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auth-rhosts.c

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1/* $OpenBSD: auth-rhosts.c,v 1.49 2018/07/09 21:35:50 markus 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 "uidswap.h"-
34#include "pathnames.h"-
35#include "log.h"-
36#include "misc.h"-
37#include "sshbuf.h"-
38#include "sshkey.h"-
39#include "servconf.h"-
40#include "canohost.h"-
41#include "sshkey.h"-
42#include "hostfile.h"-
43#include "auth.h"-
44-
45/* import */-
46extern ServerOptions options;-
47extern int use_privsep;-
48-
49/*-
50 * This function processes an rhosts-style file (.rhosts, .shosts, or-
51 * /etc/hosts.equiv). This returns true if authentication can be granted-
52 * based on the file, and returns zero otherwise.-
53 */-
54-
55static int-
56check_rhosts_file(const char *filename, const char *hostname,-
57 const char *ipaddr, const char *client_user,-
58 const char *server_user)-
59{-
60 FILE *f;-
61#define RBUFLN 1024-
62 char buf[RBUFLN];/* Must not be larger than host, user, dummy below. */-
63 int fd;-
64 struct stat st;-
65-
66 /* Open the .rhosts file, deny if unreadable */-
67 if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1)
(fd = open(fil...04000 )) == -1Description
TRUEnever evaluated
FALSEnever evaluated
0
68 return 0;
never executed: return 0;
0
69 if (fstat(fd, &st) == -1) {
fstat(fd, &st) == -1Description
TRUEnever evaluated
FALSEnever evaluated
0
70 close(fd);-
71 return 0;
never executed: return 0;
0
72 }-
73 if (!S_ISREG(st.st_mode)) {
! (((( st.st_m... == (0100000))Description
TRUEnever evaluated
FALSEnever evaluated
0
74 logit("User %s hosts file %s is not a regular file",-
75 server_user, filename);-
76 close(fd);-
77 return 0;
never executed: return 0;
0
78 }-
79 unset_nonblock(fd);-
80 if ((f = fdopen(fd, "r")) == NULL) {
(f = fdopen(fd...== ((void *)0)Description
TRUEnever evaluated
FALSEnever evaluated
0
81 close(fd);-
82 return 0;
never executed: return 0;
0
83 }-
84 while (fgets(buf, sizeof(buf), f)) {
fgets(buf, sizeof(buf), f)Description
TRUEnever evaluated
FALSEnever evaluated
0
85 /* All three must have length >= buf to avoid overflows. */-
86 char hostbuf[RBUFLN], userbuf[RBUFLN], dummy[RBUFLN];-
87 char *host, *user, *cp;-
88 int negated;-
89-
90 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
*cp == ' 'Description
TRUEnever evaluated
FALSEnever evaluated
*cp == '\t'Description
TRUEnever evaluated
FALSEnever evaluated
0
91 ;
never executed: ;
0
92 if (*cp == '#' || *cp == '\n' || !*cp)
*cp == '#'Description
TRUEnever evaluated
FALSEnever evaluated
*cp == '\n'Description
TRUEnever evaluated
FALSEnever evaluated
!*cpDescription
TRUEnever evaluated
FALSEnever evaluated
0
93 continue;
never executed: continue;
0
94-
95 /*-
96 * NO_PLUS is supported at least on OSF/1. We skip it (we-
97 * don't ever support the plus syntax).-
98 */-
99 if (strncmp(cp, "NO_PLUS", 7) == 0)
never executed: __result = (((const unsigned char *) (const char *) ( cp ))[3] - __s2[3]);
never executed: end of block
never executed: end of block
never executed: __result = (((const unsigned char *) (const char *) ( "NO_PLUS" ))[3] - __s2[3]);
never executed: end of block
never executed: end of block
(__extension__..." , 7 ))) == 0Description
TRUEnever evaluated
FALSEnever evaluated
__builtin_constant_p ( 7 )Description
TRUEnever evaluated
FALSEnever evaluated
__builtin_constant_p ( cp )Description
TRUEnever evaluated
FALSEnever evaluated
strlen ( cp ) ...size_t) ( 7 ))Description
TRUEnever evaluated
FALSEnever evaluated
__builtin_cons... ( "NO_PLUS" )Description
TRUEnever evaluated
FALSEnever evaluated
strlen ( "NO_P...size_t) ( 7 ))Description
TRUEnever evaluated
FALSEnever evaluated
__s1_len > 0Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s1_len > 1Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s1_len > 2Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s2_len > 0Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s2_len > 1Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s2_len > 2Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
0
100 continue;
never executed: continue;
0
101-
102 /*-
103 * This should be safe because each buffer is as big as the-
104 * whole string, and thus cannot be overwritten.-
105 */-
106 switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,-
107 dummy)) {-
108 case 0:
never executed: case 0:
0
109 auth_debug_add("Found empty line in %.100s.", filename);-
110 continue;
never executed: continue;
0
111 case 1:
never executed: case 1:
0
112 /* Host name only. */-
113 strlcpy(userbuf, server_user, sizeof(userbuf));-
114 break;
never executed: break;
0
115 case 2:
never executed: case 2:
0
116 /* Got both host and user name. */-
117 break;
never executed: break;
0
118 case 3:
never executed: case 3:
0
119 auth_debug_add("Found garbage in %.100s.", filename);-
120 continue;
never executed: continue;
0
121 default:
never executed: default:
0
122 /* Weird... */-
123 continue;
never executed: continue;
0
124 }-
125-
126 host = hostbuf;-
127 user = userbuf;-
128 negated = 0;-
129-
130 /* Process negated host names, or positive netgroups. */-
131 if (host[0] == '-') {
host[0] == '-'Description
TRUEnever evaluated
FALSEnever evaluated
0
132 negated = 1;-
133 host++;-
134 } else if (host[0] == '+')
never executed: end of block
host[0] == '+'Description
TRUEnever evaluated
FALSEnever evaluated
0
135 host++;
never executed: host++;
0
136-
137 if (user[0] == '-') {
user[0] == '-'Description
TRUEnever evaluated
FALSEnever evaluated
0
138 negated = 1;-
139 user++;-
140 } else if (user[0] == '+')
never executed: end of block
user[0] == '+'Description
TRUEnever evaluated
FALSEnever evaluated
0
141 user++;
never executed: user++;
0
142-
143 /* Check for empty host/user names (particularly '+'). */-
144 if (!host[0] || !user[0]) {
!host[0]Description
TRUEnever evaluated
FALSEnever evaluated
!user[0]Description
TRUEnever evaluated
FALSEnever evaluated
0
145 /* We come here if either was '+' or '-'. */-
146 auth_debug_add("Ignoring wild host/user names "-
147 "in %.100s.", filename);-
148 continue;
never executed: continue;
0
149 }-
150 /* Verify that host name matches. */-
151 if (host[0] == '@') {
host[0] == '@'Description
TRUEnever evaluated
FALSEnever evaluated
0
152 if (!innetgr(host + 1, hostname, NULL, NULL) &&
!innetgr(host ... ((void *)0) )Description
TRUEnever evaluated
FALSEnever evaluated
0
153 !innetgr(host + 1, ipaddr, NULL, NULL))
!innetgr(host ... ((void *)0) )Description
TRUEnever evaluated
FALSEnever evaluated
0
154 continue;
never executed: continue;
0
155 } else if (strcasecmp(host, hostname) &&
never executed: end of block
strcasecmp(host, hostname)Description
TRUEnever evaluated
FALSEnever evaluated
0
156 strcmp(host, ipaddr) != 0)
never executed: __result = (((const unsigned char *) (const char *) ( host ))[3] - __s2[3]);
never executed: end of block
never executed: end of block
never executed: __result = (((const unsigned char *) (const char *) ( ipaddr ))[3] - __s2[3]);
never executed: end of block
never executed: end of block
__extension__ ... )))); }) != 0Description
TRUEnever evaluated
FALSEnever evaluated
__s1_len > 0Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
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__s1_len > 1Description
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__result == 0Description
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__s1_len > 2Description
TRUEnever evaluated
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__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s2_len > 0Description
TRUEnever evaluated
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__result == 0Description
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FALSEnever evaluated
__s2_len > 1Description
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FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s2_len > 2Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
0
157 continue; /* Different hostname. */
never executed: continue;
0
158-
159 /* Verify that user name matches. */-
160 if (user[0] == '@') {
user[0] == '@'Description
TRUEnever evaluated
FALSEnever evaluated
0
161 if (!innetgr(user + 1, NULL, client_user, NULL))
!innetgr(user ... ((void *)0) )Description
TRUEnever evaluated
FALSEnever evaluated
0
162 continue;
never executed: continue;
0
163 } else if (strcmp(user, client_user) != 0)
never executed: end of block
never executed: __result = (((const unsigned char *) (const char *) ( user ))[3] - __s2[3]);
never executed: end of block
never executed: end of block
never executed: __result = (((const unsigned char *) (const char *) ( client_user ))[3] - __s2[3]);
never executed: end of block
never executed: end of block
__extension__ ... )))); }) != 0Description
TRUEnever evaluated
FALSEnever evaluated
__s1_len > 0Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s1_len > 1Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s1_len > 2Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s2_len > 0Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s2_len > 1Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
__s2_len > 2Description
TRUEnever evaluated
FALSEnever evaluated
__result == 0Description
TRUEnever evaluated
FALSEnever evaluated
0
164 continue; /* Different username. */
never executed: continue;
0
165-
166 /* Found the user and host. */-
167 fclose(f);-
168-
169 /* If the entry was negated, deny access. */-
170 if (negated) {
negatedDescription
TRUEnever evaluated
FALSEnever evaluated
0
171 auth_debug_add("Matched negative entry in %.100s.",-
172 filename);-
173 return 0;
never executed: return 0;
0
174 }-
175 /* Accept authentication. */-
176 return 1;
never executed: return 1;
0
177 }-
178-
179 /* Authentication using this file denied. */-
180 fclose(f);-
181 return 0;
never executed: return 0;
0
182}-
183-
184/*-
185 * Tries to authenticate the user using the .shosts or .rhosts file. Returns-
186 * true if authentication succeeds. If ignore_rhosts is true, only-
187 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).-
188 */-
189int-
190auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,-
191 const char *ipaddr)-
192{-
193 char buf[1024];-
194 struct stat st;-
195 static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};-
196 u_int rhosts_file_index;-
197-
198 debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",-
199 client_user, hostname, ipaddr);-
200-
201 /* Switch to the user's uid. */-
202 temporarily_use_uid(pw);-
203 /*-
204 * Quick check: if the user has no .shosts or .rhosts files and-
205 * no system hosts.equiv/shosts.equiv files exist then return-
206 * failure immediately without doing costly lookups from name-
207 * servers.-
208 */-
209 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
rhosts_files[r...ts_file_index]Description
TRUEnever evaluated
FALSEnever evaluated
0
210 rhosts_file_index++) {-
211 /* Check users .rhosts or .shosts. */-
212 snprintf(buf, sizeof buf, "%.500s/%.100s",-
213 pw->pw_dir, rhosts_files[rhosts_file_index]);-
214 if (stat(buf, &st) >= 0)
stat(buf, &st) >= 0Description
TRUEnever evaluated
FALSEnever evaluated
0
215 break;
never executed: break;
0
216 }
never executed: end of block
0
217 /* Switch back to privileged uid. */-
218 restore_uid();-
219-
220 /*-
221 * Deny if The user has no .shosts or .rhosts file and there-
222 * are no system-wide files.-
223 */-
224 if (!rhosts_files[rhosts_file_index] &&
!rhosts_files[...ts_file_index]Description
TRUEnever evaluated
FALSEnever evaluated
0
225 stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
stat("/etc/hos...uiv", &st) < 0Description
TRUEnever evaluated
FALSEnever evaluated
0
226 stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0) {
stat("/var/tmp...uiv", &st) < 0Description
TRUEnever evaluated
FALSEnever evaluated
0
227 debug3("%s: no hosts access files exist", __func__);-
228 return 0;
never executed: return 0;
0
229 }-
230-
231 /*-
232 * If not logging in as superuser, try /etc/hosts.equiv and-
233 * shosts.equiv.-
234 */-
235 if (pw->pw_uid == 0)
pw->pw_uid == 0Description
TRUEnever evaluated
FALSEnever evaluated
0
236 debug3("%s: root user, ignoring system hosts files", __func__);
never executed: debug3("%s: root user, ignoring system hosts files", __func__);
0
237 else {-
238 if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
check_rhosts_f..., pw->pw_name)Description
TRUEnever evaluated
FALSEnever evaluated
0
239 client_user, pw->pw_name)) {
check_rhosts_f..., pw->pw_name)Description
TRUEnever evaluated
FALSEnever evaluated
0
240 auth_debug_add("Accepted for %.100s [%.100s] by "-
241 "/etc/hosts.equiv.", hostname, ipaddr);-
242 return 1;
never executed: return 1;
0
243 }-
244 if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
check_rhosts_f..., pw->pw_name)Description
TRUEnever evaluated
FALSEnever evaluated
0
245 client_user, pw->pw_name)) {
check_rhosts_f..., pw->pw_name)Description
TRUEnever evaluated
FALSEnever evaluated
0
246 auth_debug_add("Accepted for %.100s [%.100s] by "-
247 "%.100s.", hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);-
248 return 1;
never executed: return 1;
0
249 }-
250 }
never executed: end of block
0
251-
252 /*-
253 * Check that the home directory is owned by root or the user, and is-
254 * not group or world writable.-
255 */-
256 if (stat(pw->pw_dir, &st) < 0) {
stat(pw->pw_dir, &st) < 0Description
TRUEnever evaluated
FALSEnever evaluated
0
257 logit("Rhosts authentication refused for %.100s: "-
258 "no home directory %.200s", pw->pw_name, pw->pw_dir);-
259 auth_debug_add("Rhosts authentication refused for %.100s: "-
260 "no home directory %.200s", pw->pw_name, pw->pw_dir);-
261 return 0;
never executed: return 0;
0
262 }-
263 if (options.strict_modes &&
options.strict_modesDescription
TRUEnever evaluated
FALSEnever evaluated
0
264 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
st.st_uid != 0Description
TRUEnever evaluated
FALSEnever evaluated
st.st_uid != pw->pw_uidDescription
TRUEnever evaluated
FALSEnever evaluated
0
265 (st.st_mode & 022) != 0)) {
(st.st_mode & 022) != 0Description
TRUEnever evaluated
FALSEnever evaluated
0
266 logit("Rhosts authentication refused for %.100s: "-
267 "bad ownership or modes for home directory.", pw->pw_name);-
268 auth_debug_add("Rhosts authentication refused for %.100s: "-
269 "bad ownership or modes for home directory.", pw->pw_name);-
270 return 0;
never executed: return 0;
0
271 }-
272 /* Temporarily use the user's uid. */-
273 temporarily_use_uid(pw);-
274-
275 /* Check all .rhosts files (currently .shosts and .rhosts). */-
276 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
rhosts_files[r...ts_file_index]Description
TRUEnever evaluated
FALSEnever evaluated
0
277 rhosts_file_index++) {-
278 /* Check users .rhosts or .shosts. */-
279 snprintf(buf, sizeof buf, "%.500s/%.100s",-
280 pw->pw_dir, rhosts_files[rhosts_file_index]);-
281 if (stat(buf, &st) < 0)
stat(buf, &st) < 0Description
TRUEnever evaluated
FALSEnever evaluated
0
282 continue;
never executed: continue;
0
283-
284 /*-
285 * Make sure that the file is either owned by the user or by-
286 * root, and make sure it is not writable by anyone but the-
287 * owner. This is to help avoid novices accidentally-
288 * allowing access to their account by anyone.-
289 */-
290 if (options.strict_modes &&
options.strict_modesDescription
TRUEnever evaluated
FALSEnever evaluated
0
291 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
st.st_uid != 0Description
TRUEnever evaluated
FALSEnever evaluated
st.st_uid != pw->pw_uidDescription
TRUEnever evaluated
FALSEnever evaluated
0
292 (st.st_mode & 022) != 0)) {
(st.st_mode & 022) != 0Description
TRUEnever evaluated
FALSEnever evaluated
0
293 logit("Rhosts authentication refused for %.100s: bad modes for %.200s",-
294 pw->pw_name, buf);-
295 auth_debug_add("Bad file modes for %.200s", buf);-
296 continue;
never executed: continue;
0
297 }-
298 /*-
299 * Check if we have been configured to ignore .rhosts-
300 * and .shosts files.-
301 */-
302 if (options.ignore_rhosts) {
options.ignore_rhostsDescription
TRUEnever evaluated
FALSEnever evaluated
0
303 auth_debug_add("Server has been configured to "-
304 "ignore %.100s.", rhosts_files[rhosts_file_index]);-
305 continue;
never executed: continue;
0
306 }-
307 /* Check if authentication is permitted by the file. */-
308 if (check_rhosts_file(buf, hostname, ipaddr,
check_rhosts_f..., pw->pw_name)Description
TRUEnever evaluated
FALSEnever evaluated
0
309 client_user, pw->pw_name)) {
check_rhosts_f..., pw->pw_name)Description
TRUEnever evaluated
FALSEnever evaluated
0
310 auth_debug_add("Accepted by %.100s.",-
311 rhosts_files[rhosts_file_index]);-
312 /* Restore the privileged uid. */-
313 restore_uid();-
314 auth_debug_add("Accepted host %s ip %s client_user "-
315 "%s server_user %s", hostname, ipaddr,-
316 client_user, pw->pw_name);-
317 return 1;
never executed: return 1;
0
318 }-
319 }
never executed: end of block
0
320-
321 /* Restore the privileged uid. */-
322 restore_uid();-
323 return 0;
never executed: return 0;
0
324}-
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