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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" | |
94ec8c6b | 17 | RCSID("$OpenBSD: auth-rhosts.c,v 1.16 2000/10/03 18:03:03 markus Exp $"); |
8efc0c15 | 18 | |
19 | #include "packet.h" | |
20 | #include "ssh.h" | |
21 | #include "xmalloc.h" | |
22 | #include "uidswap.h" | |
6fa724bc | 23 | #include "servconf.h" |
8efc0c15 | 24 | |
aa3378df | 25 | /* |
26 | * This function processes an rhosts-style file (.rhosts, .shosts, or | |
27 | * /etc/hosts.equiv). This returns true if authentication can be granted | |
28 | * based on the file, and returns zero otherwise. | |
29 | */ | |
8efc0c15 | 30 | |
6ae2364d | 31 | int |
5260325f | 32 | check_rhosts_file(const char *filename, const char *hostname, |
33 | const char *ipaddr, const char *client_user, | |
34 | const char *server_user) | |
8efc0c15 | 35 | { |
5260325f | 36 | FILE *f; |
37 | char buf[1024]; /* Must not be larger than host, user, dummy below. */ | |
38 | ||
39 | /* Open the .rhosts file, deny if unreadable */ | |
40 | f = fopen(filename, "r"); | |
41 | if (!f) | |
42 | return 0; | |
43 | ||
5260325f | 44 | while (fgets(buf, sizeof(buf), f)) { |
45 | /* All three must be at least as big as buf to avoid overflows. */ | |
46 | char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp; | |
47 | int negated; | |
48 | ||
49 | for (cp = buf; *cp == ' ' || *cp == '\t'; cp++) | |
50 | ; | |
51 | if (*cp == '#' || *cp == '\n' || !*cp) | |
52 | continue; | |
53 | ||
aa3378df | 54 | /* |
55 | * NO_PLUS is supported at least on OSF/1. We skip it (we | |
56 | * don't ever support the plus syntax). | |
57 | */ | |
5260325f | 58 | if (strncmp(cp, "NO_PLUS", 7) == 0) |
59 | continue; | |
60 | ||
aa3378df | 61 | /* |
62 | * This should be safe because each buffer is as big as the | |
63 | * whole string, and thus cannot be overwritten. | |
64 | */ | |
5260325f | 65 | switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) { |
66 | case 0: | |
67 | packet_send_debug("Found empty line in %.100s.", filename); | |
68 | continue; | |
69 | case 1: | |
70 | /* Host name only. */ | |
71 | strlcpy(userbuf, server_user, sizeof(userbuf)); | |
72 | break; | |
73 | case 2: | |
74 | /* Got both host and user name. */ | |
75 | break; | |
76 | case 3: | |
77 | packet_send_debug("Found garbage in %.100s.", filename); | |
78 | continue; | |
79 | default: | |
80 | /* Weird... */ | |
81 | continue; | |
82 | } | |
83 | ||
84 | host = hostbuf; | |
85 | user = userbuf; | |
86 | negated = 0; | |
87 | ||
88 | /* Process negated host names, or positive netgroups. */ | |
89 | if (host[0] == '-') { | |
90 | negated = 1; | |
91 | host++; | |
92 | } else if (host[0] == '+') | |
93 | host++; | |
94 | ||
95 | if (user[0] == '-') { | |
96 | negated = 1; | |
97 | user++; | |
98 | } else if (user[0] == '+') | |
99 | user++; | |
100 | ||
101 | /* Check for empty host/user names (particularly '+'). */ | |
102 | if (!host[0] || !user[0]) { | |
103 | /* We come here if either was '+' or '-'. */ | |
104 | packet_send_debug("Ignoring wild host/user names in %.100s.", | |
105 | filename); | |
106 | continue; | |
107 | } | |
108 | /* Verify that host name matches. */ | |
109 | if (host[0] == '@') { | |
110 | if (!innetgr(host + 1, hostname, NULL, NULL) && | |
111 | !innetgr(host + 1, ipaddr, NULL, NULL)) | |
112 | continue; | |
113 | } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0) | |
114 | continue; /* Different hostname. */ | |
115 | ||
116 | /* Verify that user name matches. */ | |
117 | if (user[0] == '@') { | |
118 | if (!innetgr(user + 1, NULL, client_user, NULL)) | |
119 | continue; | |
120 | } else if (strcmp(user, client_user) != 0) | |
121 | continue; /* Different username. */ | |
122 | ||
123 | /* Found the user and host. */ | |
124 | fclose(f); | |
125 | ||
126 | /* If the entry was negated, deny access. */ | |
127 | if (negated) { | |
128 | packet_send_debug("Matched negative entry in %.100s.", | |
129 | filename); | |
130 | return 0; | |
131 | } | |
132 | /* Accept authentication. */ | |
133 | return 1; | |
8efc0c15 | 134 | } |
8efc0c15 | 135 | |
5260325f | 136 | /* Authentication using this file denied. */ |
137 | fclose(f); | |
138 | return 0; | |
8efc0c15 | 139 | } |
140 | ||
aa3378df | 141 | /* |
142 | * Tries to authenticate the user using the .shosts or .rhosts file. Returns | |
143 | * true if authentication succeeds. If ignore_rhosts is true, only | |
144 | * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored). | |
145 | */ | |
8efc0c15 | 146 | |
6ae2364d | 147 | int |
5260325f | 148 | auth_rhosts(struct passwd *pw, const char *client_user) |
8efc0c15 | 149 | { |
5260325f | 150 | extern ServerOptions options; |
151 | char buf[1024]; | |
152 | const char *hostname, *ipaddr; | |
153 | struct stat st; | |
154 | static const char *rhosts_files[] = {".shosts", ".rhosts", NULL}; | |
155 | unsigned int rhosts_file_index; | |
156 | ||
94ec8c6b | 157 | /* no user given */ |
158 | if (pw == NULL) | |
159 | return 0; | |
5260325f | 160 | /* Switch to the user's uid. */ |
161 | temporarily_use_uid(pw->pw_uid); | |
aa3378df | 162 | /* |
163 | * Quick check: if the user has no .shosts or .rhosts files, return | |
164 | * failure immediately without doing costly lookups from name | |
165 | * servers. | |
166 | */ | |
5260325f | 167 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; |
168 | rhosts_file_index++) { | |
169 | /* Check users .rhosts or .shosts. */ | |
170 | snprintf(buf, sizeof buf, "%.500s/%.100s", | |
171 | pw->pw_dir, rhosts_files[rhosts_file_index]); | |
172 | if (stat(buf, &st) >= 0) | |
173 | break; | |
8efc0c15 | 174 | } |
5260325f | 175 | /* Switch back to privileged uid. */ |
176 | restore_uid(); | |
177 | ||
178 | /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */ | |
179 | if (!rhosts_files[rhosts_file_index] && | |
180 | stat("/etc/hosts.equiv", &st) < 0 && | |
181 | stat(SSH_HOSTS_EQUIV, &st) < 0) | |
182 | return 0; | |
183 | ||
5260325f | 184 | hostname = get_canonical_hostname(); |
185 | ipaddr = get_remote_ipaddr(); | |
186 | ||
187 | /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */ | |
188 | if (pw->pw_uid != 0) { | |
189 | if (check_rhosts_file("/etc/hosts.equiv", hostname, ipaddr, client_user, | |
190 | pw->pw_name)) { | |
191 | packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.", | |
192 | hostname, ipaddr); | |
193 | return 1; | |
194 | } | |
195 | if (check_rhosts_file(SSH_HOSTS_EQUIV, hostname, ipaddr, client_user, | |
196 | pw->pw_name)) { | |
197 | packet_send_debug("Accepted for %.100s [%.100s] by %.100s.", | |
198 | hostname, ipaddr, SSH_HOSTS_EQUIV); | |
199 | return 1; | |
200 | } | |
8efc0c15 | 201 | } |
aa3378df | 202 | /* |
203 | * Check that the home directory is owned by root or the user, and is | |
204 | * not group or world writable. | |
205 | */ | |
5260325f | 206 | if (stat(pw->pw_dir, &st) < 0) { |
207 | log("Rhosts authentication refused for %.100s: no home directory %.200s", | |
208 | pw->pw_name, pw->pw_dir); | |
00e6dd70 | 209 | packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s", |
5260325f | 210 | pw->pw_name, pw->pw_dir); |
211 | return 0; | |
8efc0c15 | 212 | } |
5260325f | 213 | if (options.strict_modes && |
214 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
215 | (st.st_mode & 022) != 0)) { | |
216 | log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.", | |
217 | pw->pw_name); | |
218 | packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.", | |
219 | pw->pw_name); | |
220 | return 0; | |
8efc0c15 | 221 | } |
5260325f | 222 | /* Temporarily use the user's uid. */ |
223 | temporarily_use_uid(pw->pw_uid); | |
224 | ||
225 | /* Check all .rhosts files (currently .shosts and .rhosts). */ | |
226 | for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; | |
227 | rhosts_file_index++) { | |
228 | /* Check users .rhosts or .shosts. */ | |
229 | snprintf(buf, sizeof buf, "%.500s/%.100s", | |
230 | pw->pw_dir, rhosts_files[rhosts_file_index]); | |
231 | if (stat(buf, &st) < 0) | |
232 | continue; | |
233 | ||
aa3378df | 234 | /* |
235 | * Make sure that the file is either owned by the user or by | |
236 | * root, and make sure it is not writable by anyone but the | |
237 | * owner. This is to help avoid novices accidentally | |
238 | * allowing access to their account by anyone. | |
239 | */ | |
5260325f | 240 | if (options.strict_modes && |
241 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
242 | (st.st_mode & 022) != 0)) { | |
243 | log("Rhosts authentication refused for %.100s: bad modes for %.200s", | |
244 | pw->pw_name, buf); | |
245 | packet_send_debug("Bad file modes for %.200s", buf); | |
246 | continue; | |
247 | } | |
248 | /* Check if we have been configured to ignore .rhosts and .shosts files. */ | |
249 | if (options.ignore_rhosts) { | |
250 | packet_send_debug("Server has been configured to ignore %.100s.", | |
251 | rhosts_files[rhosts_file_index]); | |
252 | continue; | |
253 | } | |
254 | /* Check if authentication is permitted by the file. */ | |
255 | if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) { | |
256 | packet_send_debug("Accepted by %.100s.", | |
257 | rhosts_files[rhosts_file_index]); | |
258 | /* Restore the privileged uid. */ | |
259 | restore_uid(); | |
260 | return 1; | |
261 | } | |
8efc0c15 | 262 | } |
8efc0c15 | 263 | |
5260325f | 264 | /* Restore the privileged uid. */ |
265 | restore_uid(); | |
266 | return 0; | |
8efc0c15 | 267 | } |