Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.36
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"
1.35 stevesk 17:
18: #include <sys/types.h>
19: #include <sys/stat.h>
1.34 stevesk 20:
21: #include <netgroup.h>
1.1 deraadt 22:
23: #include "packet.h"
24: #include "uidswap.h"
1.19 markus 25: #include "pathnames.h"
26: #include "log.h"
1.6 markus 27: #include "servconf.h"
1.19 markus 28: #include "canohost.h"
1.21 itojun 29: #include "auth.h"
1.1 deraadt 30:
1.23 markus 31: /* import */
32: extern ServerOptions options;
1.28 markus 33: extern int use_privsep;
1.23 markus 34:
1.11 markus 35: /*
36: * This function processes an rhosts-style file (.rhosts, .shosts, or
37: * /etc/hosts.equiv). This returns true if authentication can be granted
38: * based on the file, and returns zero otherwise.
39: */
1.1 deraadt 40:
1.24 itojun 41: static int
1.9 markus 42: check_rhosts_file(const char *filename, const char *hostname,
43: const char *ipaddr, const char *client_user,
44: const char *server_user)
1.1 deraadt 45: {
1.9 markus 46: FILE *f;
47: char buf[1024]; /* Must not be larger than host, user, dummy below. */
1.1 deraadt 48:
1.9 markus 49: /* Open the .rhosts file, deny if unreadable */
50: f = fopen(filename, "r");
51: if (!f)
52: return 0;
53:
54: while (fgets(buf, sizeof(buf), f)) {
55: /* All three must be at least as big as buf to avoid overflows. */
56: char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
57: int negated;
58:
59: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
60: ;
61: if (*cp == '#' || *cp == '\n' || !*cp)
62: continue;
63:
1.11 markus 64: /*
65: * NO_PLUS is supported at least on OSF/1. We skip it (we
66: * don't ever support the plus syntax).
67: */
1.9 markus 68: if (strncmp(cp, "NO_PLUS", 7) == 0)
69: continue;
70:
1.11 markus 71: /*
72: * This should be safe because each buffer is as big as the
73: * whole string, and thus cannot be overwritten.
74: */
1.30 itojun 75: switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
76: dummy)) {
1.9 markus 77: case 0:
1.28 markus 78: auth_debug_add("Found empty line in %.100s.", filename);
1.9 markus 79: continue;
80: case 1:
81: /* Host name only. */
82: strlcpy(userbuf, server_user, sizeof(userbuf));
83: break;
84: case 2:
85: /* Got both host and user name. */
86: break;
87: case 3:
1.28 markus 88: auth_debug_add("Found garbage in %.100s.", filename);
1.9 markus 89: continue;
90: default:
91: /* Weird... */
92: continue;
93: }
94:
95: host = hostbuf;
96: user = userbuf;
97: negated = 0;
98:
99: /* Process negated host names, or positive netgroups. */
100: if (host[0] == '-') {
101: negated = 1;
102: host++;
103: } else if (host[0] == '+')
104: host++;
105:
106: if (user[0] == '-') {
107: negated = 1;
108: user++;
109: } else if (user[0] == '+')
110: user++;
111:
112: /* Check for empty host/user names (particularly '+'). */
113: if (!host[0] || !user[0]) {
114: /* We come here if either was '+' or '-'. */
1.28 markus 115: auth_debug_add("Ignoring wild host/user names in %.100s.",
116: filename);
1.9 markus 117: continue;
118: }
119: /* Verify that host name matches. */
120: if (host[0] == '@') {
121: if (!innetgr(host + 1, hostname, NULL, NULL) &&
122: !innetgr(host + 1, ipaddr, NULL, NULL))
123: continue;
124: } else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
125: continue; /* Different hostname. */
126:
127: /* Verify that user name matches. */
128: if (user[0] == '@') {
129: if (!innetgr(user + 1, NULL, client_user, NULL))
130: continue;
131: } else if (strcmp(user, client_user) != 0)
132: continue; /* Different username. */
133:
134: /* Found the user and host. */
135: fclose(f);
136:
137: /* If the entry was negated, deny access. */
138: if (negated) {
1.28 markus 139: auth_debug_add("Matched negative entry in %.100s.",
1.33 djm 140: filename);
1.9 markus 141: return 0;
142: }
143: /* Accept authentication. */
144: return 1;
145: }
146:
147: /* Authentication using this file denied. */
148: fclose(f);
149: return 0;
1.1 deraadt 150: }
151:
1.11 markus 152: /*
153: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
154: * true if authentication succeeds. If ignore_rhosts is true, only
155: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
156: */
1.1 deraadt 157:
1.13 markus 158: int
1.9 markus 159: auth_rhosts(struct passwd *pw, const char *client_user)
1.1 deraadt 160: {
1.23 markus 161: const char *hostname, *ipaddr;
162:
1.31 markus 163: hostname = get_canonical_hostname(options.use_dns);
1.23 markus 164: ipaddr = get_remote_ipaddr();
1.28 markus 165: return auth_rhosts2(pw, client_user, hostname, ipaddr);
1.23 markus 166: }
167:
1.28 markus 168: static int
169: auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
1.23 markus 170: const char *ipaddr)
171: {
1.9 markus 172: char buf[1024];
173: struct stat st;
174: static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1.17 markus 175: u_int rhosts_file_index;
1.9 markus 176:
1.23 markus 177: debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
178: client_user, hostname, ipaddr);
179:
1.9 markus 180: /* Switch to the user's uid. */
1.22 markus 181: temporarily_use_uid(pw);
1.11 markus 182: /*
183: * Quick check: if the user has no .shosts or .rhosts files, return
184: * failure immediately without doing costly lookups from name
185: * servers.
186: */
1.9 markus 187: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 188: rhosts_file_index++) {
1.9 markus 189: /* Check users .rhosts or .shosts. */
190: snprintf(buf, sizeof buf, "%.500s/%.100s",
191: pw->pw_dir, rhosts_files[rhosts_file_index]);
192: if (stat(buf, &st) >= 0)
193: break;
194: }
195: /* Switch back to privileged uid. */
196: restore_uid();
197:
198: /* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
199: if (!rhosts_files[rhosts_file_index] &&
1.18 markus 200: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
201: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
1.9 markus 202: return 0;
203:
204: /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
205: if (pw->pw_uid != 0) {
1.25 deraadt 206: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
207: client_user, pw->pw_name)) {
1.28 markus 208: auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
1.25 deraadt 209: hostname, ipaddr);
1.9 markus 210: return 1;
211: }
1.25 deraadt 212: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
213: client_user, pw->pw_name)) {
1.28 markus 214: auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
1.25 deraadt 215: hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 216: return 1;
217: }
218: }
1.11 markus 219: /*
220: * Check that the home directory is owned by root or the user, and is
221: * not group or world writable.
222: */
1.9 markus 223: if (stat(pw->pw_dir, &st) < 0) {
1.29 itojun 224: logit("Rhosts authentication refused for %.100s: "
1.28 markus 225: "no home directory %.200s", pw->pw_name, pw->pw_dir);
226: auth_debug_add("Rhosts authentication refused for %.100s: "
227: "no home directory %.200s", pw->pw_name, pw->pw_dir);
1.9 markus 228: return 0;
229: }
230: if (options.strict_modes &&
231: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 232: (st.st_mode & 022) != 0)) {
1.29 itojun 233: logit("Rhosts authentication refused for %.100s: "
1.28 markus 234: "bad ownership or modes for home directory.", pw->pw_name);
235: auth_debug_add("Rhosts authentication refused for %.100s: "
236: "bad ownership or modes for home directory.", pw->pw_name);
1.9 markus 237: return 0;
238: }
239: /* Temporarily use the user's uid. */
1.22 markus 240: temporarily_use_uid(pw);
1.9 markus 241:
242: /* Check all .rhosts files (currently .shosts and .rhosts). */
243: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 244: rhosts_file_index++) {
1.9 markus 245: /* Check users .rhosts or .shosts. */
246: snprintf(buf, sizeof buf, "%.500s/%.100s",
247: pw->pw_dir, rhosts_files[rhosts_file_index]);
248: if (stat(buf, &st) < 0)
249: continue;
250:
1.11 markus 251: /*
252: * Make sure that the file is either owned by the user or by
253: * root, and make sure it is not writable by anyone but the
254: * owner. This is to help avoid novices accidentally
255: * allowing access to their account by anyone.
256: */
1.9 markus 257: if (options.strict_modes &&
258: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 259: (st.st_mode & 022) != 0)) {
1.29 itojun 260: logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
1.9 markus 261: pw->pw_name, buf);
1.28 markus 262: auth_debug_add("Bad file modes for %.200s", buf);
1.9 markus 263: continue;
264: }
265: /* Check if we have been configured to ignore .rhosts and .shosts files. */
266: if (options.ignore_rhosts) {
1.28 markus 267: auth_debug_add("Server has been configured to ignore %.100s.",
268: rhosts_files[rhosts_file_index]);
1.9 markus 269: continue;
270: }
271: /* Check if authentication is permitted by the file. */
272: if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
1.28 markus 273: auth_debug_add("Accepted by %.100s.",
274: rhosts_files[rhosts_file_index]);
1.9 markus 275: /* Restore the privileged uid. */
276: restore_uid();
1.28 markus 277: auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
278: hostname, ipaddr, client_user, pw->pw_name);
1.9 markus 279: return 1;
280: }
281: }
282:
283: /* Restore the privileged uid. */
284: restore_uid();
285: return 0;
1.28 markus 286: }
287:
288: int
289: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
290: const char *ipaddr)
291: {
292: int ret;
293:
294: auth_debug_reset();
295: ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
296: if (!use_privsep)
297: auth_debug_send();
298: return ret;
1.1 deraadt 299: }
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