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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" | |
4095f623 | 17 | |
18 | #include <sys/types.h> | |
19 | #include <sys/stat.h> | |
c38f5d19 | 20 | |
21 | #ifdef HAVE_NETGROUP_H | |
22 | # include <netgroup.h> | |
23 | #endif | |
8efc0c15 | 24 | |
25 | #include "packet.h" | |
8efc0c15 | 26 | #include "uidswap.h" |
42f11eb2 | 27 | #include "pathnames.h" |
28 | #include "log.h" | |
6fa724bc | 29 | #include "servconf.h" |
42f11eb2 | 30 | #include "canohost.h" |
5ca51e19 | 31 | #include "auth.h" |
8efc0c15 | 32 | |
8002af61 | 33 | /* import */ |
34 | extern ServerOptions options; | |
b3ad3d88 | 35 | extern int use_privsep; |
8002af61 | 36 | |
aa3378df | 37 | /* |
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. | |
41 | */ | |
8efc0c15 | 42 | |
396c147e | 43 | static int |
5260325f | 44 | check_rhosts_file(const char *filename, const char *hostname, |
45 | const char *ipaddr, const char *client_user, | |
46 | const char *server_user) | |
8efc0c15 | 47 | { |
5260325f | 48 | FILE *f; |
49 | char buf[1024]; /* Must not be larger than host, user, dummy below. */ | |
50 | ||
51 | /* Open the .rhosts file, deny if unreadable */ | |
52 | f = fopen(filename, "r"); | |
53 | if (!f) | |
54 | return 0; | |
55 | ||
5260325f | 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; | |
59 | int negated; | |
60 | ||
61 | for (cp = buf; *cp == ' ' || *cp == '\t'; cp++) | |
62 | ; | |
63 | if (*cp == '#' || *cp == '\n' || !*cp) | |
64 | continue; | |
65 | ||
aa3378df | 66 | /* |
67 | * NO_PLUS is supported at least on OSF/1. We skip it (we | |
68 | * don't ever support the plus syntax). | |
69 | */ | |
5260325f | 70 | if (strncmp(cp, "NO_PLUS", 7) == 0) |
71 | continue; | |
72 | ||
aa3378df | 73 | /* |
74 | * This should be safe because each buffer is as big as the | |
75 | * whole string, and thus cannot be overwritten. | |
76 | */ | |
013b1214 | 77 | switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf, |
78 | dummy)) { | |
5260325f | 79 | case 0: |
b3ad3d88 | 80 | auth_debug_add("Found empty line in %.100s.", filename); |
5260325f | 81 | continue; |
82 | case 1: | |
83 | /* Host name only. */ | |
84 | strlcpy(userbuf, server_user, sizeof(userbuf)); | |
85 | break; | |
86 | case 2: | |
87 | /* Got both host and user name. */ | |
88 | break; | |
89 | case 3: | |
b3ad3d88 | 90 | auth_debug_add("Found garbage in %.100s.", filename); |
5260325f | 91 | continue; |
92 | default: | |
93 | /* Weird... */ | |
94 | continue; | |
95 | } | |
96 | ||
97 | host = hostbuf; | |
98 | user = userbuf; | |
99 | negated = 0; | |
100 | ||
101 | /* Process negated host names, or positive netgroups. */ | |
102 | if (host[0] == '-') { | |
103 | negated = 1; | |
104 | host++; | |
105 | } else if (host[0] == '+') | |
106 | host++; | |
107 | ||
108 | if (user[0] == '-') { | |
109 | negated = 1; | |
110 | user++; | |
111 | } else if (user[0] == '+') | |
112 | user++; | |
113 | ||
114 | /* Check for empty host/user names (particularly '+'). */ | |
115 | if (!host[0] || !user[0]) { | |
116 | /* We come here if either was '+' or '-'. */ | |
b3ad3d88 | 117 | auth_debug_add("Ignoring wild host/user names in %.100s.", |
118 | filename); | |
5260325f | 119 | continue; |
120 | } | |
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)) | |
125 | continue; | |
126 | } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0) | |
127 | continue; /* Different hostname. */ | |
128 | ||
129 | /* Verify that user name matches. */ | |
130 | if (user[0] == '@') { | |
131 | if (!innetgr(user + 1, NULL, client_user, NULL)) | |
132 | continue; | |
133 | } else if (strcmp(user, client_user) != 0) | |
134 | continue; /* Different username. */ | |
135 | ||
136 | /* Found the user and host. */ | |
137 | fclose(f); | |
138 | ||
139 | /* If the entry was negated, deny access. */ | |
140 | if (negated) { | |
b3ad3d88 | 141 | auth_debug_add("Matched negative entry in %.100s.", |
4e2e5cfd | 142 | filename); |
5260325f | 143 | return 0; |
144 | } | |
145 | /* Accept authentication. */ | |
146 | return 1; | |
8efc0c15 | 147 | } |
8efc0c15 | 148 | |
5260325f | 149 | /* Authentication using this file denied. */ |
150 | fclose(f); | |
151 | return 0; | |
8efc0c15 | 152 | } |
153 | ||
aa3378df | 154 | /* |
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). | |
158 | */ | |
8efc0c15 | 159 | |
6ae2364d | 160 | int |
5260325f | 161 | auth_rhosts(struct passwd *pw, const char *client_user) |
8efc0c15 | 162 | { |
5260325f | 163 | const char *hostname, *ipaddr; |
8002af61 | 164 | |
c5a7d788 | 165 | hostname = get_canonical_hostname(options.use_dns); |
8002af61 | 166 | ipaddr = get_remote_ipaddr(); |
b3ad3d88 | 167 | return auth_rhosts2(pw, client_user, hostname, ipaddr); |
8002af61 | 168 | } |
169 | ||
b3ad3d88 | 170 | static int |
171 | auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname, | |
8002af61 | 172 | const char *ipaddr) |
173 | { | |
174 | char buf[1024]; | |
5260325f | 175 | struct stat st; |
176 | static const char *rhosts_files[] = {".shosts", ".rhosts", NULL}; | |
1e3b8b07 | 177 | u_int rhosts_file_index; |
5260325f | 178 | |
8002af61 | 179 | debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s", |
180 | client_user, hostname, ipaddr); | |
181 | ||
5260325f | 182 | /* Switch to the user's uid. */ |
63bd8c36 | 183 | temporarily_use_uid(pw); |
aa3378df | 184 | /* |
185 | * Quick check: if the user has no .shosts or .rhosts files, return | |
186 | * failure immediately without doing costly lookups from name | |
187 | * servers. | |
188 | */ | |
5260325f | 189 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; |
184eed6a | 190 | rhosts_file_index++) { |
5260325f | 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) | |
195 | break; | |
8efc0c15 | 196 | } |
5260325f | 197 | /* Switch back to privileged uid. */ |
198 | restore_uid(); | |
199 | ||
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] && | |
42f11eb2 | 202 | stat(_PATH_RHOSTS_EQUIV, &st) < 0 && |
203 | stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0) | |
5260325f | 204 | return 0; |
205 | ||
5260325f | 206 | /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */ |
207 | if (pw->pw_uid != 0) { | |
184eed6a | 208 | if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, |
209 | client_user, pw->pw_name)) { | |
b3ad3d88 | 210 | auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.", |
184eed6a | 211 | hostname, ipaddr); |
5260325f | 212 | return 1; |
213 | } | |
184eed6a | 214 | if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, |
215 | client_user, pw->pw_name)) { | |
b3ad3d88 | 216 | auth_debug_add("Accepted for %.100s [%.100s] by %.100s.", |
184eed6a | 217 | hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV); |
5260325f | 218 | return 1; |
219 | } | |
8efc0c15 | 220 | } |
aa3378df | 221 | /* |
222 | * Check that the home directory is owned by root or the user, and is | |
223 | * not group or world writable. | |
224 | */ | |
5260325f | 225 | if (stat(pw->pw_dir, &st) < 0) { |
bbe88b6d | 226 | logit("Rhosts authentication refused for %.100s: " |
b3ad3d88 | 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); | |
5260325f | 230 | return 0; |
8efc0c15 | 231 | } |
5260325f | 232 | if (options.strict_modes && |
233 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
184eed6a | 234 | (st.st_mode & 022) != 0)) { |
bbe88b6d | 235 | logit("Rhosts authentication refused for %.100s: " |
b3ad3d88 | 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); | |
5260325f | 239 | return 0; |
8efc0c15 | 240 | } |
5260325f | 241 | /* Temporarily use the user's uid. */ |
63bd8c36 | 242 | temporarily_use_uid(pw); |
5260325f | 243 | |
244 | /* Check all .rhosts files (currently .shosts and .rhosts). */ | |
245 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; | |
184eed6a | 246 | rhosts_file_index++) { |
5260325f | 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) | |
251 | continue; | |
252 | ||
aa3378df | 253 | /* |
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. | |
258 | */ | |
5260325f | 259 | if (options.strict_modes && |
260 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
184eed6a | 261 | (st.st_mode & 022) != 0)) { |
bbe88b6d | 262 | logit("Rhosts authentication refused for %.100s: bad modes for %.200s", |
5260325f | 263 | pw->pw_name, buf); |
b3ad3d88 | 264 | auth_debug_add("Bad file modes for %.200s", buf); |
5260325f | 265 | continue; |
266 | } | |
267 | /* Check if we have been configured to ignore .rhosts and .shosts files. */ | |
268 | if (options.ignore_rhosts) { | |
b3ad3d88 | 269 | auth_debug_add("Server has been configured to ignore %.100s.", |
270 | rhosts_files[rhosts_file_index]); | |
5260325f | 271 | continue; |
272 | } | |
273 | /* Check if authentication is permitted by the file. */ | |
274 | if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) { | |
b3ad3d88 | 275 | auth_debug_add("Accepted by %.100s.", |
276 | rhosts_files[rhosts_file_index]); | |
5260325f | 277 | /* Restore the privileged uid. */ |
278 | restore_uid(); | |
b3ad3d88 | 279 | auth_debug_add("Accepted host %s ip %s client_user %s server_user %s", |
280 | hostname, ipaddr, client_user, pw->pw_name); | |
5260325f | 281 | return 1; |
282 | } | |
8efc0c15 | 283 | } |
8efc0c15 | 284 | |
5260325f | 285 | /* Restore the privileged uid. */ |
286 | restore_uid(); | |
287 | return 0; | |
8efc0c15 | 288 | } |
b3ad3d88 | 289 | |
290 | int | |
291 | auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname, | |
292 | const char *ipaddr) | |
293 | { | |
294 | int ret; | |
295 | ||
296 | auth_debug_reset(); | |
297 | ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr); | |
298 | if (!use_privsep) | |
299 | auth_debug_send(); | |
300 | return ret; | |
301 | } |