Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.27.2.2
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"
1.27.2.1 jason 17: RCSID("$OpenBSD: auth-rhosts.c,v 1.28 2002/05/13 21:26:49 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;
1.27.2.1 jason 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: */
1.9 markus 71: switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) {
72: case 0:
1.27.2.1 jason 73: auth_debug_add("Found empty line in %.100s.", filename);
1.9 markus 74: continue;
75: case 1:
76: /* Host name only. */
77: strlcpy(userbuf, server_user, sizeof(userbuf));
78: break;
79: case 2:
80: /* Got both host and user name. */
81: break;
82: case 3:
1.27.2.1 jason 83: auth_debug_add("Found garbage in %.100s.", filename);
1.9 markus 84: continue;
85: default:
86: /* Weird... */
87: continue;
88: }
89:
90: host = hostbuf;
91: user = userbuf;
92: negated = 0;
93:
94: /* Process negated host names, or positive netgroups. */
95: if (host[0] == '-') {
96: negated = 1;
97: host++;
98: } else if (host[0] == '+')
99: host++;
100:
101: if (user[0] == '-') {
102: negated = 1;
103: user++;
104: } else if (user[0] == '+')
105: user++;
106:
107: /* Check for empty host/user names (particularly '+'). */
108: if (!host[0] || !user[0]) {
109: /* We come here if either was '+' or '-'. */
1.27.2.1 jason 110: auth_debug_add("Ignoring wild host/user names in %.100s.",
111: filename);
1.9 markus 112: continue;
113: }
114: /* Verify that host name matches. */
115: if (host[0] == '@') {
116: if (!innetgr(host + 1, hostname, NULL, NULL) &&
117: !innetgr(host + 1, ipaddr, NULL, NULL))
118: continue;
119: } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
120: continue; /* Different hostname. */
121:
122: /* Verify that user name matches. */
123: if (user[0] == '@') {
124: if (!innetgr(user + 1, NULL, client_user, NULL))
125: continue;
126: } else if (strcmp(user, client_user) != 0)
127: continue; /* Different username. */
128:
129: /* Found the user and host. */
130: fclose(f);
131:
132: /* If the entry was negated, deny access. */
133: if (negated) {
1.27.2.1 jason 134: auth_debug_add("Matched negative entry in %.100s.",
135: filename);
1.9 markus 136: return 0;
137: }
138: /* Accept authentication. */
139: return 1;
140: }
141:
142: /* Authentication using this file denied. */
143: fclose(f);
144: return 0;
1.1 deraadt 145: }
146:
1.11 markus 147: /*
148: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
149: * true if authentication succeeds. If ignore_rhosts is true, only
150: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
151: */
1.1 deraadt 152:
1.13 markus 153: int
1.9 markus 154: auth_rhosts(struct passwd *pw, const char *client_user)
1.1 deraadt 155: {
1.23 markus 156: const char *hostname, *ipaddr;
157:
1.26 markus 158: hostname = get_canonical_hostname(options.verify_reverse_mapping);
1.23 markus 159: ipaddr = get_remote_ipaddr();
1.27.2.1 jason 160: return auth_rhosts2(pw, client_user, hostname, ipaddr);
1.23 markus 161: }
162:
1.27.2.1 jason 163: static int
164: auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
1.23 markus 165: const char *ipaddr)
166: {
1.9 markus 167: char buf[1024];
168: struct stat st;
169: static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1.17 markus 170: u_int rhosts_file_index;
1.9 markus 171:
1.23 markus 172: debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
173: client_user, hostname, ipaddr);
174:
1.16 markus 175: /* no user given */
176: if (pw == NULL)
177: return 0;
1.23 markus 178:
1.9 markus 179: /* Switch to the user's uid. */
1.22 markus 180: temporarily_use_uid(pw);
1.11 markus 181: /*
182: * Quick check: if the user has no .shosts or .rhosts files, return
183: * failure immediately without doing costly lookups from name
184: * servers.
185: */
1.9 markus 186: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 187: rhosts_file_index++) {
1.9 markus 188: /* Check users .rhosts or .shosts. */
189: snprintf(buf, sizeof buf, "%.500s/%.100s",
190: pw->pw_dir, rhosts_files[rhosts_file_index]);
191: if (stat(buf, &st) >= 0)
192: break;
193: }
194: /* Switch back to privileged uid. */
195: restore_uid();
196:
197: /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
198: if (!rhosts_files[rhosts_file_index] &&
1.18 markus 199: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
200: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
1.9 markus 201: return 0;
202:
203: /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
204: if (pw->pw_uid != 0) {
1.25 deraadt 205: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
206: client_user, pw->pw_name)) {
1.27.2.1 jason 207: auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
1.25 deraadt 208: hostname, ipaddr);
1.9 markus 209: return 1;
210: }
1.25 deraadt 211: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
212: client_user, pw->pw_name)) {
1.27.2.1 jason 213: auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
1.25 deraadt 214: hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 215: return 1;
216: }
217: }
1.11 markus 218: /*
219: * Check that the home directory is owned by root or the user, and is
220: * not group or world writable.
221: */
1.9 markus 222: if (stat(pw->pw_dir, &st) < 0) {
1.27.2.1 jason 223: log("Rhosts authentication refused for %.100s: "
224: "no home directory %.200s", pw->pw_name, pw->pw_dir);
225: auth_debug_add("Rhosts authentication refused for %.100s: "
226: "no home directory %.200s", pw->pw_name, pw->pw_dir);
1.9 markus 227: return 0;
228: }
229: if (options.strict_modes &&
230: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 231: (st.st_mode & 022) != 0)) {
1.27.2.1 jason 232: log("Rhosts authentication refused for %.100s: "
233: "bad ownership or modes for home directory.", pw->pw_name);
234: auth_debug_add("Rhosts authentication refused for %.100s: "
235: "bad ownership or modes for home directory.", pw->pw_name);
1.9 markus 236: return 0;
237: }
238: /* Temporarily use the user's uid. */
1.22 markus 239: temporarily_use_uid(pw);
1.9 markus 240:
241: /* Check all .rhosts files (currently .shosts and .rhosts). */
242: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 243: rhosts_file_index++) {
1.9 markus 244: /* Check users .rhosts or .shosts. */
245: snprintf(buf, sizeof buf, "%.500s/%.100s",
246: pw->pw_dir, rhosts_files[rhosts_file_index]);
247: if (stat(buf, &st) < 0)
248: continue;
249:
1.11 markus 250: /*
251: * Make sure that the file is either owned by the user or by
252: * root, and make sure it is not writable by anyone but the
253: * owner. This is to help avoid novices accidentally
254: * allowing access to their account by anyone.
255: */
1.9 markus 256: if (options.strict_modes &&
257: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 258: (st.st_mode & 022) != 0)) {
1.9 markus 259: log("Rhosts authentication refused for %.100s: bad modes for %.200s",
260: pw->pw_name, buf);
1.27.2.1 jason 261: auth_debug_add("Bad file modes for %.200s", buf);
1.9 markus 262: continue;
263: }
264: /* Check if we have been configured to ignore .rhosts and .shosts files. */
265: if (options.ignore_rhosts) {
1.27.2.1 jason 266: auth_debug_add("Server has been configured to ignore %.100s.",
267: rhosts_files[rhosts_file_index]);
1.9 markus 268: continue;
269: }
270: /* Check if authentication is permitted by the file. */
271: if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
1.27.2.1 jason 272: auth_debug_add("Accepted by %.100s.",
273: rhosts_files[rhosts_file_index]);
1.9 markus 274: /* Restore the privileged uid. */
275: restore_uid();
1.27.2.1 jason 276: auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
277: hostname, ipaddr, client_user, pw->pw_name);
1.9 markus 278: return 1;
279: }
280: }
281:
282: /* Restore the privileged uid. */
283: restore_uid();
284: return 0;
1.27.2.1 jason 285: }
286:
287: int
288: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
289: const char *ipaddr)
290: {
291: int ret;
292:
293: auth_debug_reset();
294: ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
295: if (!use_privsep)
296: auth_debug_send();
297: return ret;
1.1 deraadt 298: }
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