Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.24.2.1
1.1 deraadt 1: /*
1.10 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
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.
1.13 markus 8: *
1.15 deraadt 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".
1.10 deraadt 14: */
1.1 deraadt 15:
16: #include "includes.h"
1.24.2.1! jason 17: RCSID("$OpenBSD: auth-rhosts.c,v 1.27 2002/03/04 12:43:06 markus Exp $");
1.1 deraadt 18:
19: #include "packet.h"
20: #include "uidswap.h"
1.19 markus 21: #include "pathnames.h"
22: #include "log.h"
1.6 markus 23: #include "servconf.h"
1.19 markus 24: #include "canohost.h"
1.21 itojun 25: #include "auth.h"
1.1 deraadt 26:
1.23 markus 27: /* import */
28: extern ServerOptions options;
29:
1.11 markus 30: /*
31: * This function processes an rhosts-style file (.rhosts, .shosts, or
32: * /etc/hosts.equiv). This returns true if authentication can be granted
33: * based on the file, and returns zero otherwise.
34: */
1.1 deraadt 35:
1.24 itojun 36: static int
1.9 markus 37: check_rhosts_file(const char *filename, const char *hostname,
38: const char *ipaddr, const char *client_user,
39: const char *server_user)
1.1 deraadt 40: {
1.9 markus 41: FILE *f;
42: char buf[1024]; /* Must not be larger than host, user, dummy below. */
1.1 deraadt 43:
1.9 markus 44: /* Open the .rhosts file, deny if unreadable */
45: f = fopen(filename, "r");
46: if (!f)
47: return 0;
48:
49: while (fgets(buf, sizeof(buf), f)) {
50: /* All three must be at least as big as buf to avoid overflows. */
51: char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
52: int negated;
53:
54: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
55: ;
56: if (*cp == '#' || *cp == '\n' || !*cp)
57: continue;
58:
1.11 markus 59: /*
60: * NO_PLUS is supported at least on OSF/1. We skip it (we
61: * don't ever support the plus syntax).
62: */
1.9 markus 63: if (strncmp(cp, "NO_PLUS", 7) == 0)
64: continue;
65:
1.11 markus 66: /*
67: * This should be safe because each buffer is as big as the
68: * whole string, and thus cannot be overwritten.
69: */
1.9 markus 70: switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) {
71: case 0:
72: packet_send_debug("Found empty line in %.100s.", filename);
73: continue;
74: case 1:
75: /* Host name only. */
76: strlcpy(userbuf, server_user, sizeof(userbuf));
77: break;
78: case 2:
79: /* Got both host and user name. */
80: break;
81: case 3:
82: packet_send_debug("Found garbage in %.100s.", filename);
83: continue;
84: default:
85: /* Weird... */
86: continue;
87: }
88:
89: host = hostbuf;
90: user = userbuf;
91: negated = 0;
92:
93: /* Process negated host names, or positive netgroups. */
94: if (host[0] == '-') {
95: negated = 1;
96: host++;
97: } else if (host[0] == '+')
98: host++;
99:
100: if (user[0] == '-') {
101: negated = 1;
102: user++;
103: } else if (user[0] == '+')
104: user++;
105:
106: /* Check for empty host/user names (particularly '+'). */
107: if (!host[0] || !user[0]) {
108: /* We come here if either was '+' or '-'. */
109: packet_send_debug("Ignoring wild host/user names in %.100s.",
110: filename);
111: continue;
112: }
113: /* Verify that host name matches. */
114: if (host[0] == '@') {
115: if (!innetgr(host + 1, hostname, NULL, NULL) &&
116: !innetgr(host + 1, ipaddr, NULL, NULL))
117: continue;
118: } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
119: continue; /* Different hostname. */
120:
121: /* Verify that user name matches. */
122: if (user[0] == '@') {
123: if (!innetgr(user + 1, NULL, client_user, NULL))
124: continue;
125: } else if (strcmp(user, client_user) != 0)
126: continue; /* Different username. */
127:
128: /* Found the user and host. */
129: fclose(f);
130:
131: /* If the entry was negated, deny access. */
132: if (negated) {
133: packet_send_debug("Matched negative entry in %.100s.",
134: filename);
135: return 0;
136: }
137: /* Accept authentication. */
138: return 1;
139: }
140:
141: /* Authentication using this file denied. */
142: fclose(f);
143: return 0;
1.1 deraadt 144: }
145:
1.11 markus 146: /*
147: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
148: * true if authentication succeeds. If ignore_rhosts is true, only
149: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
150: */
1.1 deraadt 151:
1.13 markus 152: int
1.9 markus 153: auth_rhosts(struct passwd *pw, const char *client_user)
1.1 deraadt 154: {
1.23 markus 155: const char *hostname, *ipaddr;
156: int ret;
157:
1.24.2.1! jason 158: hostname = get_canonical_hostname(options.verify_reverse_mapping);
1.23 markus 159: ipaddr = get_remote_ipaddr();
160: ret = auth_rhosts2(pw, client_user, hostname, ipaddr);
161: return ret;
162: }
163:
164: int
165: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
166: const char *ipaddr)
167: {
1.9 markus 168: char buf[1024];
169: struct stat st;
170: static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1.17 markus 171: u_int rhosts_file_index;
1.9 markus 172:
1.23 markus 173: debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
174: client_user, hostname, ipaddr);
175:
1.16 markus 176: /* no user given */
177: if (pw == NULL)
178: return 0;
1.23 markus 179:
1.9 markus 180: /* Switch to the user's uid. */
1.22 markus 181: temporarily_use_uid(pw);
1.11 markus 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: */
1.9 markus 187: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.24.2.1! jason 188: rhosts_file_index++) {
1.9 markus 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;
194: }
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] &&
1.18 markus 200: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
201: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
1.9 markus 202: return 0;
203:
204: /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
205: if (pw->pw_uid != 0) {
1.24.2.1! jason 206: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
! 207: client_user, pw->pw_name)) {
1.9 markus 208: packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
1.24.2.1! jason 209: hostname, ipaddr);
1.9 markus 210: return 1;
211: }
1.24.2.1! jason 212: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
! 213: client_user, pw->pw_name)) {
1.9 markus 214: packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
1.24.2.1! jason 215: hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 216: return 1;
217: }
218: }
1.11 markus 219: /*
220: * Check that the home directory is owned by root or the user, and is
221: * not group or world writable.
222: */
1.9 markus 223: if (stat(pw->pw_dir, &st) < 0) {
224: log("Rhosts authentication refused for %.100s: no home directory %.200s",
225: pw->pw_name, pw->pw_dir);
1.12 markus 226: packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s",
1.9 markus 227: pw->pw_name, pw->pw_dir);
228: return 0;
229: }
230: if (options.strict_modes &&
231: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.24.2.1! jason 232: (st.st_mode & 022) != 0)) {
1.9 markus 233: log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
234: pw->pw_name);
235: packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
236: pw->pw_name);
237: return 0;
238: }
239: /* Temporarily use the user's uid. */
1.22 markus 240: temporarily_use_uid(pw);
1.9 markus 241:
242: /* Check all .rhosts files (currently .shosts and .rhosts). */
243: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.24.2.1! jason 244: rhosts_file_index++) {
1.9 markus 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:
1.11 markus 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: */
1.9 markus 257: if (options.strict_modes &&
258: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.24.2.1! jason 259: (st.st_mode & 022) != 0)) {
1.9 markus 260: log("Rhosts authentication refused for %.100s: bad modes for %.200s",
261: pw->pw_name, buf);
262: packet_send_debug("Bad file modes for %.200s", buf);
263: continue;
264: }
265: /* Check if we have been configured to ignore .rhosts and .shosts files. */
266: if (options.ignore_rhosts) {
267: packet_send_debug("Server has been configured to ignore %.100s.",
268: rhosts_files[rhosts_file_index]);
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)) {
273: packet_send_debug("Accepted by %.100s.",
274: rhosts_files[rhosts_file_index]);
275: /* Restore the privileged uid. */
276: restore_uid();
277: return 1;
278: }
279: }
280:
281: /* Restore the privileged uid. */
282: restore_uid();
283: return 0;
1.1 deraadt 284: }
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