[openssh.git] / uidswap.c

/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Code for uid-swapping.
 *
 * 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: uidswap.c,v 1.24 2003/05/29 16:58:45 deraadt Exp $");

#include "log.h"
#include "uidswap.h"
#include "xmalloc.h"

/*
 * Note: all these functions must work in all of the following cases:
 *    1. euid=0, ruid=0
 *    2. euid=0, ruid!=0
 *    3. euid!=0, ruid!=0
 * Additionally, they must work regardless of whether the system has
 * POSIX saved uids or not.
 */

#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
/* Lets assume that posix saved ids also work with seteuid, even though that
   is not part of the posix specification. */
#define SAVED_IDS_WORK_WITH_SETEUID
/* Saved effective uid. */
static uid_t 	saved_euid = 0;
static gid_t	saved_egid = 0;
#endif

/* Saved effective uid. */
static int	privileged = 0;
static int	temporarily_use_uid_effective = 0;
static gid_t	*saved_egroups = NULL, *user_groups = NULL;
static int	saved_egroupslen = -1, user_groupslen = -1;

/*
 * Temporarily changes to the given uid.  If the effective user
 * id is not root, this does nothing.  This call cannot be nested.
 */
void
temporarily_use_uid(struct passwd *pw)
{
	/* Save the current euid, and egroups. */
#ifdef SAVED_IDS_WORK_WITH_SETEUID
	saved_euid = geteuid();
	saved_egid = getegid();
	debug("temporarily_use_uid: %u/%u (e=%u/%u)",
	    (u_int)pw->pw_uid, (u_int)pw->pw_gid,
	    (u_int)saved_euid, (u_int)saved_egid);
	if (saved_euid != 0) {
		privileged = 0;
		return;
	}
#else
	if (geteuid() != 0) {
		privileged = 0;
		return;
	}
#endif /* SAVED_IDS_WORK_WITH_SETEUID */

	privileged = 1;
	temporarily_use_uid_effective = 1;

	saved_egroupslen = getgroups(0, NULL);
	if (saved_egroupslen < 0)
		fatal("getgroups: %.100s", strerror(errno));
	if (saved_egroupslen > 0) {
		saved_egroups = xrealloc(saved_egroups,
		    saved_egroupslen * sizeof(gid_t));
		if (getgroups(saved_egroupslen, saved_egroups) < 0)
			fatal("getgroups: %.100s", strerror(errno));
	} else { /* saved_egroupslen == 0 */
		if (saved_egroups)
			xfree(saved_egroups);
	}

	/* set and save the user's groups */
	if (user_groupslen == -1) {
		if (initgroups(pw->pw_name, pw->pw_gid) < 0)
			fatal("initgroups: %s: %.100s", pw->pw_name,
			    strerror(errno));

		user_groupslen = getgroups(0, NULL);
		if (user_groupslen < 0)
			fatal("getgroups: %.100s", strerror(errno));
		if (user_groupslen > 0) {
			user_groups = xrealloc(user_groups,
			    user_groupslen * sizeof(gid_t));
			if (getgroups(user_groupslen, user_groups) < 0)
				fatal("getgroups: %.100s", strerror(errno));
		} else { /* user_groupslen == 0 */
			if (user_groups)
				xfree(user_groups);
		}
	}
	/* Set the effective uid to the given (unprivileged) uid. */
	if (setgroups(user_groupslen, user_groups) < 0)
		fatal("setgroups: %.100s", strerror(errno));
#ifndef SAVED_IDS_WORK_WITH_SETEUID
	/* Propagate the privileged gid to all of our gids. */
	if (setgid(getegid()) < 0)
		debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
	/* Propagate the privileged uid to all of our uids. */
	if (setuid(geteuid()) < 0)
		debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	if (setegid(pw->pw_gid) < 0)
		fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
		    strerror(errno));
	if (seteuid(pw->pw_uid) == -1)
		fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
		    strerror(errno));
}

/*
 * Restores to the original (privileged) uid.
 */
void
restore_uid(void)
{
	/* it's a no-op unless privileged */
	if (!privileged) {
		debug("restore_uid: (unprivileged)");
		return;
	}
	if (!temporarily_use_uid_effective)
		fatal("restore_uid: temporarily_use_uid not effective");

#ifdef SAVED_IDS_WORK_WITH_SETEUID
	debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
	/* Set the effective uid back to the saved privileged uid. */
	if (seteuid(saved_euid) < 0)
		fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
	if (setegid(saved_egid) < 0)
		fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
#else /* SAVED_IDS_WORK_WITH_SETEUID */
	/*
	 * We are unable to restore the real uid to its unprivileged value.
	 * Propagate the real uid (usually more privileged) to effective uid
	 * as well.
	 */
	setuid(getuid());
	setgid(getgid());
#endif /* SAVED_IDS_WORK_WITH_SETEUID */

	if (setgroups(saved_egroupslen, saved_egroups) < 0)
		fatal("setgroups: %.100s", strerror(errno));
	temporarily_use_uid_effective = 0;
}

/*
 * Permanently sets all uids to the given uid.  This cannot be
 * called while temporarily_use_uid is effective.
 */
void
permanently_set_uid(struct passwd *pw)
{
	uid_t old_uid = getuid();
	gid_t old_gid = getgid();

	if (temporarily_use_uid_effective)
		fatal("permanently_set_uid: temporarily_use_uid effective");
	debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
	    (u_int)pw->pw_gid);

#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
	if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
		fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
	if (setregid(pw->pw_gid, pw->pw_gid) < 0)
		fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
#else
	if (setegid(pw->pw_gid) < 0)
		fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
	if (setgid(pw->pw_gid) < 0)
		fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
#endif

#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
	if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
		fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
	if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
		fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
#else
# ifndef SETEUID_BREAKS_SETUID
	if (seteuid(pw->pw_uid) < 0)
		fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
# endif
	if (setuid(pw->pw_uid) < 0)
		fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
#endif

	/* Try restoration of GID if changed (test clearing of saved gid) */
	if (old_gid != pw->pw_gid &&
	    (setgid(old_gid) != -1 || setegid(old_gid) != -1))
		fatal("%s: was able to restore old [e]gid", __func__);

	/* Verify GID drop was successful */
	if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
		fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
		    __func__, (u_int)getgid(), (u_int)getegid(),
		    (u_int)pw->pw_gid);
	}

#ifndef HAVE_CYGWIN
	/* Try restoration of UID if changed (test clearing of saved uid) */
	if (old_uid != pw->pw_uid &&
	    (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
		fatal("%s: was able to restore old [e]uid", __func__);
#endif

	/* Verify UID drop was successful */
	if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
		fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
		    __func__, (u_int)getuid(), (u_int)geteuid(),
		    (u_int)pw->pw_uid);
	}
}
Commit	Line	Data
8efc0c15	1	/*
5260325f	2	* Author: Tatu Ylonen <ylo@cs.hut.fi>
	3	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	4	* All rights reserved
5260325f	5	* Code for uid-swapping.
bcbf86ec	6	*
	7	* As far as I am concerned, the code I have written for this software
	8	* can be used freely for any purpose. Any derived versions of this
	9	* software must be clearly marked as such, and if the derived work is
	10	* incompatible with the protocol description in the RFC file, it must be
	11	* called by a name other than "ssh" or "Secure Shell".
5260325f	12	*/
8efc0c15	13
8efc0c15	14	#include "includes.h"
fa5120a0	15	RCSID("$OpenBSD: uidswap.c,v 1.24 2003/05/29 16:58:45 deraadt Exp $");
8efc0c15	16
42f11eb2	17	#include "log.h"
8efc0c15	18	#include "uidswap.h"
13dff404	19	#include "xmalloc.h"
8efc0c15	20
5260325f	21	/*
	22	* Note: all these functions must work in all of the following cases:
	23	* 1. euid=0, ruid=0
	24	* 2. euid=0, ruid!=0
	25	* 3. euid!=0, ruid!=0
	26	* Additionally, they must work regardless of whether the system has
	27	* POSIX saved uids or not.
	28	*/
8efc0c15	29
0096ac62	30	#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
8efc0c15	31	/* Lets assume that posix saved ids also work with seteuid, even though that
8efc0c15	32	is not part of the posix specification. */
0096ac62	33	#define SAVED_IDS_WORK_WITH_SETEUID
	34	/* Saved effective uid. */
	35	static uid_t saved_euid = 0;
	36	static gid_t saved_egid = 0;
	37	#endif
f8252c48	38
8efc0c15	39	/* Saved effective uid. */
63bd8c36	40	static int privileged = 0;
63bd8c36	41	static int temporarily_use_uid_effective = 0;
13dff404	42	static gid_t saved_egroups = NULL, user_groups = NULL;
63bd8c36	43	static int saved_egroupslen = -1, user_groupslen = -1;
f8252c48	44
5260325f	45	/*
	46	* Temporarily changes to the given uid. If the effective user
	47	* id is not root, this does nothing. This call cannot be nested.
	48	*/
6ae2364d	49	void
63bd8c36	50	temporarily_use_uid(struct passwd *pw)
8efc0c15	51	{
f8252c48	52	/* Save the current euid, and egroups. */
0096ac62	53	#ifdef SAVED_IDS_WORK_WITH_SETEUID
f8252c48	54	saved_euid = geteuid();
0096ac62	55	saved_egid = getegid();
0df3a240	56	debug("temporarily_use_uid: %u/%u (e=%u/%u)",
	57	(u_int)pw->pw_uid, (u_int)pw->pw_gid,
	58	(u_int)saved_euid, (u_int)saved_egid);
f8252c48	59	if (saved_euid != 0) {
	60	privileged = 0;
	61	return;
	62	}
0096ac62	63	#else
	64	if (geteuid() != 0) {
	65	privileged = 0;
	66	return;
	67	}
	68	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	69
f8252c48	70	privileged = 1;
f8252c48	71	temporarily_use_uid_effective = 1;
13dff404	72
13dff404	73	saved_egroupslen = getgroups(0, NULL);
f8252c48	74	if (saved_egroupslen < 0)
f8252c48	75	fatal("getgroups: %.100s", strerror(errno));
13dff404	76	if (saved_egroupslen > 0) {
	77	saved_egroups = xrealloc(saved_egroups,
	78	saved_egroupslen * sizeof(gid_t));
	79	if (getgroups(saved_egroupslen, saved_egroups) < 0)
	80	fatal("getgroups: %.100s", strerror(errno));
	81	} else { /* saved_egroupslen == 0 */
	82	if (saved_egroups)
	83	xfree(saved_egroups);
	84	}
f8252c48	85
	86	/* set and save the user's groups */
	87	if (user_groupslen == -1) {
	88	if (initgroups(pw->pw_name, pw->pw_gid) < 0)
	89	fatal("initgroups: %s: %.100s", pw->pw_name,
	90	strerror(errno));
13dff404	91
13dff404	92	user_groupslen = getgroups(0, NULL);
f8252c48	93	if (user_groupslen < 0)
f8252c48	94	fatal("getgroups: %.100s", strerror(errno));
13dff404	95	if (user_groupslen > 0) {
	96	user_groups = xrealloc(user_groups,
	97	user_groupslen * sizeof(gid_t));
	98	if (getgroups(user_groupslen, user_groups) < 0)
	99	fatal("getgroups: %.100s", strerror(errno));
	100	} else { /* user_groupslen == 0 */
	101	if (user_groups)
	102	xfree(user_groups);
	103	}
f8252c48	104	}
f8252c48	105	/* Set the effective uid to the given (unprivileged) uid. */
d98d029a	106	if (setgroups(user_groupslen, user_groups) < 0)
63bd8c36	107	fatal("setgroups: %.100s", strerror(errno));
0096ac62	108	#ifndef SAVED_IDS_WORK_WITH_SETEUID
	109	/* Propagate the privileged gid to all of our gids. */
	110	if (setgid(getegid()) < 0)
	111	debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
	112	/* Propagate the privileged uid to all of our uids. */
	113	if (setuid(geteuid()) < 0)
	114	debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
	115	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
d98d029a	116	if (setegid(pw->pw_gid) < 0)
caa49784	117	fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
f8252c48	118	strerror(errno));
f8252c48	119	if (seteuid(pw->pw_uid) == -1)
caa49784	120	fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
f8252c48	121	strerror(errno));
8efc0c15	122	}
f8252c48	123
5260325f	124	/*
a3626e12	125	* Restores to the original (privileged) uid.
5260325f	126	*/
6ae2364d	127	void
1e3b8b07	128	restore_uid(void)
8efc0c15	129	{
63bd8c36	130	/* it's a no-op unless privileged */
0df3a240	131	if (!privileged) {
0df3a240	132	debug("restore_uid: (unprivileged)");
63bd8c36	133	return;
0df3a240	134	}
63bd8c36	135	if (!temporarily_use_uid_effective)
63bd8c36	136	fatal("restore_uid: temporarily_use_uid not effective");
0096ac62	137
0096ac62	138	#ifdef SAVED_IDS_WORK_WITH_SETEUID
13979d47	139	debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
a3626e12	140	/* Set the effective uid back to the saved privileged uid. */
5260325f	141	if (seteuid(saved_euid) < 0)
caa49784	142	fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
0096ac62	143	if (setegid(saved_egid) < 0)
caa49784	144	fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
0096ac62	145	#else /* SAVED_IDS_WORK_WITH_SETEUID */
	146	/*
	147	* We are unable to restore the real uid to its unprivileged value.
	148	* Propagate the real uid (usually more privileged) to effective uid
	149	* as well.
	150	*/
	151	setuid(getuid());
	152	setgid(getgid());
	153	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	154
d98d029a	155	if (setgroups(saved_egroupslen, saved_egroups) < 0)
63bd8c36	156	fatal("setgroups: %.100s", strerror(errno));
63bd8c36	157	temporarily_use_uid_effective = 0;
8efc0c15	158	}
8efc0c15	159
5260325f	160	/*
	161	* Permanently sets all uids to the given uid. This cannot be
	162	* called while temporarily_use_uid is effective.
	163	*/
6ae2364d	164	void
63bd8c36	165	permanently_set_uid(struct passwd *pw)
8efc0c15	166	{
688eed4a	167	uid_t old_uid = getuid();
	168	gid_t old_gid = getgid();
	169
63bd8c36	170	if (temporarily_use_uid_effective)
95f20fe8	171	fatal("permanently_set_uid: temporarily_use_uid effective");
0df3a240	172	debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
0df3a240	173	(u_int)pw->pw_gid);
688eed4a	174
9a3fe0e2	175	#if defined(HAVE_SETRESGID) && !defined(BROKEN_SETRESGID)
688eed4a	176	if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
688eed4a	177	fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
3b8dff69	178	#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
688eed4a	179	if (setregid(pw->pw_gid, pw->pw_gid) < 0)
	180	fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
	181	#else
fa5120a0	182	if (setegid(pw->pw_gid) < 0)
fa5120a0	183	fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
63bd8c36	184	if (setgid(pw->pw_gid) < 0)
caa49784	185	fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
688eed4a	186	#endif
688eed4a	187
9a3fe0e2	188	#if defined(HAVE_SETRESUID) && !defined(BROKEN_SETRESUID)
688eed4a	189	if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
688eed4a	190	fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
3b8dff69	191	#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
f5db6a03	192	if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
f5db6a03	193	fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	194	#else
688eed4a	195	# ifndef SETEUID_BREAKS_SETUID
fa5120a0	196	if (seteuid(pw->pw_uid) < 0)
fa5120a0	197	fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	198	# endif
a3626e12	199	if (setuid(pw->pw_uid) < 0)
caa49784	200	fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	201	#endif
	202
	203	/* Try restoration of GID if changed (test clearing of saved gid) */
aff51935	204	if (old_gid != pw->pw_gid &&
688eed4a	205	(setgid(old_gid) != -1 \|\| setegid(old_gid) != -1))
f5db6a03	206	fatal("%s: was able to restore old [e]gid", __func__);
688eed4a	207
	208	/* Verify GID drop was successful */
	209	if (getgid() != pw->pw_gid \|\| getegid() != pw->pw_gid) {
aff51935	210	fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
aff51935	211	__func__, (u_int)getgid(), (u_int)getegid(),
688eed4a	212	(u_int)pw->pw_gid);
	213	}
	214
51e7d820	215	#ifndef HAVE_CYGWIN
688eed4a	216	/* Try restoration of UID if changed (test clearing of saved uid) */
aff51935	217	if (old_uid != pw->pw_uid &&
688eed4a	218	(setuid(old_uid) != -1 \|\| seteuid(old_uid) != -1))
f5db6a03	219	fatal("%s: was able to restore old [e]uid", __func__);
51e7d820	220	#endif
688eed4a	221
	222	/* Verify UID drop was successful */
	223	if (getuid() != pw->pw_uid \|\| geteuid() != pw->pw_uid) {
aff51935	224	fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
aff51935	225	__func__, (u_int)getuid(), (u_int)geteuid(),
688eed4a	226	(u_int)pw->pw_uid);
688eed4a	227	}
8efc0c15	228	}