ | |
44 | ||
45 | /* Open the .rhosts file, deny if unreadable */ | |
46 | f = fopen(filename, "r"); | |
47 | if (!f) | |
48 | return 0; | |
49 | ||
50 | while (fgets(buf, sizeof(buf), f)) { | |
51 | /* All three must be at least as big as buf to avoid overflows. */ | |
52 | char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp; | |
53 | int negated; | |
54 | ||
55 | for (cp = buf; *cp == ' ' || *cp == '\t'; cp++) | |
56 | ; | |
57 | if (*cp == '#' || *cp == '\n' || !*cp) | |
58 | continue; | |
59 | ||
60 | /* | |
61 | * NO_PLUS is supported at least on OSF/1. We skip it (we | |
62 | * don't ever support the plus syntax). | |
63 | */ | |
64 | if (strncmp(cp, "NO_PLUS", 7) == 0) | |
65 | continue; | |
66 | ||
67 | /* | |
68 | * This should be safe because each buffer is as big as the | |
69 | * whole string, and thus cannot be overwritten. | |
70 | */ | |
0fff78ff | 71 | switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf, |
72 | dummy)) { | |
3c0ef626 | 73 | case 0: |
700318f3 | 74 | auth_debug_add("Found empty line in %.100s.", filename); |
3c0ef626 | 75 | continue; |
76 | case 1: | |
77 | /* Host name only. */ | |
78 | strlcpy(userbuf, server_user, sizeof(userbuf)); | |
79 | break; | |
80 | case 2: | |
81 | /* Got both host and user name. */ | |
82 | break; | |
83 | case 3: | |
700318f3 | 84 | auth_debug_add("Found garbage in %.100s.", filename); |
3c0ef626 | 85 | continue; |
86 | default: | |
87 | /* Weird... */ | |
88 | continue; | |
89 | } | |
90 | ||
91 | host = hostbuf; | |
92 | user = userbuf; | |
93 | negated = 0; | |
94 | ||
95 | /* Process negated host names, or positive netgroups. */ | |
96 | if (host[0] == '-') { | |
97 | negated = 1; | |
98 | host++; | |
99 | } else if (host[0] == '+') | |
100 | host++; | |
101 | ||
102 | if (user[0] == '-') { | |
103 | negated = 1; | |
104 | user++; | |
105 | } else if (user[0] == '+') | |
106 | user++; | |
107 | ||
108 | /* Check for empty host/user names (particularly '+'). */ | |
109 | if (!host[0] || !user[0]) { | |
110 | /* We come here if either was '+' or '-'. */ | |
700318f3 | 111 | auth_debug_add("Ignoring wild host/user names in %.100s.", |
112 | filename); | |
3c0ef626 | 113 | continue; |
114 | } | |
115 | /* Verify that host name matches. */ | |
116 | if (host[0] == '@') { | |
117 | if (!innetgr(host + 1, hostname, NULL, NULL) && | |
118 | !innetgr(host + 1, ipaddr, NULL, NULL)) | |
119 | continue; | |
120 | } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0) | |
121 | continue; /* Different hostname. */ | |
122 | ||
123 | /* Verify that user name matches. */ | |
124 | if (user[0] == '@') { | |
125 | if (!innetgr(user + 1, NULL, client_user, NULL)) | |
126 | continue; | |
127 | } else if (strcmp(user, client_user) != 0) | |
128 | continue; /* Different username. */ | |
129 | ||
130 | /* Found the user and host. */ | |
131 | fclose(f); | |
132 | ||
133 | /* If the entry was negated, deny access. */ | |
134 | if (negated) { | |
700318f3 | 135 | auth_debug_add("Matched negative entry in %.100s.", |
665a873d | 136 | filename); |
3c0ef626 | 137 | return 0; |
138 | } | |
139 | /* Accept authentication. */ | |
140 | return 1; | |
141 | } | |
142 | ||
143 | /* Authentication using this file denied. */ | |
144 | fclose(f); | |
145 | return 0; | |
146 | } | |
147 | ||
148 | /* | |
149 | * Tries to authenticate the user using the .shosts or .rhosts file. Returns | |
150 | * true if authentication succeeds. If ignore_rhosts is true, only | |
151 | * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored). | |
152 | */ | |
153 | ||
154 | int | |
155 | auth_rhosts(struct passwd *pw, const char *client_user) | |
156 | { | |
157 | const char *hostname, *ipaddr; | |
3c0ef626 | 158 | |
0fff78ff | 159 | hostname = get_canonical_hostname(options.use_dns); |
3c0ef626 | 160 | ipaddr = get_remote_ipaddr(); |
700318f3 | 161 | return auth_rhosts2(pw, client_user, hostname, ipaddr); |
3c0ef626 | 162 | } |
163 | ||
700318f3 | 164 | static int |
165 | auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname, | |
3c0ef626 | 166 | const char *ipaddr) |
167 | { | |
168 | char buf[1024]; | |
169 | struct stat st; | |
170 | static const char *rhosts_files[] = {".shosts", ".rhosts", NULL}; | |
171 | u_int rhosts_file_index; | |
172 | ||
173 | debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s", | |
174 | client_user, hostname, ipaddr); | |
175 | ||
3c0ef626 | 176 | /* Switch to the user's uid. */ |
177 | temporarily_use_uid(pw); | |
178 | /* | |
179 | * Quick check: if the user has no .shosts or .rhosts files, return | |
180 | * failure immediately without doing costly lookups from name | |
181 | * servers. | |
182 | */ | |
183 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; | |
e9a17296 | 184 | rhosts_file_index++) { |
3c0ef626 | 185 | /* Check users .rhosts or .shosts. */ |
186 | snprintf(buf, sizeof buf, "%.500s/%.100s", | |
187 | pw->pw_dir, rhosts_files[rhosts_file_index]); | |
188 | if (stat(buf, &st) >= 0) | |
189 | break; | |
190 | } | |
191 | /* Switch back to privileged uid. */ | |
192 | restore_uid(); | |
193 | ||
194 | /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */ | |
195 | if (!rhosts_files[rhosts_file_index] && | |
196 | stat(_PATH_RHOSTS_EQUIV, &st) < 0 && | |
197 | stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0) | |
198 | return 0; | |
199 | ||
200 | /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */ | |
201 | if (pw->pw_uid != 0) { | |
e9a17296 | 202 | if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, |
203 | client_user, pw->pw_name)) { | |
700318f3 | 204 | auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.", |
e9a17296 | 205 | hostname, ipaddr); |
3c0ef626 | 206 | return 1; |
207 | } | |
e9a17296 | 208 | if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, |
209 | client_user, pw->pw_name)) { | |
700318f3 | 210 | auth_debug_add("Accepted for %.100s [%.100s] by %.100s.", |
e9a17296 | 211 | hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV); |
3c0ef626 | 212 | return 1; |
213 | } | |
214 | } | |
215 | /* | |
216 | * Check that the home directory is owned by root or the user, and is | |
217 | * not group or world writable. | |
218 | */ | |
219 | if (stat(pw->pw_dir, &st) < 0) { | |
0fff78ff | 220 | logit("Rhosts authentication refused for %.100s: " |
700318f3 | 221 | "no home directory %.200s", pw->pw_name, pw->pw_dir); |
222 | auth_debug_add("Rhosts authentication refused for %.100s: " | |
223 | "no home directory %.200s", pw->pw_name, pw->pw_dir); | |
3c0ef626 | 224 | return 0; |
225 | } | |
226 | if (options.strict_modes && | |
227 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
e9a17296 | 228 | (st.st_mode & 022) != 0)) { |
0fff78ff | 229 | logit("Rhosts authentication refused for %.100s: " |
700318f3 | 230 | "bad ownership or modes for home directory.", pw->pw_name); |
231 | auth_debug_add("Rhosts authentication refused for %.100s: " | |
232 | "bad ownership or modes for home directory.", pw->pw_name); | |
3c0ef626 | 233 | return 0; |
234 | } | |
235 | /* Temporarily use the user's uid. */ | |
236 | temporarily_use_uid(pw); | |
237 | ||
238 | /* Check all .rhosts files (currently .shosts and .rhosts). */ | |
239 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; | |
e9a17296 | 240 | rhosts_file_index++) { |
3c0ef626 | 241 | /* Check users .rhosts or .shosts. */ |
242 | snprintf(buf, sizeof buf, "%.500s/%.100s", | |
243 | pw->pw_dir, rhosts_files[rhosts_file_index]); | |
244 | if (stat(buf, &st) < 0) | |
245 | continue; | |
246 | ||
247 | /* | |
248 | * Make sure that the file is either owned by the user or by | |
249 | * root, and make sure it is not writable by anyone but the | |
250 | * owner. This is to help avoid novices accidentally | |
251 | * allowing access to their account by anyone. | |
252 | */ | |
253 | if (options.strict_modes && | |
254 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
e9a17296 | 255 | (st.st_mode & 022) != 0)) { |
0fff78ff | 256 | logit("Rhosts authentication refused for %.100s: bad modes for %.200s", |
3c0ef626 | 257 | pw->pw_name, buf); |
700318f3 | 258 | auth_debug_add("Bad file modes for %.200s", buf); |
3c0ef626 | 259 | continue; |
260 | } | |
261 | /* Check if we have been configured to ignore .rhosts and .shosts files. */ | |
262 | if (options.ignore_rhosts) { | |
700318f3 | 263 | auth_debug_add("Server has been configured to ignore %.100s.", |
264 | rhosts_files[rhosts_file_index]); | |
3c0ef626 | 265 | continue; |
266 | } | |
267 | /* Check if authentication is permitted by the file. */ | |
268 | if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) { | |
700318f3 | 269 | auth_debug_add("Accepted by %.100s.", |
270 | rhosts_files[rhosts_file_index]); | |
3c0ef626 | 271 | /* Restore the privileged uid. */ |
272 | restore_uid(); | |
700318f3 | 273 | auth_debug_add("Accepted host %s ip %s client_user %s server_user %s", |
274 | hostname, ipaddr, client_user, pw->pw_name); | |
3c0ef626 | 275 | return 1; |
276 | } | |
277 | } | |
278 | ||
279 | /* Restore the privileged uid. */ | |
280 | restore_uid(); | |
281 | return 0; | |
282 | } | |
700318f3 | 283 | |
284 | int | |
285 | auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname, | |
286 | const char *ipaddr) | |
287 | { | |
288 | int ret; | |
289 | ||
290 | auth_debug_reset(); | |
291 | ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr); | |
292 | if (!use_privsep) | |
293 | auth_debug_send(); | |
294 | return ret; | |
295 | } |