[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 1.27 2002/03/04 12:43:06 markus Exp $");

#include "packet.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.verify_reverse_mapping);
	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
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"
fa1eb020	17	RCSID("$OpenBSD: auth-rhosts.c,v 1.27 2002/03/04 12:43:06 markus Exp $");
8efc0c15	18
8efc0c15	19	#include "packet.h"
8efc0c15	20	#include "uidswap.h"
42f11eb2	21	#include "pathnames.h"
42f11eb2	22	#include "log.h"
6fa724bc	23	#include "servconf.h"
42f11eb2	24	#include "canohost.h"
5ca51e19	25	#include "auth.h"
8efc0c15	26
8002af61	27	/* import */
	28	extern ServerOptions options;
	29
aa3378df	30	/*
	31	* This function processes an rhosts-style file (.rhosts, .shosts, or
	32	* /etc/hosts.equiv). This returns true if authentication can be granted
	33	* based on the file, and returns zero otherwise.
	34	*/
8efc0c15	35
396c147e	36	static int
5260325f	37	check_rhosts_file(const char filename, const char hostname,
	38	const char ipaddr, const char client_user,
	39	const char *server_user)
8efc0c15	40	{
5260325f	41	FILE *f;
	42	char buf[1024]; /* Must not be larger than host, user, dummy below. */
	43
	44	/* Open the .rhosts file, deny if unreadable */
	45	f = fopen(filename, "r");
	46	if (!f)
	47	return 0;
	48
5260325f	49	while (fgets(buf, sizeof(buf), f)) {
	50	/* All three must be at least as big as buf to avoid overflows. */
	51	char hostbuf[1024], userbuf[1024], dummy[1024], host, user, *cp;
	52	int negated;
	53
	54	for (cp = buf; cp == ' ' \|\| cp == '\t'; cp++)
	55	;
	56	if (cp == '#' \|\| cp == '\n' \|\| !*cp)
	57	continue;
	58
aa3378df	59	/*
	60	* NO_PLUS is supported at least on OSF/1. We skip it (we
	61	* don't ever support the plus syntax).
	62	*/
5260325f	63	if (strncmp(cp, "NO_PLUS", 7) == 0)
	64	continue;
	65
aa3378df	66	/*
	67	* This should be safe because each buffer is as big as the
	68	* whole string, and thus cannot be overwritten.
	69	*/
5260325f	70	switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) {
	71	case 0:
	72	packet_send_debug("Found empty line in %.100s.", filename);
	73	continue;
	74	case 1:
	75	/* Host name only. */
	76	strlcpy(userbuf, server_user, sizeof(userbuf));
	77	break;
	78	case 2:
	79	/* Got both host and user name. */
	80	break;
	81	case 3:
	82	packet_send_debug("Found garbage in %.100s.", filename);
	83	continue;
	84	default:
	85	/* Weird... */
	86	continue;
	87	}
	88
	89	host = hostbuf;
	90	user = userbuf;
	91	negated = 0;
	92
	93	/* Process negated host names, or positive netgroups. */
	94	if (host[0] == '-') {
	95	negated = 1;
	96	host++;
	97	} else if (host[0] == '+')
	98	host++;
	99
	100	if (user[0] == '-') {
	101	negated = 1;
	102	user++;
	103	} else if (user[0] == '+')
	104	user++;
	105
	106	/* Check for empty host/user names (particularly '+'). */
	107	if (!host[0] \|\| !user[0]) {
	108	/* We come here if either was '+' or '-'. */
	109	packet_send_debug("Ignoring wild host/user names in %.100s.",
	110	filename);
	111	continue;
	112	}
	113	/* Verify that host name matches. */
	114	if (host[0] == '@') {
	115	if (!innetgr(host + 1, hostname, NULL, NULL) &&
	116	!innetgr(host + 1, ipaddr, NULL, NULL))
	117	continue;
	118	} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
	119	continue; /* Different hostname. */
	120
	121	/* Verify that user name matches. */
	122	if (user[0] == '@') {
	123	if (!innetgr(user + 1, NULL, client_user, NULL))
	124	continue;
	125	} else if (strcmp(user, client_user) != 0)
	126	continue; /* Different username. */
	127
	128	/* Found the user and host. */
	129	fclose(f);
	130
	131	/* If the entry was negated, deny access. */
	132	if (negated) {
	133	packet_send_debug("Matched negative entry in %.100s.",
134	filename);
135	return 0;
136	}
137	/* Accept authentication. */
138	return 1;
8efc0c15	139	}
8efc0c15	140
5260325f	141	/* Authentication using this file denied. */
	142	fclose(f);
	143	return 0;
8efc0c15	144	}
8efc0c15	145
aa3378df	146	/*
	147	* Tries to authenticate the user using the .shosts or .rhosts file. Returns
	148	* true if authentication succeeds. If ignore_rhosts is true, only
	149	* /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
	150	*/
8efc0c15	151
6ae2364d	152	int
5260325f	153	auth_rhosts(struct passwd pw, const char client_user)
8efc0c15	154	{
5260325f	155	const char hostname, ipaddr;
8002af61	156	int ret;
8002af61	157
bf4c5edc	158	hostname = get_canonical_hostname(options.verify_reverse_mapping);
8002af61	159	ipaddr = get_remote_ipaddr();
	160	ret = auth_rhosts2(pw, client_user, hostname, ipaddr);
	161	return ret;
	162	}
	163
	164	int
	165	auth_rhosts2(struct passwd pw, const char client_user, const char *hostname,
	166	const char *ipaddr)
	167	{
	168	char buf[1024];
5260325f	169	struct stat st;
5260325f	170	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1e3b8b07	171	u_int rhosts_file_index;
5260325f	172
8002af61	173	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	174	client_user, hostname, ipaddr);
	175
94ec8c6b	176	/* no user given */
	177	if (pw == NULL)
	178	return 0;
8002af61	179
5260325f	180	/* Switch to the user's uid. */
63bd8c36	181	temporarily_use_uid(pw);
aa3378df	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	*/
5260325f	187	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	188	rhosts_file_index++) {
5260325f	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;
8efc0c15	194	}
5260325f	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] &&
42f11eb2	200	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
42f11eb2	201	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
5260325f	202	return 0;
5260325f	203
5260325f	204	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
5260325f	205	if (pw->pw_uid != 0) {
184eed6a	206	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
184eed6a	207	client_user, pw->pw_name)) {
5260325f	208	packet_send_debug("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
184eed6a	209	hostname, ipaddr);
5260325f	210	return 1;
5260325f	211	}
184eed6a	212	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
184eed6a	213	client_user, pw->pw_name)) {
5260325f	214	packet_send_debug("Accepted for %.100s [%.100s] by %.100s.",
184eed6a	215	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
5260325f	216	return 1;
5260325f	217	}
8efc0c15	218	}
aa3378df	219	/*
	220	* Check that the home directory is owned by root or the user, and is
	221	* not group or world writable.
	222	*/
5260325f	223	if (stat(pw->pw_dir, &st) < 0) {
	224	log("Rhosts authentication refused for %.100s: no home directory %.200s",
	225	pw->pw_name, pw->pw_dir);
00e6dd70	226	packet_send_debug("Rhosts authentication refused for %.100s: no home directory %.200s",
5260325f	227	pw->pw_name, pw->pw_dir);
5260325f	228	return 0;
8efc0c15	229	}
5260325f	230	if (options.strict_modes &&
5260325f	231	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	232	(st.st_mode & 022) != 0)) {
5260325f	233	log("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
	234	pw->pw_name);
	235	packet_send_debug("Rhosts authentication refused for %.100s: bad ownership or modes for home directory.",
	236	pw->pw_name);
	237	return 0;
8efc0c15	238	}
5260325f	239	/* Temporarily use the user's uid. */
63bd8c36	240	temporarily_use_uid(pw);
5260325f	241
	242	/* Check all .rhosts files (currently .shosts and .rhosts). */
	243	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	244	rhosts_file_index++) {
5260325f	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
aa3378df	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	*/
5260325f	257	if (options.strict_modes &&
5260325f	258	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	259	(st.st_mode & 022) != 0)) {
5260325f	260	log("Rhosts authentication refused for %.100s: bad modes for %.200s",
	261	pw->pw_name, buf);
	262	packet_send_debug("Bad file modes for %.200s", buf);
	263	continue;
	264	}
	265	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	266	if (options.ignore_rhosts) {
	267	packet_send_debug("Server has been configured to ignore %.100s.",
	268	rhosts_files[rhosts_file_index]);
	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)) {
	273	packet_send_debug("Accepted by %.100s.",
	274	rhosts_files[rhosts_file_index]);
	275	/* Restore the privileged uid. */
	276	restore_uid();
	277	return 1;
	278	}
8efc0c15	279	}
8efc0c15	280
5260325f	281	/* Restore the privileged uid. */
	282	restore_uid();
	283	return 0;
8efc0c15	284	}