[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 1.31 2003/06/02 09:17:34 markus 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, "%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);

	/* 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"
c5a7d788	17	RCSID("$OpenBSD: auth-rhosts.c,v 1.31 2003/06/02 09:17:34 markus 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	*/
013b1214	71	switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
013b1214	72	dummy)) {
5260325f	73	case 0:
b3ad3d88	74	auth_debug_add("Found empty line in %.100s.", filename);
5260325f	75	continue;
	76	case 1:
	77	/* Host name only. */
	78	strlcpy(userbuf, server_user, sizeof(userbuf));
	79	break;
	80	case 2:
	81	/* Got both host and user name. */
	82	break;
	83	case 3:
b3ad3d88	84	auth_debug_add("Found garbage in %.100s.", filename);
5260325f	85	continue;
	86	default:
	87	/* Weird... */
	88	continue;
	89	}
	90
	91	host = hostbuf;
	92	user = userbuf;
	93	negated = 0;
	94
	95	/* Process negated host names, or positive netgroups. */
	96	if (host[0] == '-') {
	97	negated = 1;
	98	host++;
	99	} else if (host[0] == '+')
	100	host++;
	101
	102	if (user[0] == '-') {
	103	negated = 1;
	104	user++;
	105	} else if (user[0] == '+')
	106	user++;
	107
	108	/* Check for empty host/user names (particularly '+'). */
	109	if (!host[0] \|\| !user[0]) {
	110	/* We come here if either was '+' or '-'. */
b3ad3d88	111	auth_debug_add("Ignoring wild host/user names in %.100s.",
b3ad3d88	112	filename);
5260325f	113	continue;
	114	}
	115	/* Verify that host name matches. */
	116	if (host[0] == '@') {
	117	if (!innetgr(host + 1, hostname, NULL, NULL) &&
	118	!innetgr(host + 1, ipaddr, NULL, NULL))
	119	continue;
	120	} else if (strcasecmp(host, hostname) && strcmp(host, ipaddr) != 0)
	121	continue; /* Different hostname. */
	122
	123	/* Verify that user name matches. */
	124	if (user[0] == '@') {
	125	if (!innetgr(user + 1, NULL, client_user, NULL))
	126	continue;
	127	} else if (strcmp(user, client_user) != 0)
	128	continue; /* Different username. */
	129
	130	/* Found the user and host. */
	131	fclose(f);
	132
	133	/* If the entry was negated, deny access. */
	134	if (negated) {
b3ad3d88	135	auth_debug_add("Matched negative entry in %.100s.",
b3ad3d88	136	filename);
5260325f	137	return 0;
	138	}
	139	/* Accept authentication. */
	140	return 1;
8efc0c15	141	}
8efc0c15	142
5260325f	143	/* Authentication using this file denied. */
	144	fclose(f);
	145	return 0;
8efc0c15	146	}
8efc0c15	147
aa3378df	148	/*
	149	* Tries to authenticate the user using the .shosts or .rhosts file. Returns
	150	* true if authentication succeeds. If ignore_rhosts is true, only
	151	* /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
	152	*/
8efc0c15	153
6ae2364d	154	int
5260325f	155	auth_rhosts(struct passwd pw, const char client_user)
8efc0c15	156	{
5260325f	157	const char hostname, ipaddr;
8002af61	158
c5a7d788	159	hostname = get_canonical_hostname(options.use_dns);
8002af61	160	ipaddr = get_remote_ipaddr();
b3ad3d88	161	return auth_rhosts2(pw, client_user, hostname, ipaddr);
8002af61	162	}
8002af61	163
b3ad3d88	164	static int
b3ad3d88	165	auth_rhosts2_raw(struct passwd pw, const char client_user, const char *hostname,
8002af61	166	const char *ipaddr)
	167	{
	168	char buf[1024];
5260325f	169	struct stat st;
5260325f	170	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1e3b8b07	171	u_int rhosts_file_index;
5260325f	172
8002af61	173	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	174	client_user, hostname, ipaddr);
	175
94ec8c6b	176	/* no user given */
	177	if (pw == NULL)
	178	return 0;
8002af61	179
5260325f	180	/* Switch to the user's uid. */
63bd8c36	181	temporarily_use_uid(pw);
aa3378df	182	/*
	183	* Quick check: if the user has no .shosts or .rhosts files, return
	184	* failure immediately without doing costly lookups from name
	185	* servers.
	186	*/
5260325f	187	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	188	rhosts_file_index++) {
5260325f	189	/* Check users .rhosts or .shosts. */
	190	snprintf(buf, sizeof buf, "%.500s/%.100s",
	191	pw->pw_dir, rhosts_files[rhosts_file_index]);
	192	if (stat(buf, &st) >= 0)
	193	break;
8efc0c15	194	}
5260325f	195	/* Switch back to privileged uid. */
	196	restore_uid();
	197
	198	/* Deny if The user has no .shosts or .rhosts file and there are no system-wide files. */
	199	if (!rhosts_files[rhosts_file_index] &&
42f11eb2	200	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
42f11eb2	201	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
5260325f	202	return 0;
5260325f	203
5260325f	204	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
5260325f	205	if (pw->pw_uid != 0) {
184eed6a	206	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
184eed6a	207	client_user, pw->pw_name)) {
b3ad3d88	208	auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
184eed6a	209	hostname, ipaddr);
5260325f	210	return 1;
5260325f	211	}
184eed6a	212	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
184eed6a	213	client_user, pw->pw_name)) {
b3ad3d88	214	auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
184eed6a	215	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
5260325f	216	return 1;
5260325f	217	}
8efc0c15	218	}
aa3378df	219	/*
	220	* Check that the home directory is owned by root or the user, and is
	221	* not group or world writable.
	222	*/
5260325f	223	if (stat(pw->pw_dir, &st) < 0) {
bbe88b6d	224	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	225	"no home directory %.200s", pw->pw_name, pw->pw_dir);
	226	auth_debug_add("Rhosts authentication refused for %.100s: "
	227	"no home directory %.200s", pw->pw_name, pw->pw_dir);
5260325f	228	return 0;
8efc0c15	229	}
5260325f	230	if (options.strict_modes &&
5260325f	231	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	232	(st.st_mode & 022) != 0)) {
bbe88b6d	233	logit("Rhosts authentication refused for %.100s: "
b3ad3d88	234	"bad ownership or modes for home directory.", pw->pw_name);
	235	auth_debug_add("Rhosts authentication refused for %.100s: "
	236	"bad ownership or modes for home directory.", pw->pw_name);
5260325f	237	return 0;
8efc0c15	238	}
5260325f	239	/* Temporarily use the user's uid. */
63bd8c36	240	temporarily_use_uid(pw);
5260325f	241
	242	/* Check all .rhosts files (currently .shosts and .rhosts). */
	243	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
184eed6a	244	rhosts_file_index++) {
5260325f	245	/* Check users .rhosts or .shosts. */
	246	snprintf(buf, sizeof buf, "%.500s/%.100s",
	247	pw->pw_dir, rhosts_files[rhosts_file_index]);
	248	if (stat(buf, &st) < 0)
	249	continue;
	250
aa3378df	251	/*
	252	* Make sure that the file is either owned by the user or by
	253	* root, and make sure it is not writable by anyone but the
	254	* owner. This is to help avoid novices accidentally
	255	* allowing access to their account by anyone.
	256	*/
5260325f	257	if (options.strict_modes &&
5260325f	258	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
184eed6a	259	(st.st_mode & 022) != 0)) {
bbe88b6d	260	logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
5260325f	261	pw->pw_name, buf);
b3ad3d88	262	auth_debug_add("Bad file modes for %.200s", buf);
5260325f	263	continue;
	264	}
	265	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	266	if (options.ignore_rhosts) {
b3ad3d88	267	auth_debug_add("Server has been configured to ignore %.100s.",
b3ad3d88	268	rhosts_files[rhosts_file_index]);
5260325f	269	continue;
	270	}
	271	/* Check if authentication is permitted by the file. */
	272	if (check_rhosts_file(buf, hostname, ipaddr, client_user, pw->pw_name)) {
b3ad3d88	273	auth_debug_add("Accepted by %.100s.",
b3ad3d88	274	rhosts_files[rhosts_file_index]);
5260325f	275	/* Restore the privileged uid. */
5260325f	276	restore_uid();
b3ad3d88	277	auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
b3ad3d88	278	hostname, ipaddr, client_user, pw->pw_name);
5260325f	279	return 1;
5260325f	280	}
8efc0c15	281	}
8efc0c15	282
5260325f	283	/* Restore the privileged uid. */
	284	restore_uid();
	285	return 0;
8efc0c15	286	}
b3ad3d88	287
	288	int
	289	auth_rhosts2(struct passwd pw, const char client_user, const char *hostname,
	290	const char *ipaddr)
	291	{
	292	int ret;
	293
	294	auth_debug_reset();
	295	ret = auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
	296	if (!use_privsep)
	297	auth_debug_send();
	298	return ret;
	299	}