[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"

/*
 * 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[NGROUPS_MAX], user_groups[NGROUPS_MAX];
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(NGROUPS_MAX, saved_egroups);
	if (saved_egroupslen < 0)
		fatal("getgroups: %.100s", strerror(errno));

	/* 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(NGROUPS_MAX, user_groups);
		if (user_groupslen < 0)
			fatal("getgroups: %.100s", strerror(errno));
	}
	/* 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)
	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)
	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);
	}

	/* 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__);

	/* 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"
8efc0c15	19
5260325f	20	/*
	21	* Note: all these functions must work in all of the following cases:
	22	* 1. euid=0, ruid=0
	23	* 2. euid=0, ruid!=0
	24	* 3. euid!=0, ruid!=0
	25	* Additionally, they must work regardless of whether the system has
	26	* POSIX saved uids or not.
	27	*/
8efc0c15	28
0096ac62	29	#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
8efc0c15	30	/* Lets assume that posix saved ids also work with seteuid, even though that
8efc0c15	31	is not part of the posix specification. */
0096ac62	32	#define SAVED_IDS_WORK_WITH_SETEUID
	33	/* Saved effective uid. */
	34	static uid_t saved_euid = 0;
	35	static gid_t saved_egid = 0;
	36	#endif
f8252c48	37
8efc0c15	38	/* Saved effective uid. */
63bd8c36	39	static int privileged = 0;
63bd8c36	40	static int temporarily_use_uid_effective = 0;
63bd8c36	41	static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
63bd8c36	42	static int saved_egroupslen = -1, user_groupslen = -1;
f8252c48	43
5260325f	44	/*
	45	* Temporarily changes to the given uid. If the effective user
	46	* id is not root, this does nothing. This call cannot be nested.
	47	*/
6ae2364d	48	void
63bd8c36	49	temporarily_use_uid(struct passwd *pw)
8efc0c15	50	{
f8252c48	51	/* Save the current euid, and egroups. */
0096ac62	52	#ifdef SAVED_IDS_WORK_WITH_SETEUID
f8252c48	53	saved_euid = geteuid();
0096ac62	54	saved_egid = getegid();
0df3a240	55	debug("temporarily_use_uid: %u/%u (e=%u/%u)",
	56	(u_int)pw->pw_uid, (u_int)pw->pw_gid,
	57	(u_int)saved_euid, (u_int)saved_egid);
f8252c48	58	if (saved_euid != 0) {
	59	privileged = 0;
	60	return;
	61	}
0096ac62	62	#else
	63	if (geteuid() != 0) {
	64	privileged = 0;
	65	return;
	66	}
	67	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	68
f8252c48	69	privileged = 1;
f8252c48	70	temporarily_use_uid_effective = 1;
184eed6a	71	saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
f8252c48	72	if (saved_egroupslen < 0)
	73	fatal("getgroups: %.100s", strerror(errno));
	74
	75	/* set and save the user's groups */
	76	if (user_groupslen == -1) {
	77	if (initgroups(pw->pw_name, pw->pw_gid) < 0)
	78	fatal("initgroups: %s: %.100s", pw->pw_name,
	79	strerror(errno));
184eed6a	80	user_groupslen = getgroups(NGROUPS_MAX, user_groups);
f8252c48	81	if (user_groupslen < 0)
	82	fatal("getgroups: %.100s", strerror(errno));
	83	}
	84	/* Set the effective uid to the given (unprivileged) uid. */
d98d029a	85	if (setgroups(user_groupslen, user_groups) < 0)
63bd8c36	86	fatal("setgroups: %.100s", strerror(errno));
0096ac62	87	#ifndef SAVED_IDS_WORK_WITH_SETEUID
	88	/* Propagate the privileged gid to all of our gids. */
	89	if (setgid(getegid()) < 0)
	90	debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
	91	/* Propagate the privileged uid to all of our uids. */
	92	if (setuid(geteuid()) < 0)
	93	debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
	94	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
d98d029a	95	if (setegid(pw->pw_gid) < 0)
caa49784	96	fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
f8252c48	97	strerror(errno));
f8252c48	98	if (seteuid(pw->pw_uid) == -1)
caa49784	99	fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
f8252c48	100	strerror(errno));
8efc0c15	101	}
f8252c48	102
5260325f	103	/*
a3626e12	104	* Restores to the original (privileged) uid.
5260325f	105	*/
6ae2364d	106	void
1e3b8b07	107	restore_uid(void)
8efc0c15	108	{
63bd8c36	109	/* it's a no-op unless privileged */
0df3a240	110	if (!privileged) {
0df3a240	111	debug("restore_uid: (unprivileged)");
63bd8c36	112	return;
0df3a240	113	}
63bd8c36	114	if (!temporarily_use_uid_effective)
63bd8c36	115	fatal("restore_uid: temporarily_use_uid not effective");
0096ac62	116
0096ac62	117	#ifdef SAVED_IDS_WORK_WITH_SETEUID
13979d47	118	debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
a3626e12	119	/* Set the effective uid back to the saved privileged uid. */
5260325f	120	if (seteuid(saved_euid) < 0)
caa49784	121	fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
0096ac62	122	if (setegid(saved_egid) < 0)
caa49784	123	fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
0096ac62	124	#else /* SAVED_IDS_WORK_WITH_SETEUID */
	125	/*
	126	* We are unable to restore the real uid to its unprivileged value.
	127	* Propagate the real uid (usually more privileged) to effective uid
	128	* as well.
	129	*/
	130	setuid(getuid());
	131	setgid(getgid());
	132	#endif /* SAVED_IDS_WORK_WITH_SETEUID */
	133
d98d029a	134	if (setgroups(saved_egroupslen, saved_egroups) < 0)
63bd8c36	135	fatal("setgroups: %.100s", strerror(errno));
63bd8c36	136	temporarily_use_uid_effective = 0;
8efc0c15	137	}
8efc0c15	138
5260325f	139	/*
	140	* Permanently sets all uids to the given uid. This cannot be
	141	* called while temporarily_use_uid is effective.
	142	*/
6ae2364d	143	void
63bd8c36	144	permanently_set_uid(struct passwd *pw)
8efc0c15	145	{
688eed4a	146	uid_t old_uid = getuid();
	147	gid_t old_gid = getgid();
	148
63bd8c36	149	if (temporarily_use_uid_effective)
95f20fe8	150	fatal("permanently_set_uid: temporarily_use_uid effective");
0df3a240	151	debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
0df3a240	152	(u_int)pw->pw_gid);
688eed4a	153
	154	#if defined(HAVE_SETRESGID)
	155	if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0)
	156	fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
3b8dff69	157	#elif defined(HAVE_SETREGID) && !defined(BROKEN_SETREGID)
688eed4a	158	if (setregid(pw->pw_gid, pw->pw_gid) < 0)
	159	fatal("setregid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
	160	#else
fa5120a0	161	if (setegid(pw->pw_gid) < 0)
fa5120a0	162	fatal("setegid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
63bd8c36	163	if (setgid(pw->pw_gid) < 0)
caa49784	164	fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
688eed4a	165	#endif
	166
	167	#if defined(HAVE_SETRESUID)
	168	if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0)
	169	fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
3b8dff69	170	#elif defined(HAVE_SETREUID) && !defined(BROKEN_SETREUID)
f5db6a03	171	if (setreuid(pw->pw_uid, pw->pw_uid) < 0)
f5db6a03	172	fatal("setreuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	173	#else
688eed4a	174	# ifndef SETEUID_BREAKS_SETUID
fa5120a0	175	if (seteuid(pw->pw_uid) < 0)
fa5120a0	176	fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	177	# endif
a3626e12	178	if (setuid(pw->pw_uid) < 0)
caa49784	179	fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
688eed4a	180	#endif
	181
	182	/* Try restoration of GID if changed (test clearing of saved gid) */
	183	if (old_gid != pw->pw_gid &&
	184	(setgid(old_gid) != -1 \|\| setegid(old_gid) != -1))
f5db6a03	185	fatal("%s: was able to restore old [e]gid", __func__);
688eed4a	186
	187	/* Verify GID drop was successful */
	188	if (getgid() != pw->pw_gid \|\| getegid() != pw->pw_gid) {
	189	fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
	190	__func__, (u_int)getgid(), (u_int)getegid(),
	191	(u_int)pw->pw_gid);
	192	}
	193
	194	/* Try restoration of UID if changed (test clearing of saved uid) */
	195	if (old_uid != pw->pw_uid &&
	196	(setuid(old_uid) != -1 \|\| seteuid(old_uid) != -1))
f5db6a03	197	fatal("%s: was able to restore old [e]uid", __func__);
688eed4a	198
	199	/* Verify UID drop was successful */
	200	if (getuid() != pw->pw_uid \|\| geteuid() != pw->pw_uid) {
	201	fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
	202	__func__, (u_int)getuid(), (u_int)geteuid(),
	203	(u_int)pw->pw_uid);
	204	}
8efc0c15	205	}