Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.33.2.1
1.33.2.1! brad 1: /* $OpenBSD: auth-rhosts.c,v 1.41 2006/08/03 03:34:41 deraadt Exp $ */
1.1 deraadt 2: /*
1.10 deraadt 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.
1.13 markus 9: *
1.15 deraadt 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".
1.10 deraadt 15: */
1.1 deraadt 16:
1.33.2.1! brad 17: #include <sys/types.h>
! 18: #include <sys/stat.h>
! 19:
! 20: #include <netgroup.h>
! 21: #include <pwd.h>
! 22: #include <stdio.h>
! 23: #include <string.h>
! 24: #include <stdarg.h>
1.1 deraadt 25:
26: #include "packet.h"
1.33.2.1! brad 27: #include "buffer.h"
1.1 deraadt 28: #include "uidswap.h"
1.19 markus 29: #include "pathnames.h"
30: #include "log.h"
1.6 markus 31: #include "servconf.h"
1.19 markus 32: #include "canohost.h"
1.33.2.1! brad 33: #include "key.h"
! 34: #include "hostfile.h"
1.21 itojun 35: #include "auth.h"
1.1 deraadt 36:
1.23 markus 37: /* import */
38: extern ServerOptions options;
1.28 markus 39: extern int use_privsep;
1.23 markus 40:
1.11 markus 41: /*
42: * This function processes an rhosts-style file (.rhosts, .shosts, or
43: * /etc/hosts.equiv). This returns true if authentication can be granted
44: * based on the file, and returns zero otherwise.
45: */
1.1 deraadt 46:
1.24 itojun 47: static int
1.9 markus 48: check_rhosts_file(const char *filename, const char *hostname,
49: const char *ipaddr, const char *client_user,
50: const char *server_user)
1.1 deraadt 51: {
1.9 markus 52: FILE *f;
53: char buf[1024]; /* Must not be larger than host, user, dummy below. */
1.1 deraadt 54:
1.9 markus 55: /* Open the .rhosts file, deny if unreadable */
56: f = fopen(filename, "r");
57: if (!f)
58: return 0;
59:
60: while (fgets(buf, sizeof(buf), f)) {
61: /* All three must be at least as big as buf to avoid overflows. */
62: char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
63: int negated;
64:
65: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
66: ;
67: if (*cp == '#' || *cp == '\n' || !*cp)
68: continue;
69:
1.11 markus 70: /*
71: * NO_PLUS is supported at least on OSF/1. We skip it (we
72: * don't ever support the plus syntax).
73: */
1.9 markus 74: if (strncmp(cp, "NO_PLUS", 7) == 0)
75: continue;
76:
1.11 markus 77: /*
78: * This should be safe because each buffer is as big as the
79: * whole string, and thus cannot be overwritten.
80: */
1.30 itojun 81: switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
82: dummy)) {
1.9 markus 83: case 0:
1.28 markus 84: auth_debug_add("Found empty line in %.100s.", filename);
1.9 markus 85: continue;
86: case 1:
87: /* Host name only. */
88: strlcpy(userbuf, server_user, sizeof(userbuf));
89: break;
90: case 2:
91: /* Got both host and user name. */
92: break;
93: case 3:
1.28 markus 94: auth_debug_add("Found garbage in %.100s.", filename);
1.9 markus 95: continue;
96: default:
97: /* Weird... */
98: continue;
99: }
100:
101: host = hostbuf;
102: user = userbuf;
103: negated = 0;
104:
105: /* Process negated host names, or positive netgroups. */
106: if (host[0] == '-') {
107: negated = 1;
108: host++;
109: } else if (host[0] == '+')
110: host++;
111:
112: if (user[0] == '-') {
113: negated = 1;
114: user++;
115: } else if (user[0] == '+')
116: user++;
117:
118: /* Check for empty host/user names (particularly '+'). */
119: if (!host[0] || !user[0]) {
120: /* We come here if either was '+' or '-'. */
1.28 markus 121: auth_debug_add("Ignoring wild host/user names in %.100s.",
122: filename);
1.9 markus 123: continue;
124: }
125: /* Verify that host name matches. */
126: if (host[0] == '@') {
127: if (!innetgr(host + 1, hostname, NULL, NULL) &&
128: !innetgr(host + 1, ipaddr, NULL, NULL))
129: continue;
130: } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
131: continue; /* Different hostname. */
132:
133: /* Verify that user name matches. */
134: if (user[0] == '@') {
135: if (!innetgr(user + 1, NULL, client_user, NULL))
136: continue;
137: } else if (strcmp(user, client_user) != 0)
138: continue; /* Different username. */
139:
140: /* Found the user and host. */
141: fclose(f);
142:
143: /* If the entry was negated, deny access. */
144: if (negated) {
1.28 markus 145: auth_debug_add("Matched negative entry in %.100s.",
1.33 djm 146: filename);
1.9 markus 147: return 0;
148: }
149: /* Accept authentication. */
150: return 1;
151: }
152:
153: /* Authentication using this file denied. */
154: fclose(f);
155: return 0;
1.1 deraadt 156: }
157:
1.11 markus 158: /*
159: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
160: * true if authentication succeeds. If ignore_rhosts is true, only
161: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
162: */
1.1 deraadt 163:
1.13 markus 164: int
1.9 markus 165: auth_rhosts(struct passwd *pw, const char *client_user)
1.1 deraadt 166: {
1.23 markus 167: const char *hostname, *ipaddr;
168:
1.31 markus 169: hostname = get_canonical_hostname(options.use_dns);
1.23 markus 170: ipaddr = get_remote_ipaddr();
1.28 markus 171: return auth_rhosts2(pw, client_user, hostname, ipaddr);
1.23 markus 172: }
173:
1.28 markus 174: static int
175: auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
1.23 markus 176: const char *ipaddr)
177: {
1.9 markus 178: char buf[1024];
179: struct stat st;
180: static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1.17 markus 181: u_int rhosts_file_index;
1.9 markus 182:
1.23 markus 183: debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
184: client_user, hostname, ipaddr);
185:
1.9 markus 186: /* Switch to the user's uid. */
1.22 markus 187: temporarily_use_uid(pw);
1.11 markus 188: /*
189: * Quick check: if the user has no .shosts or .rhosts files, return
190: * failure immediately without doing costly lookups from name
191: * servers.
192: */
1.9 markus 193: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 194: rhosts_file_index++) {
1.9 markus 195: /* Check users .rhosts or .shosts. */
196: snprintf(buf, sizeof buf, "%.500s/%.100s",
197: pw->pw_dir, rhosts_files[rhosts_file_index]);
198: if (stat(buf, &st) >= 0)
199: break;
200: }
201: /* Switch back to privileged uid. */
202: restore_uid();
203:
204: /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
205: if (!rhosts_files[rhosts_file_index] &&
1.18 markus 206: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
207: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
1.9 markus 208: return 0;
209:
210: /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
211: if (pw->pw_uid != 0) {
1.25 deraadt 212: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
213: client_user, pw->pw_name)) {
1.28 markus 214: auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
1.25 deraadt 215: hostname, ipaddr);
1.9 markus 216: return 1;
217: }
1.25 deraadt 218: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
219: client_user, pw->pw_name)) {
1.28 markus 220: auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
1.25 deraadt 221: hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 222: return 1;
223: }
224: }
1.11 markus 225: /*
226: * Check that the home directory is owned by root or the user, and is
227: * not group or world writable.
228: */
1.9 markus 229: if (stat(pw->pw_dir, &st) < 0) {
1.29 itojun 230: logit("Rhosts authentication refused for %.100s: "
1.28 markus 231: "no home directory %.200s", pw->pw_name, pw->pw_dir);
232: auth_debug_add("Rhosts authentication refused for %.100s: "
233: "no home directory %.200s", pw->pw_name, pw->pw_dir);
1.9 markus 234: return 0;
235: }
236: if (options.strict_modes &&
237: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 238: (st.st_mode & 022) != 0)) {
1.29 itojun 239: logit("Rhosts authentication refused for %.100s: "
1.28 markus 240: "bad ownership or modes for home directory.", pw->pw_name);
241: auth_debug_add("Rhosts authentication refused for %.100s: "
242: "bad ownership or modes for home directory.", pw->pw_name);
1.9 markus 243: return 0;
244: }
245: /* Temporarily use the user's uid. */
1.22 markus 246: temporarily_use_uid(pw);
1.9 markus 247:
248: /* Check all .rhosts files (currently .shosts and .rhosts). */
249: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 250: rhosts_file_index++) {
1.9 markus 251: /* Check users .rhosts or .shosts. */
252: snprintf(buf, sizeof buf, "%.500s/%.100s",
253: pw->pw_dir, rhosts_files[rhosts_file_index]);
254: if (stat(buf, &st) < 0)
255: continue;
256:
1.11 markus 257: /*
258: * Make sure that the file is either owned by the user or by
259: * root, and make sure it is not writable by anyone but the
260: * owner. This is to help avoid novices accidentally
261: * allowing access to their account by anyone.
262: */
1.9 markus 263: if (options.strict_modes &&
264: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 265: (st.st_mode & 022) != 0)) {
1.29 itojun 266: logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
1.9 markus 267: pw->pw_name, buf);
1.28 markus 268: auth_debug_add("Bad file modes for %.200s", buf);
1.9 markus 269: continue;
270: }
271: /* Check if we have been configured to ignore .rhosts and .shosts files. */
272: if (options.ignore_rhosts) {
1.28 markus 273: auth_debug_add("Server has been configured to ignore %.100s.",
274: rhosts_files[rhosts_file_index]);
1.9 markus 275: continue;
276: }
277: /* Check if authentication is permitted by the file. */
278: if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
1.28 markus 279: auth_debug_add("Accepted by %.100s.",
280: rhosts_files[rhosts_file_index]);
1.9 markus 281: /* Restore the privileged uid. */
282: restore_uid();
1.28 markus 283: auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
284: hostname, ipaddr, client_user, pw->pw_name);
1.9 markus 285: return 1;
286: }
287: }
288:
289: /* Restore the privileged uid. */
290: restore_uid();
291: return 0;
1.28 markus 292: }
293:
294: int
295: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
296: const char *ipaddr)
297: {
298: int ret;
299:
300: auth_debug_reset();
301: ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
302: if (!use_privsep)
303: auth_debug_send();
304: return ret;
1.1 deraadt 305: }
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