5 Author: Tatu Ylonen <ylo@cs.hut.fi>
7 Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
10 Created: Fri Mar 17 05:12:18 1995 ylo
12 Rhosts authentication. This file contains code to check whether to admit
13 the login based on rhosts authentication. This file also processes
26 /* This function processes an rhosts-style file (.rhosts, .shosts, or
27 /etc/hosts.equiv). This returns true if authentication can be granted
28 based on the file, and returns zero otherwise. */
30 int check_rhosts_file(const char *filename, const char *hostname,
31 const char *ipaddr, const char *client_user,
32 const char *server_user)
35 char buf[1024]; /* Must not be larger than host, user, dummy below. */
37 /* Open the .rhosts file. */
38 f = fopen(filename, "r");
40 return 0; /* Cannot read the .rhosts - deny access. */
42 /* Go through the file, checking every entry. */
43 while (fgets(buf, sizeof(buf), f))
45 /* All three must be at least as big as buf to avoid overflows. */
46 char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
49 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
51 if (*cp == '#' || *cp == '\n' || !*cp)
54 /* NO_PLUS is supported at least on OSF/1. We skip it (we don't ever
55 support the plus syntax). */
56 if (strncmp(cp, "NO_PLUS", 7) == 0)
59 /* This should be safe because each buffer is as big as the whole
60 string, and thus cannot be overwritten. */
61 switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy))
64 packet_send_debug("Found empty line in %.100s.", filename);
65 continue; /* Empty line? */
68 strlcpy(userbuf, server_user, sizeof(userbuf));
71 /* Got both host and user name. */
74 packet_send_debug("Found garbage in %.100s.", filename);
75 continue; /* Extra garbage */
77 continue; /* Weird... */
84 /* Process negated host names, or positive netgroups. */
103 /* Check for empty host/user names (particularly '+'). */
104 if (!host[0] || !user[0])
106 /* We come here if either was '+' or '-'. */
107 packet_send_debug("Ignoring wild host/user names in %.100s.",
112 /* Verify that host name matches. */
115 if (!innetgr(host + 1, hostname, NULL, NULL) &&
116 !innetgr(host + 1, ipaddr, NULL, NULL))
120 if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
121 continue; /* Different hostname. */
123 /* Verify that user name matches. */
126 if (!innetgr(user + 1, NULL, client_user, NULL))
130 if (strcmp(user, client_user) != 0)
131 continue; /* Different username. */
133 /* Found the user and host. */
136 /* If the entry was negated, deny access. */
139 packet_send_debug("Matched negative entry in %.100s.",
144 /* Accept authentication. */
148 /* Authentication using this file denied. */
153 /* Tries to authenticate the user using the .shosts or .rhosts file.
154 Returns true if authentication succeeds. If ignore_rhosts is
155 true, only /etc/hosts.equiv will be considered (.rhosts and .shosts
158 int auth_rhosts(struct passwd *pw, const char *client_user,
159 int ignore_rhosts, int strict_modes)
162 const char *hostname, *ipaddr;
165 static const char *rhosts_files[] = { ".shosts", ".rhosts", NULL };
166 unsigned int rhosts_file_index;
168 /* Quick check: if the user has no .shosts or .rhosts files, return failure
169 immediately without doing costly lookups from name servers. */
170 /* Switch to the user's uid. */
171 temporarily_use_uid(pw->pw_uid);
172 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
175 /* Check users .rhosts or .shosts. */
176 snprintf(buf, sizeof buf, "%.500s/%.100s",
177 pw->pw_dir, rhosts_files[rhosts_file_index]);
178 if (stat(buf, &st) >= 0)
181 /* Switch back to privileged uid. */
184 if (!rhosts_files[rhosts_file_index] && stat("/etc/hosts.equiv", &st) < 0 &&
185 stat(SSH_HOSTS_EQUIV, &st) < 0)
186 return 0; /* The user has no .shosts or .rhosts file and there are no
187 system-wide files. */
189 /* Get the name, address, and port of the remote host. */
190 hostname = get_canonical_hostname();
191 ipaddr = get_remote_ipaddr();
192 port = get_remote_port();
194 /* Check that the connection comes from a privileged port.
195 Rhosts authentication only makes sense for priviledged programs.
196 Of course, if the intruder has root access on his local machine,
197 he can connect from any port. So do not use .rhosts
198 authentication from machines that you do not trust. */
199 if (port >= IPPORT_RESERVED ||
200 port < IPPORT_RESERVED / 2)
202 log("Connection from %.100s from nonpriviledged port %d",
204 packet_send_debug("Your ssh client is not running as root.");
208 /* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
211 if (check_rhosts_file("/etc/hosts.equiv", hostname, ipaddr, client_user,
214 packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
218 if (check_rhosts_file(SSH_HOSTS_EQUIV, hostname, ipaddr, client_user,
221 packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
222 hostname, ipaddr, SSH_HOSTS_EQUIV);
227 /* Check that the home directory is owned by root or the user, and is not
228 group or world writable. */
229 if (stat(pw->pw_dir, &st) < 0)
231 log("Rhosts authentication refused for %.100: no home directory %.200s",
232 pw->pw_name, pw->pw_dir);
233 packet_send_debug("Rhosts authentication refused for %.100: no home directory %.200s",
234 pw->pw_name, pw->pw_dir);
238 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
239 (st.st_mode & 022) != 0))
241 log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
243 packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
248 /* Check all .rhosts files (currently .shosts and .rhosts). */
249 /* Temporarily use the user's uid. */
250 temporarily_use_uid(pw->pw_uid);
251 for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
254 /* Check users .rhosts or .shosts. */
255 snprintf(buf, sizeof buf, "%.500s/%.100s",
256 pw->pw_dir, rhosts_files[rhosts_file_index]);
257 if (stat(buf, &st) < 0)
258 continue; /* No such file. */
260 /* Make sure that the file is either owned by the user or by root,
261 and make sure it is not writable by anyone but the owner. This is
262 to help avoid novices accidentally allowing access to their account
265 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
266 (st.st_mode & 022) != 0))
268 log("Rhosts authentication refused for %.100s: bad modes for %.200s",
270 packet_send_debug("Bad file modes for %.200s", buf);
274 /* Check if we have been configured to ignore .rhosts and .shosts
278 packet_send_debug("Server has been configured to ignore %.100s.",
279 rhosts_files[rhosts_file_index]);
283 /* Check if authentication is permitted by the file. */
284 if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name))
286 packet_send_debug("Accepted by %.100s.",
287 rhosts_files[rhosts_file_index]);
288 /* Restore the privileged uid. */
294 /* Rhosts authentication denied. */
295 /* Restore the privileged uid. */