[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 1.35 2006/02/20 17:19:53 stevesk Exp $");

#include <sys/types.h>
#include <sys/stat.h>

#ifdef HAVE_NETGROUP_H
# include <netgroup.h>
#endif

#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;
extern int use_privsep;

/*
 * 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, "%1023s %1023s %1023s", hostbuf, userbuf,
		    dummy)) {
		case 0:
			auth_debug_add("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:
			auth_debug_add("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 '-'. */
			auth_debug_add("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) {
			auth_debug_add("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;

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

static int
auth_rhosts2_raw(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);

	/* 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)) {
			auth_debug_add("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)) {
			auth_debug_add("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) {
		logit("Rhosts authentication refused for %.100s: "
		    "no home directory %.200s", pw->pw_name, pw->pw_dir);
		auth_debug_add("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)) {
		logit("Rhosts authentication refused for %.100s: "
		    "bad ownership or modes for home directory.", pw->pw_name);
		auth_debug_add("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)) {
			logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
			    pw->pw_name, buf);
			auth_debug_add("Bad file modes for %.200s", buf);
			continue;
		}
		/* Check if we have been configured to ignore .rhosts and .shosts files. */
		if (options.ignore_rhosts) {
			auth_debug_add("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)) {
			auth_debug_add("Accepted by %.100s.",
			    rhosts_files[rhosts_file_index]);
			/* Restore the privileged uid. */
			restore_uid();
			auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
				hostname, ipaddr, client_user, pw->pw_name);
			return 1;
		}
	}

	/* Restore the privileged uid. */
	restore_uid();
	return 0;
}

int
auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
    const char *ipaddr)
{
	int ret;

	auth_debug_reset();
	ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
	if (!use_privsep)
		auth_debug_send();
	return ret;
}
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"
4095f623	17	RCSID("$OpenBSD: auth-rhosts.c,v 1.35 2006/02/20 17:19:53 stevesk Exp $");
	18
	19	#include <sys/types.h>
	20	#include <sys/stat.h>
c38f5d19	21
	22	#ifdef HAVE_NETGROUP_H
	23	# include <netgroup.h>
	24	#endif
8efc0c15	25
8efc0c15	26	#include "packet.h"
8efc0c15	27	#include "uidswap.h"
42f11eb2	28	#include "pathnames.h"
42f11eb2	29	#include "log.h"
6fa724bc	30	#include "servconf.h"
42f11eb2	31	#include "canohost.h"
5ca51e19	32	#include "auth.h"
8efc0c15	33
8002af61	34	/* import */
8002af61	35	extern ServerOptions options;
b3ad3d88	36	extern int use_privsep;
8002af61	37
aa3378df	38	/*
	39	* This function processes an rhosts-style file (.rhosts, .shosts, or
	40	* /etc/hosts.equiv). This returns true if authentication can be granted
	41	* based on the file, and returns zero otherwise.
	42	*/
8efc0c15	43
396c147e	44	static int
5260325f	45	check_rhosts_file(const char filename, const char hostname,
	46	const char ipaddr, const char client_user,
	47	const char *server_user)
8efc0c15	48	{
5260325f	49	FILE *f;
	50	char buf[1024]; /* Must not be larger than host, user, dummy below. */
	51
	52	/* Open the .rhosts file, deny if unreadable */
	53	f = fopen(filename, "r");
	54	if (!f)
	55	return 0;
	56
5260325f	57	while (fgets(buf, sizeof(buf), f)) {
	58	/* All three must be at least as big as buf to avoid overflows. */
	59	char hostbuf[1024], userbuf[1024], dummy[1024], host, user, *cp;
	60	int negated;
	61
	62	for (cp = buf; cp == ' ' \|\| cp == '\t'; cp++)
	63	;
	64	if (cp == '#' \|\| cp == '\n' \|\| !*cp)
	65	continue;
	66
aa3378df	67	/*
	68	* NO_PLUS is supported at least on OSF/1. We skip it (we
	69	* don't ever support the plus syntax).
	70	*/
5260325f	71	if (strncmp(cp, "NO_PLUS", 7) == 0)
	72	continue;
	73
aa3378df	74	/*
	75	* This should be safe because each buffer is as big as the
	76	* whole string, and thus cannot be overwritten.
	77	*/
013b1214	78	switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
013b1214	79	dummy)) {
5260325f	80	case 0:
b3ad3d88	81	auth_debug_add("Found empty line in %.100s.", filename);
5260325f	82	continue;
	83	case 1:
	84	/* Host name only. */
	85	strlcpy(userbuf, server_user, sizeof(userbuf));
	86	break;
	87	case 2:
	88	/* Got both host and user name. */
	89	break;
	90	case 3:
b3ad3d88	91	auth_debug_add("Found garbage in %.100s.", filename);
5260325f	92	continue;
	93	default:
	94	/* Weird... */
	95	continue;
	96	}
	97
	98	host = hostbuf;
	99	user = userbuf;
	100	negated = 0;
	101
	102	/* Process negated host names, or positive netgroups. */
	103	if (host[0] == '-') {
	104	negated = 1;
	105	host++;
	106	} else if (host[0] == '+')
	107	host++;
	108
	109	if (user[0] == '-') {
	110	negated = 1;
	111	user++;
	112	} else if (user[0] == '+')
	113	user++;
	114
	115	/* Check for empty host/user names (particularly '+'). */
	116	if (!host[0] \|\| !user[0]) {
	117	/* We come here if either was '+' or '-'. */
b3ad3d88	118	auth_debug_add("Ignoring wild host/user names in %.100s.",
b3ad3d88	119	filename);
5260325f	120	continue;
	121	}
	122	/* Verify that host name matches. */
	123	if (host[0] == '@') {
	124	if (!innetgr(host + 1, hostname, NULL, NULL) &&
	125	!innetgr(host + 1, ipaddr, NULL, NULL))
	126	continue;
	127	} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
	128	continue; /* Different hostname. */
	129
	130	/* Verify that user name matches. */
	131	if (user[0] == '@') {
	132	if (!innetgr(user + 1, NULL, client_user, NULL))
	133	continue;
	134	} else if (strcmp(user, client_user) != 0)
	135	continue; /* Different username. */
	136
	137	/* Found the user and host. */
	138	fclose(f);
	139
	140	/* If the entry was negated, deny access. */
	141	if (negated) {
b3ad3d88	142	auth_debug_add("Matched negative entry in %.100s.",
4e2e5cfd	143	filename);
5260325f	144	return 0;
	145	}
	146	/* Accept authentication. */
	147	return 1;
8efc0c15	148	}
8efc0c15	149
5260325f	150	/* Authentication using this file denied. */
	151	fclose(f);
	152	return 0;
8efc0c15	153	}
8efc0c15	154
aa3378df	155	/*
	156	* Tries to authenticate the user using the .shosts or .rhosts file. Returns
	157	* true if authentication succeeds. If ignore_rhosts is true, only
	158	* /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
	159	*/
8efc0c15	160
6ae2364d	161	int
5260325f	162	auth_rhosts(struct passwd pw, const char client_user)
8efc0c15	163	{
5260325f	164	const char hostname, ipaddr;
8002af61	165
c5a7d788	166	hostname = get_canonical_hostname(options.use_dns);
8002af61	167	ipaddr = get_remote_ipaddr();
b3ad3d88	168	return auth_rhosts2(pw, client_user, hostname, ipaddr);
8002af61	169	}
8002af61	170
b3ad3d88	171	static int
b3ad3d88	172	auth_rhosts2_raw(struct passwd pw, const char client_user, const char *hostname,
8002af61	173	const char *ipaddr)
	174	{
	175	char buf[1024];
5260325f	176	struct stat st;
5260325f	177	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1e3b8b07	178	u_int rhosts_file_index;
5260325f	179
8002af61	180	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	181	client_user, hostname, ipaddr);
	182
5260325f	183	/* Switch to the user's uid. */
63bd8c36	184	temporarily_use_uid(pw);
aa3378df	185	/*
	186	* Quick check: if the user has no .shosts or .rhosts files, return
	187	* failure immediately without doing costly lookups from name
	188	* servers.
	189	*/
5260325f	190	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	191	rhosts_file_index++) {
5260325f	192	/* Check users .rhosts or .shosts. */
	193	snprintf(buf, sizeof buf, "%.500s/%.100s",
	194	pw->pw_dir, rhosts_files[rhosts_file_index]);
	195	if (stat(buf, &st) >= 0)
	196	break;
8efc0c15	197	}
5260325f	198	/* Switch back to privileged uid. */
	199	restore_uid();
	200
	201	/* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
	202	if (!rhosts_files[rhosts_file_index] &&
42f11eb2	203	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
42f11eb2	204	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
5260325f	205	return 0;
5260325f	206
5260325f	207	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
5260325f	208	if (pw->pw_uid != 0) {
184eed6a	209	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
184eed6a	210	client_user, pw->pw_name)) {
b3ad3d88	211	auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
184eed6a	212	hostname, ipaddr);
5260325f	213	return 1;
5260325f	214	}
184eed6a	215	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
184eed6a	216	client_user, pw->pw_name)) {
b3ad3d88	217	auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
184eed6a	218	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
5260325f	219	return 1;
5260325f	220	}
8efc0c15	221	}
aa3378df	222	/*
	223	* Check that the home directory is owned by root or the user, and is
	224	* not group or world writable.
	225	*/
5260325f	226	if (stat(pw->pw_dir, &st) < 0) {
bbe88b6d	227	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	228	"no home directory %.200s", pw->pw_name, pw->pw_dir);
	229	auth_debug_add("Rhosts authentication refused for %.100s: "
	230	"no home directory %.200s", pw->pw_name, pw->pw_dir);
5260325f	231	return 0;
8efc0c15	232	}
5260325f	233	if (options.strict_modes &&
5260325f	234	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	235	(st.st_mode & 022) != 0)) {
bbe88b6d	236	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	237	"bad ownership or modes for home directory.", pw->pw_name);
	238	auth_debug_add("Rhosts authentication refused for %.100s: "
	239	"bad ownership or modes for home directory.", pw->pw_name);
5260325f	240	return 0;
8efc0c15	241	}
5260325f	242	/* Temporarily use the user's uid. */
63bd8c36	243	temporarily_use_uid(pw);
5260325f	244
	245	/* Check all .rhosts files (currently .shosts and .rhosts). */
	246	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	247	rhosts_file_index++) {
5260325f	248	/* Check users .rhosts or .shosts. */
	249	snprintf(buf, sizeof buf, "%.500s/%.100s",
	250	pw->pw_dir, rhosts_files[rhosts_file_index]);
	251	if (stat(buf, &st) < 0)
	252	continue;
	253
aa3378df	254	/*
	255	* Make sure that the file is either owned by the user or by
	256	* root, and make sure it is not writable by anyone but the
	257	* owner. This is to help avoid novices accidentally
	258	* allowing access to their account by anyone.
	259	*/
5260325f	260	if (options.strict_modes &&
5260325f	261	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	262	(st.st_mode & 022) != 0)) {
bbe88b6d	263	logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
5260325f	264	pw->pw_name, buf);
b3ad3d88	265	auth_debug_add("Bad file modes for %.200s", buf);
5260325f	266	continue;
	267	}
	268	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	269	if (options.ignore_rhosts) {
b3ad3d88	270	auth_debug_add("Server has been configured to ignore %.100s.",
b3ad3d88	271	rhosts_files[rhosts_file_index]);
5260325f	272	continue;
	273	}
	274	/* Check if authentication is permitted by the file. */
	275	if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
b3ad3d88	276	auth_debug_add("Accepted by %.100s.",
b3ad3d88	277	rhosts_files[rhosts_file_index]);
5260325f	278	/* Restore the privileged uid. */
5260325f	279	restore_uid();
b3ad3d88	280	auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
b3ad3d88	281	hostname, ipaddr, client_user, pw->pw_name);
5260325f	282	return 1;
5260325f	283	}
8efc0c15	284	}
8efc0c15	285
5260325f	286	/* Restore the privileged uid. */
	287	restore_uid();
	288	return 0;
8efc0c15	289	}
b3ad3d88	290
	291	int
	292	auth_rhosts2(struct passwd pw, const char client_user, const char *hostname,
	293	const char *ipaddr)
	294	{
	295	int ret;
	296
	297	auth_debug_reset();
	298	ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
	299	if (!use_privsep)
	300	auth_debug_send();
	301	return ret;
	302	}