[openssh.git] / auth-rhosts.c

/* $OpenBSD: auth-rhosts.c,v 1.38 2006/07/06 16:03:53 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 "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
b1842393	1	/* $OpenBSD: auth-rhosts.c,v 1.38 2006/07/06 16:03:53 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>
8efc0c15	26
8efc0c15	27	#include "packet.h"
8efc0c15	28	#include "uidswap.h"
42f11eb2	29	#include "pathnames.h"
42f11eb2	30	#include "log.h"
6fa724bc	31	#include "servconf.h"
42f11eb2	32	#include "canohost.h"
5ca51e19	33	#include "auth.h"
8efc0c15	34
8002af61	35	/* import */
8002af61	36	extern ServerOptions options;
b3ad3d88	37	extern int use_privsep;
8002af61	38
aa3378df	39	/*
	40	* This function processes an rhosts-style file (.rhosts, .shosts, or
	41	* /etc/hosts.equiv). This returns true if authentication can be granted
	42	* based on the file, and returns zero otherwise.
	43	*/
8efc0c15	44
396c147e	45	static int
5260325f	46	check_rhosts_file(const char filename, const char hostname,
	47	const char ipaddr, const char client_user,
	48	const char *server_user)
8efc0c15	49	{
5260325f	50	FILE *f;
	51	char buf[1024]; /* Must not be larger than host, user, dummy below. */
	52
	53	/* Open the .rhosts file, deny if unreadable */
	54	f = fopen(filename, "r");
	55	if (!f)
	56	return 0;
	57
5260325f	58	while (fgets(buf, sizeof(buf), f)) {
	59	/* All three must be at least as big as buf to avoid overflows. */
	60	char hostbuf[1024], userbuf[1024], dummy[1024], host, user, *cp;
	61	int negated;
	62
	63	for (cp = buf; cp == ' ' \|\| cp == '\t'; cp++)
	64	;
	65	if (cp == '#' \|\| cp == '\n' \|\| !*cp)
	66	continue;
	67
aa3378df	68	/*
	69	* NO_PLUS is supported at least on OSF/1. We skip it (we
	70	* don't ever support the plus syntax).
	71	*/
5260325f	72	if (strncmp(cp, "NO_PLUS", 7) == 0)
	73	continue;
	74
aa3378df	75	/*
	76	* This should be safe because each buffer is as big as the
	77	* whole string, and thus cannot be overwritten.
	78	*/
013b1214	79	switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
013b1214	80	dummy)) {
5260325f	81	case 0:
b3ad3d88	82	auth_debug_add("Found empty line in %.100s.", filename);
5260325f	83	continue;
	84	case 1:
	85	/* Host name only. */
	86	strlcpy(userbuf, server_user, sizeof(userbuf));
	87	break;
	88	case 2:
	89	/* Got both host and user name. */
	90	break;
	91	case 3:
b3ad3d88	92	auth_debug_add("Found garbage in %.100s.", filename);
5260325f	93	continue;
	94	default:
	95	/* Weird... */
	96	continue;
	97	}
	98
	99	host = hostbuf;
	100	user = userbuf;
	101	negated = 0;
	102
	103	/* Process negated host names, or positive netgroups. */
	104	if (host[0] == '-') {
	105	negated = 1;
	106	host++;
	107	} else if (host[0] == '+')
	108	host++;
	109
	110	if (user[0] == '-') {
	111	negated = 1;
	112	user++;
	113	} else if (user[0] == '+')
	114	user++;
	115
	116	/* Check for empty host/user names (particularly '+'). */
	117	if (!host[0] \|\| !user[0]) {
	118	/* We come here if either was '+' or '-'. */
b3ad3d88	119	auth_debug_add("Ignoring wild host/user names in %.100s.",
b3ad3d88	120	filename);
5260325f	121	continue;
	122	}
	123	/* Verify that host name matches. */
	124	if (host[0] == '@') {
	125	if (!innetgr(host + 1, hostname, NULL, NULL) &&
	126	!innetgr(host + 1, ipaddr, NULL, NULL))
	127	continue;
	128	} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
	129	continue; /* Different hostname. */
	130
	131	/* Verify that user name matches. */
	132	if (user[0] == '@') {
	133	if (!innetgr(user + 1, NULL, client_user, NULL))
	134	continue;
	135	} else if (strcmp(user, client_user) != 0)
	136	continue; /* Different username. */
	137
	138	/* Found the user and host. */
	139	fclose(f);
	140
	141	/* If the entry was negated, deny access. */
	142	if (negated) {
b3ad3d88	143	auth_debug_add("Matched negative entry in %.100s.",
4e2e5cfd	144	filename);
5260325f	145	return 0;
	146	}
	147	/* Accept authentication. */
	148	return 1;
8efc0c15	149	}
8efc0c15	150
5260325f	151	/* Authentication using this file denied. */
	152	fclose(f);
	153	return 0;
8efc0c15	154	}
8efc0c15	155
aa3378df	156	/*
	157	* Tries to authenticate the user using the .shosts or .rhosts file. Returns
	158	* true if authentication succeeds. If ignore_rhosts is true, only
	159	* /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
	160	*/
8efc0c15	161
6ae2364d	162	int
5260325f	163	auth_rhosts(struct passwd pw, const char client_user)
8efc0c15	164	{
5260325f	165	const char hostname, ipaddr;
8002af61	166
c5a7d788	167	hostname = get_canonical_hostname(options.use_dns);
8002af61	168	ipaddr = get_remote_ipaddr();
b3ad3d88	169	return auth_rhosts2(pw, client_user, hostname, ipaddr);
8002af61	170	}
8002af61	171
b3ad3d88	172	static int
b3ad3d88	173	auth_rhosts2_raw(struct passwd pw, const char client_user, const char *hostname,
8002af61	174	const char *ipaddr)
	175	{
	176	char buf[1024];
5260325f	177	struct stat st;
5260325f	178	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1e3b8b07	179	u_int rhosts_file_index;
5260325f	180
8002af61	181	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	182	client_user, hostname, ipaddr);
	183
5260325f	184	/* Switch to the user's uid. */
63bd8c36	185	temporarily_use_uid(pw);
aa3378df	186	/*
	187	* Quick check: if the user has no .shosts or .rhosts files, return
	188	* failure immediately without doing costly lookups from name
	189	* servers.
	190	*/
5260325f	191	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	192	rhosts_file_index++) {
5260325f	193	/* Check users .rhosts or .shosts. */
	194	snprintf(buf, sizeof buf, "%.500s/%.100s",
	195	pw->pw_dir, rhosts_files[rhosts_file_index]);
	196	if (stat(buf, &st) >= 0)
	197	break;
8efc0c15	198	}
5260325f	199	/* Switch back to privileged uid. */
	200	restore_uid();
	201
	202	/* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
	203	if (!rhosts_files[rhosts_file_index] &&
42f11eb2	204	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
42f11eb2	205	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
5260325f	206	return 0;
5260325f	207
5260325f	208	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
5260325f	209	if (pw->pw_uid != 0) {
184eed6a	210	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
184eed6a	211	client_user, pw->pw_name)) {
b3ad3d88	212	auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
184eed6a	213	hostname, ipaddr);
5260325f	214	return 1;
5260325f	215	}
184eed6a	216	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
184eed6a	217	client_user, pw->pw_name)) {
b3ad3d88	218	auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
184eed6a	219	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
5260325f	220	return 1;
5260325f	221	}
8efc0c15	222	}
aa3378df	223	/*
	224	* Check that the home directory is owned by root or the user, and is
	225	* not group or world writable.
	226	*/
5260325f	227	if (stat(pw->pw_dir, &st) < 0) {
bbe88b6d	228	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	229	"no home directory %.200s", pw->pw_name, pw->pw_dir);
	230	auth_debug_add("Rhosts authentication refused for %.100s: "
	231	"no home directory %.200s", pw->pw_name, pw->pw_dir);
5260325f	232	return 0;
8efc0c15	233	}
5260325f	234	if (options.strict_modes &&
5260325f	235	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	236	(st.st_mode & 022) != 0)) {
bbe88b6d	237	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	238	"bad ownership or modes for home directory.", pw->pw_name);
	239	auth_debug_add("Rhosts authentication refused for %.100s: "
	240	"bad ownership or modes for home directory.", pw->pw_name);
5260325f	241	return 0;
8efc0c15	242	}
5260325f	243	/* Temporarily use the user's uid. */
63bd8c36	244	temporarily_use_uid(pw);
5260325f	245
	246	/* Check all .rhosts files (currently .shosts and .rhosts). */
	247	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	248	rhosts_file_index++) {
5260325f	249	/* Check users .rhosts or .shosts. */
	250	snprintf(buf, sizeof buf, "%.500s/%.100s",
	251	pw->pw_dir, rhosts_files[rhosts_file_index]);
	252	if (stat(buf, &st) < 0)
	253	continue;
	254
aa3378df	255	/*
	256	* Make sure that the file is either owned by the user or by
	257	* root, and make sure it is not writable by anyone but the
	258	* owner. This is to help avoid novices accidentally
	259	* allowing access to their account by anyone.
	260	*/
5260325f	261	if (options.strict_modes &&
5260325f	262	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	263	(st.st_mode & 022) != 0)) {
bbe88b6d	264	logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
5260325f	265	pw->pw_name, buf);
b3ad3d88	266	auth_debug_add("Bad file modes for %.200s", buf);
5260325f	267	continue;
	268	}
	269	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	270	if (options.ignore_rhosts) {
b3ad3d88	271	auth_debug_add("Server has been configured to ignore %.100s.",
b3ad3d88	272	rhosts_files[rhosts_file_index]);
5260325f	273	continue;
	274	}
	275	/* Check if authentication is permitted by the file. */
	276	if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
b3ad3d88	277	auth_debug_add("Accepted by %.100s.",
b3ad3d88	278	rhosts_files[rhosts_file_index]);
5260325f	279	/* Restore the privileged uid. */
5260325f	280	restore_uid();
b3ad3d88	281	auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
b3ad3d88	282	hostname, ipaddr, client_user, pw->pw_name);
5260325f	283	return 1;
5260325f	284	}
8efc0c15	285	}
8efc0c15	286
5260325f	287	/* Restore the privileged uid. */
	288	restore_uid();
	289	return 0;
8efc0c15	290	}
b3ad3d88	291
	292	int
	293	auth_rhosts2(struct passwd pw, const char client_user, const char *hostname,
	294	const char *ipaddr)
	295	{
	296	int ret;
	297
	298	auth_debug_reset();
	299	ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
	300	if (!use_privsep)
	301	auth_debug_send();
	302	return ret;
	303	}