[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 1.29 2003/04/08 20:21:28 itojun 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;
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, "%s %s %s", 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.verify_reverse_mapping);
	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);

	/* 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)) {
			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"
0608f8a7	17	RCSID("$OpenBSD: auth-rhosts.c,v 1.29 2003/04/08 20:21:28 itojun 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 */
8002af61	28	extern ServerOptions options;
b3ad3d88	29	extern int use_privsep;
8002af61	30
aa3378df	31	/*
	32	* This function processes an rhosts-style file (.rhosts, .shosts, or
	33	* /etc/hosts.equiv). This returns true if authentication can be granted
	34	* based on the file, and returns zero otherwise.
	35	*/
8efc0c15	36
396c147e	37	static int
5260325f	38	check_rhosts_file(const char filename, const char hostname,
	39	const char ipaddr, const char client_user,
	40	const char *server_user)
8efc0c15	41	{
5260325f	42	FILE *f;
	43	char buf[1024]; /* Must not be larger than host, user, dummy below. */
	44
	45	/* Open the .rhosts file, deny if unreadable */
	46	f = fopen(filename, "r");
	47	if (!f)
	48	return 0;
	49
5260325f	50	while (fgets(buf, sizeof(buf), f)) {
	51	/* All three must be at least as big as buf to avoid overflows. */
	52	char hostbuf[1024], userbuf[1024], dummy[1024], host, user, *cp;
	53	int negated;
	54
	55	for (cp = buf; cp == ' ' \|\| cp == '\t'; cp++)
	56	;
	57	if (cp == '#' \|\| cp == '\n' \|\| !*cp)
	58	continue;
	59
aa3378df	60	/*
	61	* NO_PLUS is supported at least on OSF/1. We skip it (we
	62	* don't ever support the plus syntax).
	63	*/
5260325f	64	if (strncmp(cp, "NO_PLUS", 7) == 0)
	65	continue;
	66
aa3378df	67	/*
	68	* This should be safe because each buffer is as big as the
	69	* whole string, and thus cannot be overwritten.
	70	*/
5260325f	71	switch (sscanf(buf, "%s %s %s", hostbuf, userbuf, dummy)) {
5260325f	72	case 0:
b3ad3d88	73	auth_debug_add("Found empty line in %.100s.", filename);
5260325f	74	continue;
	75	case 1:
	76	/* Host name only. */
	77	strlcpy(userbuf, server_user, sizeof(userbuf));
	78	break;
	79	case 2:
	80	/* Got both host and user name. */
	81	break;
	82	case 3:
b3ad3d88	83	auth_debug_add("Found garbage in %.100s.", filename);
5260325f	84	continue;
	85	default:
	86	/* Weird... */
	87	continue;
	88	}
	89
	90	host = hostbuf;
	91	user = userbuf;
	92	negated = 0;
	93
	94	/* Process negated host names, or positive netgroups. */
	95	if (host[0] == '-') {
	96	negated = 1;
	97	host++;
	98	} else if (host[0] == '+')
	99	host++;
	100
	101	if (user[0] == '-') {
	102	negated = 1;
	103	user++;
	104	} else if (user[0] == '+')
	105	user++;
	106
	107	/* Check for empty host/user names (particularly '+'). */
	108	if (!host[0] \|\| !user[0]) {
	109	/* We come here if either was '+' or '-'. */
b3ad3d88	110	auth_debug_add("Ignoring wild host/user names in %.100s.",
b3ad3d88	111	filename);
5260325f	112	continue;
	113	}
	114	/* Verify that host name matches. */
	115	if (host[0] == '@') {
	116	if (!innetgr(host + 1, hostname, NULL, NULL) &&
	117	!innetgr(host + 1, ipaddr, NULL, NULL))
	118	continue;
	119	} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
	120	continue; /* Different hostname. */
	121
	122	/* Verify that user name matches. */
	123	if (user[0] == '@') {
	124	if (!innetgr(user + 1, NULL, client_user, NULL))
	125	continue;
	126	} else if (strcmp(user, client_user) != 0)
	127	continue; /* Different username. */
	128
	129	/* Found the user and host. */
	130	fclose(f);
	131
	132	/* If the entry was negated, deny access. */
	133	if (negated) {
b3ad3d88	134	auth_debug_add("Matched negative entry in %.100s.",
b3ad3d88	135	filename);
5260325f	136	return 0;
	137	}
	138	/* Accept authentication. */
	139	return 1;
8efc0c15	140	}
8efc0c15	141
5260325f	142	/* Authentication using this file denied. */
	143	fclose(f);
	144	return 0;
8efc0c15	145	}
8efc0c15	146
aa3378df	147	/*
	148	* Tries to authenticate the user using the .shosts or .rhosts file. Returns
	149	* true if authentication succeeds. If ignore_rhosts is true, only
	150	* /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
	151	*/
8efc0c15	152
6ae2364d	153	int
5260325f	154	auth_rhosts(struct passwd pw, const char client_user)
8efc0c15	155	{
5260325f	156	const char hostname, ipaddr;
8002af61	157
bf4c5edc	158	hostname = get_canonical_hostname(options.verify_reverse_mapping);
8002af61	159	ipaddr = get_remote_ipaddr();
b3ad3d88	160	return auth_rhosts2(pw, client_user, hostname, ipaddr);
8002af61	161	}
8002af61	162
b3ad3d88	163	static int
b3ad3d88	164	auth_rhosts2_raw(struct passwd pw, const char client_user, const char *hostname,
8002af61	165	const char *ipaddr)
	166	{
	167	char buf[1024];
5260325f	168	struct stat st;
5260325f	169	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1e3b8b07	170	u_int rhosts_file_index;
5260325f	171
8002af61	172	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	173	client_user, hostname, ipaddr);
	174
94ec8c6b	175	/* no user given */
	176	if (pw == NULL)
	177	return 0;
8002af61	178
5260325f	179	/* Switch to the user's uid. */
63bd8c36	180	temporarily_use_uid(pw);
aa3378df	181	/*
	182	* Quick check: if the user has no .shosts or .rhosts files, return
	183	* failure immediately without doing costly lookups from name
	184	* servers.
	185	*/
5260325f	186	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	187	rhosts_file_index++) {
5260325f	188	/* Check users .rhosts or .shosts. */
	189	snprintf(buf, sizeof buf, "%.500s/%.100s",
	190	pw->pw_dir, rhosts_files[rhosts_file_index]);
	191	if (stat(buf, &st) >= 0)
	192	break;
8efc0c15	193	}
5260325f	194	/* Switch back to privileged uid. */
	195	restore_uid();
	196
	197	/* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
	198	if (!rhosts_files[rhosts_file_index] &&
42f11eb2	199	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
42f11eb2	200	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
5260325f	201	return 0;
5260325f	202
5260325f	203	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
5260325f	204	if (pw->pw_uid != 0) {
184eed6a	205	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
184eed6a	206	client_user, pw->pw_name)) {
b3ad3d88	207	auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
184eed6a	208	hostname, ipaddr);
5260325f	209	return 1;
5260325f	210	}
184eed6a	211	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
184eed6a	212	client_user, pw->pw_name)) {
b3ad3d88	213	auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
184eed6a	214	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
5260325f	215	return 1;
5260325f	216	}
8efc0c15	217	}
aa3378df	218	/*
	219	* Check that the home directory is owned by root or the user, and is
	220	* not group or world writable.
	221	*/
5260325f	222	if (stat(pw->pw_dir, &st) < 0) {
bbe88b6d	223	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	224	"no home directory %.200s", pw->pw_name, pw->pw_dir);
	225	auth_debug_add("Rhosts authentication refused for %.100s: "
	226	"no home directory %.200s", pw->pw_name, pw->pw_dir);
5260325f	227	return 0;
8efc0c15	228	}
5260325f	229	if (options.strict_modes &&
5260325f	230	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	231	(st.st_mode & 022) != 0)) {
bbe88b6d	232	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	233	"bad ownership or modes for home directory.", pw->pw_name);
	234	auth_debug_add("Rhosts authentication refused for %.100s: "
	235	"bad ownership or modes for home directory.", pw->pw_name);
5260325f	236	return 0;
8efc0c15	237	}
5260325f	238	/* Temporarily use the user's uid. */
63bd8c36	239	temporarily_use_uid(pw);
5260325f	240
	241	/* Check all .rhosts files (currently .shosts and .rhosts). */
	242	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	243	rhosts_file_index++) {
5260325f	244	/* Check users .rhosts or .shosts. */
	245	snprintf(buf, sizeof buf, "%.500s/%.100s",
	246	pw->pw_dir, rhosts_files[rhosts_file_index]);
	247	if (stat(buf, &st) < 0)
	248	continue;
	249
aa3378df	250	/*
	251	* Make sure that the file is either owned by the user or by
	252	* root, and make sure it is not writable by anyone but the
	253	* owner. This is to help avoid novices accidentally
	254	* allowing access to their account by anyone.
	255	*/
5260325f	256	if (options.strict_modes &&
5260325f	257	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	258	(st.st_mode & 022) != 0)) {
bbe88b6d	259	logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
5260325f	260	pw->pw_name, buf);
b3ad3d88	261	auth_debug_add("Bad file modes for %.200s", buf);
5260325f	262	continue;
	263	}
	264	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	265	if (options.ignore_rhosts) {
b3ad3d88	266	auth_debug_add("Server has been configured to ignore %.100s.",
b3ad3d88	267	rhosts_files[rhosts_file_index]);
5260325f	268	continue;
	269	}
	270	/* Check if authentication is permitted by the file. */
	271	if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
b3ad3d88	272	auth_debug_add("Accepted by %.100s.",
b3ad3d88	273	rhosts_files[rhosts_file_index]);
5260325f	274	/* Restore the privileged uid. */
5260325f	275	restore_uid();
b3ad3d88	276	auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
b3ad3d88	277	hostname, ipaddr, client_user, pw->pw_name);
5260325f	278	return 1;
5260325f	279	}
8efc0c15	280	}
8efc0c15	281
5260325f	282	/* Restore the privileged uid. */
	283	restore_uid();
	284	return 0;
8efc0c15	285	}
b3ad3d88	286
	287	int
	288	auth_rhosts2(struct passwd pw, const char client_user, const char *hostname,
	289	const char *ipaddr)
	290	{
	291	int ret;
	292
	293	auth_debug_reset();
	294	ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
	295	if (!use_privsep)
	296	auth_debug_send();
	297	return ret;
	298	}