[openssh.git] / auth-rhosts.c

/* $OpenBSD: auth-rhosts.c,v 1.41 2006/08/03 03:34:41 deraadt Exp $ */
/*
 * 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"

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

#ifdef HAVE_NETGROUP_H
# include <netgroup.h>
#endif
#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>

#include "packet.h"
#include "buffer.h"
#include "uidswap.h"
#include "pathnames.h"
#include "log.h"
#include "servconf.h"
#include "canohost.h"
#include "key.h"
#include "hostfile.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
31652869	1	/* $OpenBSD: auth-rhosts.c,v 1.41 2006/08/03 03:34:41 deraadt Exp $ */
8efc0c15	2	/*
5260325f	3	* Author: Tatu Ylonen <ylo@cs.hut.fi>
5260325f	4	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5260325f	5	* All rights reserved
5260325f	6	* Rhosts authentication. This file contains code to check whether to admit
	7	* the login based on rhosts authentication. This file also processes
	8	* /etc/hosts.equiv.
6ae2364d	9	*
bcbf86ec	10	* As far as I am concerned, the code I have written for this software
	11	* can be used freely for any purpose. Any derived versions of this
	12	* software must be clearly marked as such, and if the derived work is
	13	* incompatible with the protocol description in the RFC file, it must be
	14	* called by a name other than "ssh" or "Secure Shell".
5260325f	15	*/
8efc0c15	16
8efc0c15	17	#include "includes.h"
4095f623	18
	19	#include <sys/types.h>
	20	#include <sys/stat.h>
c38f5d19	21
	22	#ifdef HAVE_NETGROUP_H
	23	# include <netgroup.h>
	24	#endif
b1842393	25	#include <pwd.h>
cf851879	26	#include <stdio.h>
00146caa	27	#include <string.h>
31652869	28	#include <stdarg.h>
8efc0c15	29
8efc0c15	30	#include "packet.h"
31652869	31	#include "buffer.h"
8efc0c15	32	#include "uidswap.h"
42f11eb2	33	#include "pathnames.h"
42f11eb2	34	#include "log.h"
6fa724bc	35	#include "servconf.h"
42f11eb2	36	#include "canohost.h"
31652869	37	#include "key.h"
31652869	38	#include "hostfile.h"
5ca51e19	39	#include "auth.h"
8efc0c15	40
8002af61	41	/* import */
8002af61	42	extern ServerOptions options;
b3ad3d88	43	extern int use_privsep;
8002af61	44
aa3378df	45	/*
	46	* This function processes an rhosts-style file (.rhosts, .shosts, or
	47	* /etc/hosts.equiv). This returns true if authentication can be granted
	48	* based on the file, and returns zero otherwise.
	49	*/
8efc0c15	50
396c147e	51	static int
5260325f	52	check_rhosts_file(const char filename, const char hostname,
	53	const char ipaddr, const char client_user,
	54	const char *server_user)
8efc0c15	55	{
5260325f	56	FILE *f;
	57	char buf[1024]; /* Must not be larger than host, user, dummy below. */
	58
	59	/* Open the .rhosts file, deny if unreadable */
	60	f = fopen(filename, "r");
	61	if (!f)
	62	return 0;
	63
5260325f	64	while (fgets(buf, sizeof(buf), f)) {
	65	/* All three must be at least as big as buf to avoid overflows. */
	66	char hostbuf[1024], userbuf[1024], dummy[1024], host, user, *cp;
	67	int negated;
	68
	69	for (cp = buf; cp == ' ' \|\| cp == '\t'; cp++)
	70	;
	71	if (cp == '#' \|\| cp == '\n' \|\| !*cp)
	72	continue;
	73
aa3378df	74	/*
	75	* NO_PLUS is supported at least on OSF/1. We skip it (we
	76	* don't ever support the plus syntax).
	77	*/
5260325f	78	if (strncmp(cp, "NO_PLUS", 7) == 0)
	79	continue;
	80
aa3378df	81	/*
	82	* This should be safe because each buffer is as big as the
	83	* whole string, and thus cannot be overwritten.
	84	*/
013b1214	85	switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
013b1214	86	dummy)) {
5260325f	87	case 0:
b3ad3d88	88	auth_debug_add("Found empty line in %.100s.", filename);
5260325f	89	continue;
	90	case 1:
	91	/* Host name only. */
	92	strlcpy(userbuf, server_user, sizeof(userbuf));
	93	break;
	94	case 2:
	95	/* Got both host and user name. */
	96	break;
	97	case 3:
b3ad3d88	98	auth_debug_add("Found garbage in %.100s.", filename);
5260325f	99	continue;
	100	default:
	101	/* Weird... */
	102	continue;
	103	}
	104
	105	host = hostbuf;
	106	user = userbuf;
	107	negated = 0;
	108
	109	/* Process negated host names, or positive netgroups. */
	110	if (host[0] == '-') {
	111	negated = 1;
	112	host++;
	113	} else if (host[0] == '+')
	114	host++;
	115
	116	if (user[0] == '-') {
	117	negated = 1;
	118	user++;
	119	} else if (user[0] == '+')
	120	user++;
	121
	122	/* Check for empty host/user names (particularly '+'). */
	123	if (!host[0] \|\| !user[0]) {
	124	/* We come here if either was '+' or '-'. */
b3ad3d88	125	auth_debug_add("Ignoring wild host/user names in %.100s.",
b3ad3d88	126	filename);
5260325f	127	continue;
	128	}
	129	/* Verify that host name matches. */
	130	if (host[0] == '@') {
	131	if (!innetgr(host + 1, hostname, NULL, NULL) &&
	132	!innetgr(host + 1, ipaddr, NULL, NULL))
	133	continue;
	134	} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
	135	continue; /* Different hostname. */
	136
	137	/* Verify that user name matches. */
	138	if (user[0] == '@') {
	139	if (!innetgr(user + 1, NULL, client_user, NULL))
	140	continue;
	141	} else if (strcmp(user, client_user) != 0)
	142	continue; /* Different username. */
	143
	144	/* Found the user and host. */
	145	fclose(f);
	146
	147	/* If the entry was negated, deny access. */
	148	if (negated) {
b3ad3d88	149	auth_debug_add("Matched negative entry in %.100s.",
4e2e5cfd	150	filename);
5260325f	151	return 0;
	152	}
	153	/* Accept authentication. */
	154	return 1;
8efc0c15	155	}
8efc0c15	156
5260325f	157	/* Authentication using this file denied. */
	158	fclose(f);
	159	return 0;
8efc0c15	160	}
8efc0c15	161
aa3378df	162	/*
	163	* Tries to authenticate the user using the .shosts or .rhosts file. Returns
	164	* true if authentication succeeds. If ignore_rhosts is true, only
	165	* /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
	166	*/
8efc0c15	167
6ae2364d	168	int
5260325f	169	auth_rhosts(struct passwd pw, const char client_user)
8efc0c15	170	{
5260325f	171	const char hostname, ipaddr;
8002af61	172
c5a7d788	173	hostname = get_canonical_hostname(options.use_dns);
8002af61	174	ipaddr = get_remote_ipaddr();
b3ad3d88	175	return auth_rhosts2(pw, client_user, hostname, ipaddr);
8002af61	176	}
8002af61	177
b3ad3d88	178	static int
b3ad3d88	179	auth_rhosts2_raw(struct passwd pw, const char client_user, const char *hostname,
8002af61	180	const char *ipaddr)
	181	{
	182	char buf[1024];
5260325f	183	struct stat st;
5260325f	184	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1e3b8b07	185	u_int rhosts_file_index;
5260325f	186
8002af61	187	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	188	client_user, hostname, ipaddr);
	189
5260325f	190	/* Switch to the user's uid. */
63bd8c36	191	temporarily_use_uid(pw);
aa3378df	192	/*
	193	* Quick check: if the user has no .shosts or .rhosts files, return
	194	* failure immediately without doing costly lookups from name
	195	* servers.
	196	*/
5260325f	197	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	198	rhosts_file_index++) {
5260325f	199	/* Check users .rhosts or .shosts. */
	200	snprintf(buf, sizeof buf, "%.500s/%.100s",
	201	pw->pw_dir, rhosts_files[rhosts_file_index]);
	202	if (stat(buf, &st) >= 0)
	203	break;
8efc0c15	204	}
5260325f	205	/* Switch back to privileged uid. */
	206	restore_uid();
	207
	208	/* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
	209	if (!rhosts_files[rhosts_file_index] &&
42f11eb2	210	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
42f11eb2	211	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
5260325f	212	return 0;
5260325f	213
5260325f	214	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
5260325f	215	if (pw->pw_uid != 0) {
184eed6a	216	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
184eed6a	217	client_user, pw->pw_name)) {
b3ad3d88	218	auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
184eed6a	219	hostname, ipaddr);
5260325f	220	return 1;
5260325f	221	}
184eed6a	222	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
184eed6a	223	client_user, pw->pw_name)) {
b3ad3d88	224	auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
184eed6a	225	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
5260325f	226	return 1;
5260325f	227	}
8efc0c15	228	}
aa3378df	229	/*
	230	* Check that the home directory is owned by root or the user, and is
	231	* not group or world writable.
	232	*/
5260325f	233	if (stat(pw->pw_dir, &st) < 0) {
bbe88b6d	234	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	235	"no home directory %.200s", pw->pw_name, pw->pw_dir);
	236	auth_debug_add("Rhosts authentication refused for %.100s: "
	237	"no home directory %.200s", pw->pw_name, pw->pw_dir);
5260325f	238	return 0;
8efc0c15	239	}
5260325f	240	if (options.strict_modes &&
5260325f	241	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	242	(st.st_mode & 022) != 0)) {
bbe88b6d	243	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	244	"bad ownership or modes for home directory.", pw->pw_name);
	245	auth_debug_add("Rhosts authentication refused for %.100s: "
	246	"bad ownership or modes for home directory.", pw->pw_name);
5260325f	247	return 0;
8efc0c15	248	}
5260325f	249	/* Temporarily use the user's uid. */
63bd8c36	250	temporarily_use_uid(pw);
5260325f	251
	252	/* Check all .rhosts files (currently .shosts and .rhosts). */
	253	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	254	rhosts_file_index++) {
5260325f	255	/* Check users .rhosts or .shosts. */
	256	snprintf(buf, sizeof buf, "%.500s/%.100s",
	257	pw->pw_dir, rhosts_files[rhosts_file_index]);
	258	if (stat(buf, &st) < 0)
	259	continue;
	260
aa3378df	261	/*
	262	* Make sure that the file is either owned by the user or by
	263	* root, and make sure it is not writable by anyone but the
	264	* owner. This is to help avoid novices accidentally
	265	* allowing access to their account by anyone.
	266	*/
5260325f	267	if (options.strict_modes &&
5260325f	268	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	269	(st.st_mode & 022) != 0)) {
bbe88b6d	270	logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
5260325f	271	pw->pw_name, buf);
b3ad3d88	272	auth_debug_add("Bad file modes for %.200s", buf);
5260325f	273	continue;
	274	}
	275	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	276	if (options.ignore_rhosts) {
b3ad3d88	277	auth_debug_add("Server has been configured to ignore %.100s.",
b3ad3d88	278	rhosts_files[rhosts_file_index]);
5260325f	279	continue;
	280	}
	281	/* Check if authentication is permitted by the file. */
	282	if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
b3ad3d88	283	auth_debug_add("Accepted by %.100s.",
b3ad3d88	284	rhosts_files[rhosts_file_index]);
5260325f	285	/* Restore the privileged uid. */
5260325f	286	restore_uid();
b3ad3d88	287	auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
b3ad3d88	288	hostname, ipaddr, client_user, pw->pw_name);
5260325f	289	return 1;
5260325f	290	}
8efc0c15	291	}
8efc0c15	292
5260325f	293	/* Restore the privileged uid. */
	294	restore_uid();
	295	return 0;
8efc0c15	296	}
b3ad3d88	297
	298	int
	299	auth_rhosts2(struct passwd pw, const char client_user, const char *hostname,
	300	const char *ipaddr)
	301	{
	302	int ret;
	303
	304	auth_debug_reset();
	305	ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
	306	if (!use_privsep)
	307	auth_debug_send();
	308	return ret;
	309	}