[openssh.git] / 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 1.20 2001/02/03 10:08:36 markus Exp $");

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

/*
 * 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.
 */

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)
{
	extern ServerOptions options;
	char buf[1024];
	const char *hostname, *ipaddr;
	struct stat st;
	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
	u_int rhosts_file_index;

	/* no user given */
	if (pw == NULL)
		return 0;
	/* Switch to the user's uid. */
	temporarily_use_uid(pw->pw_uid);
	/*
	 * 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;

	hostname = get_canonical_hostname(options.reverse_mapping_check);
	ipaddr = get_remote_ipaddr();

	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
	if (pw->pw_uid != 0) {
		if (check_rhosts_file("/etc/hosts.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->pw_uid);

	/* 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
8efc0c15	1	/*
5260325f	2	* Author: Tatu Ylonen <ylo@cs.hut.fi>
5260325f	3	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5260325f	4	* All rights reserved
5260325f	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.
6ae2364d	8	*
bcbf86ec	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".
5260325f	14	*/
8efc0c15	15
8efc0c15	16	#include "includes.h"
61e96248	17	RCSID("$OpenBSD: auth-rhosts.c,v 1.20 2001/02/03 10:08:36 markus Exp $");
8efc0c15	18
8efc0c15	19	#include "packet.h"
8efc0c15	20	#include "xmalloc.h"
8efc0c15	21	#include "uidswap.h"
42f11eb2	22	#include "pathnames.h"
42f11eb2	23	#include "log.h"
6fa724bc	24	#include "servconf.h"
42f11eb2	25	#include "canohost.h"
8efc0c15	26
aa3378df	27	/*
	28	* This function processes an rhosts-style file (.rhosts, .shosts, or
	29	* /etc/hosts.equiv). This returns true if authentication can be granted
	30	* based on the file, and returns zero otherwise.
	31	*/
8efc0c15	32
6ae2364d	33	int
5260325f	34	check_rhosts_file(const char filename, const char hostname,
	35	const char ipaddr, const char client_user,
	36	const char *server_user)
8efc0c15	37	{
5260325f	38	FILE *f;
	39	char buf[1024]; /* Must not be larger than host, user, dummy below. */
	40
	41	/* Open the .rhosts file, deny if unreadable */
	42	f = fopen(filename, "r");
	43	if (!f)
	44	return 0;
	45
5260325f	46	while (fgets(buf, sizeof(buf), f)) {
	47	/* All three must be at least as big as buf to avoid overflows. */
	48	char hostbuf[1024], userbuf[1024], dummy[1024], host, user, *cp;
	49	int negated;
	50
	51	for (cp = buf; cp == ' ' \|\| cp == '\t'; cp++)
	52	;
	53	if (cp == '#' \|\| cp == '\n' \|\| !*cp)
	54	continue;
	55
aa3378df	56	/*
	57	* NO_PLUS is supported at least on OSF/1. We skip it (we
	58	* don't ever support the plus syntax).
	59	*/
5260325f	60	if (strncmp(cp, "NO_PLUS", 7) == 0)
	61	continue;
	62
aa3378df	63	/*
	64	* This should be safe because each buffer is as big as the
	65	* whole string, and thus cannot be overwritten.
	66	*/
5260325f	67	switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) {
	68	case 0:
	69	packet_send_debug("Found empty line in %.100s.", filename);
	70	continue;
	71	case 1:
	72	/* Host name only. */
	73	strlcpy(userbuf, server_user, sizeof(userbuf));
	74	break;
	75	case 2:
	76	/* Got both host and user name. */
	77	break;
	78	case 3:
	79	packet_send_debug("Found garbage in %.100s.", filename);
	80	continue;
	81	default:
	82	/* Weird... */
	83	continue;
	84	}
	85
	86	host = hostbuf;
	87	user = userbuf;
	88	negated = 0;
	89
	90	/* Process negated host names, or positive netgroups. */
	91	if (host[0] == '-') {
	92	negated = 1;
	93	host++;
	94	} else if (host[0] == '+')
	95	host++;
	96
	97	if (user[0] == '-') {
	98	negated = 1;
	99	user++;
	100	} else if (user[0] == '+')
	101	user++;
	102
	103	/* Check for empty host/user names (particularly '+'). */
	104	if (!host[0] \|\| !user[0]) {
	105	/* We come here if either was '+' or '-'. */
	106	packet_send_debug("Ignoring wild host/user names in %.100s.",
	107	filename);
	108	continue;
	109	}
	110	/* Verify that host name matches. */
	111	if (host[0] == '@') {
	112	if (!innetgr(host + 1, hostname, NULL, NULL) &&
	113	!innetgr(host + 1, ipaddr, NULL, NULL))
	114	continue;
	115	} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
	116	continue; /* Different hostname. */
	117
	118	/* Verify that user name matches. */
	119	if (user[0] == '@') {
	120	if (!innetgr(user + 1, NULL, client_user, NULL))
	121	continue;
	122	} else if (strcmp(user, client_user) != 0)
	123	continue; /* Different username. */
	124
	125	/* Found the user and host. */
	126	fclose(f);
	127
	128	/* If the entry was negated, deny access. */
	129	if (negated) {
	130	packet_send_debug("Matched negative entry in %.100s.",
131	filename);
132	return 0;
133	}
134	/* Accept authentication. */
135	return 1;
8efc0c15	136	}
8efc0c15	137
5260325f	138	/* Authentication using this file denied. */
	139	fclose(f);
	140	return 0;
8efc0c15	141	}
8efc0c15	142
aa3378df	143	/*
	144	* Tries to authenticate the user using the .shosts or .rhosts file. Returns
	145	* true if authentication succeeds. If ignore_rhosts is true, only
	146	* /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
	147	*/
8efc0c15	148
6ae2364d	149	int
5260325f	150	auth_rhosts(struct passwd pw, const char client_user)
8efc0c15	151	{
5260325f	152	extern ServerOptions options;
	153	char buf[1024];
	154	const char hostname, ipaddr;
	155	struct stat st;
	156	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1e3b8b07	157	u_int rhosts_file_index;
5260325f	158
94ec8c6b	159	/* no user given */
	160	if (pw == NULL)
	161	return 0;
5260325f	162	/* Switch to the user's uid. */
5260325f	163	temporarily_use_uid(pw->pw_uid);
aa3378df	164	/*
	165	* Quick check: if the user has no .shosts or .rhosts files, return
	166	* failure immediately without doing costly lookups from name
	167	* servers.
	168	*/
5260325f	169	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
	170	rhosts_file_index++) {
	171	/* Check users .rhosts or .shosts. */
	172	snprintf(buf, sizeof buf, "%.500s/%.100s",
	173	pw->pw_dir, rhosts_files[rhosts_file_index]);
	174	if (stat(buf, &st) >= 0)
	175	break;
8efc0c15	176	}
5260325f	177	/* Switch back to privileged uid. */
	178	restore_uid();
	179
	180	/* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
	181	if (!rhosts_files[rhosts_file_index] &&
42f11eb2	182	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
42f11eb2	183	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
5260325f	184	return 0;
5260325f	185
61e96248	186	hostname = get_canonical_hostname(options.reverse_mapping_check);
5260325f	187	ipaddr = get_remote_ipaddr();
	188
	189	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
	190	if (pw->pw_uid != 0) {
	191	if (check_rhosts_file("/etc/hosts.equiv", hostname, ipaddr, client_user,
	192	pw->pw_name)) {
	193	packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
	194	hostname, ipaddr);
	195	return 1;
	196	}
42f11eb2	197	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, client_user,
5260325f	198	pw->pw_name)) {
5260325f	199	packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
42f11eb2	200	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
5260325f	201	return 1;
5260325f	202	}
8efc0c15	203	}
aa3378df	204	/*
	205	* Check that the home directory is owned by root or the user, and is
	206	* not group or world writable.
	207	*/
5260325f	208	if (stat(pw->pw_dir, &st) < 0) {
	209	log("Rhosts authentication refused for %.100s: no home directory %.200s",
	210	pw->pw_name, pw->pw_dir);
00e6dd70	211	packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s",
5260325f	212	pw->pw_name, pw->pw_dir);
5260325f	213	return 0;
8efc0c15	214	}
5260325f	215	if (options.strict_modes &&
	216	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
	217	(st.st_mode & 022) != 0)) {
	218	log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
	219	pw->pw_name);
	220	packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
	221	pw->pw_name);
	222	return 0;
8efc0c15	223	}
5260325f	224	/* Temporarily use the user's uid. */
	225	temporarily_use_uid(pw->pw_uid);
	226
	227	/* Check all .rhosts files (currently .shosts and .rhosts). */
	228	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
	229	rhosts_file_index++) {
	230	/* Check users .rhosts or .shosts. */
	231	snprintf(buf, sizeof buf, "%.500s/%.100s",
	232	pw->pw_dir, rhosts_files[rhosts_file_index]);
	233	if (stat(buf, &st) < 0)
	234	continue;
	235
aa3378df	236	/*
	237	* Make sure that the file is either owned by the user or by
	238	* root, and make sure it is not writable by anyone but the
	239	* owner. This is to help avoid novices accidentally
	240	* allowing access to their account by anyone.
	241	*/
5260325f	242	if (options.strict_modes &&
	243	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
	244	(st.st_mode & 022) != 0)) {
	245	log("Rhosts authentication refused for %.100s: bad modes for %.200s",
	246	pw->pw_name, buf);
	247	packet_send_debug("Bad file modes for %.200s", buf);
	248	continue;
	249	}
	250	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	251	if (options.ignore_rhosts) {
	252	packet_send_debug("Server has been configured to ignore %.100s.",
	253	rhosts_files[rhosts_file_index]);
	254	continue;
	255	}
	256	/* Check if authentication is permitted by the file. */
	257	if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
	258	packet_send_debug("Accepted by %.100s.",
	259	rhosts_files[rhosts_file_index]);
	260	/* Restore the privileged uid. */
	261	restore_uid();
	262	return 1;
	263	}
8efc0c15	264	}
8efc0c15	265
5260325f	266	/* Restore the privileged uid. */
	267	restore_uid();
	268	return 0;
8efc0c15	269	}