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8efc0c15 | 1 | /* |
5260325f | 2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> |
5260325f | 3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
4 | * All rights reserved | |
5260325f | 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. | |
6ae2364d | 8 | * |
bcbf86ec | 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". | |
5260325f | 14 | */ |
8efc0c15 | 15 | |
16 | #include "includes.h" | |
c38f5d19 | 17 | RCSID("$OpenBSD: auth-rhosts.c,v 1.34 2006/02/07 01:08:04 stevesk Exp $"); |
18 | ||
19 | #ifdef HAVE_NETGROUP_H | |
20 | # include <netgroup.h> | |
21 | #endif | |
8efc0c15 | 22 | |
23 | #include "packet.h" | |
8efc0c15 | 24 | #include "uidswap.h" |
42f11eb2 | 25 | #include "pathnames.h" |
26 | #include "log.h" | |
6fa724bc | 27 | #include "servconf.h" |
42f11eb2 | 28 | #include "canohost.h" |
5ca51e19 | 29 | #include "auth.h" |
8efc0c15 | 30 | |
8002af61 | 31 | /* import */ |
32 | extern ServerOptions options; | |
b3ad3d88 | 33 | extern int use_privsep; |
8002af61 | 34 | |
aa3378df | 35 | /* |
36 | * This function processes an rhosts-style file (.rhosts, .shosts, or | |
37 | * /etc/hosts.equiv). This returns true if authentication can be granted | |
38 | * based on the file, and returns zero otherwise. | |
39 | */ | |
8efc0c15 | 40 | |
396c147e | 41 | static int |
5260325f | 42 | check_rhosts_file(const char *filename, const char *hostname, |
43 | const char *ipaddr, const char *client_user, | |
44 | const char *server_user) | |
8efc0c15 | 45 | { |
5260325f | 46 | FILE *f; |
47 | char buf[1024]; /* Must not be larger than host, user, dummy below. */ | |
48 | ||
49 | /* Open the .rhosts file, deny if unreadable */ | |
50 | f = fopen(filename, "r"); | |
51 | if (!f) | |
52 | return 0; | |
53 | ||
5260325f | 54 | while (fgets(buf, sizeof(buf), f)) { |
55 | /* All three must be at least as big as buf to avoid overflows. */ | |
56 | char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp; | |
57 | int negated; | |
58 | ||
59 | for (cp = buf; *cp == ' ' || *cp == '\t'; cp++) | |
60 | ; | |
61 | if (*cp == '#' || *cp == '\n' || !*cp) | |
62 | continue; | |
63 | ||
aa3378df | 64 | /* |
65 | * NO_PLUS is supported at least on OSF/1. We skip it (we | |
66 | * don't ever support the plus syntax). | |
67 | */ | |
5260325f | 68 | if (strncmp(cp, "NO_PLUS", 7) == 0) |
69 | continue; | |
70 | ||
aa3378df | 71 | /* |
72 | * This should be safe because each buffer is as big as the | |
73 | * whole string, and thus cannot be overwritten. | |
74 | */ | |
013b1214 | 75 | switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf, |
76 | dummy)) { | |
5260325f | 77 | case 0: |
b3ad3d88 | 78 | auth_debug_add("Found empty line in %.100s.", filename); |
5260325f | 79 | continue; |
80 | case 1: | |
81 | /* Host name only. */ | |
82 | strlcpy(userbuf, server_user, sizeof(userbuf)); | |
83 | break; | |
84 | case 2: | |
85 | /* Got both host and user name. */ | |
86 | break; | |
87 | case 3: | |
b3ad3d88 | 88 | auth_debug_add("Found garbage in %.100s.", filename); |
5260325f | 89 | continue; |
90 | default: | |
91 | /* Weird... */ | |
92 | continue; | |
93 | } | |
94 | ||
95 | host = hostbuf; | |
96 | user = userbuf; | |
97 | negated = 0; | |
98 | ||
99 | /* Process negated host names, or positive netgroups. */ | |
100 | if (host[0] == '-') { | |
101 | negated = 1; | |
102 | host++; | |
103 | } else if (host[0] == '+') | |
104 | host++; | |
105 | ||
106 | if (user[0] == '-') { | |
107 | negated = 1; | |
108 | user++; | |
109 | } else if (user[0] == '+') | |
110 | user++; | |
111 | ||
112 | /* Check for empty host/user names (particularly '+'). */ | |
113 | if (!host[0] || !user[0]) { | |
114 | /* We come here if either was '+' or '-'. */ | |
b3ad3d88 | 115 | auth_debug_add("Ignoring wild host/user names in %.100s.", |
116 | filename); | |
5260325f | 117 | continue; |
118 | } | |
119 | /* Verify that host name matches. */ | |
120 | if (host[0] == '@') { | |
121 | if (!innetgr(host + 1, hostname, NULL, NULL) && | |
122 | !innetgr(host + 1, ipaddr, NULL, NULL)) | |
123 | continue; | |
124 | } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0) | |
125 | continue; /* Different hostname. */ | |
126 | ||
127 | /* Verify that user name matches. */ | |
128 | if (user[0] == '@') { | |
129 | if (!innetgr(user + 1, NULL, client_user, NULL)) | |
130 | continue; | |
131 | } else if (strcmp(user, client_user) != 0) | |
132 | continue; /* Different username. */ | |
133 | ||
134 | /* Found the user and host. */ | |
135 | fclose(f); | |
136 | ||
137 | /* If the entry was negated, deny access. */ | |
138 | if (negated) { | |
b3ad3d88 | 139 | auth_debug_add("Matched negative entry in %.100s.", |
4e2e5cfd | 140 | filename); |
5260325f | 141 | return 0; |
142 | } | |
143 | /* Accept authentication. */ | |
144 | return 1; | |
8efc0c15 | 145 | } |
8efc0c15 | 146 | |
5260325f | 147 | /* Authentication using this file denied. */ |
148 | fclose(f); | |
149 | return 0; | |
8efc0c15 | 150 | } |
151 | ||
aa3378df | 152 | /* |
153 | * Tries to authenticate the user using the .shosts or .rhosts file. Returns | |
154 | * true if authentication succeeds. If ignore_rhosts is true, only | |
155 | * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored). | |
156 | */ | |
8efc0c15 | 157 | |
6ae2364d | 158 | int |
5260325f | 159 | auth_rhosts(struct passwd *pw, const char *client_user) |
8efc0c15 | 160 | { |
5260325f | 161 | const char *hostname, *ipaddr; |
8002af61 | 162 | |
c5a7d788 | 163 | hostname = get_canonical_hostname(options.use_dns); |
8002af61 | 164 | ipaddr = get_remote_ipaddr(); |
b3ad3d88 | 165 | return auth_rhosts2(pw, client_user, hostname, ipaddr); |
8002af61 | 166 | } |
167 | ||
b3ad3d88 | 168 | static int |
169 | auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname, | |
8002af61 | 170 | const char *ipaddr) |
171 | { | |
172 | char buf[1024]; | |
5260325f | 173 | struct stat st; |
174 | static const char *rhosts_files[] = {".shosts", ".rhosts", NULL}; | |
1e3b8b07 | 175 | u_int rhosts_file_index; |
5260325f | 176 | |
8002af61 | 177 | debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s", |
178 | client_user, hostname, ipaddr); | |
179 | ||
5260325f | 180 | /* Switch to the user's uid. */ |
63bd8c36 | 181 | temporarily_use_uid(pw); |
aa3378df | 182 | /* |
183 | * Quick check: if the user has no .shosts or .rhosts files, return | |
184 | * failure immediately without doing costly lookups from name | |
185 | * servers. | |
186 | */ | |
5260325f | 187 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; |
184eed6a | 188 | rhosts_file_index++) { |
5260325f | 189 | /* Check users .rhosts or .shosts. */ |
190 | snprintf(buf, sizeof buf, "%.500s/%.100s", | |
191 | pw->pw_dir, rhosts_files[rhosts_file_index]); | |
192 | if (stat(buf, &st) >= 0) | |
193 | break; | |
8efc0c15 | 194 | } |
5260325f | 195 | /* Switch back to privileged uid. */ |
196 | restore_uid(); | |
197 | ||
198 | /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */ | |
199 | if (!rhosts_files[rhosts_file_index] && | |
42f11eb2 | 200 | stat(_PATH_RHOSTS_EQUIV, &st) < 0 && |
201 | stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0) | |
5260325f | 202 | return 0; |
203 | ||
5260325f | 204 | /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */ |
205 | if (pw->pw_uid != 0) { | |
184eed6a | 206 | if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, |
207 | client_user, pw->pw_name)) { | |
b3ad3d88 | 208 | auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.", |
184eed6a | 209 | hostname, ipaddr); |
5260325f | 210 | return 1; |
211 | } | |
184eed6a | 212 | if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, |
213 | client_user, pw->pw_name)) { | |
b3ad3d88 | 214 | auth_debug_add("Accepted for %.100s [%.100s] by %.100s.", |
184eed6a | 215 | hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV); |
5260325f | 216 | return 1; |
217 | } | |
8efc0c15 | 218 | } |
aa3378df | 219 | /* |
220 | * Check that the home directory is owned by root or the user, and is | |
221 | * not group or world writable. | |
222 | */ | |
5260325f | 223 | if (stat(pw->pw_dir, &st) < 0) { |
bbe88b6d | 224 | logit("Rhosts authentication refused for %.100s: " |
b3ad3d88 | 225 | "no home directory %.200s", pw->pw_name, pw->pw_dir); |
226 | auth_debug_add("Rhosts authentication refused for %.100s: " | |
227 | "no home directory %.200s", pw->pw_name, pw->pw_dir); | |
5260325f | 228 | return 0; |
8efc0c15 | 229 | } |
5260325f | 230 | if (options.strict_modes && |
231 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
184eed6a | 232 | (st.st_mode & 022) != 0)) { |
bbe88b6d | 233 | logit("Rhosts authentication refused for %.100s: " |
b3ad3d88 | 234 | "bad ownership or modes for home directory.", pw->pw_name); |
235 | auth_debug_add("Rhosts authentication refused for %.100s: " | |
236 | "bad ownership or modes for home directory.", pw->pw_name); | |
5260325f | 237 | return 0; |
8efc0c15 | 238 | } |
5260325f | 239 | /* Temporarily use the user's uid. */ |
63bd8c36 | 240 | temporarily_use_uid(pw); |
5260325f | 241 | |
242 | /* Check all .rhosts files (currently .shosts and .rhosts). */ | |
243 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; | |
184eed6a | 244 | rhosts_file_index++) { |
5260325f | 245 | /* Check users .rhosts or .shosts. */ |
246 | snprintf(buf, sizeof buf, "%.500s/%.100s", | |
247 | pw->pw_dir, rhosts_files[rhosts_file_index]); | |
248 | if (stat(buf, &st) < 0) | |
249 | continue; | |
250 | ||
aa3378df | 251 | /* |
252 | * Make sure that the file is either owned by the user or by | |
253 | * root, and make sure it is not writable by anyone but the | |
254 | * owner. This is to help avoid novices accidentally | |
255 | * allowing access to their account by anyone. | |
256 | */ | |
5260325f | 257 | if (options.strict_modes && |
258 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
184eed6a | 259 | (st.st_mode & 022) != 0)) { |
bbe88b6d | 260 | logit("Rhosts authentication refused for %.100s: bad modes for %.200s", |
5260325f | 261 | pw->pw_name, buf); |
b3ad3d88 | 262 | auth_debug_add("Bad file modes for %.200s", buf); |
5260325f | 263 | continue; |
264 | } | |
265 | /* Check if we have been configured to ignore .rhosts and .shosts files. */ | |
266 | if (options.ignore_rhosts) { | |
b3ad3d88 | 267 | auth_debug_add("Server has been configured to ignore %.100s.", |
268 | rhosts_files[rhosts_file_index]); | |
5260325f | 269 | continue; |
270 | } | |
271 | /* Check if authentication is permitted by the file. */ | |
272 | if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) { | |
b3ad3d88 | 273 | auth_debug_add("Accepted by %.100s.", |
274 | rhosts_files[rhosts_file_index]); | |
5260325f | 275 | /* Restore the privileged uid. */ |
276 | restore_uid(); | |
b3ad3d88 | 277 | auth_debug_add("Accepted host %s ip %s client_user %s server_user %s", |
278 | hostname, ipaddr, client_user, pw->pw_name); | |
5260325f | 279 | return 1; |
280 | } | |
8efc0c15 | 281 | } |
8efc0c15 | 282 | |
5260325f | 283 | /* Restore the privileged uid. */ |
284 | restore_uid(); | |
285 | return 0; | |
8efc0c15 | 286 | } |
b3ad3d88 | 287 | |
288 | int | |
289 | auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname, | |
290 | const char *ipaddr) | |
291 | { | |
292 | int ret; | |
293 | ||
294 | auth_debug_reset(); | |
295 | ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr); | |
296 | if (!use_privsep) | |
297 | auth_debug_send(); | |
298 | return ret; | |
299 | } |