Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.23
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"
1.23 ! markus 17: RCSID("$OpenBSD: auth-rhosts.c,v 1.22 2001/04/06 21:00:06 markus Exp $");
1.1 deraadt 18:
19: #include "packet.h"
20: #include "xmalloc.h"
21: #include "uidswap.h"
1.19 markus 22: #include "pathnames.h"
23: #include "log.h"
1.6 markus 24: #include "servconf.h"
1.19 markus 25: #include "canohost.h"
1.21 itojun 26: #include "auth.h"
1.1 deraadt 27:
1.23 ! markus 28: /* import */
! 29: extern ServerOptions options;
! 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:
1.13 markus 37: 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:
73: packet_send_debug("Found empty line in %.100s.", filename);
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:
83: packet_send_debug("Found garbage in %.100s.", filename);
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 '-'. */
110: packet_send_debug("Ignoring wild host/user names in %.100s.",
111: filename);
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) {
134: packet_send_debug("Matched negative entry in %.100s.",
135: filename);
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: int ret;
! 158:
! 159: hostname = get_canonical_hostname(options.reverse_mapping_check);
! 160: ipaddr = get_remote_ipaddr();
! 161: ret = auth_rhosts2(pw, client_user, hostname, ipaddr);
! 162: return ret;
! 163: }
! 164:
! 165: int
! 166: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
! 167: const char *ipaddr)
! 168: {
1.9 markus 169: char buf[1024];
170: struct stat st;
171: static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1.17 markus 172: u_int rhosts_file_index;
1.9 markus 173:
1.23 ! markus 174: debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
! 175: client_user, hostname, ipaddr);
! 176:
1.16 markus 177: /* no user given */
178: if (pw == NULL)
179: return 0;
1.23 ! markus 180:
1.9 markus 181: /* Switch to the user's uid. */
1.22 markus 182: temporarily_use_uid(pw);
1.11 markus 183: /*
184: * Quick check: if the user has no .shosts or .rhosts files, return
185: * failure immediately without doing costly lookups from name
186: * servers.
187: */
1.9 markus 188: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
189: rhosts_file_index++) {
190: /* Check users .rhosts or .shosts. */
191: snprintf(buf, sizeof buf, "%.500s/%.100s",
192: pw->pw_dir, rhosts_files[rhosts_file_index]);
193: if (stat(buf, &st) >= 0)
194: break;
195: }
196: /* Switch back to privileged uid. */
197: restore_uid();
198:
199: /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
200: if (!rhosts_files[rhosts_file_index] &&
1.18 markus 201: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
202: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
1.9 markus 203: return 0;
204:
205: /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
206: if (pw->pw_uid != 0) {
1.21 itojun 207: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, client_user,
1.9 markus 208: pw->pw_name)) {
209: packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
210: hostname, ipaddr);
211: return 1;
212: }
1.18 markus 213: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, client_user,
1.9 markus 214: pw->pw_name)) {
215: packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
1.18 markus 216: hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 217: return 1;
218: }
219: }
1.11 markus 220: /*
221: * Check that the home directory is owned by root or the user, and is
222: * not group or world writable.
223: */
1.9 markus 224: if (stat(pw->pw_dir, &st) < 0) {
225: log("Rhosts authentication refused for %.100s: no home directory %.200s",
226: pw->pw_name, pw->pw_dir);
1.12 markus 227: packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s",
1.9 markus 228: pw->pw_name, pw->pw_dir);
229: return 0;
230: }
231: if (options.strict_modes &&
232: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
233: (st.st_mode & 022) != 0)) {
234: log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
235: pw->pw_name);
236: packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
237: pw->pw_name);
238: return 0;
239: }
240: /* Temporarily use the user's uid. */
1.22 markus 241: temporarily_use_uid(pw);
1.9 markus 242:
243: /* Check all .rhosts files (currently .shosts and .rhosts). */
244: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
245: rhosts_file_index++) {
246: /* Check users .rhosts or .shosts. */
247: snprintf(buf, sizeof buf, "%.500s/%.100s",
248: pw->pw_dir, rhosts_files[rhosts_file_index]);
249: if (stat(buf, &st) < 0)
250: continue;
251:
1.11 markus 252: /*
253: * Make sure that the file is either owned by the user or by
254: * root, and make sure it is not writable by anyone but the
255: * owner. This is to help avoid novices accidentally
256: * allowing access to their account by anyone.
257: */
1.9 markus 258: if (options.strict_modes &&
259: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
260: (st.st_mode & 022) != 0)) {
261: log("Rhosts authentication refused for %.100s: bad modes for %.200s",
262: pw->pw_name, buf);
263: packet_send_debug("Bad file modes for %.200s", buf);
264: continue;
265: }
266: /* Check if we have been configured to ignore .rhosts and .shosts files. */
267: if (options.ignore_rhosts) {
268: packet_send_debug("Server has been configured to ignore %.100s.",
269: rhosts_files[rhosts_file_index]);
270: continue;
271: }
272: /* Check if authentication is permitted by the file. */
273: if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
274: packet_send_debug("Accepted by %.100s.",
275: rhosts_files[rhosts_file_index]);
276: /* Restore the privileged uid. */
277: restore_uid();
278: return 1;
279: }
280: }
281:
282: /* Restore the privileged uid. */
283: restore_uid();
284: return 0;
1.1 deraadt 285: }
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