Annotation of src/crypto/external/bsd/openssh/dist/auth-rhosts.c, Revision 1.1.1.3
1.1.1.2 adam 1: /* $OpenBSD: auth-rhosts.c,v 1.44 2010/03/07 11:57:13 dtucker Exp $ */
1.1 christos 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 <sys/types.h>
18: #include <sys/stat.h>
19:
20: #include <fcntl.h>
21: #include <netgroup.h>
22: #include <pwd.h>
23: #include <stdio.h>
24: #include <string.h>
25: #include <stdarg.h>
26: #include <unistd.h>
27:
28: #include "packet.h"
29: #include "buffer.h"
30: #include "uidswap.h"
31: #include "pathnames.h"
32: #include "log.h"
33: #include "servconf.h"
34: #include "canohost.h"
35: #include "key.h"
36: #include "hostfile.h"
37: #include "auth.h"
38: #include "misc.h"
39:
40: /* import */
41: extern ServerOptions options;
42: extern int use_privsep;
43:
44: /*
45: * This function processes an rhosts-style file (.rhosts, .shosts, or
46: * /etc/hosts.equiv). This returns true if authentication can be granted
47: * based on the file, and returns zero otherwise.
48: */
49:
50: static int
51: check_rhosts_file(const char *filename, const char *hostname,
52: const char *ipaddr, const char *client_user,
53: const char *server_user)
54: {
55: FILE *f;
56: char buf[1024]; /* Must not be larger than host, user, dummy below. */
57: int fd;
58: struct stat st;
59:
60: /* Open the .rhosts file, deny if unreadable */
61: if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1)
62: return 0;
63: if (fstat(fd, &st) == -1) {
64: close(fd);
65: return 0;
66: }
67: if (!S_ISREG(st.st_mode)) {
68: logit("User %s hosts file %s is not a regular file",
69: server_user, filename);
70: close(fd);
71: return 0;
72: }
73: unset_nonblock(fd);
74: if ((f = fdopen(fd, "r")) == NULL) {
75: close(fd);
76: return 0;
77: }
78: while (fgets(buf, sizeof(buf), f)) {
79: /* All three must be at least as big as buf to avoid overflows. */
80: char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
81: int negated;
82:
83: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
84: ;
85: if (*cp == '#' || *cp == '\n' || !*cp)
86: continue;
87:
88: /*
89: * NO_PLUS is supported at least on OSF/1. We skip it (we
90: * don't ever support the plus syntax).
91: */
92: if (strncmp(cp, "NO_PLUS", 7) == 0)
93: continue;
94:
95: /*
96: * This should be safe because each buffer is as big as the
97: * whole string, and thus cannot be overwritten.
98: */
99: switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
100: dummy)) {
101: case 0:
102: auth_debug_add("Found empty line in %.100s.", filename);
103: continue;
104: case 1:
105: /* Host name only. */
106: strlcpy(userbuf, server_user, sizeof(userbuf));
107: break;
108: case 2:
109: /* Got both host and user name. */
110: break;
111: case 3:
112: auth_debug_add("Found garbage in %.100s.", filename);
113: continue;
114: default:
115: /* Weird... */
116: continue;
117: }
118:
119: host = hostbuf;
120: user = userbuf;
121: negated = 0;
122:
123: /* Process negated host names, or positive netgroups. */
124: if (host[0] == '-') {
125: negated = 1;
126: host++;
127: } else if (host[0] == '+')
128: host++;
129:
130: if (user[0] == '-') {
131: negated = 1;
132: user++;
133: } else if (user[0] == '+')
134: user++;
135:
136: /* Check for empty host/user names (particularly '+'). */
137: if (!host[0] || !user[0]) {
138: /* We come here if either was '+' or '-'. */
139: auth_debug_add("Ignoring wild host/user names in %.100s.",
140: filename);
141: continue;
142: }
143: /* Verify that host name matches. */
144: if (host[0] == '@') {
145: if (!innetgr(host + 1, hostname, NULL, NULL) &&
146: !innetgr(host + 1, ipaddr, NULL, NULL))
147: continue;
148: } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
149: continue; /* Different hostname. */
150:
151: /* Verify that user name matches. */
152: if (user[0] == '@') {
153: if (!innetgr(user + 1, NULL, client_user, NULL))
154: continue;
155: } else if (strcmp(user, client_user) != 0)
156: continue; /* Different username. */
157:
158: /* Found the user and host. */
159: fclose(f);
160:
161: /* If the entry was negated, deny access. */
162: if (negated) {
163: auth_debug_add("Matched negative entry in %.100s.",
164: filename);
165: return 0;
166: }
167: /* Accept authentication. */
168: return 1;
169: }
170:
171: /* Authentication using this file denied. */
172: fclose(f);
173: return 0;
174: }
175:
176: /*
177: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
178: * true if authentication succeeds. If ignore_rhosts is true, only
179: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
180: */
181:
182: int
183: auth_rhosts(struct passwd *pw, const char *client_user)
184: {
185: const char *hostname, *ipaddr;
186:
187: hostname = get_canonical_hostname(options.use_dns);
188: ipaddr = get_remote_ipaddr();
189: return auth_rhosts2(pw, client_user, hostname, ipaddr);
190: }
191:
192: static int
193: auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
194: const char *ipaddr)
195: {
196: char buf[1024];
197: struct stat st;
198: static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
199: u_int rhosts_file_index;
200:
201: debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
202: client_user, hostname, ipaddr);
203:
204: /* Switch to the user's uid. */
205: temporarily_use_uid(pw);
206: /*
207: * Quick check: if the user has no .shosts or .rhosts files, return
208: * failure immediately without doing costly lookups from name
209: * servers.
210: */
211: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
212: rhosts_file_index++) {
213: /* Check users .rhosts or .shosts. */
214: snprintf(buf, sizeof buf, "%.500s/%.100s",
215: pw->pw_dir, rhosts_files[rhosts_file_index]);
216: if (stat(buf, &st) >= 0)
217: break;
218: }
219: /* Switch back to privileged uid. */
220: restore_uid();
221:
222: /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
223: if (!rhosts_files[rhosts_file_index] &&
224: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
225: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
226: return 0;
227:
228: /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
229: if (pw->pw_uid != 0) {
230: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
231: client_user, pw->pw_name)) {
232: auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
233: hostname, ipaddr);
234: return 1;
235: }
236: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
237: client_user, pw->pw_name)) {
238: auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
239: hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
240: return 1;
241: }
242: }
243: /*
244: * Check that the home directory is owned by root or the user, and is
245: * not group or world writable.
246: */
247: if (stat(pw->pw_dir, &st) < 0) {
248: logit("Rhosts authentication refused for %.100s: "
249: "no home directory %.200s", pw->pw_name, pw->pw_dir);
250: auth_debug_add("Rhosts authentication refused for %.100s: "
251: "no home directory %.200s", pw->pw_name, pw->pw_dir);
252: return 0;
253: }
254: if (options.strict_modes &&
255: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
256: (st.st_mode & 022) != 0)) {
257: logit("Rhosts authentication refused for %.100s: "
258: "bad ownership or modes for home directory.", pw->pw_name);
259: auth_debug_add("Rhosts authentication refused for %.100s: "
260: "bad ownership or modes for home directory.", pw->pw_name);
261: return 0;
262: }
263: /* Temporarily use the user's uid. */
264: temporarily_use_uid(pw);
265:
266: /* Check all .rhosts files (currently .shosts and .rhosts). */
267: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
268: rhosts_file_index++) {
269: /* Check users .rhosts or .shosts. */
270: snprintf(buf, sizeof buf, "%.500s/%.100s",
271: pw->pw_dir, rhosts_files[rhosts_file_index]);
272: if (stat(buf, &st) < 0)
273: continue;
274:
275: /*
276: * Make sure that the file is either owned by the user or by
277: * root, and make sure it is not writable by anyone but the
278: * owner. This is to help avoid novices accidentally
279: * allowing access to their account by anyone.
280: */
281: if (options.strict_modes &&
282: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
283: (st.st_mode & 022) != 0)) {
284: logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
285: pw->pw_name, buf);
286: auth_debug_add("Bad file modes for %.200s", buf);
287: continue;
288: }
289: /* Check if we have been configured to ignore .rhosts and .shosts files. */
290: if (options.ignore_rhosts) {
291: auth_debug_add("Server has been configured to ignore %.100s.",
292: rhosts_files[rhosts_file_index]);
293: continue;
294: }
295: /* Check if authentication is permitted by the file. */
296: if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
297: auth_debug_add("Accepted by %.100s.",
298: rhosts_files[rhosts_file_index]);
299: /* Restore the privileged uid. */
300: restore_uid();
301: auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
302: hostname, ipaddr, client_user, pw->pw_name);
303: return 1;
304: }
305: }
306:
307: /* Restore the privileged uid. */
308: restore_uid();
309: return 0;
310: }
311:
312: int
313: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
314: const char *ipaddr)
315: {
1.1.1.2 adam 316: return auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
1.1 christos 317: }
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