Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.33
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"
1.33 ! djm 17: RCSID("$OpenBSD: auth-rhosts.c,v 1.32 2003/11/04 08:54:09 djm 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;
1.28 markus 29: extern int use_privsep;
1.23 markus 30:
1.11 markus 31: /*
32: * This function processes an rhosts-style file (.rhosts, .shosts, or
33: * /etc/hosts.equiv). This returns true if authentication can be granted
34: * based on the file, and returns zero otherwise.
35: */
1.1 deraadt 36:
1.24 itojun 37: static int
1.9 markus 38: check_rhosts_file(const char *filename, const char *hostname,
39: const char *ipaddr, const char *client_user,
40: const char *server_user)
1.1 deraadt 41: {
1.9 markus 42: FILE *f;
43: char buf[1024]; /* Must not be larger than host, user, dummy below. */
1.1 deraadt 44:
1.9 markus 45: /* Open the .rhosts file, deny if unreadable */
46: f = fopen(filename, "r");
47: if (!f)
48: return 0;
49:
50: while (fgets(buf, sizeof(buf), f)) {
51: /* All three must be at least as big as buf to avoid overflows. */
52: char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
53: int negated;
54:
55: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
56: ;
57: if (*cp == '#' || *cp == '\n' || !*cp)
58: continue;
59:
1.11 markus 60: /*
61: * NO_PLUS is supported at least on OSF/1. We skip it (we
62: * don't ever support the plus syntax).
63: */
1.9 markus 64: if (strncmp(cp, "NO_PLUS", 7) == 0)
65: continue;
66:
1.11 markus 67: /*
68: * This should be safe because each buffer is as big as the
69: * whole string, and thus cannot be overwritten.
70: */
1.30 itojun 71: switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
72: dummy)) {
1.9 markus 73: case 0:
1.28 markus 74: auth_debug_add("Found empty line in %.100s.", filename);
1.9 markus 75: continue;
76: case 1:
77: /* Host name only. */
78: strlcpy(userbuf, server_user, sizeof(userbuf));
79: break;
80: case 2:
81: /* Got both host and user name. */
82: break;
83: case 3:
1.28 markus 84: auth_debug_add("Found garbage in %.100s.", filename);
1.9 markus 85: continue;
86: default:
87: /* Weird... */
88: continue;
89: }
90:
91: host = hostbuf;
92: user = userbuf;
93: negated = 0;
94:
95: /* Process negated host names, or positive netgroups. */
96: if (host[0] == '-') {
97: negated = 1;
98: host++;
99: } else if (host[0] == '+')
100: host++;
101:
102: if (user[0] == '-') {
103: negated = 1;
104: user++;
105: } else if (user[0] == '+')
106: user++;
107:
108: /* Check for empty host/user names (particularly '+'). */
109: if (!host[0] || !user[0]) {
110: /* We come here if either was '+' or '-'. */
1.28 markus 111: auth_debug_add("Ignoring wild host/user names in %.100s.",
112: filename);
1.9 markus 113: continue;
114: }
115: /* Verify that host name matches. */
116: if (host[0] == '@') {
117: if (!innetgr(host + 1, hostname, NULL, NULL) &&
118: !innetgr(host + 1, ipaddr, NULL, NULL))
119: continue;
120: } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
121: continue; /* Different hostname. */
122:
123: /* Verify that user name matches. */
124: if (user[0] == '@') {
125: if (!innetgr(user + 1, NULL, client_user, NULL))
126: continue;
127: } else if (strcmp(user, client_user) != 0)
128: continue; /* Different username. */
129:
130: /* Found the user and host. */
131: fclose(f);
132:
133: /* If the entry was negated, deny access. */
134: if (negated) {
1.28 markus 135: auth_debug_add("Matched negative entry in %.100s.",
1.33 ! djm 136: filename);
1.9 markus 137: return 0;
138: }
139: /* Accept authentication. */
140: return 1;
141: }
142:
143: /* Authentication using this file denied. */
144: fclose(f);
145: return 0;
1.1 deraadt 146: }
147:
1.11 markus 148: /*
149: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
150: * true if authentication succeeds. If ignore_rhosts is true, only
151: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
152: */
1.1 deraadt 153:
1.13 markus 154: int
1.9 markus 155: auth_rhosts(struct passwd *pw, const char *client_user)
1.1 deraadt 156: {
1.23 markus 157: const char *hostname, *ipaddr;
158:
1.31 markus 159: hostname = get_canonical_hostname(options.use_dns);
1.23 markus 160: ipaddr = get_remote_ipaddr();
1.28 markus 161: return auth_rhosts2(pw, client_user, hostname, ipaddr);
1.23 markus 162: }
163:
1.28 markus 164: static int
165: auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
1.23 markus 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:
1.9 markus 176: /* Switch to the user's uid. */
1.22 markus 177: temporarily_use_uid(pw);
1.11 markus 178: /*
179: * Quick check: if the user has no .shosts or .rhosts files, return
180: * failure immediately without doing costly lookups from name
181: * servers.
182: */
1.9 markus 183: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 184: rhosts_file_index++) {
1.9 markus 185: /* Check users .rhosts or .shosts. */
186: snprintf(buf, sizeof buf, "%.500s/%.100s",
187: pw->pw_dir, rhosts_files[rhosts_file_index]);
188: if (stat(buf, &st) >= 0)
189: break;
190: }
191: /* Switch back to privileged uid. */
192: restore_uid();
193:
194: /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
195: if (!rhosts_files[rhosts_file_index] &&
1.18 markus 196: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
197: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
1.9 markus 198: return 0;
199:
200: /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
201: if (pw->pw_uid != 0) {
1.25 deraadt 202: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
203: client_user, pw->pw_name)) {
1.28 markus 204: auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
1.25 deraadt 205: hostname, ipaddr);
1.9 markus 206: return 1;
207: }
1.25 deraadt 208: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
209: client_user, pw->pw_name)) {
1.28 markus 210: auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
1.25 deraadt 211: hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 212: return 1;
213: }
214: }
1.11 markus 215: /*
216: * Check that the home directory is owned by root or the user, and is
217: * not group or world writable.
218: */
1.9 markus 219: if (stat(pw->pw_dir, &st) < 0) {
1.29 itojun 220: logit("Rhosts authentication refused for %.100s: "
1.28 markus 221: "no home directory %.200s", pw->pw_name, pw->pw_dir);
222: auth_debug_add("Rhosts authentication refused for %.100s: "
223: "no home directory %.200s", pw->pw_name, pw->pw_dir);
1.9 markus 224: return 0;
225: }
226: if (options.strict_modes &&
227: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 228: (st.st_mode & 022) != 0)) {
1.29 itojun 229: logit("Rhosts authentication refused for %.100s: "
1.28 markus 230: "bad ownership or modes for home directory.", pw->pw_name);
231: auth_debug_add("Rhosts authentication refused for %.100s: "
232: "bad ownership or modes for home directory.", pw->pw_name);
1.9 markus 233: return 0;
234: }
235: /* Temporarily use the user's uid. */
1.22 markus 236: temporarily_use_uid(pw);
1.9 markus 237:
238: /* Check all .rhosts files (currently .shosts and .rhosts). */
239: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 240: rhosts_file_index++) {
1.9 markus 241: /* Check users .rhosts or .shosts. */
242: snprintf(buf, sizeof buf, "%.500s/%.100s",
243: pw->pw_dir, rhosts_files[rhosts_file_index]);
244: if (stat(buf, &st) < 0)
245: continue;
246:
1.11 markus 247: /*
248: * Make sure that the file is either owned by the user or by
249: * root, and make sure it is not writable by anyone but the
250: * owner. This is to help avoid novices accidentally
251: * allowing access to their account by anyone.
252: */
1.9 markus 253: if (options.strict_modes &&
254: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 255: (st.st_mode & 022) != 0)) {
1.29 itojun 256: logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
1.9 markus 257: pw->pw_name, buf);
1.28 markus 258: auth_debug_add("Bad file modes for %.200s", buf);
1.9 markus 259: continue;
260: }
261: /* Check if we have been configured to ignore .rhosts and .shosts files. */
262: if (options.ignore_rhosts) {
1.28 markus 263: auth_debug_add("Server has been configured to ignore %.100s.",
264: rhosts_files[rhosts_file_index]);
1.9 markus 265: continue;
266: }
267: /* Check if authentication is permitted by the file. */
268: if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
1.28 markus 269: auth_debug_add("Accepted by %.100s.",
270: rhosts_files[rhosts_file_index]);
1.9 markus 271: /* Restore the privileged uid. */
272: restore_uid();
1.28 markus 273: auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
274: hostname, ipaddr, client_user, pw->pw_name);
1.9 markus 275: return 1;
276: }
277: }
278:
279: /* Restore the privileged uid. */
280: restore_uid();
281: return 0;
1.28 markus 282: }
283:
284: int
285: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
286: const char *ipaddr)
287: {
288: int ret;
289:
290: auth_debug_reset();
291: ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
292: if (!use_privsep)
293: auth_debug_send();
294: return ret;
1.1 deraadt 295: }