[openssh.git] / auth-rhosts.c

/* $OpenBSD: auth-rhosts.c,v 1.40 2006/08/01 23:22:47 stevesk 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 "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
cf851879	1	/* $OpenBSD: auth-rhosts.c,v 1.40 2006/08/01 23:22:47 stevesk 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>
8efc0c15	28
8efc0c15	29	#include "packet.h"
8efc0c15	30	#include "uidswap.h"
42f11eb2	31	#include "pathnames.h"
42f11eb2	32	#include "log.h"
6fa724bc	33	#include "servconf.h"
42f11eb2	34	#include "canohost.h"
5ca51e19	35	#include "auth.h"
8efc0c15	36
8002af61	37	/* import */
8002af61	38	extern ServerOptions options;
b3ad3d88	39	extern int use_privsep;
8002af61	40
aa3378df	41	/*
	42	* This function processes an rhosts-style file (.rhosts, .shosts, or
	43	* /etc/hosts.equiv). This returns true if authentication can be granted
	44	* based on the file, and returns zero otherwise.
	45	*/
8efc0c15	46
396c147e	47	static int
5260325f	48	check_rhosts_file(const char filename, const char hostname,
	49	const char ipaddr, const char client_user,
	50	const char *server_user)
8efc0c15	51	{
5260325f	52	FILE *f;
	53	char buf[1024]; /* Must not be larger than host, user, dummy below. */
	54
	55	/* Open the .rhosts file, deny if unreadable */
	56	f = fopen(filename, "r");
	57	if (!f)
	58	return 0;
	59
5260325f	60	while (fgets(buf, sizeof(buf), f)) {
	61	/* All three must be at least as big as buf to avoid overflows. */
	62	char hostbuf[1024], userbuf[1024], dummy[1024], host, user, *cp;
	63	int negated;
	64
	65	for (cp = buf; cp == ' ' \|\| cp == '\t'; cp++)
	66	;
	67	if (cp == '#' \|\| cp == '\n' \|\| !*cp)
	68	continue;
	69
aa3378df	70	/*
	71	* NO_PLUS is supported at least on OSF/1. We skip it (we
	72	* don't ever support the plus syntax).
	73	*/
5260325f	74	if (strncmp(cp, "NO_PLUS", 7) == 0)
	75	continue;
	76
aa3378df	77	/*
	78	* This should be safe because each buffer is as big as the
	79	* whole string, and thus cannot be overwritten.
	80	*/
013b1214	81	switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
013b1214	82	dummy)) {
5260325f	83	case 0:
b3ad3d88	84	auth_debug_add("Found empty line in %.100s.", filename);
5260325f	85	continue;
	86	case 1:
	87	/* Host name only. */
	88	strlcpy(userbuf, server_user, sizeof(userbuf));
	89	break;
	90	case 2:
	91	/* Got both host and user name. */
	92	break;
	93	case 3:
b3ad3d88	94	auth_debug_add("Found garbage in %.100s.", filename);
5260325f	95	continue;
	96	default:
	97	/* Weird... */
	98	continue;
	99	}
	100
	101	host = hostbuf;
	102	user = userbuf;
	103	negated = 0;
	104
	105	/* Process negated host names, or positive netgroups. */
	106	if (host[0] == '-') {
	107	negated = 1;
	108	host++;
	109	} else if (host[0] == '+')
	110	host++;
	111
	112	if (user[0] == '-') {
	113	negated = 1;
	114	user++;
	115	} else if (user[0] == '+')
	116	user++;
	117
	118	/* Check for empty host/user names (particularly '+'). */
	119	if (!host[0] \|\| !user[0]) {
	120	/* We come here if either was '+' or '-'. */
b3ad3d88	121	auth_debug_add("Ignoring wild host/user names in %.100s.",
b3ad3d88	122	filename);
5260325f	123	continue;
	124	}
	125	/* Verify that host name matches. */
	126	if (host[0] == '@') {
	127	if (!innetgr(host + 1, hostname, NULL, NULL) &&
	128	!innetgr(host + 1, ipaddr, NULL, NULL))
	129	continue;
	130	} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
	131	continue; /* Different hostname. */
	132
	133	/* Verify that user name matches. */
	134	if (user[0] == '@') {
	135	if (!innetgr(user + 1, NULL, client_user, NULL))
	136	continue;
	137	} else if (strcmp(user, client_user) != 0)
	138	continue; /* Different username. */
	139
	140	/* Found the user and host. */
	141	fclose(f);
	142
	143	/* If the entry was negated, deny access. */
	144	if (negated) {
b3ad3d88	145	auth_debug_add("Matched negative entry in %.100s.",
4e2e5cfd	146	filename);
5260325f	147	return 0;
	148	}
	149	/* Accept authentication. */
	150	return 1;
8efc0c15	151	}
8efc0c15	152
5260325f	153	/* Authentication using this file denied. */
	154	fclose(f);
	155	return 0;
8efc0c15	156	}
8efc0c15	157
aa3378df	158	/*
	159	* Tries to authenticate the user using the .shosts or .rhosts file. Returns
	160	* true if authentication succeeds. If ignore_rhosts is true, only
	161	* /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
	162	*/
8efc0c15	163
6ae2364d	164	int
5260325f	165	auth_rhosts(struct passwd pw, const char client_user)
8efc0c15	166	{
5260325f	167	const char hostname, ipaddr;
8002af61	168
c5a7d788	169	hostname = get_canonical_hostname(options.use_dns);
8002af61	170	ipaddr = get_remote_ipaddr();
b3ad3d88	171	return auth_rhosts2(pw, client_user, hostname, ipaddr);
8002af61	172	}
8002af61	173
b3ad3d88	174	static int
b3ad3d88	175	auth_rhosts2_raw(struct passwd pw, const char client_user, const char *hostname,
8002af61	176	const char *ipaddr)
	177	{
	178	char buf[1024];
5260325f	179	struct stat st;
5260325f	180	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1e3b8b07	181	u_int rhosts_file_index;
5260325f	182
8002af61	183	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	184	client_user, hostname, ipaddr);
	185
5260325f	186	/* Switch to the user's uid. */
63bd8c36	187	temporarily_use_uid(pw);
aa3378df	188	/*
	189	* Quick check: if the user has no .shosts or .rhosts files, return
	190	* failure immediately without doing costly lookups from name
	191	* servers.
	192	*/
5260325f	193	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	194	rhosts_file_index++) {
5260325f	195	/* Check users .rhosts or .shosts. */
	196	snprintf(buf, sizeof buf, "%.500s/%.100s",
	197	pw->pw_dir, rhosts_files[rhosts_file_index]);
	198	if (stat(buf, &st) >= 0)
	199	break;
8efc0c15	200	}
5260325f	201	/* Switch back to privileged uid. */
	202	restore_uid();
	203
	204	/* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
	205	if (!rhosts_files[rhosts_file_index] &&
42f11eb2	206	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
42f11eb2	207	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
5260325f	208	return 0;
5260325f	209
5260325f	210	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
5260325f	211	if (pw->pw_uid != 0) {
184eed6a	212	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
184eed6a	213	client_user, pw->pw_name)) {
b3ad3d88	214	auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
184eed6a	215	hostname, ipaddr);
5260325f	216	return 1;
5260325f	217	}
184eed6a	218	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
184eed6a	219	client_user, pw->pw_name)) {
b3ad3d88	220	auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
184eed6a	221	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
5260325f	222	return 1;
5260325f	223	}
8efc0c15	224	}
aa3378df	225	/*
	226	* Check that the home directory is owned by root or the user, and is
	227	* not group or world writable.
	228	*/
5260325f	229	if (stat(pw->pw_dir, &st) < 0) {
bbe88b6d	230	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	231	"no home directory %.200s", pw->pw_name, pw->pw_dir);
	232	auth_debug_add("Rhosts authentication refused for %.100s: "
	233	"no home directory %.200s", pw->pw_name, pw->pw_dir);
5260325f	234	return 0;
8efc0c15	235	}
5260325f	236	if (options.strict_modes &&
5260325f	237	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	238	(st.st_mode & 022) != 0)) {
bbe88b6d	239	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	240	"bad ownership or modes for home directory.", pw->pw_name);
	241	auth_debug_add("Rhosts authentication refused for %.100s: "
	242	"bad ownership or modes for home directory.", pw->pw_name);
5260325f	243	return 0;
8efc0c15	244	}
5260325f	245	/* Temporarily use the user's uid. */
63bd8c36	246	temporarily_use_uid(pw);
5260325f	247
	248	/* Check all .rhosts files (currently .shosts and .rhosts). */
	249	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	250	rhosts_file_index++) {
5260325f	251	/* Check users .rhosts or .shosts. */
	252	snprintf(buf, sizeof buf, "%.500s/%.100s",
	253	pw->pw_dir, rhosts_files[rhosts_file_index]);
	254	if (stat(buf, &st) < 0)
	255	continue;
	256
aa3378df	257	/*
	258	* Make sure that the file is either owned by the user or by
	259	* root, and make sure it is not writable by anyone but the
	260	* owner. This is to help avoid novices accidentally
	261	* allowing access to their account by anyone.
	262	*/
5260325f	263	if (options.strict_modes &&
5260325f	264	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	265	(st.st_mode & 022) != 0)) {
bbe88b6d	266	logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
5260325f	267	pw->pw_name, buf);
b3ad3d88	268	auth_debug_add("Bad file modes for %.200s", buf);
5260325f	269	continue;
	270	}
	271	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	272	if (options.ignore_rhosts) {
b3ad3d88	273	auth_debug_add("Server has been configured to ignore %.100s.",
b3ad3d88	274	rhosts_files[rhosts_file_index]);
5260325f	275	continue;
	276	}
	277	/* Check if authentication is permitted by the file. */
	278	if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
b3ad3d88	279	auth_debug_add("Accepted by %.100s.",
b3ad3d88	280	rhosts_files[rhosts_file_index]);
5260325f	281	/* Restore the privileged uid. */
5260325f	282	restore_uid();
b3ad3d88	283	auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
b3ad3d88	284	hostname, ipaddr, client_user, pw->pw_name);
5260325f	285	return 1;
5260325f	286	}
8efc0c15	287	}
8efc0c15	288
5260325f	289	/* Restore the privileged uid. */
	290	restore_uid();
	291	return 0;
8efc0c15	292	}
b3ad3d88	293
	294	int
	295	auth_rhosts2(struct passwd pw, const char client_user, const char *hostname,
	296	const char *ipaddr)
	297	{
	298	int ret;
	299
	300	auth_debug_reset();
	301	ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
	302	if (!use_privsep)
	303	auth_debug_send();
	304	return ret;
	305	}