[gssapi-openssh.git] / openssh / 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
9108f8d9	1	/* $OpenBSD: auth-rhosts.c,v 1.41 2006/08/03 03:34:41 deraadt Exp $ */
3c0ef626	2	/*
	3	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	4	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	5	* All rights reserved
	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.
	9	*
	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".
	15	*/
	16
	17	#include "includes.h"
9108f8d9	18
	19	#include <sys/types.h>
	20	#include <sys/stat.h>
	21
	22	#ifdef HAVE_NETGROUP_H
	23	# include <netgroup.h>
	24	#endif
	25	#include <pwd.h>
	26	#include <stdio.h>
	27	#include <string.h>
	28	#include <stdarg.h>
3c0ef626	29
3c0ef626	30	#include "packet.h"
9108f8d9	31	#include "buffer.h"
3c0ef626	32	#include "uidswap.h"
	33	#include "pathnames.h"
	34	#include "log.h"
	35	#include "servconf.h"
	36	#include "canohost.h"
9108f8d9	37	#include "key.h"
9108f8d9	38	#include "hostfile.h"
3c0ef626	39	#include "auth.h"
	40
	41	/* import */
	42	extern ServerOptions options;
700318f3	43	extern int use_privsep;
3c0ef626	44
	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	*/
	50
	51	static int
	52	check_rhosts_file(const char filename, const char hostname,
	53	const char ipaddr, const char client_user,
	54	const char *server_user)
	55	{
	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
	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
	74	/*
	75	* NO_PLUS is supported at least on OSF/1. We skip it (we
	76	* don't ever support the plus syntax).
	77	*/
	78	if (strncmp(cp, "NO_PLUS", 7) == 0)
	79	continue;
	80
	81	/*
	82	* This should be safe because each buffer is as big as the
	83	* whole string, and thus cannot be overwritten.
	84	*/
0fff78ff	85	switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
0fff78ff	86	dummy)) {
3c0ef626	87	case 0:
700318f3	88	auth_debug_add("Found empty line in %.100s.", filename);
3c0ef626	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:
700318f3	98	auth_debug_add("Found garbage in %.100s.", filename);
3c0ef626	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 '-'. */
700318f3	125	auth_debug_add("Ignoring wild host/user names in %.100s.",
700318f3	126	filename);
3c0ef626	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) {
700318f3	149	auth_debug_add("Matched negative entry in %.100s.",
665a873d	150	filename);
3c0ef626	151	return 0;
	152	}
	153	/* Accept authentication. */
	154	return 1;
	155	}
	156
	157	/* Authentication using this file denied. */
	158	fclose(f);
	159	return 0;
	160	}
	161
	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	*/
	167
	168	int
	169	auth_rhosts(struct passwd pw, const char client_user)
	170	{
	171	const char hostname, ipaddr;
3c0ef626	172
0fff78ff	173	hostname = get_canonical_hostname(options.use_dns);
3c0ef626	174	ipaddr = get_remote_ipaddr();
700318f3	175	return auth_rhosts2(pw, client_user, hostname, ipaddr);
3c0ef626	176	}
3c0ef626	177
700318f3	178	static int
700318f3	179	auth_rhosts2_raw(struct passwd pw, const char client_user, const char *hostname,
3c0ef626	180	const char *ipaddr)
	181	{
	182	char buf[1024];
	183	struct stat st;
	184	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
	185	u_int rhosts_file_index;
	186
	187	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
	188	client_user, hostname, ipaddr);
	189
3c0ef626	190	/* Switch to the user's uid. */
	191	temporarily_use_uid(pw);
	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	*/
	197	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
e9a17296	198	rhosts_file_index++) {
3c0ef626	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;
	204	}
	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] &&
	210	stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
	211	stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0)
	212	return 0;
	213
	214	/* If not logging in as superuser, try /etc/hosts.equiv and shosts.equiv. */
	215	if (pw->pw_uid != 0) {
e9a17296	216	if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
e9a17296	217	client_user, pw->pw_name)) {
700318f3	218	auth_debug_add("Accepted for %.100s [%.100s] by /etc/hosts.equiv.",
e9a17296	219	hostname, ipaddr);
3c0ef626	220	return 1;
3c0ef626	221	}
e9a17296	222	if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
e9a17296	223	client_user, pw->pw_name)) {
700318f3	224	auth_debug_add("Accepted for %.100s [%.100s] by %.100s.",
e9a17296	225	hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
3c0ef626	226	return 1;
	227	}
	228	}
	229	/*
	230	* Check that the home directory is owned by root or the user, and is
	231	* not group or world writable.
	232	*/
	233	if (stat(pw->pw_dir, &st) < 0) {
0fff78ff	234	logit("Rhosts authentication refused for %.100s: "
700318f3	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);
3c0ef626	238	return 0;
	239	}
	240	if (options.strict_modes &&
	241	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
e9a17296	242	(st.st_mode & 022) != 0)) {
0fff78ff	243	logit("Rhosts authentication refused for %.100s: "
700318f3	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);
3c0ef626	247	return 0;
	248	}
	249	/* Temporarily use the user's uid. */
	250	temporarily_use_uid(pw);
	251
	252	/* Check all .rhosts files (currently .shosts and .rhosts). */
	253	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
e9a17296	254	rhosts_file_index++) {
3c0ef626	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
	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	*/
	267	if (options.strict_modes &&
	268	((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
e9a17296	269	(st.st_mode & 022) != 0)) {
0fff78ff	270	logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
3c0ef626	271	pw->pw_name, buf);
700318f3	272	auth_debug_add("Bad file modes for %.200s", buf);
3c0ef626	273	continue;
	274	}
	275	/* Check if we have been configured to ignore .rhosts and .shosts files. */
	276	if (options.ignore_rhosts) {
700318f3	277	auth_debug_add("Server has been configured to ignore %.100s.",
700318f3	278	rhosts_files[rhosts_file_index]);
3c0ef626	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)) {
700318f3	283	auth_debug_add("Accepted by %.100s.",
700318f3	284	rhosts_files[rhosts_file_index]);
3c0ef626	285	/* Restore the privileged uid. */
3c0ef626	286	restore_uid();
700318f3	287	auth_debug_add("Accepted host %s ip %s client_user %s server_user %s",
700318f3	288	hostname, ipaddr, client_user, pw->pw_name);
3c0ef626	289	return 1;
	290	}
	291	}
	292
	293	/* Restore the privileged uid. */
	294	restore_uid();
	295	return 0;
	296	}
700318f3	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	}