[gssapi-openssh.git] / openssh / auth-rhosts.c

/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Rhosts authentication.  This file contains code to check whether to admit
 * the login based on rhosts authentication.  This file also processes
 * /etc/hosts.equiv.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

#include "includes.h"
RCSID("$OpenBSD: auth-rhosts.c,v 1.24 2001/06/23 15:12:17 itojun Exp $");

#include "packet.h"
#include "xmalloc.h"
#include "uidswap.h"
#include "pathnames.h"
#include "log.h"
#include "servconf.h"
#include "canohost.h"
#include "auth.h"

/* import */
extern ServerOptions options;

/*
 * This function processes an rhosts-style file (.rhosts, .shosts, or
 * /etc/hosts.equiv).  This returns true if authentication can be granted
 * based on the file, and returns zero otherwise.
 */

static int
check_rhosts_file(const char *filename, const char *hostname,
		  const char *ipaddr, const char *client_user,
		  const char *server_user)
{
	FILE *f;
	char buf[1024];	/* Must not be larger than host, user, dummy below. */

	/* Open the .rhosts file, deny if unreadable */
	f = fopen(filename, "r");
	if (!f)
		return 0;

	while (fgets(buf, sizeof(buf), f)) {
		/* All three must be at least as big as buf to avoid overflows. */
		char hostbuf[1024], userbuf[1024], dummy[1024], *host, *user, *cp;
		int negated;

		for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
			;
		if (*cp == '#' || *cp == '\n' || !*cp)
			continue;

		/*
		 * NO_PLUS is supported at least on OSF/1.  We skip it (we
		 * don't ever support the plus syntax).
		 */
		if (strncmp(cp, "NO_PLUS", 7) == 0)
			continue;

		/*
		 * This should be safe because each buffer is as big as the
		 * whole string, and thus cannot be overwritten.
		 */
		switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) {
		case 0:
			packet_send_debug("Found empty line in %.100s.", filename);
			continue;
		case 1:
			/* Host name only. */
			strlcpy(userbuf, server_user, sizeof(userbuf));
			break;
		case 2:
			/* Got both host and user name. */
			break;
		case 3:
			packet_send_debug("Found garbage in %.100s.", filename);
			continue;
		default:
			/* Weird... */
			continue;
		}

		host = hostbuf;
		user = userbuf;
		negated = 0;

		/* Process negated host names, or positive netgroups. */
		if (host[0] == '-') {
			negated = 1;
			host++;
		} else if (host[0] == '+')
			host++;

		if (user[0] == '-') {
			negated = 1;
			user++;
		} else if (user[0] == '+')
			user++;

		/* Check for empty host/user names (particularly '+'). */
		if (!host[0] || !user[0]) {
			/* We come here if either was '+' or '-'. */
			packet_send_debug("Ignoring wild host/user names in %.100s.",
					  filename);
			continue;
		}
		/* Verify that host name matches. */
		if (host[0] == '@') {
			if (!innetgr(host + 1, hostname, NULL, NULL) &&
			    !innetgr(host + 1, ipaddr, NULL, NULL))
				continue;
		} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
			continue;	/* Different hostname. */

		/* Verify that user name matches. */
		if (user[0] == '@') {
			if (!innetgr(user + 1, NULL, client_user, NULL))
				continue;
		} else if (strcmp(user, client_user) != 0)
			continue;	/* Different username. */

		/* Found the user and host. */
		fclose(f);

		/* If the entry was negated, deny access. */
		if (negated) {
			packet_send_debug("Matched negative entry in %.100s.",
					  filename);
			return 0;
		}
		/* Accept authentication. */
		return 1;
	}

	/* Authentication using this file denied. */
	fclose(f);
	return 0;
}

/*
 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
 * true if authentication succeeds.  If ignore_rhosts is true, only
 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
 */

int
auth_rhosts(struct passwd *pw, const char *client_user)
{
	const char *hostname, *ipaddr;
	int ret;

	hostname = get_canonical_hostname(options.reverse_mapping_check);
	ipaddr = get_remote_ipaddr();
	ret = auth_rhosts2(pw, client_user, hostname, ipaddr);
	return ret;
}

int
auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
    const char *ipaddr)
{
	char buf[1024];
	struct stat st;
	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
	u_int rhosts_file_index;

	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	    client_user, hostname, ipaddr);

	/* no user given */
	if (pw == NULL)
		return 0;

	/* Switch to the user's uid. */
	temporarily_use_uid(pw);
	/*
	 * Quick check: if the user has no .shosts or .rhosts files, return
	 * failure immediately without doing costly lookups from name
	 * servers.
	 */
	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
	     rhosts_file_index++) {
		/* Check users .rhosts or .shosts. */
		snprintf(buf, sizeof buf, "%.500s/%.100s",
			 pw->pw_dir, rhosts_files[rhosts_file_index]);
		if (stat(buf, &st) >= 0)
			break;
	}
	/* Switch back to privileged uid. */
	restore_uid();

	/* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
	if (!rhosts_files[rhosts_file_index] &&
	    stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
	    stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
		return 0;

	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
	if (pw->pw_uid != 0) {
		if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, client_user,
				      pw->pw_name)) {
			packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
					  hostname, ipaddr);
			return 1;
		}
		if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, client_user,
				      pw->pw_name)) {
			packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
				      hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
			return 1;
		}
	}
	/*
	 * Check that the home directory is owned by root or the user, and is
	 * not group or world writable.
	 */
	if (stat(pw->pw_dir, &st) < 0) {
		log("Rhosts authentication refused for %.100s: no home directory %.200s",
		    pw->pw_name, pw->pw_dir);
		packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s",
				  pw->pw_name, pw->pw_dir);
		return 0;
	}
	if (options.strict_modes &&
	    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
	     (st.st_mode & 022) != 0)) {
		log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
		    pw->pw_name);
		packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
				  pw->pw_name);
		return 0;
	}
	/* Temporarily use the user's uid. */
	temporarily_use_uid(pw);

	/* Check all .rhosts files (currently .shosts and .rhosts). */
	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
	     rhosts_file_index++) {
		/* Check users .rhosts or .shosts. */
		snprintf(buf, sizeof buf, "%.500s/%.100s",
			 pw->pw_dir, rhosts_files[rhosts_file_index]);
		if (stat(buf, &st) < 0)
			continue;

		/*
		 * Make sure that the file is either owned by the user or by
		 * root, and make sure it is not writable by anyone but the
		 * owner.  This is to help avoid novices accidentally
		 * allowing access to their account by anyone.
		 */
		if (options.strict_modes &&
		    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
		     (st.st_mode & 022) != 0)) {
			log("Rhosts authentication refused for %.100s: bad modes for %.200s",
			    pw->pw_name, buf);
			packet_send_debug("Bad file modes for %.200s", buf);
			continue;
		}
		/* Check if we have been configured to ignore .rhosts and .shosts files. */
		if (options.ignore_rhosts) {
			packet_send_debug("Server has been configured to ignore %.100s.",
					  rhosts_files[rhosts_file_index]);
			continue;
		}
		/* Check if authentication is permitted by the file. */
		if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
			packet_send_debug("Accepted by %.100s.",
					  rhosts_files[rhosts_file_index]);
			/* Restore the privileged uid. */
			restore_uid();
			return 1;
		}
	}

	/* Restore the privileged uid. */
	restore_uid();
	return 0;
}
Commit	Line	Data
3c0ef626	1	/*
	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.
	8	*
	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".
	14	*/
	15
	16	#include "includes.h"
	17	RCSID("$OpenBSD: auth-rhosts.c,v 1.24 2001/06/23 15:12:17 itojun Exp $");
	18
	19	#include "packet.h"
	20	#include "xmalloc.h"
	21	#include "uidswap.h"
	22	#include "pathnames.h"
	23	#include "log.h"
	24	#include "servconf.h"
	25	#include "canohost.h"
	26	#include "auth.h"
	27
	28	/* import */
	29	extern ServerOptions options;
	30
	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	*/
	36
	37	static int
	38	check_rhosts_file(const char filename, const char hostname,
	39	const char ipaddr, const char client_user,
	40	const char *server_user)
	41	{
	42	FILE *f;
	43	char buf[1024]; /* Must not be larger than host, user, dummy below. */
	44
	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
	60	/*
	61	* NO_PLUS is supported at least on OSF/1. We skip it (we
	62	* don't ever support the plus syntax).
	63	*/
	64	if (strncmp(cp, "NO_PLUS", 7) == 0)
65	continue;
66
67	/*
68	* This should be safe because each buffer is as big as the
69	* whole string, and thus cannot be overwritten.
70	*/
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;
145	}
146
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	*/
152
153	int
154	auth_rhosts(struct passwd pw, const char client_user)
155	{
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	{
169	char buf[1024];
170	struct stat st;
171	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
172	u_int rhosts_file_index;
173
174	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
175	client_user, hostname, ipaddr);
176
177	/* no user given */
178	if (pw == NULL)
179	return 0;
180
181	/* Switch to the user's uid. */
182	temporarily_use_uid(pw);
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	*/
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] &&
201	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
202	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
203	return 0;
204
205	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
206	if (pw->pw_uid != 0) {
207	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, client_user,
208	pw->pw_name)) {
209	packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
210	hostname, ipaddr);
211	return 1;
212	}
213	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, client_user,
214	pw->pw_name)) {
215	packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
216	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
217	return 1;
218	}
219	}
220	/*
221	* Check that the home directory is owned by root or the user, and is
222	* not group or world writable.
223	*/
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);
227	packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s",
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. */
241	temporarily_use_uid(pw);
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
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	*/
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;
285	}