Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.39
1.39 ! stevesk 1: /* $OpenBSD: auth-rhosts.c,v 1.38 2006/07/06 16:03:53 stevesk 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:
17: #include "includes.h"
1.35 stevesk 18:
19: #include <sys/types.h>
20: #include <sys/stat.h>
1.34 stevesk 21:
22: #include <netgroup.h>
1.38 stevesk 23: #include <pwd.h>
1.39 ! stevesk 24: #include <string.h>
1.1 deraadt 25:
26: #include "packet.h"
27: #include "uidswap.h"
1.19 markus 28: #include "pathnames.h"
29: #include "log.h"
1.6 markus 30: #include "servconf.h"
1.19 markus 31: #include "canohost.h"
1.21 itojun 32: #include "auth.h"
1.1 deraadt 33:
1.23 markus 34: /* import */
35: extern ServerOptions options;
1.28 markus 36: extern int use_privsep;
1.23 markus 37:
1.11 markus 38: /*
39: * This function processes an rhosts-style file (.rhosts, .shosts, or
40: * /etc/hosts.equiv). This returns true if authentication can be granted
41: * based on the file, and returns zero otherwise.
42: */
1.1 deraadt 43:
1.24 itojun 44: static int
1.9 markus 45: check_rhosts_file(const char *filename, const char *hostname,
46: const char *ipaddr, const char *client_user,
47: const char *server_user)
1.1 deraadt 48: {
1.9 markus 49: FILE *f;
50: char buf[1024]; /* Must not be larger than host, user, dummy below. */
1.1 deraadt 51:
1.9 markus 52: /* Open the .rhosts file, deny if unreadable */
53: f = fopen(filename, "r");
54: if (!f)
55: return 0;
56:
57: while (fgets(buf, sizeof(buf), f)) {
58: /* All three must be at least as big as buf to avoid overflows. */
59: char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
60: int negated;
61:
62: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
63: ;
64: if (*cp == '#' || *cp == '\n' || !*cp)
65: continue;
66:
1.11 markus 67: /*
68: * NO_PLUS is supported at least on OSF/1. We skip it (we
69: * don't ever support the plus syntax).
70: */
1.9 markus 71: if (strncmp(cp, "NO_PLUS", 7) == 0)
72: continue;
73:
1.11 markus 74: /*
75: * This should be safe because each buffer is as big as the
76: * whole string, and thus cannot be overwritten.
77: */
1.30 itojun 78: switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
79: dummy)) {
1.9 markus 80: case 0:
1.28 markus 81: auth_debug_add("Found empty line in %.100s.", filename);
1.9 markus 82: continue;
83: case 1:
84: /* Host name only. */
85: strlcpy(userbuf, server_user, sizeof(userbuf));
86: break;
87: case 2:
88: /* Got both host and user name. */
89: break;
90: case 3:
1.28 markus 91: auth_debug_add("Found garbage in %.100s.", filename);
1.9 markus 92: continue;
93: default:
94: /* Weird... */
95: continue;
96: }
97:
98: host = hostbuf;
99: user = userbuf;
100: negated = 0;
101:
102: /* Process negated host names, or positive netgroups. */
103: if (host[0] == '-') {
104: negated = 1;
105: host++;
106: } else if (host[0] == '+')
107: host++;
108:
109: if (user[0] == '-') {
110: negated = 1;
111: user++;
112: } else if (user[0] == '+')
113: user++;
114:
115: /* Check for empty host/user names (particularly '+'). */
116: if (!host[0] || !user[0]) {
117: /* We come here if either was '+' or '-'. */
1.28 markus 118: auth_debug_add("Ignoring wild host/user names in %.100s.",
119: filename);
1.9 markus 120: continue;
121: }
122: /* Verify that host name matches. */
123: if (host[0] == '@') {
124: if (!innetgr(host + 1, hostname, NULL, NULL) &&
125: !innetgr(host + 1, ipaddr, NULL, NULL))
126: continue;
127: } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
128: continue; /* Different hostname. */
129:
130: /* Verify that user name matches. */
131: if (user[0] == '@') {
132: if (!innetgr(user + 1, NULL, client_user, NULL))
133: continue;
134: } else if (strcmp(user, client_user) != 0)
135: continue; /* Different username. */
136:
137: /* Found the user and host. */
138: fclose(f);
139:
140: /* If the entry was negated, deny access. */
141: if (negated) {
1.28 markus 142: auth_debug_add("Matched negative entry in %.100s.",
1.33 djm 143: filename);
1.9 markus 144: return 0;
145: }
146: /* Accept authentication. */
147: return 1;
148: }
149:
150: /* Authentication using this file denied. */
151: fclose(f);
152: return 0;
1.1 deraadt 153: }
154:
1.11 markus 155: /*
156: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
157: * true if authentication succeeds. If ignore_rhosts is true, only
158: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
159: */
1.1 deraadt 160:
1.13 markus 161: int
1.9 markus 162: auth_rhosts(struct passwd *pw, const char *client_user)
1.1 deraadt 163: {
1.23 markus 164: const char *hostname, *ipaddr;
165:
1.31 markus 166: hostname = get_canonical_hostname(options.use_dns);
1.23 markus 167: ipaddr = get_remote_ipaddr();
1.28 markus 168: return auth_rhosts2(pw, client_user, hostname, ipaddr);
1.23 markus 169: }
170:
1.28 markus 171: static int
172: auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
1.23 markus 173: const char *ipaddr)
174: {
1.9 markus 175: char buf[1024];
176: struct stat st;
177: static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1.17 markus 178: u_int rhosts_file_index;
1.9 markus 179:
1.23 markus 180: debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
181: client_user, hostname, ipaddr);
182:
1.9 markus 183: /* Switch to the user's uid. */
1.22 markus 184: temporarily_use_uid(pw);
1.11 markus 185: /*
186: * Quick check: if the user has no .shosts or .rhosts files, return
187: * failure immediately without doing costly lookups from name
188: * servers.
189: */
1.9 markus 190: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 191: rhosts_file_index++) {
1.9 markus 192: /* Check users .rhosts or .shosts. */
193: snprintf(buf, sizeof buf, "%.500s/%.100s",
194: pw->pw_dir, rhosts_files[rhosts_file_index]);
195: if (stat(buf, &st) >= 0)
196: break;
197: }
198: /* Switch back to privileged uid. */
199: restore_uid();
200:
201: /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
202: if (!rhosts_files[rhosts_file_index] &&
1.18 markus 203: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
204: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
1.9 markus 205: return 0;
206:
207: /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
208: if (pw->pw_uid != 0) {
1.25 deraadt 209: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
210: client_user, pw->pw_name)) {
1.28 markus 211: auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
1.25 deraadt 212: hostname, ipaddr);
1.9 markus 213: return 1;
214: }
1.25 deraadt 215: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
216: client_user, pw->pw_name)) {
1.28 markus 217: auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
1.25 deraadt 218: hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 219: return 1;
220: }
221: }
1.11 markus 222: /*
223: * Check that the home directory is owned by root or the user, and is
224: * not group or world writable.
225: */
1.9 markus 226: if (stat(pw->pw_dir, &st) < 0) {
1.29 itojun 227: logit("Rhosts authentication refused for %.100s: "
1.28 markus 228: "no home directory %.200s", pw->pw_name, pw->pw_dir);
229: auth_debug_add("Rhosts authentication refused for %.100s: "
230: "no home directory %.200s", pw->pw_name, pw->pw_dir);
1.9 markus 231: return 0;
232: }
233: if (options.strict_modes &&
234: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 235: (st.st_mode & 022) != 0)) {
1.29 itojun 236: logit("Rhosts authentication refused for %.100s: "
1.28 markus 237: "bad ownership or modes for home directory.", pw->pw_name);
238: auth_debug_add("Rhosts authentication refused for %.100s: "
239: "bad ownership or modes for home directory.", pw->pw_name);
1.9 markus 240: return 0;
241: }
242: /* Temporarily use the user's uid. */
1.22 markus 243: temporarily_use_uid(pw);
1.9 markus 244:
245: /* Check all .rhosts files (currently .shosts and .rhosts). */
246: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 247: rhosts_file_index++) {
1.9 markus 248: /* Check users .rhosts or .shosts. */
249: snprintf(buf, sizeof buf, "%.500s/%.100s",
250: pw->pw_dir, rhosts_files[rhosts_file_index]);
251: if (stat(buf, &st) < 0)
252: continue;
253:
1.11 markus 254: /*
255: * Make sure that the file is either owned by the user or by
256: * root, and make sure it is not writable by anyone but the
257: * owner. This is to help avoid novices accidentally
258: * allowing access to their account by anyone.
259: */
1.9 markus 260: if (options.strict_modes &&
261: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 262: (st.st_mode & 022) != 0)) {
1.29 itojun 263: logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
1.9 markus 264: pw->pw_name, buf);
1.28 markus 265: auth_debug_add("Bad file modes for %.200s", buf);
1.9 markus 266: continue;
267: }
268: /* Check if we have been configured to ignore .rhosts and .shosts files. */
269: if (options.ignore_rhosts) {
1.28 markus 270: auth_debug_add("Server has been configured to ignore %.100s.",
271: rhosts_files[rhosts_file_index]);
1.9 markus 272: continue;
273: }
274: /* Check if authentication is permitted by the file. */
275: if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
1.28 markus 276: auth_debug_add("Accepted by %.100s.",
277: rhosts_files[rhosts_file_index]);
1.9 markus 278: /* Restore the privileged uid. */
279: restore_uid();
1.28 markus 280: auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
281: hostname, ipaddr, client_user, pw->pw_name);
1.9 markus 282: return 1;
283: }
284: }
285:
286: /* Restore the privileged uid. */
287: restore_uid();
288: return 0;
1.28 markus 289: }
290:
291: int
292: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
293: const char *ipaddr)
294: {
295: int ret;
296:
297: auth_debug_reset();
298: ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
299: if (!use_privsep)
300: auth_debug_send();
301: return ret;
1.1 deraadt 302: }
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